The acetylene plant maintenance calendar: 10 daily 18 weekly, 15 monthly and 20 yearly tasks, grouped by system

A carbide-to-water acetylene plant is maintained to a calendar, not by waiting for faults. KIGL's regime has 63 scheduled tasks: 10 checked every day before start-up, 18 every week, 15 every month and 20 every year, plus the hourly round recorded on the shift log and work triggered by the volume of gas made. Each list is a controlled record with satisfactory, non-satisfactory and remarks columns, signed by the person who did the work.

The tiers are layered. The same device is often checked at more than one frequency, each check testing something different: the generator safety valves are lifted daily, soap-tested weekly and monthly, and bench-set yearly. A reader who sees an item three times should read it as design, not duplication.

1. Agitator runs 5 minutes in every 15 minutes.
2. Agitator runs during each hopper run.
3. Agitator stuffing boxes not leaking.
4. Residue drain valve not leaking water.
5. Each generator safety valve opened by its lever to prove it lifts and reseats.
6. Hydraulic piping free of oil leaks.
7. Scrubber water level checked and topped up.
8. Water condensate drained from the acetylene compressor oil.
9. Compressor oil level checked, SAE 30 non-detergent added if needed.
10. High-pressure drier refilled with anhydrous calcium chloride, because the manual warns that a void could result in an explosion.

Before every start, and at each hopper filling, the generator water level is also confirmed at the two check valves: water from the lower, gas from the upper.

1. High water level alarm tested by raising the level through the bypass; also after any work on the level transmitter or slurry valve.
2. Residue drain valve sensitivity: 200 to 400 litres on the water meter between successive drain openings.
3. Temperature safety instrument tested by lowering its setting below the indicated value and confirming the alarm.
4. Generator safety valves soap-tested at the vent-side union.
5. Hopper vent valves soap-tested the same way.
6. Agitator gear reducer topped up with SERVO Gear HP 85.
7. Both screw-feed gear reducers topped up.
8. Compressor cooling tank drained, cleaned, piping inspected for corrosion, refilled.
9. Screw-feed drive belt checked; static-conducting belts only.
10. Compressor motor drive belt checked.
11. Compressor oil-pump belt checked; it is a cog belt and runs slack.
12. All acetylene piping, low and high pressure, inspected and soap-tested; repairs only with the plant shut down and purged.
13. Instrument-air compressor belts cleaned or changed.
14. Instrument-air compressor oil drained and refilled with SAE 30 non-detergent; drier silica gel replaced.
15. All air piping checked for leaks.

1. Withdraw the generator from service, letting both hoppers run empty on the last shift.
2. Clean and inspect the tank interior.
3. Check agitator packing and shaft for wear.
4. Check the water inlet spray system.
5. Check control diaphragms.
6. Check carbide valve seats and the rubber disc.
7. Inspect hoppers and hopper gaskets.
8. Check and adjust safety relief valves on the bench: tight below the set pressure, free discharge at it, and clean reseating after pressure is reduced, to the values on the approved drawing.
9. Check the hydraulic system for leaks and reservoir level.
10. Check hydraulic cylinders for operation, leaks and rod damage.
11. Check gearbox oil levels.
12. Check screw-feed drive chain and belt tension.
13. Drain, clean and refill the flashback arrestors.
14. Check generator valves and gauges.
15. Check the slurry drain valve opens on level rise.
16. Check the water inlet valve opens on temperature rise and spring-closes on loss of air.
17. Purge the air-acetylene mixture from the generator on restart.
18. Function-test the alarm and drain valve control system: low level, high level, high temperature and instrument air.
19. Clean and lap acetylene and air compressor suction and discharge valves; head bolts to 60 ft-lb (8.3 kg-m).
20. Check and clean all valves and valve seats, renew gland packing.

The annual list also carries cleaning of the high-pressure drier flange and the charging manifold, blown out with nitrogen and checked for amines that can clog check valves where no purifier is used.

The tank clean is the yearly job most likely to hurt someone, because a generator opened after service still holds acetylene in sludge and pockets. Fill the tank to normal level with the agitator on to thin the sludge; vent through the safety valve handle; drain fully; remove the flexible coupling between agitator and gearbox and isolate the control panel so nothing can start; remove the manholes and feed-tube top plates; flush with a hose and scrape only with a wooden paddle, never a metal tool. Clear the spray nozzles, the build-up around the feed-tube ends and the centre riser, flush the arrestor bottoms, refit plates with new gaskets tightened alternately across, refill, purge all air through the safety and hopper vent valves, soap-test and refit the coupling. Lime burns: protective clothing, goggles, rubber boots, gloves and apron, with fresh water to wash off. The hot work and maintenance guide covers the purge rules.

Plant audits find that the tasks left undone are the ones that look routine. At one audited plant, soot below the arrestor water line proved the arrestors had been run dry and the weekly drain and refill was not being logged; at another the hopper had no interference vent valve at all, although the monthly checklist assumes one is fitted and tests it; at a third no hourly record of plant readings was being kept. The regime already exists; the gap is running it.