Baker Hughes’ Mooney™ Flexflo™ Model 887 Surge Reliever

A transient pressure surge develops when there is a change in liquid flow velocity. The greater the change in flow velocity, the higher the pressure will rise. These pressure surges can travel through a pipeline at sonic velocities, and if left unabated, can cause serious damage and costly inspection of the line.

The primary concern in surge scenarios is the rapid changes in fluid pressure, often referred to as ‘hydraulic transients’ or ‘water hammer’.

Rapidly shutting a valve or changes in pump operation can abruptly stop fluid flow, generating a pressure wave that propagates through the system.

When one of these events occurs, surge waves create pressure spikes that exceed the design limits of pipelines and tanks, leading to ruptures or leaks.

Surge events also generate significant vibration and noise, resulting in equipment damage or environmental concerns.

To mitigate these risks, a surge reliever in a storage tank farm is a crucial safety device designed to protect tanks and pipelines from damage caused by pressure surges.

Surge relief valves are designed specifically to protect against damage from high-speed transient pressure surges. Terminals, often near bodies of water, critically require surge relief protection to prevent pipeline breaks.

Surge relief valves are typically installed as close to the surge potential as possible, on a bypass line leading away from the main pipeline. When the main pipeline pressure exceeds the jacket pressure in the surge relief valve, the inner tube is forced away from the core of the device, allowing for fluid media to pass through the barrier to a downstream line and be captured in a collecting tank. The fluid can be pumped or trucked back into the main line at lower pressure once the surge subsides.

Any transient pressure surges should be analysed for root cause. Under normal operation, the pipeline pressure (blue) is less than the jacket pressure plus cracking pressure. The jacket pressure (green) forces the tube against the core of the device and the valve is closed. When the valve set point is reached, the pipeline pressure exceeds the jacket pressure, the tube is forced away from the core, permitting fluid to flow around the barrier into a downstream line.

When the surge event passes and the main pipeline pressure returns to normal, the jacket pressure reseats the tube against the core, closing the valve.

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