A proper flushing and support system is essential for reliable operation and long service life of cartridge mechanical seals. The correct API Plan should be selected according to the process medium, pressure, temperature, viscosity, solids content, and sealing requirements.
API Plan 11 – Process Recirculation
Process fluid is taken from the pump discharge and circulated into the seal chamber. It provides basic cooling and lubrication.
Typical applications: clean liquids, water, hydrocarbons, and general process fluids.
API Plan 21 – Cooled Recirculation
Similar to Plan 11, but a heat exchanger is installed in the flush line to reduce the temperature of the flushing fluid.
Typical applications: hot liquids and applications requiring additional temperature control.
API Plan 23 – Closed-Loop Cooling
Seal chamber fluid is circulated through a cooler and returned to the seal chamber, normally with a pumping ring.
Advantages: excellent temperature control and reduced thermal loading on the seal.
API Plan 32 – External Flush
A clean external fluid is injected directly into the seal chamber. It helps keep contaminants away from the seal faces.
Typical applications: dirty liquids, slurries, crystallizing or polymerizing fluids.
API Plan 52 – Unpressurized Dual Seal
A buffer fluid reservoir is used with a dual mechanical seal. The buffer pressure is normally lower than the process pressure.
Typical applications: hazardous or environmentally sensitive fluids where leakage monitoring is required.
API Plan 53A/B/C – Pressurized Dual Seal
A clean barrier fluid is maintained at a pressure higher than the process pressure.
* 53A: gas-pressurized reservoir
* 53B: bladder accumulator
* 53C: piston accumulator
These systems provide reliable lubrication, cooling, and process-fluid isolation.
API Plan 54 – External Barrier Fluid System
A dedicated external system continuously circulates clean, pressurized barrier fluid through the dual mechanical seal.
Typical applications: high-pressure, high-temperature, hazardous, and critical services.
API Plan 62 – External Quench
A quench fluid such as nitrogen, steam, or water is supplied to the atmospheric side of the seal.
Typical applications: crystallizing, coking, or solidifying fluids.
Selection Guide
The flushing plan should be selected according to actual operating conditions:
Clean liquid → Plan 11
Hot liquid → Plan 21 / 23
Dirty or abrasive liquid → Plan 32 / 41
Hazardous liquid → Plan 52 / 53
High-pressure or critical service → Plan 53 / 54
Crystallizing or coking liquid → Plan 62
Jiaxing Burgmann Mechanical Seal Co., Ltd
Email: doris@mechanicalseal.com.cn
Skype: kathysunlin
Fax: 86-573-84072317
Mob: 86-15381220188
WhatsApp: 8615958372402
Website: www.industrial-mechanicalseals.com
Add: A-5 Wanyangzhongchuangcheng, Ganyao Town, Jiashan county, Jiaxing, Zhejiang, China. 314107
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