m330_01_gas_cabinet气柜 - 第27页

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.

MAINTENANCE

GAS CABINET REFERENCE MANUAL

5-3

5.5 Preventive maintenance Gassystem

Daily maintenance:

Check gas pressures approx. 25 psi.

Check for visible signs of leakage (liquid supply lines)

Check Touchscreen and/or TSC system for any alarms.

Check gasflows of MFC’s take in account that certain hardware interlocks are

implemented in the gassystem.

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Weekly maintenance

For Metal Alloy tubes the Hydrogen filaments should be visually checked.

If applicable check the liquid source level

If applicable check the External Torch on flame shape (there should be no

red color in the flame “tip burning”, and check for condensation.

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Monthly maintenance:

Check amount of exhaust flow (see facility drawing for values).

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MAINTENANCE

GAS CABINET REFERENCE MANUAL

5-4

Yearly Maintenance:

Replace the filters once a year to avoid clogging.

Pressure Leak-check: Perform a pressure leak-check once a year

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