API 682 Plan 65 Seal Support System
Plan 65 is an atmospheric-side leakage collection and detection system defined in the API 682 standard, specifically designed for single mechanical seals. It is intended to capture and monitor liquid leakage from the seal, providing an early warning to operators before complete seal failure occurs.

The system was initially applied in the pipeline industry for remote or unattended pump stations to detect seal failures, and was subsequently incorporated into the API 682 standard. In the fourth edition of API 682, Plan 65 was further subdivided into two sub-types: Plan 65A and Plan 65B.

The working principle of the Plan 65 system is relatively straightforward. Leakage liquid from the seal is collected through the drain port in the gland plate and routed to a collection reservoir.

Application Scope
Suitable Services: Primarily applicable to processes where the fluid is condensable and generally non-hazardous.
Seal Type: Typically used with single mechanical seals, where the expected leakage is primarily liquid rather than gas.
Typical Industries: Widely applied in refining, oil & gas, petrochemical, chemical, and power generation industries.
Typical Arrangement: Commonly used with API 682 Arrangement 1 seals.

Comparison with Other Plans
Plan 65 is often confused with Plan 62 (Quench) .
The fundamental difference between the two is:
Plan 62 actively injects a quench medium such as steam, nitrogen, or water into the atmospheric side of the seal, with the purpose of preventing process fluid crystallization or coking.
Plan 65 passively collects and monitors liquid leakage from the atmospheric side of the seal.
In short, Plan 62 is "quenching," while Plan 65 is "monitoring."

Summary
API 682 Plan 65 is a cost-effective liquid leakage monitoring solution for single mechanical seals. Through its two variants, 65A and 65B, it provides effective early warning for both sudden (catastrophic) and progressive (gradual) seal failures, making it an important support system for ensuring equipment safety and operational reliability.