While duct sealant is designed to repel moisture, it is primarily used to seal air leaks rather than pipe leaks. Therefore, it has somewhat limited plumbing applications and is most often used to repair air ducts and for other electrical or HVAC purposes. By understanding how these values are determined, you get a better selection of seals for critical installations. Therefore, by introducing an air pressure of 21.7 psi (156 kPa) over the water on the sample seal, the desired pressure in the water head is mimicked.
Therefore, the selection of duct seals must be an informed process based on the parameters of the application and on the well-tested technical specifications of the chemical or mechanical sealing product. Water pressure in a joint is usually expressed in feet or meters of water height, which is simply visualized as the depth of water above the joint. Direct and constant water pressure is a rigorous hydrostatic test that yields consistent results and more accurately predicts seal performance. A seal that passes inspection only to fail soon after or later, when the crisis looms, isn't really a seal.
Using dye in water for this test can be useful for tracing the source of any leaks that occur, as the dye will leave “fingerprints”. In this test, sprayed water is applied from three spray heads to the joint or joint at a pressure of 5 psi (34.5 kPa) for 1 hour. To perform hydrostatic tests, a seal is installed in a duct, leaving approximately 12 inches (30.5 cm) of empty duct at one end. Sealing electrical or communication ducts and ducts is not just a measure of code compliance.
The open duct must be sealed and it may also be necessary to seal the attachment point of the housing wall and the outside of the duct. Kept upright with the test seal underwater, air pressure is introduced into the duct above the water, mimicking a much higher water pressure. There are many chemical and mechanical sealing solutions available for the full range of duct applications. Testing and classifying gaskets based on their resistance to higher water pressures is an important consideration.
The costs related to the failure of seals do not usually end with damaged cables and equipment, but also extend to the resulting service interruptions, which can be particularly devastating for 911 call centers, hospitals, petrochemical plants, nuclear plants and other crucial facilities.
