Unsafe pressure test and acid spill during a 2 ha installation
Site: a 2 ha drip system under installation in a cotton field near Aurangabad. The 75 mm PVC mainline is buried 0.6 m, submains are 63 mm, there are eight valves, and the source is a 7.5 HP submersible. The panel is 5 m from the pump. Crew: six workers, a tractor-mounted trencher, and no supervisor on site. Incident: during a pressure test at 3 kg/cm², a solvent-welded 90° elbow at the pump outlet blows off. Water sprays across the trench and a worker standing nearby is soaked but not hurt. Observations: the panel has no ELCB and the pump body is not earthed; a cable joint with taped insulation lies in a puddle; two cans of 33% hydrochloric acid are open near the filter and a worker is wiping a spill with a cloth; the backwash line discharges across a village path; a 1.2 m deep sump pit is unshored. The contractor had filled the mainline, pressurized it for 10 minutes, and then gone to lunch. Pressure: the farmer wants to start irrigation that evening because the cotton is wilting.
1. List the stop-work hazards and rank them. What immediate controls must be in place before any further work?
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Stop work immediately. Rank: (1) electrical: no ELCB, no earth, taped joint in a puddle - potentially lethal; isolate and lock the panel, appoint a licensed electrician, install a 30 mA ELCB, earth the pump body and route the cable in conduit above ground; (2) pressure-test zone: the failed elbow shows the joint was not properly cured or the pipe was not restrained; keep workers out of the trench and barricade the area; (3) acid: 33% HCl is corrosive; stop the worker, remove the cloth, irrigate the skin with plenty of water for 15 minutes, use goggles/face shield, acid-resistant gloves, apron and boots, and move the acid to a vented HDPE carboy with secondary containment; (4) excavation: a 1.2 m unshored pit is a cave-in risk; shore or slope it and keep spoil back; (5) backwash discharge across a village path is a slip, erosion and public nuisance hazard; redirect it to a vegetated buffer. Only after these controls should the elbow be repaired. The farmer's wilting crop is urgent, but an unsafe system cannot be commissioned; provide temporary furrow irrigation with a portable pump if it can be done safely, or prioritize the repair.
2. Describe the correct pressure-test procedure and the repair of the failed elbow. When can the line be pressurized again?
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Pressure test procedure: isolate the pump and all valves; fill the mainline slowly from the lowest point with the air release open; flush until clear; close the air release; pressurize to 1.5 times the design working pressure, or the manufacturer's test pressure, whichever is lower - for a 3 kg/cm² working main, 4.5 kg/cm², but do not exceed the pipe rating. Hold for 1 hour, not 10 minutes; check all joints, thrust blocks and the pump connection. Do not test with workers in the trench. Repair the elbow: cut out the failed fitting, remove all old solvent, use fresh PVC primer and cement, apply even coats, insert with a quarter turn, hold for 30 seconds, wipe the bead, and cure for at least 24 hours at 30°C before pressurizing (longer for large diameter or damp conditions). Install a thrust block at the bend and support the pipe so the elbow does not carry the pump thrust. Re-test at 1.5× working pressure for 1 hour before backfilling. Record the test pressure, duration and result.
3. Explain the safe handling of 33% hydrochloric acid and the emergency response to the spill. Should the system be commissioned that evening?
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HCl 33% causes severe burns and fumes; never use a cloth to wipe a spill. Wear chemical goggles plus face shield, acid-resistant gloves, apron and boots. Add acid to water, never water to acid. Store in a labelled, vented HDPE carboy in a locked, shaded, bunded area with lime or soda ash for neutralization, and keep water and an eyewash within 10 m. For skin contact, irrigate for at least 15 minutes and seek medical advice; for eye contact, irrigate and go to hospital. Dispose of neutralized spill according to the SDS and local rules; do not wash it into a drain or field. Commissioning that evening: no. The electrical defects, the unshored pit, the uncured repair and the acid spill are all unresolved. Set a written handover: electrical certificate, successful 1-hour pressure test, flushed and chlorinated lines, filter backwash to a safe outlet, and a trained operator. The farmer can furrow-irrigate the wilting cotton in the short term, but the drip system should start only after the punch list is closed.