Operating Instructions for C3F8 Supply Lines ATLAS Project Doc. No: Institute Doc. No: Created: 28/4/2004 Modified: 26/1/05 Page: 1 of 12 Rev: C Operating Instructions for C3F8 Supply Lines This manual gives instructions for purging, evacuating, and filling the C3F8 cooling system, and connecting/disconnecting discs to the cooling system. Prepared by: N.P. Hessey Checked by: Nobody Distribution List: A-P. Colijn, H. Boer Rookhuizen, P. Werneke, R. Buis Approved by: Nobody ATLAS Project Document No: Page: 2 of 12 Rev. No.: C History of Changes Rev. No. A B C Date 28/4/04 28/7/04 26/1/05 Pages All Many Many Made by NP Hessey NP Hessey NP Hessey Description of changes Original document Safety warnings + dP protection + new fig. 1 etc. V13 and 14; many small improvements learnt from experience. List of Figures 1 Supply lines between C3F8 Plant and Test Boxes, with valve labels. . . . . . . . . 3 Contents 1 Operation 1: Flush With Nitrogen 5 2 Operation 2: Evacuate lines to atmosphere 6 3 Operation 3: Fill Plant With C3F8 7 4 Operation 4: Preparing for Disc Cooldown 4.1 Operation 4.1: Flushing with Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Operation 4.2: Evacuating to Atmosphere . . . . . . . . . . . . . . . . . . . . . . 4.3 Operation 4.3: Filling with C3F8 . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8 9 9 5 Operation 5: Evacuating C3F8 to Plant and Preparing For Disc Removal 10 6 Operation 6: Final Removal of C3F8 6.1 Operation 6.1: Removal of most of the C3F8 . . . . . . . . . . . . . . . . . . . . 6.2 Operation 6.2: Recuperation of residual C3F8 gas . . . . . . . . . . . . . . . . . . 11 11 12 ATLAS Project Document No: Page: 3 of 12 Rev. No.: C Introduction This document gives instructions for operating the C3F8 cooling system for the ATLAS SCT Discs. The cooling system can broadly be split into four components: the C3F8 Cooling Plant (“C3F8 Plant”), the supply and return lines with their associated valves, vacuum system, purge lines etc. (“Supply Lines”); the disc test box (“Disc Box”); and the cylinder test box (“Cylinder Box”). Figure 1 shows how the supply lines interconnect the cooling plant with the test boxes, and labels the valves with the names used in this document. R V Vent to atmosphere Version 4, 26/1/05 V12 Vacuum pump V11 Pvac N2 Supply V7 V9 V13 V8 V6 V10 Disc test box C3F8 plant Fridge V2 V4 FM2 SV FM1 V5 V1 V3 By−pass valve Filter Vent to atmosphere Cylinder test box V14 FM1: precision low−rate flow meter. Used to set restrictors and check individual circuit flows. FM2: High rate flow meter, used for monitoring most of the time. Figure 1: Supply lines between C3F8 Plant and Test Boxes, with valve labels. Certain operations can cause damage to equipment, loss of C3F8 (which is expensive and bad for global warming), or risk of personal injury. Hence it is important to follow the instructions closely. Use gloves to avoid contact with cold surfaces. Use goggles if there is a risk of C3F8 escape, especially relevant if adjusting the restrictors. Once the Cooling Plant and Supply Lines are ready for use, they have to be filled with C3F8. ATLAS Project Document No: Page: 4 of 12 Rev. No.: C This requires a sequence of operations detailed below: Operation 1 (Flush lines with nitrogen); Operation 2 (Evacuate lines to atmosphere); Operation 3 (Fill plant with C3F8). Thereafter each time a disc is put in a circuit Operation 4 (Preparing for Disc Cooldown) has to be carried out. Each time the disc tests are finished, Operation 5 (Preparing for Disc Removal) has to be carried out before removing a disc or opening its cooling circuits. In the event of problems with the C3F8 Plant or the Supply Lines, and at the end of all tests, the C3F8 has to be removed from the system. Operation 6 (Final Removal of C3F8) achieves this. For all operations, start the DCS and make sure at least one inlet and one outlet electro-valves are open to the differential pressure sensor: this will avoid putting too large a pressure across it. Valves V13 and V14: these were added later, and are not mentioned in the instructions. They should generally be left open. They are for the specific purpose of leak checking the on-disc cooling circuits: by reducing the closed-off volume, they make the check more sensitive. ATLAS Project Document No: Page: 5 of 12 Rev. No.: C 1 Operation 1: Flush With Nitrogen Initial state: Compressor off; liquid pump off; vacuum pump off; C3F8 Plant, Supply Lines, and any disc circuits full of air at atmospheric pressure. N 2 bottle closed. If preparing for initial C3F8 fill, connect the C3F8 bottle to the schraeder valve first, with the bottle-valve closed. Then the connecting tube is also purged with N2 and evacuated. Step 1 2 3 4 5 6 Action Close V4, V5, V6, V7 Close V9, V11, V12 Open V1, V2, V3, V10 and SV in C3F8 plant Set nitrogen pressure regulator to 0 bar (anti-clockwise); Open V8; slowly raise regulator pressure till you hear gas flowing Wait till flushed Close V8 then V3 immediately after Result/Comments Disc Box and Cylinder Box isolated from system Vacuum pump isolated from system Flush circuit is open and at atmospheric pressure Flushing begins (gently, avoiding damage to flow meters) Circuit is full of dry nitrogen at atmospheric pressure Flushing stops; circuit is sealed Final state: The circuit is full of dry nitrogen, sealed from the atmosphere. Note: Leak checks can be carried out by pressurising the lines via V8 with V3 closed, and watching how fast the pressure drops. Make sure the circuit is leak-tight before proceeding. ATLAS Project Document No: Page: 6 of 12 Rev. No.: C 2 Operation 2: Evacuate lines to atmosphere Initial state: Compressor off, liquid pump off, vacuum off; circuit full of dry nitrogen at atmospheric pressure; V3, V4, V5, V6, V7, V8, V9, V11, V12 closed; V1, V2, V10 open; i.e. following Operation 1. DO NOT CARRY OUT THIS OPERATION WITH C3F8 IN THE SYSTEM! Step 1 2 3 4 5 6 7 Action Check all valves are in the appropriate initial state Check Pvac is about 1 bar absolute; if above, open V3 briefly to bring down to 1 bar; if below, open V8 briefly to top up with dry nitrogen Close V1 and V2 Open V12 and turn on the vacuum pump Open V9 Wait till Pvac and other pressure meters show circuit is evacuated (about 1 mbar) Close V12 and V9 then turn vacuum pump off Result/Comments Safety of flow meters, vacuum pump etc. Avoid putting excess pressure on vacuum pump Prevent reverse flow through flow meters Inlet side of vacuum pump pressure drops Circuit evacuation starts Circuit is evacuated with remnant dry nitrogen Final state: C3F8 Plant and Supply Lines are at vacuum from V6/V7 to V1/V2, with 1 mbar dry nitrogen. Circuit lines from V1/V2 to V4/V5 have nitrogen at 1 bar. Circuit lines from V4/V5 to V6/V8 unchanged. The circuit can again be checked for leaks by watching how fast the pressure rises. Do not proceed until the circuit is leak tight. ATLAS Project Document No: Page: 7 of 12 Rev. No.: C 3 Operation 3: Fill Plant With C3F8 Initial state: Compressor off, liquid pump off, vacuum off; circuit full of dry nitrogen at vacuum of 1 mbar; V1, V2, V3, V4, V5, V6, V7, V8, V9, V11, V12 closed; V10 open. C3F8 bottle on scales, connected to schraeder valve, with bottle valve closed. I.e. following Operation 2. Step 1 2 3 4 5 6 7 8 9 Action Record weight of C3F8 bottle Check/put (safely) all valves are in the appropriate initial state Check Pvac is low (below 30 mbar on DCS) Close V10 Open valve on C3F8 bottle. Turn on compressor (separate instructions), cool HE1 to minimum temperature (See C3F8 plant instructions) Watch weight of C3F8 bottle. When desired amount (3 kg = 2 l) transferred, close valve on C3F8 bottle Remove C3F8 tube from schraeder valve, replace seal on valve. Turn compressor off Date 21/10/04 21/10/04 Time 85.5 82.5 Weight (kg) 09:00 09:45 Result/Comments So you know when to stop. Safety of flow meters, vacuum pump etc. Do not waste C3F8 by mixing it with moist air etc. Isolate C3F8 Plant from supply pipes C3F8 Plant is full of C3F8 gas at about 6.9 bar g C3F8 evaporates in bottle and condenses in HE1. Desired quantity of C3F8 is in the C3F8 Plant Bottle can be removed to storage C3F8 pressure rises slowly to about 6.9 bar g. Comments Start cooling and open valve Close bottle valve Table 1: Bottle weight history ATLAS Project Document No: Page: 8 of 12 Rev. No.: C 4 Operation 4: Preparing for Disc Cooldown In the following, V4, V6 and V13 apply to the Disc Box; V5, V7 and V14 apply to the Cylinder Box. 4.1 Operation 4.1: Flushing with Nitrogen Initial state: Compressor off, liquid pump off, vacuum pump off; C3F8 Plant full of warm C3F8 at about 6 bar; supply lines full of air at pressure of 1 bar; disc cooling circuits connected up and sealed; unused cooling circuits in test boxes sealed off; V1, V2, V3, V4, V5, V6, V7, V8, V9, V10, V11, V12 closed. Step 1 2 3 4 5 6 7 Action Check all Supply Line valves are closed and supply lines on discside of V1, V2, V10 have no C3F8 in (or maximum 1 mbar C3F8 as after Operation 5) Open (V4 and V6) or (V5 and V7) N2 regulator to 0; Open V8; slowly raise N2 regulator to high pressure (e.g. 19 bar g); close V8 Open V3 Set nitrogen regulator to about 2 bar and open V8 Wait for sufficient flushing Close V8 followed soon after by V3 Result/Comments Avoid loss of C3F8 to atmosphere Circuit is open for flushing Allows leak check: see how quickly the pressure drops. Probably want to close inlet valves on disc and V13 or V14. Vent the nitrogen to atmosphere Flushing starts. Note the disc circuits are flushed “backwards” Supply Lines and disc cooling circuits are full of dry nitrogen Flushing stops; circuit is sealed Final state: C3F8 Plant is full of warm C3F8; Supply Lines and disc circuits are full of dry nitrogen at about atmospheric pressure. Do not proceed until the circuit is leak tight. ATLAS Project Document No: Page: 9 of 12 Rev. No.: C 4.2 Operation 4.2: Evacuating to Atmosphere Initial state: Compressor off, liquid pump off, vacuum pump off; C3F8 Plant full of warm C3F8 at about 6 bar; Supply Lines and disc circuits full of dry nitrogen at about atmospheric pressure; unused cooling circuits in test boxes sealed off; V1, V2, V3, V8, V9, V10, V11, V12 closed; for disc in Disc Box, V4 and V6 open, V5 and V7 closed; for disc in Cylinder Box V5 and V7 open, V4 and V6 closed. Step 1 2 3 4 5 Action Check (Pvac) system is at about atmospheric pressure with dry nitrogen; all valves are in correct initial state. Open V12, turn vacuum pump on, open V9 Wait till pressure is about 1 mbar Close V9, turn the vacuum pump off, close V12 Leak Check Result/Comments Avoid putting excess pressure on vacuum pump and wasting C3F8 Start evacuating nitrogen from lines to atmosphere Circuit is evacuated with residual dry nitrogen Vacuum pump is isolated from Supply Lines Make sure all leaks are cured before introducing C3F8 Final state: lines are leak tight, with about 1 mbar of dry nitrogen. 4.3 Operation 4.3: Filling with C3F8 Initial state: Compressor off, liquid pump off, vacuum pump off; C3F8 Plant full of warm C3F8 at about 6 bar; supply lines and disc circuits at or below 1 mbar with residual dry nitrogen; unused cooling circuits in test boxes sealed off; V1, V2, V3, V8, V9, V10, V11, V12 closed; for disc in Disc Box, V4 and V6 open, V5 and V7 closed; for disc in Cylinder Box V5 and V7 open, V4 and V6 closed. Step 1 2 3. 4. 5. Action Check pressure is below 30 mbar in DCS with all valves in correct initial state Partially open V10 slowly. Open V10 fully. Open SV Open V1 or V2, depending on which flow-meter is wanted Result/Comments Avoid excess pressure on vacuum pump and avoid wasting C3F8 7 bar C3F8 to vacuum! Discs fill with C3F8; flowmeters fill backwards, slowly via restrictors. By-pass liquid pump. Cooling circuit is open, ready to start cooling Final state: C3F8 Plant, Supply Lines, Disc circuits are full of warm C3F8 at about 6 bar. Circuit is ready for cooling, with flow via required flow meter. ATLAS Project Document No: Page: 10 of 12 Rev. No.: C 5 Operation 5: Evacuating C3F8 to Plant and Preparing For Disc Removal Initial state: Cooling running (Compressor on; liquid pump on); vacuum pump off; disc in place full of C3F8; Either V1 or V2 open, the other closed; either V4 and V6 or V5 and V7 open, the other two closed; V10 open; V3, V8, V9, V11, V12 closed. Make sure all cooling circuit components (including the heat exchangers) in the Disc or Cylinder Box are open for coolant flow. Do not leave unattended while evacuating! If cooling machine trips off, the pressure in the vacuum pump rises very quickly, unless V10 and V11 are quickly closed off. Step 1 2 3 Action Turn off all power to the disc Close V2 or V1 (so both are closed) Open SV 4 Turn R404 set-point temperature to the minimum possible 5 Wait till disc has warmed up 6 Make sure V12 is closed and Pvac is low (below 2 bar a on DCS, 1 bar g on PVAC ) Open V9 and V11 and close V10 Turn vacuum pump on 7 8 9 10 11 12 13 14 15 Wait till Pvac is low enough (below 30 mbar in DCS) Close V11 Close V9 and turn off vacuum pump Turn off compressor Open V12 slowly Close any of V4, V5, V6, V7 that were open Close any valves inside Disc or Cylinder Box to circuits Result/Comments Cooling no longer needed. C3F8 supply to disc stopped Keep C3F8 circulating via by-pass – cools C3F8 better C3F8 in HE1 cools down further, pressure in circuits drops, C3F8 in circuits evaporates and condenses in HE1 Discs warms up when all C3F8 has evaporated: now there is no more liquid in the circuits, only vapour at about 1 bar if HE1 is at -36 C Avoid C3F8 loss and protect vacuum pump Put vacuum pump in circuit Start evacuating Supply Lines and disc circuits, returning C3F8 gas into C3F8 Plant Very little C3F8 left in lines C3F8 secured in C3F8 plant Vacuum pump isolated from circuit C3F8 in Plant will slowly warm up and reach 6 bar Supply Lines and disc circuits fill with air. Open slowly to not damage flow meters by large reverse flow. Isolate Supply Lines from Disc and Cylinder Boxes, to reduce risk of damage to Supply Lines Protect lines inside Boxes Final State: The disc circuits and supply lines are full of air at atmospheric pressure. The C3F8 is contained in the C3F8 plant. Connections to the disc can be opened, e.g. for disc removal. ATLAS Project Document No: Page: 11 of 12 Rev. No.: C 6 Operation 6: Final Removal of C3F8 Needed for C3F8 Plant maintenance, or at end-of-life. Aim is to recover C3F8 clean and ready for re-use; and to minimise atmospheric pollution (C3F8 is a powerful greenhouse gas). These instructions are now obsolete because we have bought a special refrigerant recovery plant. Follow the plant instructions instead of the following. However, the following is left in place until we have worked out just how to use the new recovery unit. This procedure requires a C3F8 bottle, either with some C3F8 in or evacuated (no moisture!), and with a valve and pressure gauge. This container has to be cooled e.g. by placing in a chiller and cooling to as low a temperature as reachable (but not below -40 C). 6.1 Operation 6.1: Removal of most of the C3F8 Initial state: Compressor off, liquid pump off, vacuum pump off; All valves closed. C3F8 is in C3F8 Plant following operation 5, but OMITTING step 12 so no air is allowed into the lines. Then Supply Lines are at vacuum with residual C3F8 at 1 mbar. Step 1 2 3 4 Action Carry out Operation 5 (Evacuating C3F8 to Plant and Preparing For Disc Removal) but OMITTING step 12, and check all valves are closed Slowly open V2 5 Open SV valve in C3F8 Plant Connect the C3F8 bottle to the vent line at V3; open bottle’s valve Open valve V3 6 Start cooling the bottle 7 Wait until C3F8 in plant is at room temperature and it’s pressure is appropriate to the bottle temperature Close V3 and the valve on the bottle, and disconnect the bottle 8 Result/Comments Initial state check Prepare for venting through V3; open slowly to protect flow meter By-pass the liquid pump Bottle ready to receive C3F8 If bottle was at vacuum, some C3F8 gas flows in; otherwise pressures in C3F8 Plant and bottle equalize C3F8 condenses in bottle, pressure reduces in C3F8 plant, C3F8 evaporates in plant All C3F8 liquid in C3F8 Plant has evaporated Most of the C3F8 is now in the bottle Final state: Most of the C3F8 is in the bottle, and being kept cold by a chiller. The C3F8 Plant and some of the Supply Lines contain C3F8 gas at a pressure corresponding to the temperature achieved in the bottle; this may be upto 3 bar. Ready for final C3F8 Recuperation. ATLAS Project Document No: Page: 12 of 12 Rev. No.: C 6.2 Operation 6.2: Recuperation of residual C3F8 gas This is only possible if the bottle can be cooled so that the C3F8 pressure in it is below the maximum pressure that the vacuum pump can handle. If not, either the residual C3F8 has to be vented to air or a second pump stage has to be attached to V12 so that the outlet pressure of the vacuum pump is low enough. Initial state: after Operation 6.1, i.e. compressor off, liquid pump off, vacuum pump off; SV (the liquid pump by-pass) and V2 open; all other valves closed. C3F8 bottle cold and pressure below 2 bar absolute (maximum outlet pressure of vacuum pump). Step 1 2 3 4 5 6 7 8 9 10 11 12 12 Action Check inital state Read instruction 11 and take appropriate action Close V2 Connect C3F8 bottle to V12 vent and open bottle valve Open V10 Check Pvac is safe for vacuum pump; open V9 Check bottle pressure is low enough for vacuum outlet; open V12 Turn vacuum pump on Wait till Pvac stops decreasing Close bottle valve, V9 and V12; turn off vacuum pump Turn off bottle chiller Open V3 13 14 Set nitrogen regulator to just above 1 bar absolute; open V8 until circuit is just above atmospheric pressure; close V8 Slowly open V2 Close V10 and V2 15 Open V4, V5, V6, V7 Result/Comments Safety and avoid escape of C3F8 from bottle to Plant Decide if you want to also recover C3F8 from flowmeters Protect flow-meter against reverse flow Bottle ready to receive more C3F8 C3F8 will flow opposite direction to normal through V10 Vacuum inlet prepared Vacuum outlet prepared Residual C3F8 is pumped to the bottle Maximum vacuum achieved As much C3F8 as possible is in the bottle Bottle is ready for removal and storage Vent small quantity of C3F8 from mass flow meters. Alternatively this volume could also be return to the bottle via the Disc-Box evaporator by opening V4 and V6 before step 5. C3F8 Plant is full of nitrogen (to avoid moisture in it) Adjust nitrogen pressure to atmospheric C3F8 Plant is isolated and full of nitrogen at atmospheric pressure, ready for maintenance/storage All lines brought to atmospheric pressure with air Final state: As much C3F8 as possible is recovered into the bottle; small amount vented to atmosphere; C3F8 plant full of nitrogen at atmospheric pressure; lines open to air. Plant can be maintained or stored; bottle can be stored or returned to supplier.
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