Fire protection device with conformal coating
A bursting capsule includes a hollow cavity completely enclosed and delimited by a vessel wall that includes a frangible material, a rupturing fluid disposed in the hollow cavity, an electrical conductor disposed on the vessel wall, and a conformal coating on at least a portion of the electrical conductor.
1 . A bursting capsule configured for use in a sprinkler head, the bursting capsule comprising a hollow cavity completely enclosed and delimited by a vessel wall comprising a frangible material; a rupturing fluid disposed in the hollow cavity; an electrical conductor disposed on the vessel wall; and a thermally conductive conformal coating covering at least a portion of the electrical conductor.
2 . The bursting capsule of claim 1 , wherein the conformal coating has an average thickness of about 25 μm to 750 μm.
3 . The bursting capsule of claim 1 , wherein the conformal coating comprises a polyurethane polymer.
4 . The bursting capsule of claim 3 , wherein the polyurethane polymer comprises polyester urethane polymer and/or oil-modified polyurethane polymer.
5 . The bursting capsule of claim 1 , wherein the bursting capsule has a predetermined trigger temperature in a range from 50 to 275° C.
6 . The bursting capsule of claim 1 , wherein the bursting capsule has an electrical actuation response time of no more than about 10 seconds.
7 . The bursting capsule of claim 1 , wherein the electrical conductor has an electrical resistance of no more than about 5 ohms.
8 . The bursting capsule of claim 1 , wherein the electrical conductor has an electrical resistance, which is increased by no more than a ten (10) multiple after exposure to a moist hydrogen sulfide-air mixture pursuant to UL 199 10-day corrosion test conditions.
9 . The bursting capsule of claim 5 , wherein the bursting capsule has an initial predetermined response time at the predetermined trigger temperature; and after exposure to a moist hydrogen sulfide-air mixture pursuant to UL 199 10-day corrosion test conditions, the bursting capsule has a response time at the predetermined trigger temperature which is not greater than about two (2) times the initial predetermined response time.
10 . The bursting capsule of claim 5 , wherein the rupturing fluid is configured to rupture the vessel wall after the bursting capsule has been at the predetermined trigger temperature for a predetermined response time of no more than about 30 seconds.
11 . The bursting capsule of claim 1 , wherein the conformal coating is formed by a process comprising application of a prepolymer as an aerosol formulation; and curing the applied prepolymer to form the conformal coating.
12 . The bursting capsule of claim 1 , comprising the rupturing fluid and a gas bubble disposed in the hollow cavity;
wherein:
the conformal coating has an average thickness of about 25 μm to 500 μm;
the frangible material comprises glass;
the electrical conductor has an electrical resistance of no more than about 5 ohms; and
the bursting capsule has a predetermined trigger temperature in a range from 50 to 275° C. and an electrical actuation response time of no more than about 2 seconds.
13 . The bursting capsule of claim 12 , wherein the conformal coating comprises a polyurethane polymer.
14 . A fire protection device comprising the bursting capsule of claim 1 .