11699 Brookpark Road Cleveland, OH 44130 USA P: 216-749-2992 F: 216-398-8403 www.combustionsafety.com Why Test? Main and pilot safety shutoff valves keep fuel out of the firebox when equipment is shut down. Valves that leak fuel downstream past their seats could allow an accumulation of unburned fuel in firing chambers. This can possibly result in an explosion. Codes and manufacturers of safety shutoff valves require that leak and tightness testing be performed regularly. Standard: NFPA 86 Process Ovens and Furnaces NFPA 85 Boiler and Combustion Systems Hazards Code ASME CSD-1 Controls and Safety Devices for Automatically Fired Boilers Equipment Mode This test requires that the equipment be shut down. Tools/Instruments Required Plastic tubing Clear cup of water Hose barbs and fittings Wrench/Allen key Electrical schematic Hose Barbs and Fittings
Page 2 TEST PROCEDURE The main gas train valves must be tested in the sequence given in this procedure: 1. Main gas train Blocking valve 2. Main gas train Vent valve 3. Safety shutoff valve 4. Pilot gas train safety shutoff valve The test for each valve requires the same basic procedure: Make gas pressure available on the upstream side of the valve. Close off the piping downstream of the valve to trap any leakage. Position a test port just downstream of the test valve to force the bubbles out of the tubing. TEST PROCEDURE (continued) 5 4 L H 1 6 * Note: Venting removed for clarity 2 Testing This Valve 3
Page 3 Step 1. Main as Train Blocking Valve (BV) 1. Close the manual shutoff valve downstream of the blocking valve (BV). 2. With test cock closed on the downstream side of the blocking valve, remove the plug and connect the bubble test hose. 3. Insert the hose into a vessel of water. 4. Power the vent valve closed. 5. Power the safety shutoff valve (SSOV) open to bring line pressure up to the blocking valve. 6. Slowly open the test cock to the bubble test hose. NOTE: By opening the test cock, an initial release of bubbles is common since the gas trapped between BV and the downstream valve must escape. 7. Wait approximately one (1) minute per inch of pipe diameter. 8. Count the bubbles for one minute. 9. Close the test cock, remove hose and replace the plug. 10. De-energize the valves to return them to their correct positions. TEST PROCEDURE (continued) 4 3 Testing This Valve L H 1 2 * Note: Venting removed for clarity
Page 4 Step 2. Main as Train Vent Valve 1. Close the manual shutoff valve downstream of the blocking valve (BV). 2. With test cock closed on the downstream side of the safety shutoff valve (SSOV), remove the plug and install a reliable gauge with a range appropriate for the line pressure. 3. Power the vent valve closed. 4. Power the safety shutoff valve (SSOV) open to pressurize the gas train up to the blocking valve. 5. Remove power to the SSOV thereby trapping live gas pressure between the automatic shutoff valves (SSOV & BV). 6. Record the pressure on the gauge. 7. Wait approximately 5 minutes. 8. Observe the pressure on the gauge. 9. Close the test cock and remove the gauge. TEST PROCEDURE (continued) 4 L H 1 5 * Note: Venting removed for clarity 2 Testing This Valve 3
Page 5 Step 3. Main as Train Safety Shutoff Valve (SSOV) 1. Close the manual shutoff valve downstream of the blocking valve (BV). 2. With test cock closed on the downstream side of the safety shutoff valve (SSOV), remove the plug and connect the bubble test hose. 3. Insert the hose into a vessel of water. 4. Power the vent valve closed. 5. Slowly open the test cock to the bubble test hose. 6. Wait approximately 1 minute per inch of pipe diameter. 7. Count the bubbles for one minute. 8. Close the test cock, remove hose, and replace the plug. 9. De-energize the vent valve to return it to the correct position. Step 4. Pilot as Train Safety Shutoff Valves If the pilot has a vent valve, follow all three sets of procedures. If the pilot does not have a vent valve, follow: (1) Step 1 omitting action #4 (2) Step 3 omitting action #4
Page 6 Test Results *Table 1: Valve Tightness Testing Ranges Valve passes: Valve Size Bubbles Per Minute Valve leaks less than 15 bubbles per minute or no discernable pressure loss on gauge for vent valve test. Valve fails: Leakage rates above 15 bubbles per minute require valve replacement or one of the following interim actions. 1. Quarterly leak testing 2. Standby closure with manual valve Up to 0.75" 15-26 1 15-26 1.25 15-26 1.5 15-29 2 15-39 2.5 15-59 3 15-72 4 15-72 6 15-98 RESOLVIN and PREVENTIN TEST FAILURE *Table 1 is derived from the ANSI Z21.21, CA 3.9 and UL 429 standards. Immediate Actions: Leakage rates above the allowable ranges shown in Table 1 are a critical issue requiring one of the following actions: Shut down the equipment. Replace the valve immediately. et supervisor authorization for an interim procedure that will allow continued safe operation of machinery. Interim procedures require the authorization of Plant Engineering and the concurrence of the Plant Safety Engineer. All critical failures must be reported to your Division Core Team member.
Page 7 Preventing Failure Maxon has a published maintenance procedure that calls for cycling leaking valves 10 to 15 times, then calling for a retest. This is a very successful maintenance procedure and should be tried if you happen to have a Maxon valve that s slightly out of specification. The proper maintenance of strainers and drip legs will help to prevent contaminants from damaging or hindering the valve seal. CEC Combustion Safety, LLC has been in business since 1984. With engineers and staff members that sit on Code committees such as ASME CSD-1, NFPA 56, NFPA 85, NFPA 86, and NFPA 87, our inside expertise is integrated within all of our practices and our global reach ensures that customers around the world are kept safe. CEC offers Testing and Inspections, Engineering & Upgrades/Retrofits, as Hazards Management, Training, and Field Services for all industrial facilities and different types of fuel fired equipment. By assisting organizations and their personnel with the safe maintenance and operation of their combustion equipment, CEC aims to save lives and prevent explosions while increasing efficiency and reliability of combustion equipment. Contact CEC at +1 216.749.2992 or visit www.combustionsafety.com for additional information.