SAFETY & OPERATIONAL ASPECTS IN IN-SITU ELECTRICAL BAKING OF LARGE VACUUM SYSTEMS OF INDUS ACCELERATORS Prateek Bhatnagar*, Nilesh Bhange, Sujata Joshi, R Sridhar Ultra High Vacuum Instrumentation laboratory, Ultra High Vacuum Technology section Raja Ramanna Centre for Advanced Technology, Indore – 452013, India. *e-mail: [email protected]33rd DAE Safety Meet 1
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SAFETY & OPERATIONAL ASPECTS IN IN-SITU
ELECTRICAL BAKING OF
LARGE VACUUM SYSTEMS
OF
INDUS ACCELERATORS
Prateek Bhatnagar*, Nilesh Bhange, Sujata Joshi, R Sridhar
Ultra High Vacuum Instrumentation laboratory,
Ultra High Vacuum Technology section
Raja Ramanna Centre for Advanced Technology, Indore – 452013, India.
Indus machines have more than 323 m. length of vacuum
chambers which have vacuum ranging from ultra high vacuum
(< 10-10 mbar) to high vacuum (<10-8 mbar).
Often different parts of Indus accelerators are opened up and
exposed to atmosphere for carrying out modifications either for
maintenance or modifications such as introduction of ID’s
(Insertion devices).
Ultra High Vacuum (UHV)has to be restored after closing the
vacuum systems
A systematic Baking procedure ranging from 36 hrs to 48 hrs.
(depending on Type of Material, Type of seals)is carried out after
which the Indus vacuum systems are in UHV.
Outgassing rate of the
metal used for chamber is
the principle vacuum
parameter and should be
as low as possible.
Baking effectively removes
the weakly bound surface
water & hydrocarbon
molecules
Gas adsorbed at the surface
of material on re exposure
to atmosphere can be
effectively removed by a 36
hrs to 48 hrs. bakeout at a
temperature of 250c
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A Typical Baking Load Distribution in a Vacuum Segment of Indus-2
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Heaters , Thermocouple Positions, Heating Hardware For a Typical Vacuum segment of Indus-2
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Hardware
Electrical Heaters
Temperature Control Unit(TCU)
Temperature Sensor
Custom Made Flexible Type
Glass Wool Type Silicon insulated
Jacket Type Band Type Strip Type
Thermocouple ‘K’ Type
Grounded Ungrounded
8 channel modular units
Bus Bar Trunking System ( 3 Ø; 200 A)
Hardware & Software
All Electrical hardware & components must be sufficiently rated to withstand normal operating conditions as well as fault conditions.
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Operating temperature max. 250°C with moisture-proofing of the heating element.
Heating Element Nichrome ; (80% Ni , 20% Chromium)
Rated voltage 230 V AC +/- 10%
Rated power designed for special applications for TSP Body 1Kw,750 w,500w,250w
Material stainless steel
Height max. 1000 mm
Inner diameter 75 mm to 250 mm
Temperature sensor Type ‘K’ ,
Connection cable 1.5 m ,HFFR & FRLS Type
Plug connection Iron Top
Protection type IP40 (basic version), IP54 (on request), protection class I
Custom built Metal sheathed Heating Jackets for
Vacuum Chambers
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Operating temperature Length 5.0 m max.(200 °C - 450°C )
Rated voltage 230 V AC +/- 10%
Power rating approx. 250 W/m
Minimum bend radius 10 mm
Outer dimensions approx. 5.5 x 30 mm (thickness x width)
Outer jacket Glass fabric
Connection cable 0.5 m with connection box
Protection type IP20 (EN 60529), protection class I
PE conductor braiding Nickel
Custom built Flexible Glass fabric heating Jackets for
Vacuum Chambers
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Custom built heaters for Flanges of Vacuum Chambers
Different sizes, capacities of Band Heaters for Vacuum flanges
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To provide controlled baking of UHV (Ultra High Vacuum) components for Indus accelerator An intelligent ON/OFF control system was needed. For that purpose distributed control system was suitable. For fulfillment of this need modular baking system was developed.
System contains Temperature controller unit (TCU), Pressure Monitoring Unit (PMU), and Temperature control & pressure Monitoring Interface Software (TCPMIS). Each TCU is an eight channel temperature controlling unit.
Each TCU is 8-channel temperature controller, which can communicate the computer through RS-485 network.
Temperature Control Unit(TCU)
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Each module unit (TCU-Temperature Controlling Unit) is having provision of 8 channels.
TCU is capable of monitoring as well as controlling the temperature & able to communicate with computer by using half-duplex RS485 network.
The address of each TCU can be changed by using DIP switches.
TCU measurement range of temperature is up to 500ºC, having resolution of 1ºC.
Module is able to handle grounded as well as ungrounded thermocouple
TCU has been provisioned with open sensor detection as well as input voltage protection up to 75V
Temperature Control Unit(TCU)
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Each channel is having SSR (Solid state Relay-Zero crossing) which can give ON/OFF type of control to heaters (up to 2KW).
These relays can be controlled manually as well by using switches provided on unit’s front panel. Heat sink & cooling fan provision is made for reliable operation of SSR.
Three phase supply indication is displayed by neon & distributed among 8 SSR.
Each channel is provided with Fuses for short circuit protection at the load side .
Temperature Control Unit(TCU)
• Thermocouples, designed, fabricated and calibrated in house.
• Fused Junction is terminated with copper lug and long enough to be mounted at thermally sensitive part of the chamber.
• These Sensors are rugged, reliable and easily fabricated out of standard ‘K’ type IS (Indian Standard) certified wires.
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Temperature Sensor
Sensor : Thermocouple
Type : ‘K’ Type
Grounded Silicon Sheathed 22SWG
Miniature Connector
Junction(Cu Lug)
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Software
Graphical User Interface software Controls & Datalogs upto 5 TCU & 1 PMU TCU communicates with RS 485 mode
TCPMIS Temperature Control & Pressure
Monitoring Software
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Graphical user interfacing software TCPMIS is a user interface software developed for, controlling & Data Logging up to 5 TCU’s & 1 PMU
In all distributed system resulted in 40 channel temperature controlling & 8 channel pressure monitoring
SET POINT is the required temperature value at controlling point, can be entered by user for each channel. The temperature data is logged in EXCEL FILE format.
Various safety features such as restoring of the ‘SET POINT’ in the event of control power failure, Alarm indication in case of ‘Thermocouple Open’, ‘Temperature overshoot’ display via change in colour trend.
Temperature Control & Pressure Monitoring Interface Software(TCPMIS)
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Temperature Control & Pressure Monitoring Interface Software(TCPMIS)
Screen Shot of the Main GUI
Set Temp.
TCU (4 Nos.)
Auto/Manual
Heater State
Real Temp.
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A Busbar trunking systems meet all the stipulated safety requirements covering Efficient power distribution by being easily planned Quickly installed , and Providing a high degree of flexibility, and Safety.
Low expense as the tap-off units are hot pluggable
Principally free from halogen
Only the total load is required for the planning
Bus Bar Trunking system
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Temperature Control & Pressure Monitoring Interface Software (TCPMIS)
Safety Features
1. Restoring of the ‘SET POINT’ in the event of control power failure
2. ‘ Status Display’ & ‘Alarm’ annunciation in case of ‘Thermocouple Open’
3. ‘Heater ON’ and ‘Heater OFF’ Status Display individually for all the channels.
4. ‘Auto /Manual’ Mode selection individually for all the channels.
5. ‘ Hysteresis for ON-OFF’ control for all the channels.
6. Communication status for all the TCU’s are known.
7. Logged data in .xls .
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A Typical View of Baking Hardware of a Vacuum segment in Indus-2
Titanium Sublimation Pumps with Custom built Jackets Heaters
Sputter Ion Pumps with Custom built Band Heating Jackets
Flexible heaters over Straight section chambers
Hot Bus Trunking system; 3 Ø 200A All metal Sector Isolation Valve With Custom built heating Jacket
System & Process Safety
Elaborate & Systematic Testing of electrical hardware
& deployment of safe procedures before employing Full Baking Cycle.
Physical Inspection of Jacket Heaters, Flexible heaters & Strip Heaters.
Individual resistance test, Continuity Test & Earth Test.
Litmus confirmatory test of “Hot Testing” on individual heaters confirms the health of the heaters.
Full Load short term testing. Avoiding short cuts.
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System & Process Safety
System Safety
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Temperature Profile During Baking & Activation of
Undulator Chamber
Each Thermocouple is subjected to ‘Hot Test’ to test the pattern of rise and fall of temperature for verifying any temperature offsets , loose contacts between miniature connectors and compensating cables.
The interconnecting 2 core & 5 core cables have HFFR (Halogen Free Fire Retardant) & FRLS (Fire retardent and Low Smoke) Ratings as per statutory regulations stipulated by AERB
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System & Process Safety
System Safety
Safe Work Practices
In-Situ Electrical baking involves exposed surface temperature of more than 2500C, extreme precaution and safe work practices are exercised.
A mock up of full load electrical testing per channel is taken up
The 48 hours to 72hours of baking operation taken up in round the clock three shifts mode is under strict supervision of trained & qualified manpower.
Manpower are trained with skills and techniques for high current & high temperature exigencies.
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Safe Work Practices
The Trained manpower is equipped with
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Safe Work Practices
Protective hand gloves
Safety Shoes
Aprons
Insulated Tools & Handling Equipments
Provision of Physical barricading from exposed high temperature parts inside the tunnel
Sign boards of Baking, High Temperature
Tags
Provision of Fire extinguishers
Fresh air change by ventilation
In-situ Electrical baking of vacuum segments of Indus accelerators are systematically crafted procedures which are executed complying with highest electrical safety norms and imbibing safe work practices to ensure that our supporting & supervising manpower health & safety are uncompromised.
The supervising manpower are trained in basic electrical safety procedures with specific emphasis in UHV conditioning & troubleshooting procedures.
The task assumes importance as these bake-outs are successfully executed within the stipulated timeframe of Indus shutdown periods