What’s inside the ‘Box’ When Considering API Piping Plan 54

Abstract

API Piping Plan 54 utilizes an external source to provide a clean pressurized barrier fluid to a dual pressurized mechanical seal designed to allow minimal leakage across the primary sealing interface into the process stream. The measured leakage rate is typically a volumetric (mL/hr or fl. oz/hr) or mass rate (g/hr or lb/hr) and requires end-user approval with regards to process dilution. While given coverage in API Standard 682, there is little description or guidance given when compared to more traditional piping plans and rightfully so considering the multiple variations that could carry the description allotted to this piping plan. Graphically, API Plan 54 is denoted in the standard by a piping diagram where the barrier fluid comes from a blank space or “box” external to the mechanical seal or seals, pressurized from an external source. In reality, a Piping Plan 54 designation could cover anything from a process pump supplying conditioned barrier fluid under pressure, to a once through water system in a chemical plant, all the way up to a stand-alone lubrication system designed to API 614 specifications (Lubrication, Shaft-Sealing, and Control-Oil Systems and Auxiliaries for Petroleum, Chemical and Gas Industry Services). The common determinant in arriving at this support system choice is the requirement for conditioned barrier fluid to adequately maintain the mechanical seal design integrity.