API Plan 13

API Plan 13 is a piping arrangement that recirculates leaked fluid from the seal chamber back to the pump suction.

It is used with single mechanical seals to maintain a controlled seal chamber environment by removing excess fluid and preventing pressure build up.

Features

Fluid that leaks across the seal faces is drained from the bottom of the seal chamber.
This leaked fluid is routed back to the pump suction through a return line.
A flow control orifice is often used to regulate the fluid movement and maintain proper pressure balance in the seal chamber.

Effectiveness depends on the pressure differential between the seal chamber and pump suction. If not designed properly, it may not function efficiently.
Not suitable for high-viscosity or high-solids applications, as fluid recirculation may become restricted.
Can introduce aeration if not properly installed, leading to pump performance issues.
Requires careful control of flow rates to avoid excessive seal leakage.

Centrifugal Pumps Handling Clean Liquids – Used in cases where recirculating the fluid back to suction is feasible.
Petroleum Refining & Oil & Gas – Applied in light hydrocarbon and low-pressure crude oil pumps.
Chemical Processing – Used in chemical transfer pumps with clean, low-viscosity fluids.
Power Generation – Cooling water and lubrication oil circulation pumps.
Water Treatment & Desalination – Suitable for clean water or treated fluid recirculation.

API Plan 13 is commonly used when maintaining a controlled seal chamber pressure is necessary while keeping the system simple and cost-effective.