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Control philosophy _ JSPL Pellet Plant-II
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SPECIFICATION
Department: Control Systems
Document No: I010S
Document Title: CONTROL PHILOSOPHY
PROJECT REFERENCE 3 Project No.: TS120100 Project Location:
Barbil, Odisha, India. Project Title: Iron Ore Pelletizing Plant II
Client: Jindal Steel and Power Ltd.
PM Authorisation: Date: 13th July, 2013 Client Authorisation:
Date:
APPROVALS Rev Issue Date Revision Description Prepared Checked
Disp.App Proj. App
0 16 Oct 2012 Issued for Design JR RC RC TC 1 20 Nov 2012 Issued
for Design KT RC RC TC 2 28 Nov 2012 Issued for Design KT RC RC TC
3 6 Mar 2013 Issued for Design JR RC RC 4 25 June 2013 Revised in
line with Vendor Control
Philosophy SSG SD JS CPn
5 13 July 2013 Revised in line with discussion with JSPL SSG SB
JS CPn
Entire Document DOCUMENT ISSUED FOR: Issued this Revision
In-house Review Purchase
Revised Pages Only Client Approval Construction Issued this
Revision Enquiry Tender
Copyright 2010 by Jacobs Engineering Group Inc. All rights
reserved. The contents of this document are proprietary and
produced for the exclusive benefit of Jacobs Engineering Groups
Inc. and its affiliated companies. No part of this document may be
reproduced, stored in a retrieval system, or transmitted, in any
form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without the prior written approval of
Jacobs Engineering Group Inc.
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Control philosophy _ JSPL Pellet Plant-II
TABLE OF CONTENTS
1.0 INTENT OF THE DOCUMENT
2.0 CONVENTIONS
3.0 IRON ORE RECEIVING & WET GRINDING SECTION- AREA 1
4.0 ADDITIVE RECEIVING AND DRY GRINDING -AREA 2
5.0 MIXING AREA 3
6.0 BALLING AREA 4
7.0 INDURATING AREA 5
8.0 PRODUCT SCREENING AREA 6
9.0 POLLUTION CONTROL AREA 7
10.0 UTILITIES AREA 8
11.0 CONTROL SYSTEM OVERVIEW & PHILOSOPHY
12.0 ANNEXURE I PID LOOP LIST
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1.0 INTENT OF THIS DOCUMENT
This document describes the control system for iron ore
pelletizing facility, based on the Dravo Traveling Grate Process,
located at the site of Jindal Steel and Power Limited (JSPL) in
Barbil, Odisha, India. This plant is designated as JSPL Pellet
Plant 2 and is located adjacent to the existing JSPL Pellet Plant
1.
Specific vendor document for equipment/package is used as a
basis to provide detailed philosophy.
The pellet plant is conceived as a versatile operation capable
of producing a variety of product types, as predicated by the ore
supply and/or the consumer demand. Thus, from time to time,
campaigns may be run to produce varieties ranging from acid pellets
to fluxed pellets.
The pellet plant conveyors and hardware will be mechanically
designed to handle 4,500,000 direct reduction grade (DR-grade) ore
pellets per year in 330 days of operation (7,920 scheduled hours
per year), taking into account all design safety factors. Actual
indurating capacity is dependent upon the specific ore being
utilized, the type of pellets being produced, and quality
specifications of the consumer.
Total plant availability is dependent upon the specific
operating and maintenance practice employed at the site. JSPLs
target production is 4,000,000 tonnes per annum of fired
pellets.
2.0 CONVENTIONS
The sections on control philosophy for each area include
references to Loops with associated numbers. These loops are
instrument loops identified by number on the Piping and
Instrumentation Diagrams (P&IDs).
3.0 IRON ORE RECEIVING & WET GRINDING SECTION- AREA 1
3.1 Iron Ore Receiving (P&ID: R-01-1001)
Blended Iron ore is delivered by owners blended ore conveyor
directly onto the Ore Concentrate Conveyor OF-11 (B43001D). OF-11
discharges blended ore on conveyor OF-12 (B43001C). OF-12 delivers
ore to OF-13 (B43001B) and finally OF-13 delivers on shuttle
conveyor OF-14 (B43001A), which in turn feeds to Ball mill feed
bins (B43510-1&2). Conveyor OF-11, 12, 13 and OF-14 are
equipped with standard conveyor control packages for this project.
Each conveyor is equipped with adequate safety switches.
The receiving rates for wet iron ore to the ball mill feed bins
at 8% H2O (by weight) are:
Operating : 590 TPH Design : 2000 TPH
Each Ball mill feed bin has a four (4) hour design storage
capacity.
Individual start-up of blended ore conveyors OF-11, 12 &13
and shuttle conveyor OF-14 will depend on healthy signal from the
safety switches placed on the conveyors.
Group start up will depend on the level signal from level
transmitters placed over bins. Low (20%) signal from bin level
transmitters will start shuttle conveyor OF-14 first followed by
blended ore conveyors OF-13, OF-12 & OF-11 sequentially,
provided there is healthy signal from safety switches of these
conveyors.
The unidirectional Ore Concentrate shuttle conveyor OF-14 feeds
the Ball Mill Feed Bin2 (B43510-2) when positioned under the
discharge of blended ore conveyor (OF-13). The shuttle car is
fitted
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with a chute at the back end. When Bin-2 is full (High alarm),
OF-14 moves ahead and the chute fitted with the shuttle car comes
in line with the discharge chute of OF-13 and Bin-1 starts getting
filled up.
The filling of each bin will be controlled by the level
transmitter High & Low Set points. The position for the shuttle
car filling BIN-01 directly will be determined by a limit switch
installed corresponding to desired position which will stop the
shuttle car motor. On receipt of H signal (70%) from Bin-01 the
shuttle car starts traveling to fill Bin-02. After receipt of H
signal from any of the bins if the shuttle car fails to move to the
other bin due to any reason within 2 minutes the shuttle conveyor
will stop and subsequently all upstream conveyors will stop
sequentially.
H-H alarm (90%) from both bin level transmitters and/or
unhealthy signal from any conveyor safety switch will stop
up-stream conveyors in a sequential manner.
There are 2 weigh belt feeders WF-1 and WF-2 (B55201-1, 2) (Loop
No: WIC-01B0107 & WIC-01B0117, P&ID: R-01-1001) located
under Ball Mill Feed Bins-1 & 2 respectively. The weigh belt
feeders feed blended ore to respective ball mill feed conveyors
BMF-1 & BMF-2 (B43002-1&2).
Group start-up of weigh belt feeders and mill feed conveyors
will depend on the following factors:
Healthy signal from the safety switches placed on the conveyors
Ball mill (B46201 / B46202) is running Low-Low alarm not present at
the respective bin.
The feed rate set point to the weigh feeders is from the Ball
Mill Specific Energy Consumption (JIC-01B0206, JIC-01B0506,
P&ID: R-01-1002 & R-01-1005). Ball mill feed set point is
based on mill specific energy, kWh/T as formulated below:
Feed (TPH) = (Mill kWh per h) / (Mill kWh per T)
Mill Specific energy will be set by an operator at 12.5
(Constant) [Refer P&ID: R-01-1001, Note-5]
The action on a bin alarm of low-low (5%) is to stop the belt
weigh feeder (B55201-1, 2) under the bin. This will prevent the bin
emptying out with the consequential damage to the belt weigh
feeders caused by material falling from the top of the bin directly
on them.
Stopping of weigh belt feeders and mill feed conveyors will
depend on the following factors:
Unhealthy signal from the safety switches placed on the
conveyors Ball mill stops Low-Low alarm at the respective bin
HH, H, and LL, L set points are indicative only and will be
finalized by the commissioning engineer.
3.2 Shutdown
Prior to a planned shutdown the decision must be made as to
whether or not to empty off all or any of the conveyors. This
decision will determine the sequence and timing of each conveyor
shutdown. The units are designed so they can be safely be restarted
if stopped under full load.
3.3 Wet Grinding System (R-01-1002, 1003, 1004, 1005, 1006 &
1007) (Inputs received from package vendor FLSmidth)
3.3.1 Process Description
Wet Grinding System is a dual motor driven Ball Mill with
Hydrocyclone in a closed loop circuit.
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Iron ore feed size of -12mm (F100) with moisture content 8% is
fed into the ball mill in a controlled rate .Water added at the
ball mill inlet to cater to grinding and to maintain the
consistency in percentage solids at the trommel discharge. The
discharge from ball mill is pumped to a classifying Hydrocyclone
for separating -70 to -75 microns fractions (P80). The oversize
will be recycled to Ball Mill for further grinding. The Product
will be collected from the Hydrocyclone over flow.
Hydrocyclone underflow is taken as a recycle into ball mill
feed, this forms the closed circuit. Required dilution water
through flow control valves FV0021/FV1021 can be added to the
slurry tank to maintain density of slurry to the Hydrocyclone (Loop
No: FIC-B01-0020 / FIC-B01-1020, P&ID: R-01-1003 /
R-01-1006)
A flow transmitter FIT0037 / FIT1037 and Density meter DIT0036 /
DIT1036 (Loop No: DIC-B01-0036 / 1036, P&ID: R-01-1003 /
R-01-1006) is provided in the discharge of the slurry pumps
(331.PU210/B41101-1, 2 / 3, 4) to maintain the slurry density and
flow rate to the Hydrocyclone. The readings of the same will be
available at the Main Automation System. A Flow control valve
FCV0044 / FCV1042 located in the ball mill feed water pipe to
ensure proper control on the water addition to mill (Loop No:
FIC-B01-0042 / 1040, P&ID: R-01-1002 / R-01-1005).
Protective trips/alarms for the mill motor, lubrication system
etc would be actuated from the Main Automation System. A local
control panel monitors girth gear pinion grease lubrication system.
Main Automation System obtains only healthy and unhealthy signals
from the Girth gear local control panel. However, the start/ stop
command can be initiated from the Main Automation System.
3.3.2 Normal Start-up Sequence
This section describes the functional group startup sequence. If
the group has an automatic start sequence, time delays between
equipment will also be listed. Any group preconditions required
prior to startup are also listed herein. However, interlocks
required for individual or predefined groups of equipment are
listed in the Interlocks section.
3.3.3 Normal Operation
This section describes the functional group normal operation,
including operator functions. There are three modes of operation,
as described below:
Automatic
Automatic mode is when functional groups are controlled
automatically and in sequence by the equipment control system. A
functional group is a set of items such as motors, valves, etc.
which are started by a single operator action when in Automatic
Mode. All Protective, Safety, Machine, Operational and Start
Interlocks must be met in order to operate.
Manual
Manual mode is when items such as motors, valves, etc. are
controlled individually by the operator using the equipment control
system. Functional groups have no meaning in Manual Mode. All
Protective, Safety, and Start Interlocks must be met in order to
operate.
Local
Local mode is when items such as motors, valves, etc. are
controlled individually in the field, usually by local pushbutton
stations located near the equipment. Functional groups have no
meaning in Local Mode. Since the operator interface in Local Mode
is often physical devices rather than a display screen, extra care
must be taken to ensure that interlocking continues to be enforced.
All Protective, Safety, and Start Interlocks must be met in order
to operate.
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Main Automation System Control
Commands to operate the equipment control system are made by an
operator using the Main Automation System HMI. The Main Automation
System can only operate equipment in Automatic Mode.
3.3.4 Normal Shutdown Sequence
This section describes the group shutdown sequence. If the group
has an automatic shutdown sequence, time delays to allow for
equipment cleanout or deceleration will also be listed.
3.3.5 Abnormal and Emergency Shutdowns
This section describes abnormal shutdown conditions caused by
isolated process or equipment abnormalities or activation of
individual equipment safety devices. It also describes emergency
shutdowns due to automatic activation of personnel safety systems
or field emergency stop pushbuttons.
3.3.6 Interlocks
The Interlocks section describes all interlocks for the
individual equipment or functional group of equipment within the
associated software function group. Interlock is defined herein as
an input/output signal or a Main Automation System/Main Automation
System internal logic condition, which automatically prevents the
operation of an individual or functional group of equipment from
the Plant Main Automation System HMI. When the condition of an
interlock(s) is such that operation of a related piece of equipment
or an equipment group is permitted, the interlock(s) is defined as
being satisfied.
Specific devices in the Interlock table may be preceded by NOT.
This is the condition for the analog threshold (i.e. NOT Bearing
Temperature High-High = Bearing Temperature is NOT ABOVE the
High-High Set point). However, in the case of discrete switches the
Interlock is stated from the ON perspective of the switch. For
example the Oil Reservoir Low switch is ON when the oil level is
NOT Low (fail-safe), so the required interlock in the switch being
true.
Interlocks consist of five types and are described in detail
below:
Safety interlocks:
Safety interlocks are those interlocks which prevent damage to
that associated piece of equipment. As a result, safety interlocks
apply when operating in Automatic Mode, Manual Mode and Local
Mode.
Example
Safety interlock for a pump would be no high-high bearing
temperature.
Safety interlocks for every motor will also include the
MCC/motor ready signal and receipt of a run confirmation from the
motor contactor after a run command is sent. These interlocks apply
to all motors and are not listed in the interlock table for this
reason.
Start interlocks:
Start interlocks are those interlocks necessary ONLY for
starting the machine. As soon as the motor is running the start
interlock has no influence. As a result, start interlocks apply
when operating in Automatic Mode, Manual Mode and Local Mode.
Example
A start interlock for a fixed speed fan with automatic damper
would be that the damper be closed (limit switch or position
transmitter) prior to starting.
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Protective Interlocks:
Protective interlocks are those interlocks for the protection of
the motor itself. As a result, protective interlocks apply when
operating in Automatic Mode, Manual Mode and Local Mode.
Example
A protective interlock for an equipment motor would be motor
bearing temperature or motor winding temperature.
Machine Interlocks:
Machine interlocks are those interlocks for the protection of
the machine that is operating in Automatic Mode. As a result,
machine interlocks apply only when operating in Automatic Mode.
Example
A machine interlock for a belt conveyor would be a belt drift
switch.
Operational Interlocks:
Operational interlocks are those interlocks that are related to
the process, but not to the equipment, that is necessary for the
normal operation of the item. As a result, operational interlocks
apply only when operating in Automatic Mode.
Example:
An operational interlock would be downstream equipment
running.
3.3.7 Overview
The mill plant incorporates the following features: Feed system
(Described in section 3.1)
Ball mill
Hydrocyclone
Product Slurry system
3.3.7.1 Ball mill
Iron ore size reduction is carried out in the Ball mill. Water
spray system is installed on the discharge chute for cleaning the
trommel screen and process water addition is installed at the feed
chute to maintain the percentage solids consistency. Temperature
Scanner at the feed end and discharge end measures the inlet and
outlet mill bearing temperature. Slurry from the trommel discharge
is transported to Slurry Tank. The mill is equipped with internal
liners and the balls are charged in different size.
The efficiency of wet grinding action depends mainly on the
solids present in the feed slurry to the Ball mill. The Ball mill
outlet is fed to hydro cyclone through slurry pumps for coarser and
finer classification.
Trommel screen functions for the removal of grinding media scats
and tramp oversize material from mill discharge slurry which fed
into mill discharge tank. Mill scats are then discharged to the
area below mill and are manually shoveled.
3.3.7.2 Hydrocyclone
Hydrocyclone are density separators that convert pressure energy
into rotational momentum. The rotational momentum provides the
centrifugal force to classify solids from slurry. Separation
efficiency is determined by the Hydro cyclone geometrical
parameters. The interaction between parameters dedicates the Hydro
cyclone efficiency.
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In operation, pressurized slurry is fed to the Hydro cyclone and
the centrifugal force generated causes the heavier suspended solids
to move toward the wall while the radial velocity forces the liquid
and lighter gravity solids to move inward toward the central axis.
Primary and secondary vortex develops. The primary vortex carries
the solids to the apex. The apex orifice permits the heavier solids
and a small amount of the liquor to be discharged. A secondary
developing vortex carries the cleaned primary liquid (liquor) and
light gravity solids out through the Vortex Finder Tube.
The performance of the hydro cyclone is based on the particle
size distribution of the cyclone overflow. The underflow slurry
from the hydro cyclone is fed in to the ball mill. The hydro
cyclone overflow is fed to the Thickener Feed Well by gravity.
3.3.7.3 Product Slurry System
Each grinding mill will have a dedicated mill discharge slurry
pump tank which collects the ground iron ore slurry from the mill.
Each slurry pump tank with conical bottom, is of approximately 50
m3 capacity. The tank base will preferably be above grade level.
Water addition to the Ball Mill Slurry Tank is to control the
Density of the slurry being fed to the Hydro Cyclone which is
monitored by density meter at the slurry pump discharge. This is
controlled by a Control Valve in the Water Addition Line to the
slurry tank. Slurry Pumps are equipped the Variable speed drive to
maintain consistent pressure in the Hydro Cyclone for better
classification and the slurry tank is equipped with Level
transmitter to maintain level in tank.
3.3.8 Operation Philosophy and Plant Sequencing
Starting of the mill system is divided into a number of groups.
Each drive/ equipment/ Valves in a particular group has a specified
sequence of operation. Each group in itself has a specified
sequence of operation during start and stop. This means that no
equipment can be started before the subsequent equipment has been
started. Inversely, stop of any equipment will cause the stop of
the preceding equipment, unless until specified herein.
This section outlines the division of groups; the basic
terminology used in numbering of the groups, sequential Interlocks
between groups and between equipment/ drives/ Valves in every
particular group.
This section basically outlines the various process Interlocks
that are to be satisfied for successful operation of a sequence.
The operator has to ensure that the power source, remote selection
etc., are properly ensured. In case, the same has not been ensured,
the HMI would initiate the respective alarms as described in the
earlier section(s)/ sub section(s).
The philosophy goes into details on the various process related
Interlocks and sequences only. Zero speed switch indication has not
been included due to the commonality to all drives. Interlocks like
pull chord switch, belt sway switch, instrument air pressure etc,
and are not included in the write up.
General Notes:
a. Temperature, pressure, flow, level and any other process
parameter set point will be adjusted and set during commissioning.
Access to the set point is provided only for Engineers and not for
the Operators.
b. For all the analog inputs, trends are configured in the Main
Automation System.
c. Pressure switch is provided in the discharge line of all
Slurry pumps for monitoring low pressure alarm in the Main
Automation System.
d. Considering the safety of the equipment, the AUTO changeover
of any drives is not permitted in the mill.
e. During the Re-start of the plant after the power failure, the
operator has to ensure that the mill drive is ready for operation
before starting the mill discharge tank group and Hydro cyclone
group to avoid overflow of slurry at the mill feed end and
discharge end. (After starting the
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Hydro cyclone and Mill discharge tank group, the mill drive has
to be started immediately).
f. After ensuring that the utilities are ready the operator
initiates the starting of the plant.
3.3.9 Equipment Grouping
The various sections of the wet grinding circuit are assigned
group numbers to assist the definition of discrete areas. Groups
can be started up individually in preparation for overall plant
start-up. These numbers will also be used for plant start-up and
commissioning planning activities. Details of the groups are
included in the relevant sections.
The total process is broken down into four discrete groups to
allow for easy description of the facilities. These are as
follows:
Group 1 Slurry Classification Group 2 Ball mill Lubrication
Group 3 Ball Mill
Group 4 Ball mill Feed
3.3.10 Slurry Classification Group-1 (P&ID: R-01-1003,
R-01-1004, R-01-1006, R-01-1007)
3.3.10.1 Group description:
The ground product from the ball mill discharges into the slurry
tank (331. TK200/B35101-1).Slurry tank is provided with a level
transmitter LT0023 to monitor and maintain the level with the
slurry pump speed control.
Pair of slurry pumps (331.PU210/331.PU220/B41101-1, 2), (one
operating and the other stand by) are located adjacent to the tank
transport the slurry to the Hydro cyclones. Both slurry pumps are
provided with Variable frequency Drive (VFD).
A low level in the tank (331.TK200/B35101-1), (LAL0023 set at
20%) inhibits the starting of the slurry pumps. A low low level in
the tank (331.TK200 /B35101-1),(LALL0023 set at 30%) is used to
trip the Hydro cyclone feed pumps. The normal operating level is
expected to be 65%.Slurry pump speed shall be varied to maintain
the targeted level.
Slurry is classified for fines and coarse in a cluster of
hydro-cyclone (331.HN300/B45801-1,2,3,4).Slurry is distributed to
individual cyclones from a common feed distribution manifold.
Pressure transmitter PT0039 located on the hydro cyclone manifold
monitors inlet pressure of feed slurry.
Consistent pressure is maintained for efficient classification
in the hydro-cyclone. There are four cyclones in the cluster.
Typically, at rated production one cyclone remain as a spare with
all other cyclones on line. At lower capacity operation it might be
necessary to reduce the number of cyclones in operation to maintain
the desired pressure to achieve targeted classification. The field
technician can add or reduce the number of cyclones in operation by
opening or closing the cyclone feed valve.
Overflow and underflow from the hydro-cyclone cluster discharges
into common overflow and underflow launders respectively. The
overflow product slurry is sent through pipeline to the storage
tank and flows by gravity.
Coarse underflow Slurry is discharged into the ball mill for
further grinding to target fineness.
Transmitters FIT0037 and DIT0036 measure the flow and density of
the slurry as fed to the hydro-cyclones respectively. The hydro
cyclone feed slurry percent solid is maintained at 55% w/w by
adding water to the slurry tank. Water addition is controlled via
the automated flow control valve FCV0021.
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3.3.10.2 Group-1 Equipment summary:
The operator can select only one slurry pump at any point of
time. Selection of a pump would automatically de-select the other
pump from operation. By default slurry pump (331.PU210/B41101-1) is
selected for operation.
a. Suction and Discharge valves (XV0025)for(331
PU210/B41101-1)
b. Suction and Discharge valves (XV0024)for(331
PU220/B41101-2)
c. Hydro cyclone feed pumps (331.PU210/331.PU220/B41101-1,2)
3.3.10.3 Group-1 starting sequence:
The SCG group is a single drive group slurry pumps. By default
(331. PU210 /B41101-1) pump is selected for operation. A start
command to the SCG group starts the selected pump
(331.PU210/331.PU220/B41101-1, 2).
a. Open discharge knife gate valve XV0034/0035 with respect to
the selected pump (331.PU210/B41101-1) &
(331.PU220/B41101-2).
b. Open suction knife gate valve XV0025/0024 with respect to the
selected pump (331.PU210/B41101-1) & (331.PU220/B41101-2).
c. Start the slurry pump (331.PU210/B41101-1) &
(331.PU220/B41101-2).
It will be the responsibility of the Control room operator to
confirm from the field technician that the gland seal water line
valve of the selected pump is open and drain valves of the selected
pump are closed and stand by pump is open before embarking a start
command. A knife gate valves is provided at the discharge of the
pumps to isolate the non-operating pump.
3.3.10.4 Group-1 Starting interlocks:
The following general interlocks are valid for starting SCG
Group.
a. A level low alarm LAL0023 (set at 30%) on the tank
(331.TK200/B35101-inhibits starting of the selected slurry
pump.
b. Open Limit switch of the suction and discharge valves (ZSO
0024/0025) and (ZSO0034/0035) is healthy for the selected pump.
3.3.10.5 Group-1 Running interlocks:
a. A level low low alarm, LALL0023 (Set at 20%) on the tank
(331.TK200/B35101-1) inhibits running of the selected slurry
pump.
b. Open Limit switch of the suction and discharge valves (ZSO
0024/0025) and (ZSO0034/0035) is healthy for the selected pump.
3.3.10.6 Group-1 stopping sequence:
A stop command initiates a stop of the operating selected slurry
pump.
a. Stop the selected slurry pump (331.PU210/B41101-1) &
(331.PU220/B41101-2).
b. Close limit (ZSC0034/0035) healthy for discharge knife gate
valve XV0034/0035 with respect to the selected pump
(331.PU210/B41101-1) & (331.PU220/B41101-2).
c. Close limit (ZSC0024/0025) healthy for suction knife gate
valve XV0025/0024 with respect to the selected pump
(331.PU210/B41101-1) & (331.PU220/B41101-2).
It will be the responsibility of the control room operator to
confirm from the field technician that the gland seal water line
valve of the selected pump is closed and drain valves of the
selected pump are opened and flush the casing and discharge line of
the selected pump.
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3.3.11 Ball Mill Lubrication Group 2
This group is divided into following functional groups for easy
operation and logical control.
1. Ball Mill Main Lubrication system Group 2A
2. Main Gearbox Lubrication system Group 2B
3.3.11.1 Ball Mill Main Lubrication system Group 2A (P&ID:
R-01-1009, R-01-1010)
3.3.11.1.1 Group Description:
The mill lubrication system (331.LQ110) consists of 3 parts:
Reservoir assembly and oil conditioning circuit;
HP hydrostatic bearings lube circuit;
Pinion bearings LP lube circuit.
Reservoir Assembly & Oil Conditioning
Capacity of the Reservoir is 2310 litres. Tank utilises the
drain lines from the bearing housings to return the "dirty hot oil"
back to tank by gravity. This passes through a basket strainer
which is accessible through a hinged inspection door, for on-line
inspection and cleaning.
The sump tank is a 3 compartment design,
1. Return oil
2. Settling
3. Clean compartments.
The clean compartment is approx. 710 litres (3 minutes
retention) and the balance 1600 litres in the dirty side (6 minutes
retention). The correct oil temperature in the sump tank is
maintained by 3 kW heater elements (3 Nos), monitored by
Temperature transmitter (TT4033). Heaters operate between sump oil
temperatures of 32 38C. The dirty compartment temperature
transmitter is indicative and for heater control only. Two oil
level transmitters (LT4032/38) are also interlocked for oil level
monitoring.
Oil level sight glasses fitted to the tank gives visual
indication of oil level & temperature (LG4034/36 &
TG4035/37). Air breather / filter allow clean air to enter the
tank. 3 (nos) BSP drain valves plugs are available to drain the
tank, when required. Access to the tank internals is gained by
removing the tank lid and removal of the man-hole cover, which are
bolted down.
The LP conditioning circuit is fitted with 2 LP oil gear pumps
LP (One Working & One Standby), driven by an 18.5 kW TEFC
electric motor, fitted with integral pressure relief valves, set at
10 bars. Suction is isolated from the tank via a butterfly valve;
discharge end isolated via both a non return valve and ball
valve.
The LP oil flow rate is approx. 430 lpm, which is supplied to
the oil conditioning circuit and the pinion bearings and returned
to tank as a closed loop system via the over-flow and pinion brgs
drain line.
A pressure gauge (PG4009) & pressure transmitter (PT4011),
oil flow (FIT4010) and temperature transmitters (TT4008) in the
line confirms that the conditioning circuit is functional, allowing
the use of the pinion LP & hydrostatic HP pumps.
The dirty & hot oil" from the sump tank settling compartment
is pumped to a high capacity LP duplex filter and thereafter to a
Plate Heat Exchanger (PHE). The duplex filter unit is fitted with 2
filter clogged visual indicators and a common indicating
differential pressure transmitter
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(DPIT4023),which indicates to "change-over and clean filter unit
on-line, thereafter, allowing the artisan to isolate the clogged
filter housing ( close both butterfly valves ) and to replace the
clogged filter element with a new unit, resetting the visual
indicator, re-opening the isolating butterfly valves after
completion, bleeding and equalising the filter housing pressure,
which is now ready for use.
A Manual valve Controls the water flow rate through the cooler,
maintaining a constant oil temperature exiting the cooler of 47C.
Temperature gauges (TG4022) before and after(TG4006) the cooler
give visual indication of the water and oil temperature across the
cooler. The temperature transmitter (TT4008) fitted to the cooler
oil exit line, interlocked to raise an alarm if the oil Temperature
exceeds 520C.
The conditioned oil (clean & cool oil) exits the cooler and
a bleed line return back to the sump tank clean compartment (414
lpm). Clean compartment oil level and temperatures (level
LT4038> 90% and oil temp TT4039> 380C) shall meet to start
the HP pumps. The conditioning pump should run continuously, even
when the mill is stopped.
High Pressure Hydrostatic Oil Lube
The HP oil is pumped to the mill bearings via a 4 port flow
divider, as follows: FE (Feed End) bearing at 118 lpm; 59 lpm per
pocket
DE (Discharge End) bearing at 118 lpm; 59 lpm per pocket
HP Pressure gauges, HP pressure transmitters (PT 4050/ 53/ 56/
59), HP flow transmitter (FIT4038) exist to monitor and
inter-locked. The oil flow rates are balanced using rotary geared
flow divider to achieve the correct flow rates to the various
bearing pockets. The HP tandem gear pumps HP 01 /02 (One Working
& One Standby) are isolated from the sump tank by ball valves,
and protected against over-pressure by an individual pressure
relief valve, set at 103 bar. Non return and ball valves isolate
the pump feed lines, and a pressure gauge, oil flow transmitter are
fitted for visual and MAIN AUTOMATION SYSTEM interlocking for HP
system pressure. The 2750 kW TEFC mill main motors will be tripped
if the pressure drops below 25 bar or oil flow drops
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3.3.11.1.3 Group 2A Start sequence
Start command of the Group 2A initiate the following
sequence
a. Start heater HE 01
b. Start heater HE 02
c. Start heater HE 03
Note: Start the above sequence if the oil temperature is 520C
for running HP01 or HP02.
e. Flow low-low alarm(FI 4014/4016/4018/4020)(Set at (34lpm)
alarm is generated, if any of the pinion lube line oil flow low low
alarm FITS (3lpm) is not true then mill main motor trips.
f. Flow low-low alarm FI4048 (Set at
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d. Stop mill main motor.
e. Stop the running HP pump, either HP01 or HP02
f. Stop the running LP pump, either LP01 or LP02
3.3.11.2 Main Gearbox Lubrication system Group 2B (R-01-1011,
R-01-1012)
The ball mill main gear reducer is lubricated utilizing a forced
lubrication system.
The reducer lube system 331.LQ145 contains an oil reservoir. Two
oil-circulating pumps 331.GB 01/02 (one working + one standby) are
utilized for oil circulation inside the reducer. An oil-water
cooler is provided in the downstream to cool the oil before
entering the main reservoir.
The pressure of oil to the gearbox lubrication system and the
oil circulation pump discharge line will be monitored by the
pressure switches PSL4081. TemperatureTG4080 and pressure gauges
PG4083 are provided in the line for local display. The discharge
piping of the pump is connected to a differential pressure switch
DPSH4084 monitors the pressure drop across the filter unit. The
switch provides an input to the control system to alarm on
high-pressure drop across the filter alerting the operator to
change the filter.
The pumps used for oil recirculation, in case failure of main
pump auxiliary shall be manually started by the standby pump and
will trip the working pump by the low pressure switch PSL is
activated will trip the oil pump.
3.3.13 Ball Mill Group 3 (P&ID: R-01-1002, R-01-1005,
R-01-1010, R-01-1012)
3.3.12.1 Group description:
Ground ore from the Ball mill (331.BM100/B46201) discharge to
the tank (331.TK200/B35101-1) and pumped through slurry pumps
(331.PU210/B41101-1) to the hydro cyclone cluster
(331.HN300/B45801-1, 2, 3, 4) for classification.
Ball mill Inching Mode
It is to be noted that inching drive engage or disengage status
has also to be monitored locally. A proximity Switch (ZSC0017) is
provided in the jaw clutch coupling to ensure the disengage before
the start-up of the mill main motor.
3.3.12.2 Group 3 equipment summary:
a. Ball mill Main Drive 331.MD 135/140
b. Ball mill grease spray system 331.GS137
3.3.12.3 Ball Mill Girth-gear grease spray system Group
Prior to mill start up, the Main Automation System should have a
healthy signal from the grease drum low level switch.
As soon as the mill main motor runs, the Main Automation System
will energises the 3/2 way air solenoid valve which operates the
pneumatic grease pump, and a monitoring timer is activated. The
grease is pumped through the grease strainer via the tubing to the
Master distributor, splitting the flow equally to the 2 Slave
distributors, which in turn discharges fixed quantities of grease
into all 10 nozzles. Once this cycle is complete, the indicator pin
on the slave distributors will activate the limit switches
(ZS4064/71), which re-sets the monitoring timer and the Main
Automation System will energise the 2/2 way air spray solenoids for
a set time period (time required for the mill to do 1 full
revolution, approx. 4 sec. plus time required complete the 7
distributor cycles)
The air pressure switches (PSL4062) in the air line will confirm
to the Main Automation System that the solenoid valves are
operational and that the plant air pressure is sufficient. The
grease pump runs for the duration of the set pulses, pulsed by the
distributor limit switches ZS. As soon as the
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pulses are complete, i.e. 7 pulses, the Main Automation System
will de-energise the pump solenoid valve and the system is put on
PAUSE for a set time period (10 minutes).
The above cycle will be repeated as long as the mill runs. The
indicator pin will not activate the limit switches if:
no grease flow to the nozzles occurs
the nozzles are blocked
the pipeline is broken / blocked
the distributor and/or limit switch is faulty
the grease strainer is blocked
The air pressure switch PSL4062 will fail to signal the Main
Automation System if the 2/2 way solenoid valve is faulty, or if
the plant air pressure is low or off line. The pressure gauge gives
visual indication of the system air & grease pressure. The pump
should trip if no pulses are generated from the distributors, or
the air pressure switches are not activated. The mill should then
also trip.
3.3.12.4 Group 3 starting Sequence:
Start command of the Group 3 initiate the following sequence
a. Start Lube System 331.LQ110
b. Start Ball mill main motors 331. MD 135 & 140.
c. Start the Grease spray system 331.GS137.
d. Start Reducer Lube system 331.LQ145
3.3.12.6 Group 3 starting interlocks:
The ball mill 331.BM100 can start if the following conditions
are met:
Pinion bearing temperature TI0018 high alarm not true (Set at
800C)
Feed end trunnion bearing temperature TI0011 high alarm not true
(Set at 60oC)
Discharge end trunnion bearing temperature TI0019 high alarm not
true (Set at 600C)
Mill main bearing lubrication system 331 LQ110 operation is
valid for a minimum period of 600 seconds prior to start of mill
drive
Mill main motor gearbox lubrication system 331 LQ145 operation
is valid for a minimum period of 600 seconds prior to start of mill
drive
Motor bearing temperature T1 0014/0004 high alarm not true (Set
at 650C) Motor winding temperature T1 0012/0006 high alarm not true
(Set at 650C) Mill discharge slurry tank 331.TK200 level LAH0023
high alarm not true
Grease spray system false alarm is not present.
Inching Drive (ZSC0017) engaged limit is not true.
3.3.12.6 Group 3 running interlocks:
The ball mill (331.BM100/B46201) can remain in operation if the
following conditions are met:
Mill bearing lube oil pumps is in valid operation.
'Low Low oil reservoir level LSL LT4032 alarm 15% is not true.
'Low Low oil reservoir level LSL LT4038 alarm 15% is not true.
Lubrication Oil
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pressure low low alarm
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Mill operation with high solid percentage by weight than that
recommended and a subsequent emergency shutdown.
The permanent remedy for case one would be to feed clean ore in
to the mill.
In both cases jamming could possibly be cleared by pressurized
fresh water into the trommel screen and carefully extracting with
proper tools from the discharge of the mill.
If needed, stop the mill operation to clear the jam.
3.3.13.3 Integrated Start Sequence
In summary the system is started with the following
sequence.
Start the Group 1 Start the Group 2
Start the Group 3
Start the Group 4
Put the liquor flow controllers in to cascade Control.
3.3.14 Integrated Stop Sequence
In summary the system is stopped with the following
sequence.
Put the liquor flow controllers in to Auto mode to maintain
their current set points Stop the Group 4 Wait for the mill to
empty of solids Stop the Group 3 Stop mill main drives Set the
liquor flow rates to low values Wait for the mill discharge tank to
empty of solids Flushing the mill discharge slurry transfer pipe
Close the water flow control valves Stop the Group 1 Drain the
slurry from mill discharge tanks. Stop the Group 2
Allowance is also made for flushing the mill and tanks as much
as possible after an equipment trip. This sequence is still
initiated by the operator.
3.3.14 Emergency Operation
If any trip or failures occur in any of the drives in this
group, all preceding equipment will also stop as a result of the
interlock system.
This could result in increased difficulty while re-starting the
group due to the improper shut down. If the quantity of the
material is huge that remain in the system, it might be necessary
for the operator to resort to the Individual mode of start during
re-start of group.
3.3.14.1 Failure of feeding arrangement to Mill
In this instance, a number of simultaneous interlock actions
need to occur. Those include immediately.
Mill main motor stops if the weigh feeder operation is not
restored within 300 seconds from the fault occurred.
Mill water controls automatically with the ratio control.
Main bearing lubrication system stops after 600sec if run
feedback of mill main motor fails.
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Mill discharge pumps speed would come to a preset value (Say
50%) if the mill discharge tank level reaches Low-Low (30%).
3.3.14.2 Failure of main bearing lubrication system
In this instance, a number of simultaneous interlock actions
need to occur. Those include immediately.
Failure of mill main bearing lubrication system will stop the
mill main motor.
Mill feed system (apron feeder & mill feed conveyor) trips
immediately if mill main motor stops/trips.
Mill water addition controls automatically with the ratio
control.
Speed of mill discharge pumps would come to a preset value if
the mill discharge slurry tank level reaches Low-Low (30%).
3.3.14.3 Failure of Gearbox lubrication system
In this instance, the simultaneous interlock actions need to
occur. Those include immediately.
Mill main motor stops if the gearbox lubrication system is not
resorted within 300 seconds from the fault occurred.
3.3.14.4 Failure of Grease Spray system
In this instance, the simultaneous interlock actions need to
occur. Those include immediately.
Mill main motor stops if the grease spray system is not resorted
within 1200 seconds from the fault occurred.
3.3.14.5 Failure of mill discharge slurry pump
In this instance, a number of simultaneous interlock actions
need to occur. Those include immediately.
Mill discharge slurry pump feedback fails.
Mill main motor stops if the mill discharge slurry tank level
remains High-High for 240 seconds.
Mill feed system (apron feeder & mill feed conveyor) trips
if mill discharge slurry tank level reaches High-High.
Mill water controls automatically with the ratio control.
Main bearing lubrication system stops after 600sec if run
feedback of mill main motor fails.
The drain valve should be opened manually to drain the slurry in
the pump and the line.
3.3.14.6 Failure of mill
Mill Weigh feeder operation stops.
Mill Water controls automatically with the ratio control.
3.4 Thickener & Flocculent dosing system (Inputs received
from package vendor Outotec)
The thickener treats the concentrate from the wet grinding
section using a flocculent solution to produce thickened
concentrate for transport to the next process and Clarified water
for reuse in the plant.
Local control of the thickener is via the control panel mounted
on the bridge. The drive can be
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started and stopped and the rakes raised and lowered via
pushbuttons on the front of the panel. The panel displays all of
the alarms as well as the main process signals, viz: Torque.
3.4.1 Principle of Operation Feed slurry enters the thickener
from the top via a feed pipe, and is discharged tangentially into
the feed well. The slurry is diluted with filtrate (From Filtrate
tank) and a chemical agent (a poly electrolyte) is added to bind
solid particles to form suitably large and stable flocs that settle
under gravitational forces. The flocculated slurry settles over a
bed with a well-defined interface with clarified water above it.
Clarified water flows to a peripheral collection launder at the top
of the thickener and finally flow into the process water tank and
again re-circulated as process water. Rake arms fastened to the
drive shaft coupled with gear box, scrape the precipitated and
deposited sludge towards to the centre of thickener bottom cone.
Concentrated Sludge is withdrawn from central underflow nozzle
located at base of the thickener and then pumped to the slurry
holding tanks (B36101-1&2).
3.4.2 Control Logic for Thickener Local Control Panel
The main controls for the Thickener are as follows:
1. Manually Start or Stop the Hydraulic power pack Electric
motor through local control panel.
2. Manually raise and lower the rake base.
3. Rake raising and lowering through Auto mode.
4. Manual trip Reset.
5. Selection of operation (Auto/Manual operation) through
selector switch.
3.4.2.1 Manual operation
Manual mode shall be selected in the selector switch.
The electric motor shall be started manually. The motor shall
start only if oil level is above the specified level in the power
pack and the pressure switch has not exceeded the maximum set
pressure (95% of set pressure).
The Hydraulic Cylinder is actuated manually up to the maximum
stroke or the rake base raised up to maximum level. Once the
cylinder reaches to max. Stroke, the Upper limit switch turn NC
thereby restricting further raising of the rake.
The Hydraulic Cylinder is retracted manually or the rake base is
lowered up to the minimum level. Once it reaches to the minimum set
point, the Lower limit switch turn NC, thereby restricting further
lowering.
When the oil level reaches low level in the hydraulic power pack
or pressure switch experience maximum pressure (95%) or pre-set
pressure governed by the pressure transmitter is more than 60% -
The Hooter siren turns ON.
While lifting the rake mechanism, the rake arms shall
continuously rotate and scrape the slurry. Hooter will turn OFF if
trip reset is being activated.
The electric motor shall be stopped manually.
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3.4.2.2 Auto operation
1. Auto Mode shall be selected by selector switch.
2. The Hydraulic Power pack electric motor shall be manually
started. The motor shall start only if oil level is just above the
specified level in the power pack and pressure switch has not
exceeded maximum set pressure (95%).
3. If torque is less than 60% of the set pressure in the
pressure transmitter, rake shall rotate at the lower most position
and lower limit switch shall turn NC.
4. Accordingly indication shows as Rake is fully lowered.
5. Once torque reaches to 60 % or more of the preset pressure
transmitter reading, rake shall raise automatically and will be
held at the position so that pressure drops to 60 % of the set
pressure. In any case if rake pressure reaches 95% of the set
pressure, pressure switch shall be activated and the electric motor
turns OFF.
6. If the rake lift carriage reaches the maximum level and still
the pressure shows more than 95%, the electric motor shall turn OFF
(Upper limit switch turn to NC).
7. Accordingly indication shows as Rake is fully raised.
8. After lifting, if pressure drops to less than 40% of set
pressure, rake shall lower automatically by timer circuit relay.
Rake shall lower every 180 sec. interval and spike of 2 sec ON,
process shall be repeated till this reaches the lower most
position.
9. When oil level reaches the low level in the hydraulic power
pack or pressure switch experiences maximum pressure (95%) or more
than 60% of pre set pressure governed by the pressure transmitter,
the Hooter siren turns ON.
3.4.2.3 Local control panel Indication
a) Hydraulic power pack electric motor ON.
b) Hydraulic power pack electric motor TRIP.
c) Rake fully RAISED (max. stroke).
d) Rake fully LOWERED.
e) High torque TRIP.
f) Low hydraulic oil level TRIP.
g) High torque ALRAM (Hooter turned ON).
3.4.2.4 Local control panel PUSH BUTTON
a) Hydraulic power pack electric motor START.
b) Hydraulic power pack electric motor STOP.
c) Rake RAISED.
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d) Rake fully LOWERED
e) Trip RE-SET.
f) Lamp TEST.
g) Emergency STOP.
h) Selector switch (Manual/Auto Mode)
i) Duel set controller (Micro process based).
j) Hooter
3.4.2.5 Feed back to Main Automation System (Potential free
contacts)
a. Pressure transmitter/Torque transducer (4 to 20 mA)
b. Rake Fully lowered.
c. Rake fully raised.
d. Hydraulic oil level-Low trip.
e. High torque trip (Pressure switch).
f. Hydraulic Power pack Motor ON.
g. Hydraulic Power pack Motor TRIP.
Note:
1. In primary duel set controller, 100% (20 mA) set point
corresponds to 120 bar/Maximum operating pressure/torque and 0% (4
mA) set point (Torque Duel set Controller) corresponds to 0
bar.
2. In secondary duel set controller, 100% (20 mA) set point
corresponds to height from sensor face and free board and 0% (4 mA)
set point corresponds to 2 mtr depth from the dual crystal
sensor/source.
3.4.3 Control Logic For Flocculent Dosing System
The operation logic for complete flocculent dosing system is
designed and defined to prepare and dose the required quantity of
flocculent automatically from Main Automation System.
Provision for manual operation is also enabled through a
selector switch.
The flocculent solution of 0.25% concentration gets pumped by
the dosing pump. If required, further dilution will be done by
addition of water. Proper mixing takes place inside the static
mixture before the diluted flocculent solution enters the
thickener.
Once the flocculent drops below certain level (1-FDS-LS-04) in
dosing tank (1-FDS-DOT-02), the level switch gives the signal to
Transfer Pump (1 - FDS - TP 01), which starts and pumps the
prepared solution from preparation tank (1-FDS-PRT-01) to dosing
tank (1-FDS-DOT-02).The Transfer Pump (1 - FDS - TP 01) Stops at LL
level of the tank. This batch Displacement volume
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is pre calculated. Dosing Tank Volume above Low level
(1-FDS-LS-04) is slightly more than this Pre calculated Volume
(Effective Volume). Hence there is no possibility of overflow.
When the preparation tank (1-FDS-PRT-01) gets emptied, this
signal is transferred to panel by level switch (1-FDS-LS-03) and
the Transfer Pump stops (1 - FDS - TP 01). Simultaneously, water
inlet solenoid valve (1-FDS-SOV-01) actuates to open & allow
water inside preparation tank (1-FDS-PRT-01). When the water just
submerges agitator blades, level switch (1-FDS-LS-02) gives signal
again to panel, which in turn starts Screw feeder (1-FDS-SF-01) and
agitator (1-FDS-AG-01).
Screw feeder is allowed to operate only for few seconds thro
timer (T2) to allow just enough quantity of flocculent powder
required for preparing fresh batch of solution at 0.25%
concentration. It will be automatically stopped through Timer. It
will also invariably stop at high level (1-FDS-LS-01), overriding
the timer as a safety interlock, depending on the status.
The water inlet to the preparation tank stops when the high
level (1-FDS-LS-01) is reached. Agitator (1-FDS-AG-01) continues to
mix water and powder to make homogeneous solution and stops when
solution is transferred to dosing tank.
The whole cycle repeats when the dosing tank level hits low
level again.
The safety interlock is provided, in case the level goes further
low (very low) (1-FDS-LS-05) in dosing tank (approximately 50mm.
lower than low level), very low level switch is actuated, trips the
dosing pump (1-FDS-DP-01)
In such conditions, manual building up of level in dosing tank
needs to be done, till very low level signal goes off.
The auto manual switch is provided on panel which enables
following operations manually provided the very low dosing tank
level alarm is not actuated.
1. Transfer valve operation 2. Agitator operation 3. Screw
feeder operation 4. Water feed valve operation
3.5 Thickener Underflow Slurry Handling
The Thickener (B45701) receives slurry from many sources. The
ball mill area sump pumps and filter area sump pumps go to the
Sieve Bend (B45451) to reject trash and oversize material.
Density and flow meters (DT-01B0820), (DT-01B0830) and
(FT-01B0821), (FT-01B0831) measure the Thickener Underflow Pumps
(B41101-1, 2, 3) discharge. There are two underflow pumps running
with one spare. Thickener underflow slurry density is maintained at
a specific gravity of approximately 2.13. There are two density
controllers that control the discharge either to the slurry
distributer or to the thickener. Underflow travels to the Slurry
Distributor (B48201) and is directed by two Dart Valves (B48201-1,
2) to the Slurry Holding Tanks (B36101-1, 2). An overflow at the
Distributor returns slurry to the thickener.
The three Thickener Underflow Pumps have individual Hand Speed
Controllers at the Main Automation System.
The thickener underflow rate will be controlled to maintain
equilibrium between the solids going into the thickener from all
sources and the solids pumped as underflow at the proper density to
the slurry holding tanks. One indication that the thickener is not
in equilibrium is that the level in the slurry tank will begin
dropping. Another indication is the torque measured from the
thickener rake will increase as a result of excessive solids
building. The underflow pump rate may then be
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adjusted by the operator to re-establish the solids balance. The
variable speed control will only be used for small adjustments. The
operator may also increase the solids flow to the upstream ball
mills to balance the solids into and out of the thickener.
If there are large changes in the flow of solids to the
thickener, then the thickener underflow will be recycled until the
desired density has been re-established. One of the thickener
underflow pumps may be shutdown if the one of the upstream ball
mills is shutdown.
The flow and density instruments on the thickener underflow
pumps allow operators to compute the mass flow from the thickener.
Once equilibrium is reached in the thickener, the underflow pump
speed may be adjusted to yield the same mass flow to the
distributor as the new solids feeding the thickener. The primary
source of new solids enters the thickener from the cyclone
overflow.
3.6 Thickener Overflow Water handling
Overflow from the thickener goes to Process Water sump (B15701)
fitted with pumps (B41105-1, 2, 3). Two pumps would be in operating
condition and 1 pump will be standby.
The process water sump level controller (Loop No: LIC-01B-0804,
P&ID: R-01-1023) will control makeup water addition through
LV-01B0804A in case of low level of the sump or divert water to
Blow down through LV-01B0804B in case of High High level of the
sump. At Low Low level of the sump, process water pumps will
stop.
3.7 Slurry Holding tanks
Two Dart Valves (B48201-1, 2) direct the thickener underflow
slurry to Slurry holding tanks. The dart valves are operated
manually from Main Automation System. Operator will allow the Dart
valves to fill one Slurry Holding Tank at a time. The third dart
valve is for future.
Agitators (B39102-1, 2) are fitted to keep the slurry in
suspension in the Slurry Holding Tanks. Slurry level (LIT-01B1304
and LIT-01B1305) should be maintained to keep the agitator below
slurry level.
3.8 Filter Press Feed Pumps
Manual valves allow the Filter Press Pumps (B41103-1, 2, 3) to
be fed from either Slurry Holding Tank. If both Slurry Holding
tanks are empty, then all three Filter Press Feed pumps (B41103-1,
2, 3) stop. The Filter Press Feed Pumps are designed for one pump
for (2) Filter Presses. The logic will allow the pump to fill only
one filter press at a time.
3.9 Pressure filter (Inputs received from package vendor
METSO)
The pressure filter operates on a batch basis and comprises a
series of filter plates supported in a fabricated frame with a
hydraulic system to open and close the filter plate pack.
Slurry is fed into the chambers; the filtrate formed in the
filter plates passes through the filter cloths while the solids are
retained in the chambers. After filtration the membranes are
activated to stabilize the cake and the filter cake is air dried by
passing Compressed air through the cake. The filter is then opened
to discharge the cake, the cloths are rinsed and the filter starts
next cycle.
The operation of the VPA Pressure Filter (VPA 20 of METSO) is
fully automatic requiring only periodical operator routine
inspection and operational checks.
A complete filter cycle comprises of following individual
steps
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Low pressure closing High pressure closing Feed - filtration
Membrane compression Air through blow Top blow High pressure
drainage Cake chute doors opening Filter opening cake discharge
Cloth vibration (only if required) Cake chute doors closing Cloth
washing with vibrations Waiting for next cycle to commence
These individual steps are generally described as follows
reference is also made to the valve sequence diagram.
3.9.1 Low pressure closing
The cycle begins with filter closing where the low-pressure
high-capacity hydraulic pump is started and oil is directed by
appropriate valves to retract the cylinder rods. This pump actually
consists of multiple pumps mounted on a common shaft. Each pump
operating one cylinder to ensure equal extension and retraction
speed of all cylinders to maintain parallel movement of the
pressure piece and filter plates. When the movable head reached the
inner closed position indicated by proximity switches the filter
Low Pressure is closed.
3.9.2 High pressure Closing
When the filter has reached the low pressure closed position,
the step high pressure closing will commence. The hydraulic high
pressure pump will create the required pressure to retract the
cylinder rods a little bit further to accomplish compressive
closing. High pressure closing pressure is indicated by a pressure
transmitter.
3.9.3 Feed - filtration
The feed pump needs be controlled by a variable speed drive
unit. The pump speed control is necessary to cater for the
difference in the pump operating conditions at the start and end of
the filtering step, where high flow/low pressure and low flow/high
pressure conditions are required respectively.
With this system, the feed pump speed will be controlled to
provide a filling rate of the correct flow m/hr, which should fill
the filter under controlled forms. As the pressure increases, the
pump speed will be increased to achieve and maintain the required
6-8 bar filtering pressure. Signals to start and stop the feed
pump, as well as the pump speed reference signals could be provided
from the filter control system.
Feed - Filtration starts as soon as the correct filter closing
pressure is reached.
Feed valve V1 opens and the feed pump starts. An automatic feed
control system will control the speed of the pump, the first part
of the feed step under flow control to limit the flow rate, then a
ramped speed increase until the 6-8 bar filtering pressure is
achieved and maintained. The pump speed reference signals can be
provided by the filter control system.
The cloth damage detection system is activated a short time
after the filtration starts to avoid the normal initial turbid
filtrate flow period.
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Filtration continues for the timed period, or by using
derivative calculation algorithm. The feed pump then stops and feed
valve V1 closes.
3.9.4 Membrane Compression
The membrane air evacuation valve (V10) closes and the membrane
compression air feed valve (V7) opens to inflate the membranes.
The primary membrane compression step continues for the timed
period.
3.9.5 Air Through Blow
The filtrate valve V3 (V3, V12 and V13 on VPA 20 size filters)
closes, air valve V5 opens and air is entering into the filter via
two of the side channels and further into the surface of the
membrane plates. The air has to pass through the filter cake
forcing the water around the particles, out on the drainage surface
on the filter plates, and out again of the filter through the two
filtrate ports.
The membranes are kept inflated with a higher pressure than the
air through blow pressure during the complete step to compensate
for the reduction in the filter cake volume as the moisture is
displaced.
To secure a higher pressure behind the membranes during the air
through blow, the valve V11 opens for booster air to pressurize the
membranes at the same time as valve V5 opens for air
through-blow.
The booster air is delivered from a booster air compressor.
The procedure described above will prevent the filter cake from
cracking and consequently minimize the air consumption.
The air through-blow step continues for the timed period and
then valve V5 is closed.
3.9.6 Top Blow
The filtrate valve V3 (V3, V12 and V13 on the VPA 20 size
machines) opens. The Slurry return valve V4 and valve V41
opens.
The air inlet valve V6 and water inlet valve V8 opens for a
short time (V8 only if needed), to displace slurry from the feed
channel in the filter plate pack.
The Top blow step continues for the timed period. The top blow
step is completed when valve V4 and valve V41 are closed.
Then the membrane air valves V7 and V11 close and the membrane
air evacuation valve V10 opens to release the membrane
pressure.
3.9.7 High Pressure Drainage (Hydraulic)
The hydraulic closing pressure in the hydraulic cylinders is
relieved allowing the filter to open slightly to drain any
remaining filtrate from the filter.
The filter weighing system records the filter weight. High
pressure drainage completion is indicated by a pressure
transmitter.
3.9.8 Cake Chute Doors opening
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The two chute doors open, operated by hydraulic cylinders.
Proximity switches indicate when the both doors are in open
position.
3.9.9 Filter Opening cake discharge
The relevant hydraulic system valves are activated and the low
pressure high capacity pumps extend the cylinders, pushing the
movable head open.
The filter plates are connected together to the movable head by
a link system so as the movable head starts to move the plate pack
is opened according to the concertina style allowing the cake to
fall from the filter by gravity in the chambers one by one.
When the movable head reached the outer limit of its travel
indicated by proximity switches the filter is open.
3.9.10 Cloth Vibration
When the machine is in open position the weight will be
checked.
If the weight is above maximum allowed empty weight, the motor
vibrators will start and run for short timed period to vibrate the
filter cloths and to ensure that all cakes are removed from the
filter cloths.
If the empty weight is too high after the automatically repeated
vibrations, the machine will stop. An alarm will follow which is
visible on the screen and the remaining weight needs to be removed
manually by further vibrations or washing.
3.9.11 Cake Chute Doors Closing
The two chute doors operated by hydraulic cylinders close.
Proximity switches indicate when the both doors are in closed
position.
3.9.12 Cloth wash
When the cake chute doors are closed the wash water valve V9
opens and cloth flushing starts. During flushing the vibrators may
be activated to ensure that all remaining cake residue is
removed.
The cloth flushing step continues for the timed period and a
after valve 9 closes.
3.9.13 Waiting time
A waiting time setting between the cycles can be used. Waiting
continues for the timed period. The VPA Pressure Filter is then
ready to start next cycle.
OPERATION DESCRIPTION
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Automatic Cycle Steps Schematic
3.10 Control system VPA-press filter
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The VPA-press filter control system consists mainly of the
following items:
Main control cabinet, -K1 containing PLC, Industrial-PC and MCC
functions, (designed to be installed on the filter platform).
Pneumatic valve control, -PV1-2, (designed to be installed on the
filter platform). Hydraulic control, -HV1 the hydraulic junction
box, (preinstalled on the hydraulic unit). Weight system with 4
load cells and a weight central.
3.10.1 Description
The VPA-press filter is operated from the Industrial PC screen
on the main control cabinet -K1 located on the filter platform. The
industrial PC is connected to a PLC which handles the control
logics. The VPA-press filter can be operated either in Automatic,
Semi-automatic or Manually.
In AUTO the VPA-press filter operates automatically by the
programmed sequence. In SEMI-AUTOMATIC the filter is operated step
by step through the sequence and in MANUAL some of the filter
functions can be manually operated from the monitor.
All process specific Data & Parameters can be set and
adjusted in the Settings-menu.
Statistics, like Cycle time, Press weight etc. is presented on
the Statistics-menu.
Alarm & Fault handling is implemented in the operators
panel; each alarm will be displayed with text, status, date and
time in the Alarm-menu.
The main power supply are connected to the Main control cabinet,
all other supply and control voltages are created internally by use
of transformers and distributed to all other different units. The
cabinet are placed on rubber dampers to eliminate vibrations from
the environment.
The process air supply will only be connected to one point at
the Pneumatic control panel, -PV1, that together with PV2 controls
all pneumatic process valves located around the press filter.
Inductive proximity switches supervise the process valve
positions.
The Hydraulics will be controlled from the Main control cabinet
via the junction box located on the hydraulic station. Inductive
proximity switches supervise all hydraulic movements.
A number of sensors, pressure switches, inductive proximity
switches etc. for control and supervision of the process are
connected to the Main control cabinet via junction boxes.
A weighing system consisting of 4 load cells, (one in each
corner of the VPA -press filter), connected to the weight-central
via a junction box delivers the actual weight of the pressed
material to the control system for process control and
statistics.
3.10.2 Interfaces Between Metso And Customer
There are two types of interfaces between Metso VPA-press filter
control system and JSPL. One is for the process control and the
other is for starting & stopping the VPA Press filter from a
Remote location. Both interfaces will preferably be Ethernet TCP/IP
between the different units.
3.10.2.1 Process equipment interface
Following signals will be exchanged between the Metso VPA
control system and JSPL process equipment:
From Metso JSPL From JSPL Metso
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Control Room Emergency Stop
Slurry tank OK = Tank level OK and/or Density OK
Dry Air OK = Pressure OK or Flow OK Wash Water OK = Tank level,
or Pressure or Flow OK Start order Slurry pump Slurry Pump is
running, acknowledge signal
Slurry Pump Fault Start order Wash water pump Wash water pump is
running, acknowledge signal
Wash water Fault Conveyor Increase speed order Conveyor is
running, acknowledge signal
Conveyor Fault
3.10.2.2 Remote control interface
The VPA Press filter can be Started & Stopped from Main
Automation System, (i.e. an overriding computer).
Following signals will be exchanged between the Metso VPA Press
filter control system and customer overriding control:
From Metso JSPL From JSPL Metso Remote mode is selected Run/Stop
order, (pulse, toggle Run and Stop) VPA in operation To Neutral,
(pulse) VPA No Fault To Parking, (pulse) Completed press cycle,
(pulse)
In Neutral
In Parking
3.11 Filter cake and Filtrate handling
Pressure filtration occurs in several steps to dewater the iron
ore concentrate. The typical filtration cycle starts with the
feeding step, followed by compression, followed by air drying, then
cake discharge, and finally cloth washing. In the Feeding step,
slurry is pumped to the operating filter via the Filter Press Feed
Pumps. Pumping pressure provides the pressure for the initial
dewatering of the slurry. When the pumping pressure is no longer
high enough to dewater the slurry, the feeding step is complete.
The Filter Press Feed Pump then begins pumping either to another
filter press or back to the three-way slurry distributor. Filtrate
from the pressure filter drains to the Filtrate and Wash Water
Tank.
In the compression step, a pressurized bladder in the filter
press compresses the filter cake to remove additional water from
the filter cake.
In the drying step, compressed air from the Drying Air
Compressors removes additional water from the filter cake.
Commands from each filter press will signal the Main Automation
System to supply high pressure slurry. When not filling, the Filter
Press Feed Pumps recycle slurry to the Slurry Distributor
(B48201).
There are six (6) Filter Presses (B45101, 2, 3, 4, 5, and 6).
These presses work on a cycle that is part of the METSO supplied
PLC system with Profibus link to the Main Automation System. If
Slurry is not needed at a filter press, the slurry is recycled back
to the Slurry Distributor (B48201).
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High Pressure water sprays are also used to clean the cloth when
the filter frames are opened.
There are 4 air compressors feeding 6 Filter Presses. The Filter
Cake drops on the Filter Cake Conveyor (FC-11A, B, C, D, E & F)
(B43010-1, 2, 3, 4, 5, 6) and is transported to common conveyor
FC-12 (B43015).
From here the filter cake will travel over conveyors FC- 13, 14,
15 & 16.
Individual start-up of Filter cake collecting conveyors (FC-11A
to F) and Filter cake transport conveyors FC-12, 13, 14, 15 &
16 will depend on healthy signal from the safety switches placed on
the conveyors.
Group start of FC-12, 13, 14, 15 & 16 will depend on the low
level signal from level transmitters placed over filter cake
storage bins (43502-1,2). Low signal from bin level transmitters
will start FC-16 first then filter cake conveyors FC-15, 14, 13
& 12 in a sequential manner provided there is healthy signal
from safety switches on these conveyors.
The Filter cake conveyor plow (B48005) is lowered to the
conveyor in order to fill Iron ore filter cake storage bin-2
(B43502-2). Plow is equipped with two position switches, up and
down. They signal the DCS which indicates to the control room
operator the position of the plow. The plow is operated in manual
mode; the operator raises and lowers the plow to suit. Full (High,
High) bin will cause its plow to raise by the operator
manually.
HH alarm from both bin level transmitters and unhealthy signal
from any conveyor safety switch will stop up-stream conveyors in a
sequential manner.
The Filtrate and Wash Water Tank (B35104) has two variable speed
pumps (B41104-1, 2) to move the filtrate back to the Thickener. If
the Filtrate level gets below the set point of LIT-01B1801A, then
makeup water enters through LV-01AB1801. Level controller (Loop No:
LIC-01B1801B, P&ID: R-01-1019) controls the speed of the
Filtrate Pumps (B41104-1, 2).
The set point of Level Controller (Loop No: LIC-01B1801A,
P&ID: R-01-1019) is set at about 25 % while level controller
LIC-01B1801B is set to 60 %. When the level reduces to 25% the
control valve will attain its full opening condition in order to
fill the tank. When the rising level is at 60% the valve will
attain its full close condition and the pumps will start in order
to pump-out the filtrate from the tank.
4.0 ADDITIVE RECEIVING AND DRY GRINDING -AREA 2
4.1 Additive Receiving & Storage (P&ID: R-02-1001)
Additive Feed can travel to Line 1 or Line 2. When directed to
line 2, the material travels from reversing shuttle conveyor AF-4
(B43120) to Additive Feed Conveyor AF-15 (B43110) to reversing
shuttle AF-16 (B43115). The shuttle car (B43120A) of AF-4 can
position at the existing limestone bin, the existing coal bin, or
at the Additive Feed conveyor AF-15.
AF-15 will feed AF-16 (additive feed bin reversing shuttle
conveyor, B43115). AF-16 will fill limestone bin (B16207) and coal
bin (B16205).
Individual start-up of blended ore conveyors AF-15 and shuttle
conveyor AF-16 will depend on healthy signal from the safety
switches placed on the conveyors.
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Group start up will depend on the level signal from level
transmitters placed over bins. Low (20%) signal from bin level
transmitters will start shuttle conveyor AF-16 first then additive
feed conveyors AF-15 in a sequential manner provided there is
healthy signal from safety switches of these conveyors.
The Additive feed bin reversing shuttle conveyor AF-16 feeds the
Lime stone feed bin (B16207) and Coal feed bin (B16205) depending
on the high level signal from level transmitters LIT 2212 &
2213 placed at the bins. The position limit switch (ZS 0132 &
ZS 0134) placed suitably for lime stone bin and coal bin positions
will allow the shuttle car to stop over the respective bins in
order to achieve un-interrupted filling of the bins.
When the limestone bin (B16207) and coal bin (B16205) level
reaches the High (70%) level (LAH-02B2212 and LAH-02B2213) a light
will blink at the filling location to warn operators that the bin
is nearly full. If the level in both the bins should continue to
rise to High, High (95%) the feed belt and feed shuttle conveyor
will stop.
Lime stone feed bin and Coal feed bin are equipped with
individual weigh belt feeders (B43119 & B43068). Belt feeders
discharge material to conveyors AMF-11 (B43079) at a controlled
rate, set by the operator (Loop No: WIC - 2215 & 2216,
P&ID: R-02-1001) for a capacity which is compatible with the
Mill grinding capacity for that particular additive. Once the
system is started, operator controls the respective belt feeder
speed to obtain the desired set point as mentioned below:
Low-Low (5%) bin level will stop the Weigh Belt Feeders LSF-11,
CF-11 and subsequently additive mill feed conveyor AMF-11.
The receiving rates for coal (10% H2O) and Lime stone (8% H2O)
to the feed bins are:
Operating - TPH Design - TPH Coal: 100 100 Lime Stone: 100
100
Storage capacity of Coal and Lime stone storage bin is as
follows:
Operating - Hours Design - Hours Coal feed bin: 9 4
Lime Stone: 16 9
The feed rate to the Additive mill feed conveyor is as
follows:
Coal - TPH Lime stone - TPH Operating 21.2 22.7
Design: 43.5 43.5
The additive mill feed conveyor (AMF-11) feeds the additives to
the Ball mill (B46203)
4.2 Dry Grinding System
4.2.1 Process Description (P&ID: R-02-1003, R-02-1005)
(Inputs received from package vendor FL Smidth)
The proposed Limestone-Anthracite coal mixture Additive dry
grinding system consists of an air swept Ball Mill with its
accessories. The mill is sized for grinding Limestone-Anthracite
coal mixture at a maximum moisture content of 9% with a feed size
of Limestone as -7 mm (100%) & Anthracite coal as -7 mm (100%)
to a product fineness of 80% < 53 microns, with a residual
moisture content
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of 1% at a combined Bond Work Index of 16 KWH/MT. Hot Air
Generator Supplies hot air to the mill which will dry the
limestone-Anthracite coal mixture during grinding.
Mill exhaust Gases are vented through a dynamic Classifier which
recycles coarser particles back to the mill through a flap valve
and an air slide. Ground product is collected in a cyclone and a
bag filter placed after the dynamic Classifier. In this system, air
flow is induced by two fans, mill ID fan and filter ID fan. The
clean air from Bag filter shall be released to atmosphere through a
stack. Product collected by the cyclone and bag filter is
transferred to a product bin which is located inside mixer
building.
4.2.2 Normal Start-up Sequence
This section describes the functional groups start-up sequence.
If the group has an automatic start sequence, time delays between
equipment will also be listed. Any group preconditions required
prior to start-up are also listed herein. However, interlocks
required for individual or predefined groups of equipment are
listed in the Interlocks section.
4.2.4 Normal Operation
This section describes the functional groups normal operation,
including operator functions. There are three modes of operation,
as described below:
Automatic: Automatic mode is when functional groups are
controlled automatically and in sequence by the control system. A
functional group is a set of items such as motors, valves, etc.
which are started by a single operator action when it is in
Automatic Mode. All Protective, Safety, Machine, Operational and
Start Interlocks must be met in order to operate.
Manual: Manual mode is when items such as motors, valves, etc.
are con-trolled individually by the operator using the control
system. Functional groups have no meaning in Manual Mode. All
Protective, Safety, and Start Interlocks must be met in order to
operate.
Local: Local mode is when items such as motors, valves, etc. are
controlled individually in the field, usually by local pushbutton
stations located at the item. Functional groups have no meaning in
Local Mode. Since the operator interface in Local Mode is often
physical devices rather than a display screen, extra care must be
taken to ensure that interlocking continues to be enforced. All
Protective, Safety, and Start Interlocks must be met in order to
operate.
Main Automation System Control: Commands to operate the control
system are made by an operator using the Main Automation System
HMI. Main Automation System can only operate in Automatic Mode.
Main Automation System sets the equipment control mode to Main
Automation System control.
4.2.4 Normal Shutdown Sequence
This section describes the group shutdown sequence. If the group
has an automatic shutdown sequence, time delays to allow for
equipment cleanout or deceleration will also be listed.
4.2.5 Abnormal and Emergency Shutdowns
This section describes abnormal shutdown conditions caused by
isolated process or equipment abnormalities or activation of
individual equipment safety devices. It also describes emergency
shutdowns due to automatic activation of personnel safety systems
or field emergency stop pushbuttons.
4.2.6 Interlocks
The Interlocks section describes all interlocks for the
individual equipment or functional groups of equipment within the
associated software function group. Interlock is defined herein as
an
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input/output signal or a Main Automation System/Main Automation
System internal logic condition, which automatically prevents the
operation of an individual or functional group of equipment from
the Plant MAIN AUTOMATION SYSTEM HMI. When the condition of an
interlock(s) is such that operation of a related piece of equipment
or an equipment group is permitted, the interlock(s) is defined as
being satisfied.
Specific devices in the Interlock table may be preceded by NOT.
This is the condition for the analog threshold (i.e. NOT Bearing
Temperature High-High = Bearing Temperature is NOT ABOVE the
High-High Set point). However, in the case of discrete switches the
Interlock is stated from the ON perspective of the switch. For
example the Oil Reservoir Low switch is ON when the oil level is
NOT Low (fail-safe), so the required interlock is the switch being
true
Interlocks consist of five types and are described in detail
below:
Safety interlocks: Safety interlocks are those interlocks which
prevent damage to that associated piece of equipment. As a result,
safety interlocks apply when operating in Automatic Mode, Manual
Mode and Local Mode.
Example
Safety interlock for a fan or pump would be no high-high bearing
temperature. Safety interlocks for every motor will also include
the MCC/motor ready signal and receipt of a
run confirmation from the motor contactor after a run command is
sent. These interlocks apply to all motors and are not listed in
the interlock table for this reason.
Start interlocks: Start interlocks are those interlocks
necessary ONLY for starting the machine. As soon as the motor is
running the start interlock has no influence. As a result, start
interlocks apply when operating in Automatic Mode, Manual Mode and
Local Mode.
Example
A start interlock for a fixed speed fan with automatic damper
would be that the damper be closed (limit switch or position
transmitter) prior to starting.
Protective Interlocks: Protective interlocks are those
interlocks for the protection of the motor itself. As a result,
protective interlocks apply when operating in Automatic Mode,
Manual Mode and Local Mode.
Example
A protective interlock for a crusher motor would be motor
bearing temperature or motor winding temperature.
Machine Interlocks: Machine interlocks are those interlocks for
the protection of the machine that is operating in Automatic Mode.
As a result, machine interlocks apply only when operating in
Automatic Mode.
Example
A machine interlock for a belt conveyor would be a belt drift
switch.
Operational Interlocks: Operational