Outrigger hose repair on a concrete pump
A 37 m concrete pump is on a high-rise site. The outrigger hydraulic hose bursts while the boom is being unfolded; 60 L of oil is lost and the reservoir sight glass is below minimum. The replacement hose in stores is marked 350 bar, SAE 100R2, 1.2 m long, with 3/4 in BSPP fittings. The machine’s relief valve is set at 320 bar and the port is 3/4 in JIC 37°. The fitter uses a BSPP-to-JIC adapter and refits the hose with a bend radius of 90 mm against a manufacturer minimum of 150 mm. The hose is routed close to a hot exhaust pipe. The pump is needed for a pour in four hours. The store also has a 420 bar 4-wire hose with JIC fittings but it is 2.1 m long. Evaluate the repair and decide what to release.
1. Assess the proposed repair against pressure rating, fitting compatibility, routing and contamination.
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The proposed repair is not acceptable as described. The 350 bar hose rating is only 30 bar above the 320 bar relief setting, about 9% margin; that is too close for a pressure line with pressure spikes and does not allow for hose age or temperature derating. The 3/4 BSPP-to-JIC adapter adds a joint and a possible mismatch of sealing faces; BSPP and JIC are not interchangeable, and an adapter can loosen or restrict flow. The 90 mm bend radius against a 150 mm minimum will fatigue the wire reinforcement every time the boom unfolds. Routing near the exhaust adds heat ageing. The 60 L loss and low reservoir level mean the pump may have cavitated and the system may have ingested air and dirt. The 2.1 m 420 bar hose is a better pressure rating, but it must be routed without tight bends and supported; length alone is not a reason to reject it.
2. What must be done before the pump is returned to service?
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Before return to service: isolate and clean the area; replace the burst hose with the correct pressure-rated hose and JIC fittings; drain and flush the affected circuit, replace the return filter and inspect the suction strainer; fill with clean oil to the specified level and bleed air. Check the pump for cavitation damage and the relief valve for contamination. Pressure-test the repaired circuit at the manufacturer’s test pressure, not above the relief setting, and cycle the outrigger and boom functions through full stroke at low idle while watching for leaks and unusual noise. Take an oil sample after 30 minutes of operation. Record the hose batch, pressure rating, bend radius and route. If the 420 bar hose cannot be routed with at least 150 mm bend radius and heat protection, do not release the pump.
3. Which hose would you select and why? Include any restrictions on the pour.
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Select the 420 bar 4-wire hose with JIC fittings if it can be routed with a minimum 150 mm bend radius, supported every 600–900 mm and shielded from the exhaust. Do not use the 350 bar 2-wire hose with the BSPP adapter for the outrigger pressure line. If the 2.1 m hose is too long, route it in a safe loop rather than cutting and re-crimping on site; field-crimped hoses are a contamination and quality risk unless the crimper is calibrated. Restrict the pour until the repair is pressure-tested and the reservoir is at the correct level. If the correct hose is not available, the pump should not be released for boom work; a manual or lower-pressure function is not an acceptable substitute for an outrigger circuit. Document the decision and the hose identification in the maintenance record.