sprinklernotes
Groove Couplings in Dry Systems
You have asked the following question: "What is the purpose for Section 6.5.3.2
requiring a gasket listed for dry service in grooved couplings for dry
systems?" In response to your question, we have reviewed NFPA 13, 2016 edition
as the applicable standard. Our informal interpretation is gaskets listed for
dry service are required due to potential failures of non-listed gaskets.
Section 6.5.3.2 does require gaskets listed for dry service in grooved
couplings. This is because dry systems are traditionally exposed to extreme
conditions, thus the gaskets need to be evaluated per UL 213, Standard for
Safety: Rubber Gasketed Fittings for Fire-Protection Services, for their
ability to hold air and water pressure. The gasket's ability to maintain three
or four times their rated pressure (depending on the pipe size) for five
minutes, degree of flexibility at a rated pressure, ability to maintain 40 psi
when exposed to -40 degrees for 24 hours followed by 24 hours of ambient
temperatures, ability to withstand fire conditions, and effects on friction
loss are evaluated. The product data from different manufacturers state
different materials are used in their grooved coupling gaskets for dry systems
as well as lubricants that won't freeze at the lower temperatures. Manufacturer
installation requirements should always be consulted and followed when
installing these syst
ems. Being exposed to extreme cold could cause the gasket to become brittle and
not keep the appropriate seal, allowing air and water to leak past the gasket.
Air leaking could potentially cause enough drop in pressure to allow the dry
valve to open and charge the piping, and in a system installed in areas subject
to freezing could have drastic consequences. If the leak is not large enough to
open the valve, it could potentially cause the air compressor to cycle more
frequently to maintain the required air pressure causing it to fail
prematurely. Another possible failure is during trip testing when water could
potentially get behind the gasket and when the system is exposed to freezing
temperatures the coupling could fail.
