Before you start: work safely
Acetylene is flammable and the plant runs on live water, gas and electrical systems. Diagnose with the plant in a known state, isolate before you open anything, and never test for leaks with a flame — always soap solution. If a fault involves the flashback arrestors, safety valves or pressure switches, treat it as safety-critical and do not defeat the interlock to keep running.
Generator — water level and temperature
The generator alarms are your first line of defence. A low-water alarm means the reaction can run hot and dry; a high-temperature alarm means the carbide-to-water ratio or cooling is off. Both trip the carbide feed by design.
| Symptom | Probable cause | Remedy |
|---|---|---|
| Low-water alarm rings | Water level has dropped below the low mark | Confirm on the low-water check valve; add water via the by-pass or water-control valve; check the slurry-drain valve and its instrument-air line for leaks |
| High-water alarm rings | Water level above the high mark, or a faulty level transmitter | Drain to level; if no leaks, clean or change the level-transmitter diaphragm; confirm on the upper check valve |
| High-temperature alarm | Low water supply, inlet valve not opening, or wrong water-to-carbide ratio | Raise water-supply pressure; check the water-control valve; reset the inlet-water instrument so the ratio is 3–4 litre per kg carbide; clean the generator spray nozzles if dirty |
| Bottom of tank a different temperature to just below water level | Insufficient agitation of the sludge | Check the agitator is turning at the far end; increase the agitator run time; if carbide dust is 10%+, run the agitator longer |
Carbide feed and hydraulics
If the generator pressure will not hold or the screw feed stalls, the problem is almost always in the carbide feed, the hydraulic pump that drives the hopper valves, or an electrical trip.
| Symptom | Probable cause | Remedy |
|---|---|---|
| No gas generation | Carbide not falling into the generator — bridged hopper, oversized lumps, or reverse screw-feed rotation | Weed out oversized carbide; tap a bridged hopper neck with a wooden mallet; correct the screw-feed direction; recharge if empty |
| Screw feed will not run | Hopper starter overload tripped, water level too high/low, temperature too high, or low air supply | Reset the hopper-starter overload; correct water level and instruments; reduce temperature; restore air-supply pressure |
| Screw-feed motor overloads or shears its pin often | Sprocket mis-alignment, worn shaft/bushes, or carbide chips jammed in the housing | Re-align the sprockets; inspect and change worn parts, clean and lubricate the bushings; remove trapped carbide chips |
| Hydraulic oil pressure not developing (gauge below 5 kg/cm²g) | Low oil level, by-pass valve open too wide, or reverse pump rotation | Top up oil; close the by-pass then open ¾–1 turn; correct the pump direction; re-calibrate a faulty gauge |
| Reduction gearbox overheats or buzzes | Wrong / low / excess lubricant, damaged gear, or worn bearings | Set oil to the specified grade and level; replace damaged gears or bearings; check the actual loading |
Slurry drain, agitator and safety valves
| Symptom | Probable cause | Remedy |
|---|---|---|
| Slurry drain valve not opening at set level | Instrument-air leak to the valve, or a punctured drain-valve diaphragm | Locate and arrest the air leak; change the diaphragm (Parts B-02/B-03) |
| Slurry not draining, level keeps rising | Clogged slurry line or a non-functioning level transmitter | Drain through the bottom plug and flush the generator and pipe with fresh water; clean or change the transmitter diaphragm |
| Agitator gland leakage | Loose gland nut or worn asbestos packing | Tighten the gland nut moderately; a slight leak often self-seals — if it continues, add / change packing and apply grease |
| Safety valve passes below set pressure | Foreign particles on the seat, or the setting disturbed | Clean the seat (replace if damaged); reset the safety valve to its correct pressure |
| Gas leak through a safety-valve manual vent arm | Ruptured safety-valve diaphragm | Change the diaphragm |
Pressure switches, cooler-condenser and scrubber
| Symptom | Probable cause | Remedy |
|---|---|---|
| Pressure switch not actuating at cut-out | Clogged impulse line, punctured Bourdon tube, or obstructed switch bulb | Clean and flush the impulse line then purge with nitrogen; locate and rectify the leak; free the switch bulb movement |
| Gas leaving cooler-condenser above room temperature | Insufficient cooling-water flow, or air trapped in the water section | Increase cooling-water flow; open the water valve to vent trapped air |
| Lime build-up in the cooler-condenser (typically after 4–6 years, sooner on dusty carbide) | Scale forming in the pipework / outlet cell | Clean the pipe wherever build-up is found; clean the check valve ahead of the scrubber |
| Pressure drop from generator to compressor above normal | Flashback-arrestor check valve clogged, or arrestor filled with sludge | Replace the check valve; vent and clean out the flashback arrestor and its horizontal pipe |
Acetylene compressor and high-pressure driers
Compressor symptoms nearly always trace to worn valves, worn rings, an oil problem, or a mis-set pressure switch. Cylinder-filling delays and rapid safety-valve discharge are the two you will meet most.
| Symptom | Probable cause | Remedy |
|---|---|---|
| Compressor will not start | No / single-phase power, defective motor-starter, or low suction pressure tripping the LP switch | Confirm three-phase supply; rectify the starter; raise generator pressure; check free rotation and keep interstage purge valves open |
| Cylinder filling slower than normal | Worn piston rings (or first-stage valves leaking) | Check and replace the piston rings; clean or lap the first-stage valves |
| Interstage / final-stage safety valve discharges rapidly | Leaky or dirty stage valves, or an isolation valve stuck shut | Remove the affected stage head and clean the valves; replace a broken valve or spring; open a stuck isolation valve |
| Compressor oil pressure below 0.5 kg/cm²g | Broken oil-pump belt, low oil, clogged oil suction line, or defective oil pump | Fit a loose (not tight) oil-pump belt; top up oil; clean the suction line; repair or replace the pump |
| Compressor oil turns grey | Water in the crankcase, or detergent oil used | Drain the oil-and-water emulsion and refill with the correct non-detergent grade; find and repair the water leak |
| Compressor stops before max charging pressure | HP pressure switch set too low, or a mis-calibrated gauge | Reset the high indicator to 24 kg/cm²g / low to 3 kg/cm²g; re-calibrate so it trips at the true pressure |
| HP drier condensate-drain valve clogs repeatedly | Not enough flushing water for the temperature change | Use more water when flushing; if nothing drains, isolate, vent the drier and clean or replace the valve |
One rule underlies the whole compressor table: never run the machine harder to overcome a fault. Rapid safety-valve discharge, slow filling or falling oil pressure are all telling you to stop and fix the cause.
When to stop and call IIGAS
Correct the routine faults above with confidence. But stop the plant and call us if a flashback arrestor is bypassed or damaged, if a safety valve will not reseat, if gas leaks persist after the obvious remedy, or if any fault repeats after being "fixed" — a recurring fault is a symptom of a deeper cause. As the plant builder we can diagnose from your log-book readings and get you running safely.