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Valve Trip Time Information <br />The actuator that operates the Model DDX-LP Low -Pressure <br />Dry System has a variable differential trip ratio that limits the <br />supervisory air/nitrogen pressure needed as the water supply <br />pressure increases. The differential trip ratio is the ratio of the <br />water supply pressure to the supervisory air/nitrogen pressure <br />when the actuator fully opens. (Note: The actuator may <br />partially open prior to reaching the differential trip ratio which <br />could trip the valve; therefore, always provide the minimum <br />supervisory pressure indicated in Table F of this bulletin, which <br />includes an appropriate safety factor.) <br />For a valve without an accelerator, use the following differential <br />trip ratio in valve trip time calculations: <br />For other static water pressures, the differential trip ratio may <br />be calculated using the following equations: <br />• [psi] Differential Trip Ratio = 0.056 x Static Water Supply <br />Pressure in PSI + 4 <br />• [bar] Differential Trip Ratio = 0.811 x Static Water Supply <br />Pressure in BAR + 4 <br />For a valve with a Model B1 mechanical accelerator, use a <br />differential trip ratio of 0 and a time delay of 10 seconds for the <br />valve to trip. <br />For a valve with an electronic accelerator, use a differential <br />trip ratio of 0 and a time delay of 5 seconds for the valve to <br />trip when the supervisory pressure is more than 15 psi, and 15 <br />seconds when the supervisory pressure is 15 psi and less. <br />Static Water Supply <br />Pressure in psi (bar) <br />Differential Trip Ratio for <br />Trip Time Calculations <br />100 (6.9) <br />10 <br />175 (12.1) <br />14 <br />250 (17.2) <br />18 <br />300 (20.7) <br />21 <br />Installation <br />The Model DDX-LP Dry Pipe Valve System shall be installed <br />in accordance with NFPA 13, "Standard for the Installation <br />of Sprinkler Systems," as well as the requirements of any <br />authorities having jurisdiction. The direction of flow shall be up <br />through the assembly. Failure to follow installation instructions <br />may void the warranty and/or listing of the valve. Verify <br />compatibility of the Model DDX-LP Dry Pipe Valve System <br />materials with the water supply and the environment where the <br />valve will be installed prior to installation. <br />The Model DDX-LP Dry Pipe Valve System must be installed <br />in a readily visible and accessible location where a minimum <br />temperature of 40°F (4°C) or above must be maintained. Heat <br />tracing of the Model DDX-LP Dry Pipe Valve System and trim <br />is not permitted. Heat tracing can result in the formation of <br />hardened mineral deposits that can prevent proper operation <br />of the dry pipe valve. <br />Whenever ambient temperature conditions are high, the water <br />temperature in the Model DDX-LP Dry Pipe Valve System <br />pushrod chamber may rise, thereby increasing the pressure <br />in the chamber to values exceeding the rated pressure of the <br />system. Where normal temperature and pressure is exceeded, <br />a pressure relief kit (P/N 6503050003; ordered separately) can <br />be installed into the pushrod chamber release line to limit the <br />pressure to 250 psi (17.2 bar). <br />The valve and trim kit has been tested, approved, and listed in <br />accordance with UL and FM standards. Hydrostatically testing <br />the valve and trim to pressures higher than their rating is <br />limited to the hydrostatic test as referenced by NFPA 13. The <br />clapper can remain in the closed position and the trim kit need <br />not be isolated. <br />Normal operation and hydrostatic testing does not address <br />the occurrence of a water hammer which may damage the <br />valve. A water hammer can create pressure greater than the <br />rated pressure of the equipment and should be avoided by <br />all necessary means. Water hammer may occur from (but <br />is not limited to) improper fire pump settings, underground <br />construction work, or improper venting of trapped air in piping. <br />DO NOT use bleeder valves for testing of the low-pressure <br />switch on the trim. Release of pneumatic pressure from the <br />actuator trim will result in operation of the system. <br />Air/Nitrogen Pressure Requirement <br />System Air or Nitrogen Pres- <br />sure psi (bar) <br />Maximum <br />Not Less Than <br />20(1.4) <br />8(0.6) <br />30(2.1) <br />10(0.7) <br />50(3.4) <br />12(.8) <br />75(5.2) <br />13(.9) <br />100 (6.9) <br />15 (1.) <br />125 (8.6) <br />16(1.1) <br />150 (10.3) <br />17(1.2) <br />175(12.1) <br />18(1.2) <br />200 (13.8) <br />19(1.3) <br />225 (15.5) <br />21(1.4) <br />250 (17.2) <br />22(1.5) <br />275 (19.0) <br />23(1.6) <br />300 (20.7) <br />24(1.7) <br />Notes: <br />1. Supervisory air or nitrogen pressure should not exceed 30 psi <br />(2.1 bar). Excess pressure may result in damage to the actuator. <br />2. Fastest valve operation is achieved with supervisory air or <br />nitrogen pressure indicated; however, pressure must never be <br />less than the minimum specified in the table above. <br />3. Air maintenance devices that maintain a constant pressure are <br />recommended; however, if a tank -less compressor is used, the <br />"compressor on" setting of the pressure switch must never be <br />lower than the minimum pressure in the table above. <br />Bulletin 338 <br />June 2021 <br />Page 4 of 7 <br />www.reliablesprinkler.com <br />