When using nitrogen loaded surge relief valves it is believed that the relief valve is in control of the upper pressure limit of the pipeline. In reality, it is the nitrogen system together with the valve in a master and slave relationship that sets the upper threshold. The negative effects of changing temperature on the stability of a nitrogen loaded relief valve’s set point is well known but poorly understood. There have been many attempts to minimize this effect. Burying the plenum and using the soil as an insulator has proven to be ineffective. Manual adjustments are not cost effective. Regulators offer inconsistent performance and are often misapplied. Evolving technology now allows for this process to be automated. Set points can be held with remarkable accuracy and plenums no longer need to be buried.

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