safety & operational aspects in in-situ … aspects_electrical... · electrical baking of large...

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


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



A Typical Baking Load Distribution in a Vacuum Segment of Indus-2


Heaters , Thermocouple Positions, Heating Hardware For a Typical Vacuum segment of Indus-2


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.


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


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


Custom built heaters for Flanges of Vacuum Chambers

Different sizes, capacities of Band Heaters for Vacuum flanges


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.



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



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 .


• 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.


Temperature Sensor

Sensor : Thermocouple

Type : ‘K’ Type

Grounded Silicon Sheathed 22SWG

Miniature Connector

Junction(Cu Lug)


Software

Graphical User Interface software Controls & Datalogs upto 5 TCU & 1 PMU TCU communicates with RS 485 mode

TCPMIS Temperature Control & Pressure

Monitoring Software


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)


Temperature Control & Pressure Monitoring Interface Software(TCPMIS)

Screen Shot of the Main GUI

Set Temp.

TCU (4 Nos.)

Auto/Manual

Heater State

Real Temp.


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


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 .


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.



System Safety


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



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.


Safe Work Practices

The Trained manpower is equipped with


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


Conclusion


Thanks For the Attention !

safety & operational aspects in in-situ … aspects_electrical... · electrical baking of large...

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