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FLUOR - New Delhi Control systems engineering Control Valves By KK Varma
26
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Page 1: Control Valves

FLUOR - New Delhi Control systems engineering

Control Valves

By KK Varma

Page 2: Control Valves

2

Inclusions

Introduction

What is a Control Valve (concept)

Classification

Control Valve symbols

Control Valve Assembly

Valve Actuator

Valve Positioner

Exclusions

Preparation of data sheets

Sizing calculations

Flow Characteristics

Valve sizing coefficient

Selection criteria

Interface with other depts...

Applicable codes and standard

Major vendors

Lastly…

Page 3: Control Valves

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Introduction (why the need for valves)

Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale.

Each of these control loop is designed to keep some important process variable such as pressure, flow, level, temperature etc. within a required operation range to ensure quality of end product.

Each of these loops receives and internally creates disturbances that might detrimentally affect the process.

We gather the information from sensors in field, A controller will process this info. decide what must be done to get the process back on track.

Page 4: Control Valves

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Control valve is the final control element in a system.

Control valve is a power-operated device used to manipulate the fluid (gas, steam, liquid) flow rate in a process system and keep the regulated process variable as close as possible to the desired set point.

There are two basic types of control valves :

OBJECTIVE: Control valve concept

Linear Rotary

Each type of valve has its special generic features, which may, in a given situation, be either an advantage or a disadvantage

Page 5: Control Valves

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OBJECTIVE: Control valve concept

Linear Rotary

Page 6: Control Valves

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Control valve classification

Control Valve

Rotary Motion

Linear Motion

Butterfly

Eccentric Plug

Ball

Swing Through

Lined

Eccentric

Segmented

Full

V-Notch

Globe

Diaphragm

Pinch or Clamp

Globe

Angle

3-Way

Single Seated

Double Seated

Split body

Page 7: Control Valves

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Control valves symbols

P&ID symbols of various control valves per ISA S5.1

Page 8: Control Valves

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Control valves symbols ...

P&ID symbols of various valves actuator per ISA S5.1

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Control valves assembly

Control valve assembly typically consists of - the valve body, the internal trim parts, an actuator to provide the motive power to operate the valve.

Valve Actuator

Valve Body

PositionerValve stem

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Actuator operating modes - Linear vlv.

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Actuator operating modes - Linear vlv.

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Actuator operating modes - Rotary vlv.

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Valve positioner

A valve positioner is a air relay which is used between the controller output and the valve diaphragm. It assures exact positioning of the valve stem in accordance with controller output

Page 14: Control Valves

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Flow characteristics

The relationship between valve capacity and valve stem travel is known as the flow characteristics of the valve..

Inherent flow characteristics

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Selection criteria

Body size and flow capacity

End connections

Shutoff leakage

Actuator sizing

Valve assembly material

Packing selection

Valve accessories

Special requirement

Noise calculation

Quality requirement

Page 16: Control Valves

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Interface with other depts...

Process

For sizing of valves

For process conditions

Piping

For face to face dimensions

For PDS envelop - (supports if required)

For P&ID markup

Electrical

For electrical actuator power supply (solenoid vlvs.)

Page 17: Control Valves

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Applicable codes and standards ASME B16.34 - valves - flanged, threaded and welding ends

ASME B1.20.1 - Pipe threads

ANSI FCI 70-2 - Control valve seat leakage

ISA 71.01 - Environmental conditions for process measurement & control systems: Temperature and Humidity

ISA 75.01 - Flow equation for sizing control valves

ISA 75.03 - Face to face dimensions for flanges globe-style control valve bodies

ISA 75.04 - Face to face dimensions for flangeless control valves

ISA 75.17 - Control valves aerodynamic noise prediction

NEMA ICS 6 - Enclosures for Industrial controls and systems

IEC 529 - Specification for degree of protection provided by enclosure

NFPA 70 - National electric code

Page 18: Control Valves

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Major vendors

Valve Assembly

Masoneilan Dresser

Fisher

Flowserve (Valtek)

Tyco

Instrumentation Limited

Actuators

EIM

Bettis

Keystone

Automax

Rotork

Limitork

Page 19: Control Valves

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Lastly...

There are lot of other stuff on control valve that should be looked into...

Sizing calculations (including vendor sizing software’s, INtools)

Datasheets Generation

Valve Packing

Valve Accessories Details

Valve Noise

Valve Installations

Hook up

Page 20: Control Valves

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Questions?

Over an’ out !

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Selection criteria contd.

Body size and flow capacity

- Select valve type

- Calculate Cv required

- Select valve/ trim size

End connections

- End connection type

- End connection rating

Page 22: Control Valves

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Valve sizing coefficient Cv (basics)

Valve sizing coefficient ‘Cv’ is defined as the number of US gallons per minute of water that will pass through a given restriction with a pressure drop of one psi.

Cv = Q

(P1- P2)/G

This is basic equation for liquid calculations, in volumetric flow Where -

Q - flow rate in US gpm

P1 - upstream pressure in psia

P2 - downstream pressure in psia

G - liquid specific gravity @ flowing temp.

Back

Page 23: Control Valves

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Selection criteria contd.

Shutoff leakage

- Select seat leakage

- Class I, II, III, IV, V, VI

Actuator type and size

- Spring diaphragm, Piston, Cylinder, Double acting cylinder, Hand wheel, Electric.

- Check either inlet pressure or maximum shutoff pressure for actuator sizing

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Selection criteria contd.

Valve assembly material

- Select valve body material

- trim material (plug, seat, stem or shaft)

- guide bushing material

- seat construction as dictated by seat leakage

Packing material and bonnet type

- Packing - Standard, Teflon (asbestos/ V-rings), Graphoil, others

- Bonnet type - Standard (450OF or less), Extended (450OF or above/ even for cryogenic services)

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Selection criteria contd.

Select valve accessories

- Positioner, Airset, I/P convertor, Solenoid valve, volume booster, limit switches, travel stop

- Lo-Db plates or cartridges

Special requirements

- Cavitation

- Flashing

- Two phase flow

Page 26: Control Valves

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Selection criteria contd.

Valve noise

- Gas and steam noise

- Liquid noise (cavitation only)

- Noise treatment (insulation, pipe schedule, noise attenuation design within valve body, Lo-Db plate, cartridge…)

Quality requirement

- Non destructive testing

- Special painting

- Special packing