I. Introduction to Plan 32 (API 682 External Flush) Seal Support System

Plan 32 is the most commonly used external flush type seal support system in the API 682 standard. Its core function is to inject clean, cool, and higher-pressure flush fluid from an external source into the seal chamber, providing cooling, lubrication, cleaning, and isolation for the seal faces, making it suitable for severe operating conditions.

II. Core Advantages
1. Thorough cleaning of the seal chamber
External clean fluid directly displaces process fluid, completely isolating solids, coking-prone, and highly corrosive media, preventing face wear, coking, and corrosion.

2. Precise temperature control
The temperature of the external fluid source is easily controlled, offering far better cooling performance than self-flushing systems (Plan 11/21). It is suitable for high-temperature and polymerizing fluids.

3. Controllable pressure
A positive pressure gradient prevents process fluid from leaking to the atmosphere, making it especially suitable for toxic, flammable, and explosive media.

4.Extended seal life
A clean, cooled, and lubricated environment significantly reduces face wear and thermal failure, increasing seal service life by 3–5 times.

5. Strong adaptability
Compatible with both single and dual mechanical seals. It is a cost-effective solution especially for single seals in severe service conditions.

III. Applicable Operating Conditions

1. Fluid Characteristics
Fluids containing solid particles (slurries, catalyst particles, etc.)
Coking-prone, polymerizing, and crystallizing fluids (high-temperature resins, molten salts, aromatics, etc.)
Highly corrosive, high-viscosity, and poorly lubricating fluids (concentrated acids, alkalis, tar, etc.)
Toxic, flammable, and explosive fluids (to prevent leakage of pure process fluid)

2. Process Conditions
Seal chamber temperature > 80 °C (requiring forced cooling)
Process fluid unsuitable for seal lubrication or cooling
Self-flushing schemes (Plan 11/21) cannot meet cleaning or cooling requirements

3. Typical Applications
Chemical pumps (high-temperature oil, slurry, acid/alkali pumps)
Refinery applications (residual oil, wax oil, catalytic slurry pumps)
Coal chemical industry (coal slurry, high-temperature ash water pumps)
Wastewater treatment (sludge, solids-containing wastewater pumps)