5.5.7.12  System Operation

Pre-Startup Checklist

Before initial use with a flammable gas or after a significant down-time the following checks should be made to insure the safety and integrity of the HAWGS:

1.

Leak-Check the entire gas system using a ÒsafeÓ gas such as Argon or Nitrogen.

2.

Calibrate over-pressure relief valves: RV121, 122, 123 should release at 55-65 psig, RV271 must release at 20-25 psig).

3.

Check calibration of Excess-Flow valves (should close at 4-5 slpm).

4.

Check proper operation of each interlock circuit and that interlock system shuts off gas supply.

5.

Measure the detectors leak rates and verify that each is below 7 slph (or current administrative limit - note that current physical limit is 500 sccm Ethane and 1450 sccm Argon based on flow controller full scales for N₂ and correction factors for Ethane and Argon).

6.

Verify that flammable gas leak sensors are appropriately calibrated.

Startup Procedure

1.

Close gas shed outlet valves MV-302-A, -B, -C to isolate the mixing/delivery system from the spectrometer detectors.

2.

Activate the "Kill Gas" crash button. Interlock panel should alarm. Silence the alarm by pressing "Alarm Silence". Reset the Crash Button by pulling outward. If any fault conditions (red LED) other than "Low Pressure" and "Main Relay" are indicated, clear them by correcting the indicated fault.

3.

Check alcohol supply and Bubbler temperature. Fill and/or adjust as necessary (see Adding Alcohol) .

4.

Check that adequate supply bottles of appropriate gasses are attached to the high pressure supply manifolds and valve one bottle ON for each manifold.

5.

Verify that all used main pressure regulators (outside) are set for 45-50 psig.

6.

Select "Manual / Expert" pressure control using toggle switch on panel in rear of mixing station, behind flow controller. Note that while in "Expert" mode there is no automatic delivery pressure control! Overpressure is prevented only by the overpressure shutoff switch and the alcohol reservoir relief valve.

7.

Verify that the Dynamass Flow Control System DM-2401 is in "Non-VG" mode by

• Press PROGRAM SELECT pushbutton ÔAÕ.
• Put the DM-2401 in ÒNO-MODEÓ mode (if it is not already) by pressing the MODE pushbutton until all LEDÕs in the column of LEDÕs on the left of the unit are off.
• Simultaneously press and release PROGRAM SELECT buttons ÔAÕ and ÔCÕ.
• Press the MODE pushbutton until the ÒOPT 1Ó LED is lighted. Verify that the display for channel 4 reads all zeros.
• Return the DM-2401 to ÒNO-MODEÓ.

8.

Set Dynamass Flow-Control System to Program "D: Zero Flow". Put the DM-2401 in "FLOW-MODE" and verify that all flow settings are at zero.

9.

With the DM-2401 in "FLOW-MODE", set up flow program "C" to provide the desired mixture at about 10% higher total flow than the detectors are expected to consume.

10.

Return the DM-2401 to "NO-MODE".

11.

Select "Auto" pressure control using toggle switch on panel in rear of mixing station, behind flow controller.

12.

Actuate the Low Pressure Override on interlock panel. "Main Relay" light should become green.

13.

Set Excess-Flow Valves and Manual valves at regulators to full OPEN, wait about ten (10) seconds for supply lines to come up to pressure, then set all three Excess Flow Valves to AUTO SHUTOFF. - "Low-Pressure" interlock circuit should go to green during this step³.

14.

Verify proper operation of flow/mix control system and outlet pressure regulation by observing flow rates on the mixer control and outlet pressure at the supply rack (pressure gauges 301B, -301C). If the alcohol bubbler loop is valved on it may take several minutes for its volume to fill with gas and come up to pressure. Be patient. When the pressure indicated on gauges PG301-B/C reaches about 15 psig the DM2401 system should cycle to flow program D. To bleed down the outlet pressure in order to cause the pressure loop to cycle, you may crack valve MV-299 (located in the rear of the mixer rack). When the pressure drops back to about 13 psig the control system should switch back to program C. Re-close valve MV-299 when tests are complete.

15.

Check/Adjust the Purge gas pressure regulator (PR 301) to insure that the delivery pressure of the inert gas (taken from gas supply 3 - nominally Argon) is about 15 psig as registered on pressure gauge PG-301A.

16.

Slowly open gas shed outlet valves MV-302-A, -B, -C to bring up the pressure in the supply lines to the spectrometers. After pressure has equalized open these three valves fully. Note that one or more Excess Flow Valves will trip (close) if the total gas flow through the three rotameters associated with these valves exceeds (roughly) 150 units (full scale on one rotameter).

17.

At each of the Hadron and Electron shield house gas distribution racks, verify the presence of supply pressures (gauges PG401A,B and PG501A,B,C) and set gas selection valves and needle valves to desired gasses and flow rates for each chamber.

Normal Operation

Changing gas bottles

Warning: High pressure gas bottles contain significant stored energy and are potentially hazardous. Handling of gas bottles should be done only by qualified, trained personnel.

For smoothest operation, used gas bottles should be replaced before their internal pressure drops below the desired regulator output pressure.

The sequence of steps for replacing an empty gas bottle is as follows:

1.

Make sure that the backup bottle is full, then open its bottle valve and its manifold valve. The in-line check-valves will prevent back-filling of the empty bottle. As a precaution, set the corresponding Excess Flow Valve to OPEN/RESET, wait ten seconds, then set the Excess Flow Valve back to AUTO.

2.

Close both the bottle and manifold valves for the empty bottle.

3.

Disconnect the empty bottle from the high-pressure flex-line, replace the bottleÕs cap, and move the empty bottle to the EMPTIES storage rack. Note that ethane bottle fittings, type CGA-350, have left-handed threads.

4.

Place a full bottle of gas in the on-line rack, remove the bottle cap, and connect the bottle to the flex-line.

5.

Open the new bottleÕs valve, check for leaks at the bottle fitting, then re-close the bottle valve.

Adding Alcohol

Warning: Never open gas flow into the alcohol bubbler without an outlet valve being open.

As long as the level in the RESERVOIR is such that some alcohol is visible in the sight glass the bubbler will be maintained at its normal fill. An effort should be made to prevent the RESERVOIR level from getting too low.

1.

To fill the RESERVOIR close valves MV-243 and MV-244 to isolate the RESERVOIR from the pressure equalization line.

2.

Open valve MV-241 to vent the RESERVOIR.

3.

Remove the cover of the REFILL CANISTER and fill the canister with alcohol. Put the cover back on but do not seal it (if you seal the cover at this point the flow of alcohol out of the REFILL CANISTER will be impeded).

4.

Open valve MV-242 to let the alcohol into the RESERVOIR. The liquid level can be monitored in the sight glass on the side of the RESERVOIR. Fill until the liquid level is near the top of the sight glass then close MV-242. Do not overfill (to or above the top of the sight glass).

5.

Close valve MV-241, then open valves MV-243 and MV-244.

6.

Seal the cover on the REFILL CANISTER to prevent contamination.

Setting a Flow Rate

The flow of each individual gas component, and therefore the final gas mixture, is controlled by the Dynamass DM-2401 System, the FM-8 Flow/Ratio Modules, and the Tylan General FC-280 Mass Flow Controllers. The DM-2401 accepts and stores programs for the set of FM-8's. Each FM-8 controls one or two Mass Flow Controllers.

To set or alter a flow rate: (Refer to Figures Figures )

1.

Prevent the mixed-gas outlet pressure from exceeding its 18 psig interlock trip level by either a) closing valves MV-201,2,3, or b) insuring that the detectors are consuming a sufficient quantity of gas to prevent this overpressure from occurring during the time it takes you to perform steps 3-11, below.

2.

Set the Auto/Expert pressure control switch (rear of mixer rack) to EXPERT.

3.

Verify that the DM-2401 is in the NO-MODE mode, indicated by none of the LEDÕs in the column on the extreme left of the unit being illuminated. If necessary, press the MODE pushbutton until this condition is achieved.

4.

Press program select button ÒCÓ and verify that the corresponding LED illuminates.

5.

At the DM-2401 Keyboard module, press the MODE switch until the FLOW LED illuminates. The window value for channel 1 will begin to flash.

6.

Select the channel you wish to alter by pressing the STEP button until the window value of the desired channel is flashing.

7.

Press the UP or DOWN SET buttons to alter the value as desired. Legal flow values are 0.0-100.0 sccm for channel 1, 0-1000 sccm for channels 2 and 3.

8.

If the Red ÒONÓ LED for the desired channel (immediately to the right of the value window) is not lit, press the ON/OFF button for that channel to illuminate this LED.

9.

Repeat steps 6-8 as necessary to program all desired gas flows.

10.

Return the DM-2401 to NO-MODE as in step 3.

11.

Return the Auto/Expert pressure control switch (rear of mixer rack) to AUTO.

12.

Re-Open valves MV201, 202, 203, if closed in step 1.

13.

Observe system flow and pressure control and verify that it is correct.