Initial Seal: The gasket forms an initial seal as it is stretched over the pipe ends,similar as O-ring sealing principle. Secondary Seal: The gasket is then slightly compressed as the housings are tightened to secure the gasket lips in a firm seat on the pipe,between the grooves and the pipe ends,it forms a secondary seal. Final Seal: Line pressure serves to strengthen the seal through the combination of normal gasket resillence,housing reinforcement and the action of pressure downward to the lips,it forms a final seal. Dry Fire-fighting system is applicable for the frozen/ince-cold oc...