Hydraulic pump-assembly replacement for fire pump system

New hydraulic pump-assembly and system flushing extends life of fire pump system for many years to come.


  • Obsolete series hydraulic pump-assembly replaced with modern equivalent
  • Contaminated hydraulic oil replaced and system pipework / tubing flushed
  • Faulty system with pressure fluctuations returned to service
  • Extended life of field with the removal of obsolete parts and returning equipment to service.


  • The client contacted Sparrows to mobilise personnel to undertake troubleshooting on a faulty fire pump hydraulic system (pressure fluctuations reported)
  • A hydraulic supervisor and hydraulic technician were mobilised at short notice to undertake troubleshooting and the hydraulic pump-assembly was identified as the root cause
  • The decision was taken to remove the hydraulic pump-assembly and return to our specialist hydraulic pump and motor refurbishment workshop for strip down and inspection
  • The hydraulic pump-assembly consisted of an A4VSO500+A4VSO355+A4FO125 (22 series). On strip down and inspection, the internals of the pumps were showing signs of break-up / damage. During the fault-finding trip, the last oil analysis lab report found the system to be contaminated (ISO 4406:1999 22/19/13) / operating outwith the required cleanliness level of the system (ISO 4406: 16/12).


  • The option to refurbish the existing hydraulic pump-assembly and supply of new were both investigated. The supply of a new hydraulic pump-assembly was chosen, as this offered the benefit of removing the obsolete units and the shortest lead time
  • The new hydraulic pump-assembly was supplied pre-set for application. An Engineering Management of Change (EMOC) was undertaken to compare the existing vs new hydraulic pump-assembly. As part of the EMOC process, a difference in the overall length of the A4VSO355 was discovered which changed the position of the outlet and inlet ports on the A4FO125 pump
  • The existing pipe spool, installed between the outlet of the A4FO125 pump and manifold assembly on the outlet of the A4VSO500 pump, was too long / unable to fit
  • The pipe spool and manifold were returned from site to allow the pipe spool to be modified to suit the new hydraulic pump-assembly. The modified pipe spool was cut back, re-welded, Magnetic Particle Inspection (MPI) completed (pre-pressure test), pressure tested, MPI completed (post-pressure test), chemically cleaned / pickled and flushed
  • Prior to delivery, the manifold and modified pipe spool were installed on the new hydraulic pump assembly to ensure they fit correctly
  • Sparrows re-mobilised a hydraulic supervisor and hydraulic technician to undertake the flushing, hydraulic pump-assembly and commissioning during a planned shutdown. The scope included:
    • Flushing of all hydraulic system pipework / tubing and heat exchanger (note: the hydraulic system pipework 114.3mm OD and 90mm OD were flushed in-situ) to ISO 4406:1999 17/15/12 or better
    • Drain and clean hydraulic tank internals
    • Installation of the new hydraulic pump-assembly
    • Replacement of hydraulic hoses installed within the hydraulic tank and reinstatement of manifold and pipework
    • Reinstall hydraulic pump-assembly coupling half to pump shaft / engine (note: this required the coupling half to be heated to +80 to 100OC and press fit onto the pump shaft, as per the coupling OEM instructions)
    • Refill hydraulic tank with new pre-flushed (to ISO 4406:1999 17/15/12 or better) hydraulic oil
    • Commissioning and testing
  • The scope was successfully completed and the fire pump system returned to service within the timescale of the shutdown, avoiding any delays to startup operations
  • A full close-out / certification package for the scope was provided to the client.


Integrated solutions

  • Equipment upgrade
  • Fault finding and repair

Capabilities / services

  • Fluid power / hydraulics

Equipment sale and rental

  • Hydraulic rental equipment.

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Hydraulic pump-assembly replacement for fire pump system

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