API 682 Piping Plans Explained: When to Use Plan 11, 23, 32, 52, 53 and 54

Mechanical seals rarely operate alone. The auxiliary piping system determines the operating environment of the seal, and API 682 standardizes them into numbered diagrams (piping plan). Understanding these diagrams helps you read drawings and specify technical requirements more accurately.

Role of auxiliary diagrams

Auxiliary diagrams help to dissipate heat at the seal face, maintain sufficient pressure so that the seal face does not evaporate, remove solid particles from the liquid to the seal, or provide barrier fluid for double seals.

Drain and circulation group (single seal)

Plan 01, 02: internal circulation or sealed chamber without flow.
Plan 11: leads liquid from the pump discharge through the orifice to the seal, the simplest and most common.
Plan 13: circulates back from the seal chamber to the pump suction, suitable for vertical pumps and self-priming pumps.
Plan 21: like Plan 11 but with an added cooler, used for high temperatures.
Plan 23: seal pump circulates liquid through the cooler, suitable for hot water and high-temperature media.

Liquid treatment group

Plan 31: uses a cyclone to separate solid particles from the liquid stream entering the seal.
Plan 32: supplies clean liquid from an external source, used when the medium contains solid particles or is easy to evaporate.

Group for double seals

Plan 52: unpressurized buffer liquid in the tank, for unpressurized double seals.
Plan 53A, 53B, 53C: pressurized barrier liquid, respectively using a tank, a bladder-type accumulator, and a piston-type accumulator.
Plan 54: supplies pressurized barrier liquid from an external system.

External supplement group to the seal

Plan 61 and 62 provide connection ports for water or steam flushing (quench) and atmospheric discharge of the seal. Plans from 71 onwards are for configurations with buffer gas or cushion gas.

How to choose a diagram

Need to consider toxicity, flammability, temperature, solid particles, saturated vapor pressure, and emission requirements of the medium. The more hazardous the medium, the more a closed and pressurized configuration is needed. A simpler diagram is always more economical and less prone to failure if it can be used.

Note

Please refer to the current API 682 standard when specifying technical requirements. Contact SNS-VN for consultation.

Reference

Compiled from API 682 standard and common technical documents in the industry.