Fire Protection Engineering (FPE) is Norway’s leading supplier of firefighting equipment for the offshore oil and petrochemical industries. Both management and key employees have been engaged in the offshore firefighting industry for more than 10 years.
FPE designs, manufactures and supplies all types of firefighting equipment, such as deluge and sprinkler systems, monitors, hydrants and hosereels and foam systems, as well as gaseous systems (CO2 and inert gas) and fine water spray systems.
Lately, FPE has been involved in the development and marketing of a very promising new technology, designed to overcome problems with pressure surges in the firewater system on oil platforms.
Active Pressure Pulse Compensator Prevents Waterhammer
High pressure surges, also known as ‘waterhammer’, have traditionally been a problem with operation of water-based firefighting systems on offshore oil rigs.
The Problem
The firewater system on an offshore oil installation is normally built around a firewater ring main (FRM), fed by large-capacity firewater pumps (FPs), located at sea level. Jockey pumps are used to maintain FRM pressure at all times. Branches and risers distribute the firewater to individual users, such as deluge systems, hydrants and monitors.
Figure 1: Stand By
Firewater piping is pressurised by the jockey pump.
The APPC system is in stand-by mode.
Figure 2: Deluge System Activated
Deluge valve is opened, water flows to the nozzles,
but main fire pump is not yet running at capacity.
The APPC system is activated, injecting air into
piping (green).
Figure 3: Fire Pumps Running
Fire Pumps are running at full capacity and water is slowly
filling the riser. Water hammer is prevented
When a deluge system (i.e. a high-flow firewater user) is activated, the jockey pump cannot keep up with the demand, and the FPs are activated. The run-up time of the main FP (normally 20–60 seconds) will, however, cause the upper parts of the firewater distribution piping to be drained, due to gravitational force, which in turn will create a vacuum (column separation). When the fire pumps are running at capacity, the firewater will rapidly refill the drained piping, at high flow and pressure, accelerated by the vacuum. Furthermore, because of the vacuum, an ‘air cushion’ is absent and this will create a very large pressure surge in the system. Pressures exceeding 100 Barg have been experienced.
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Drilling & Well Services
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