Plan 53B

Plan 53B 是 API 682 标准中定义的加压隔离液系统，适用于双端面承压密封（双重密封）。系统通过囊式蓄能器对隔离液循环系统加压，蓄能器内部以弹性气囊将加压气体（通常为氮气）与隔离液物理隔离，避免气体溶入隔离液影响密封性能。

隔离液循环依靠密封腔内自带的内置泵送环驱动，在闭式回路中循环：隔离液从蓄能器流出→流经密封腔带走热量→经换热器冷却后返回蓄能器。换热器可采用水冷式或翅片管风冷式，根据现场条件灵活选择。

系统压力下降时指示密封泄漏，需通过手动补液泵定期补充隔离液。该系统特别适用于封液压力超过 16 bar 的高压工况，广泛用于炼油、石化、化工等领域，尤其适合高蒸汽压流体、轻质烃、危险/有毒介质、传热流体，以及脏、腐蚀、易聚合等苛刻工况。

Plan 53B is a pressurized barrier fluid system defined in API 682, suitable for dual pressurized mechanical seals (double seals). The system uses a bladder accumulator to pressurize the barrier fluid circulation loop. The elastic bladder inside the accumulator physically isolates the pressurizing gas (typically nitrogen) from the barrier fluid, preventing gas entrainment that could compromise seal performance.

Barrier fluid circulation is driven by the integral pumping ring within the seal chamber in a closed-loop system: barrier fluid flows from the accumulator → passes through the seal chamber to remove heat → returns to the accumulator via the heat exchanger for cooling. The heat exchanger can be water-cooled or finned-tube air-cooled, offering flexible selection based on site conditions.

A drop in system pressure indicates seal leakage, requiring periodic refill via the manual refill pump. This system is particularly suitable for applications where barrier fluid pressure exceeds 16 bar, and is widely used in refining, petrochemical, and chemical industries. It is especially ideal for high vapor pressure fluids, light hydrocarbons, hazardous/toxic media, heat transfer fluids, as well as dirty, corrosive, and polymerizing fluids.