What is the difference between an accelerator used with a Model D dry valve and an accelerator used with the DDX-LP Low Pressure Dry System?
There is no difference in the accelerator model used with either the Model D dry valve or the DDX-LP. Both dry systems use the Reliable Model B-1 accelerator when a quick opening device is needed. However, the trim associated with the accelerator for each system is different, as well as where the air pressure is directed from the outlet of the accelerator. When used with a Model D dry valve, air pressure flowing through the accelerator is directed into the intermediate chamber of the dry valve. Pressurizing this chamber destroys the differential between the air side and the water side of the clapper, causing the dry valve to trip faster. On a DDX-LP system, the accelerator is mounted on the valve trim near the low-pressure actuator and the accelerator outlet piping is open to atmosphere. Since the DDX-LP system utilizes a hydraulically operated valve, the actuator is the releasing device for this system. The faster the air pressure is removed off the air side of the actuator, the faste