What does secondary containment mean?
For pumps, this term generally relates to sealless canned motor pump (CMP) or magnetic drive pump (MDP) types. These pumps are often used when pumping toxic or dangerous liquids so they are designed with containment of the pumped liquid in mind. They do not use a dynamic shaft seal for primary containment.
For CMP and MDP pumps, secondary containment is defined as a secondary pressure boundary that provides absolute containment of the pumped liquid in the event of a breached primary containment system. Pumps with secondary containment design may also have a secondary containment system that includes additional features such as sensors and feedback circuits designed to indicate a breach of the primary containment.
Secondary containment should not be confused with a secondary control design. Secondary control designs include a secondary pressure boundary to confine the pumped liquid, but the design allows for residual amounts of the leakage beyond the pressure barrier in the event of the primary containment becoming breached.
The principal design consideration for sealless pumps is to prevent leakage into the atmosphere. Because the primary containment may develop leakage as a result of wear by adjacent rotating parts, corrosion or abrasion, secondary leakage containment or control may be specified by the purchaser. The requirements and solutions for secondary containment and control will vary based on the application and pump configuration; therefore, when specified, these points must be discussed by the purchaser and pump supplier.
If testing of the secondary containment is required, the purchaser can specify testing per section 5.6.5 of ANSI/HI 5.1-5.6 Sealless Rotodynamic Pumps for Nomenclature, definitions, Design, Application, Operation, and Test.
For more information on installation of pump and piping systems refer to ANSI/HI 5.1-5.6 Sealless Rotodynamic Pumps for Nomenclature, definitions, Design, Application, Operation, and Test at Pumps.org/standards.