TWIST GAS SYSTEM RECOVERY PROCEDURE

     The following describes the procedure for restarting the TWIST gas
system after a
complete power outage.  After a power outage, all 4 chamber isolation
interlocks (PC_IN,
PC_OUT, DC_IN, DC_OUT) will be tripped.  The following procedure (suitably
modified) can
also be used if some lesser number of interlocks have been tripped ... the
only proviso being that
some effort should be made to try to understand why the system has tripped
before restarting it.

BOTH SYSTEMS (assuming both have tripped off)

1) ENSURE CHAMBER HV'S ARE TURNED OFF

2) Close the chamber isolation manual ball valves (PC_IN, PC_OUT, DC_IN,
DC_OUT).  This
prevents nasty surprises when the interlocks are later reset.

3) Close DC_RET and PC_RET MFC control valves.

4) Verify that the pumps are running, and power has been restored to all the
instrumentation.

RESTARTING DC GAS SYSTEM

1) Attempt to reset DC_IN and DC_OUT interlocks.  Since the manual isolation
valves are
closed, there should be no flow into or out of the chambers, and DC_Diff
should be unchanged
by the reset.  If DC_Diff pressure is between the upper and lower interlock
setpoints, both
interlocks should reset (green lights on relay box).  If so, go to Step 2.
If not ....

     a) If DC_Diff < lower interlock setpoint,  DC_OUT will not reset .....

     - arrange DVM and/or HPDVM to monitor one of the DC chamber input flows
          - open DC_IN manual ball valve ==> flow response in DC chamber
inputs
          - monitor increasing DC-Diff pressure until its comfortably above
lower setpoint
            BUT ALSO much below DC_PID setpoint (to prevent DC_RET MFC
opening
          up).
          - close DC_IN manual ball valve ==> DC chamber input flows slowly
go to zero
          - reset DC_OUT
          - go to Step 2

          b) If DC_Diff > upper interlock setpoint, DC_IN will not reset
....

     - attach a short piece of 1/4" polyflo to  DC_Ret Sample needle valve
(back of
          rack) to prevent accidental activation of flammable gas alarm
          - open DC_Ret Sample valve ~ 1/2 turn
          - monitor DC_Diff pressure and DC_Ret MFC setpoint
          - adjust DC_Ret Sample valve for faster/slower flow if necessary
          - allow DC_Diff pressure to fall below DC_PID setpoint until
DC_Ret MFC
          setpoint = 0.
          - close DC_Ret Sample needle valve
          - reset DC_IN

2) Ensure DC_Ret MFC setpoint = 0.  If DC_Ret MFC setpoint >0, do Step 1b
above.

3) Switch DC_Ret MFC control valve to "auto" (middle) position ... nothing
happens ... good

4) Open DC_OUT manual ball valve ... nothing happens.

5) Monitor DC input chamber flows and open DC_IN manual ball valve.

6) Monitor DC_Diff and DC_Ret MFC setpoint as pressure slowly increases.
When DC_Diff
approaches DC_PID setpoint, DC_Ret MFC setpoint will start to increase and a
short time later
DC_Ret MFC flow will start.

7) Monitor DC_Diff for a few minutes to ensure system is under control and
DC_Diff pressure is
converging on DC_PID setpoint.

RESTARTING PC GAS SYSTEM

The PC Gas System recycles a portion of the return gas flow.  If mistakes
are made during the
recovery procedure there is some probablity that the bubblers could allow
air to enter the pump
inlet.  Since air contamination could require a lengthy purging of the PC's,
to avoid this, the PC
Gas System should be put into non-recycling mode before attempting the
restart.

1) Open PC_EXH Rotameter needle valve.  There should be some flow from the
pressurised gas
in the PC_Pump outlet buffer tank.  Adjust the flow until the SS float is ~
120.

2) Monitor PC-REC MFC flow.  If PC_REC MFC flow goes negative, tap on the
check valve at
the physical o/p of the PC_REC MFC (it sometimes sticks open).

3) Use the "Restarting DC Gas System" procedure to restart the PC Gas System
(substituting
"PC" for "DC" in equipment designations).

4) Once PC_Diff pressure has more or less stabilised, close PC_EXH Rotameter
needle valve.

5) Monitor PC_REC MFC flow.  It takes several minutes for sufficient
pressure to build up in
the PC_Pump outlet buffer tank to drive the recycle flow thru PC_REC MFC.
Verify that
PC_REC flow has stabilised near normal value (~ 117 cc/min) before leaving
system
unattended.

GAS SYSTEM WALK-AROUND

Report anything unusual to R. Openshaw or M. Goyette.

GAS SHACK  - Once/shift

1. Check DME, CF4/IsoB input/output flows ~ normal and equal.

2. Check Helium input flow ~ normal

MESON HALL GROUND LEVEL  - once/shift

1. Check He/N2 flows normal ( Totflo ~1 l/min), and ~ 97:03

2. Check CF4/IsoB flows normal (Totflo ~ 32 cc/min)  and ~ 80:20

NETSCAPE (Any Terminal) - a few times/shift

1. Check pressure histories: (should be stable)
     PC_diff ~ 205.5 mTorr
     DC_diff ~ 110.0 mTorr
     He_diff ~ 109 mTorr
     PC_pump ~ 250 Torr
     DC_pump ~ 200 Torr

2. Check DC and PC chamber flow histories - should be reasonably stable with
small
temperature related drifts.  Nominal flow rates ~ 20 cc/min/chamber.

M13 AREA

All important flows/pressures can be remotely monitored using Netscape.
However, when you
have access to the area, keep your eyes, ears and nostrils open for any
strange sights, sounds or
odours.