Case Study 2

5 Yearly Hydrant Testing

High Rise Commercial Building, Sydney CBD, March 2016

AFT Fire performed the 5 yearly “Fire Brigade Hydrant Test” within a high rise commercial building in the Sydney CBD –we were engaged by a main stream fire protection services company.

The highest hydrant valve is at 81m above ground level and the hydrant system has two pressure zones which are serviced by a Fire Brigade relay pump.

Details of System and Testing Testing – in accordance with AS1851 (2012), Table 4.4.4, items 4.2 & 4.3

Hydrant System Design:

  • AS2419.1 (2005)
  • The system designed working pressures/flows are provided on the block plan
    • 20l/s @ 700kpaat the most remote hydrant valve

Hydrant System Configuration:

  • Fire Brigade Boosters  –adjacent the driveway
    • 2 x feed hydrant – Town’s main supply
  • Water storage tank supply – 25,000 litre on L19
  • 48 x internal attack hydrants
  • 1 x diesel fire pump at L19 1 x electric fire pump at L19
  • Fire Brigade Relay Pump and PRV station – L6
  • Most hydraulically remote hydrant –Level 19 and L6

Results from the Hydrostatic Pressure Test

The 2 x zones were pressurised to 1.5 times the working pressure – 1050kpa.

Lower pressure zones PASSED
Upper pressure zone PASSED

Booster Flow Testing Results

The 1st booster flow was conducted as per standard procedures and FAILED

The system was flowed via the boosters the feed the relay pump on level 6 tp achieve the required flow and pressure at the most hydraulically remote hydrant.This was producing excessively high and unsafe pressure and the test was aborted. It appeared that pipe configuration caused the pump to boost in a loop and over pressurised the system. the 2nd test was conducted as follows and PASSED. The system was flowed via the boosters to feed the relay pump on level 6 to achieve the required flow and pressure at the most hydraulically remote hydrant.

To prevent the relay pump from over pressurising the system the stop valves above the pressure relief valves were closed. This ensured the pump did not feed itself and relied solely on water fed from the boosters in the driveway.The measured system working pressure was 700kPa at the boosters to achieve the required pressure at the inlet of the Fire Brigade relay pump on L6. The relay pump provided the most hydraulically remote hydrants (L19) with 20l/s @ 700kpa. The L6 hydrant valve (fed off the tank and PRV station) was flow tested and achieved the required flow/pressure.

Conclusion of Findings

The system failed the test

The system had been generally installed to the requirements of AS2419.1 (2005).The original installation could not have been commissioned to the requirements of AS2419.1 (utilising the boosters) – the deficiencies encountered during our testing would have been identified at that time.

The Fire Brigade could not effectively operate the relay booster system, in its current state, without manipulating certain isolation valves in a specific sequence.

Recommendations

1. Seek Fire Brigade approval to post instructions at the boosters and in fire control centre detailing the required boosting procedure and the sequence of valve closers required to operate the boosting system via the relay pump.

OR

2.Install additional piping and reconfigure the water supply pipework servicing the relay booster pump. This would avoid the need for complicated valve manipulation during boosting by the Fire Brigade.

Additionally:
Installation of a pressure gauge above the pressure relief valve(relay pump)to show the true system pressure when boosting -as per AS 2419.1-2005

Provide a working pressure sign that states “working pressure of 700kPa -when boosting with the onsite relay pump running”