m330_01_gas_cabinet气柜 - 第25页
MAINTENANCE G AS CABINET R EFERENCE M ANUAL 5-1 5.Maintenance 5.1 Introduction Maintenance for the gascabinet and its components is limited due to the use of high quality components and high purity elements. Routine chec…
START UP
GAS CABINET REFERENCE MANUAL
4-2
• Mark pressure reading
• Leave gassystem pressurized for
at least 12 hours
• Mark pressure reading. Any drop
in pressure indicates a gas leak.
• Use suitable gasleak detector
(such as Snoopy or electronic) to
trace any leak
• When no pressure drop is
detected open the facility gas
supply.
• The gassystem is ready for use.
• Pump until base pressure
• Open handvalve
• Pump until base pressure
• Open regulator fully
• Pump until base pressure
• Open facility gas supply slowly
• Pump until base pressure
• Leakcheak max 20 mtor/min right
up to the bottle
• Open N
2
purge at gas bottle
cabinet briefly. Pressure should
not exceed the safety setpoint of
1.4 torr measured at the tube.
• Pump until base pressure
• Repeat N
2
purge/ Pump cycle 20
times.
• Leakcheck max. 20 mtor/min
• Close facility gas supply
• Close regulator
• Close handvalve
• Close MFC
• Close process valve
• Slowly open the gas bottle
• Slowly open facility gas supply
• Slowly open the regulator
• Set pressure at 20 psi. If gaslines
are shared with other tubes use 30
psi for N
2
and 20-25 psi for O
2
• Slowly open the handvalve at all
applicable tube levels
• Close facility gas supply
• Mark pressure reading
• Leave gassystem pressurized for at
least 12 hours
• Mark pressure reading. Any drop
in pressure indicates a gasleak.
• Use suitable gas leak detector
(such as Snoopy or electronic) to
trace any leak
• When no pressure drop is
detected open the facility gas
supply.
• The gassystem is ready for use.
MAINTENANCE
GAS CABINET REFERENCE MANUAL
5-1
5.Maintenance
5.1 Introduction
Maintenance for the gascabinet and its components is limited due to the use of high quality
components and high purity elements.
Routine checks include pressure gauge readings every day and inline filter replacement every
year.
5.2 Leak-checks
Whenever a component in the gasline (either the preplumbing or gaspanel) is replaced a full
leakcheck is required.
Two different kinds of leak-checks are possible. There are a helium- and a pressure leak-
check.
5.2.1
Helium Leak check
A Helium leak check is used to test the integrity of the components or complete gasline.
• Connect the leaktester on a gas-inlet;
• Open the pressure regulator fully to maximum;
• Open the handvalve at tube level;
• Open the MFC (this must be done by the DPC, for more information, look at the
manual of the DPC);
• Open all valves in the gassystem (this must also be done by the DPC);
• Leak check may now begin;
• If no leak is found, repeat steps, mentioned above, in reversed and opposed
order. However, if a leak has been found, tighten/repair the relating nut/coupling
(etc.).
NOTE
Leak must be below 1 * 10
-8
atm. cm
3
/sec.
NOTE
If a checkvalve is present then a leak-check must be done
at both sides of this valve.
MAINTENANCE
GAS CABINET REFERENCE MANUAL
5-2
5.2.2
Pressure Leak-check
A pressure test is used to test all connections at supply pressures see Gas Cabinet start up 4.3.
5.3 Disassembly and cleaning of MFC’s
MFC’s are complex components, which require specialist tools and skills. It is
recommendable to return the MFC to the supplier for cleaning and/or repair (make sure to
include the proper contamination reports).
Evacuate upstream and downstream of the MFC in case it is inside a gasline for toxic or
flammable gases.
5.4 Disassembly and Cleaning of all flowmeters
The metering tube, float and float stops may be removed as an assembly for cleaning or
replacement, without removing the meter from the line. To disassemble, use the following
procedure:
1. Remove the plastic safety shield.
2. Loosen the seal spindle by turning it counter clockwise with a 4 mm hex wrench. The
tube must be pushed into the direction of the seal spindle and may now be canted out of
the meter housing. If it is desired to clean the metering tube, float and float stops as an
assembly (using a solvent or ultrasonic cleaner) only the above two-steps are required.
However, if complete disassembly is required, use the remaining steps.
3. Using a small hook, remove both Teflon float stops from the metering tube and remove
the float. Be careful not to chip tube ends.
4. Packing seats and packing inserts now may be removed.
5. With the metering tube out, the seal spindle may be rotated clockwise for removal. It
should not be necessary to remove the seal spindle unless the 0-ring that seals the spindle
requires replacement. The O-ring may be used as long as it is not torn or distorted.
6. The needle control valve assembly may be removed by turning the valve body counter
clockwise. The valve seat, stem and packing then may be carefully removed from the
valve body for cleaning or replacement.
7. The metering tube, made of Borosilicate glass, may be cleaned with any solvent that does
not attack glass.
Reassembly Procedure
1. Use the reverse of steps 1 through 7 of the disassembly procedure to reassemble the
meter.
2. When replacing the packing seats in the flowmeter body be sure the packing inserts are
approximately 1,5 mm above the top of the packing seat. Also be certain the tube seats
firmly on the packing seats and does not overlap onto the end block.
3. The seal spindle serves to radial compress the tube seat gasket and exert a uniform
pressure on the metering tube to prevent any possibility of leakage. Do not over tighten
the seal spindle.