Blowdown Cap Operation and Troubleshooting

Technical Support Subject Blowdown Cap Operation and Troubleshooting Document Version Department Revision Details Revised by Tech Engineering Implemented EXT-ALL-006 A Tech Document Release SP 14 Oct 2015 BC 14 OCT 2015 N/A 14 Oct 2015 Page 1 of 4 Knowledge Base: www.kb.vmacair.com Email: tech@vmacair.com Web: www.vmacair.com Technical Support: 1(888)241-2289 Toll Free:1(800)738-8622 Fax: 1(877)740-3201 System or Parts affected Underhood VR70 Underhood VR150 PREDATAIR Blowdown Cap P/N# 9200437 Blowdown Cap P/N# 9210028 Blowdown Cap P/N# 9400059 Index System or Parts affected ............................................................. 1 Overview ....................................................................................... 1 Symptoms ..................................................................................... 1 Components ................................................................................. 1 Trouble shooting .......................................................................... 2 Blowdown constantly venting during compressor operation ..... 2 Blowdown does not vent ........................................................... 2 Oil comes out of Blowdown Muffler .......................................... 2 System takes a long time to Blowdown .................................... 2 How it works ................................................................................. 3 When the Compressor is Turned On ........................................ 3 When the Compressor is Turned Off ........................................ 4 Overview The blowdown cap depressurizes the compressor system when it is shut down. We do this to reduce the chance that the clutch will engage while there is air pressure in the system as this will cause premature wear to the clutch. Symptoms  Oil out the sintered muffler  Premature clutch wear  Blowdown does not vent after compressor shut down  Blowdown constantly venting during compressor operation  System takes a long time to blow down Components  200 PSI Pressure Relief Valve: a safety valve, used to protect the system from over pressurizing and damaging components.  Blowdown Muffler: This is used to lower the noise level when the system depressurizes.  3/16” Pressure Control Line: Supplies “system air pressure” to the compressor.  1/4” scavenge line: Goes to compressor inlet valve, is used to scavenge oil and control blowdown cap. Figure 1 Blowdown Cap Air Oil Separator Tank Technical Support Subject Blowdown Cap Operation and Troubleshooting Document Version Department Revision Details Revised by Tech Engineering Implemented EXT-ALL-006 A Tech Document Release SP 14 Oct 2015 BC 14 OCT 2015 N/A 14 Oct 2015 Page 2 of 4 Knowledge Base: www.kb.vmacair.com Email: tech@vmacair.com Web: www.vmacair.com Technical Support: 1(888)241-2289 Toll Free:1(800)738-8622 Fax: 1(877)740-3201 Figure 2 Trouble shooting Blowdown constantly venting during compressor operation  Determine if venting is from Blowdown Muffler or 200PSI Pressure Relief Valve.  Check the ¼” scavenge line for leaks, kinks or obstructions.  Check ¼” scavenge fittings for leaks, or obstructions.  Check the Scavenge port in the blowdown cap, ensure it is not obstructed.  Ensure the scavenge screen is not plugged. Blowdown does not vent  Plugged muffler: This will prevent the air pressure from venting.  Ball seized onto seat: Remove cap from tank, and shake the cap, can you hear the ball move freely inside? Oil comes out of Blowdown Muffler  Blowdown diaphragm damaged.  Tank or cap mounted upside down (Arrow on discharge cap should be pointing upwards). System takes a long time to Blowdown  Restricted Blowdown muffler.  External receiver tank installed without check valve. 200 PSI Pressure Relief Valve 3/16” Pressure Control Line 1/4” Scavenge Line Sintered Exhaust (Blowdown Muffler) Diaphragm Technical Support Subject Blowdown Cap Operation and Troubleshooting Document Version Department Revision Details Revised by Tech Engineering Implemented EXT-ALL-006 A Tech Document Release SP 14 Oct 2015 BC 14 OCT 2015 N/A 14 Oct 2015 Page 3 of 4 Knowledge Base: www.kb.vmacair.com Email: tech@vmacair.com Web: www.vmacair.com Technical Support: 1(888)241-2289 Toll Free:1(800)738-8622 Fax: 1(877)740-3201 Figure 3 How it works When the Compressor is Turned On Suction from the ¼” scavenge line pulls on the diaphragm, allowing the blowdown pin to move towards the diaphragm, the blowdown ball is forced against the internal seat which does not allow any air to flow through the blowdown muffler. (Figure 4) Figure 4 1/4” Fitting Scavenger Line 3/16” Fitting Pressure Control Line 200 PSI Safety Release Valve Sintered Exhaust (Blowdown Muffler) Suction Port Scavenge Screen Port Mechanical Force Suction System Air Pressure Technical Support Subject Blowdown Cap Operation and Troubleshooting Document Version Department Revision Details Revised by Tech Engineering Implemented EXT-ALL-006 A Tech Document Release SP 14 Oct 2015 BC 14 OCT 2015 N/A 14 Oct 2015 Page 4 of 4 Knowledge Base: www.kb.vmacair.com Email: tech@vmacair.com Web: www.vmacair.com Technical Support: 1(888)241-2289 Toll Free:1(800)738-8622 Fax: 1(877)740-3201 When the Compressor is Turned Off System air pressure is applied to the blowdown diaphragm (suction only occurs when the compressor is turning). While the pressure is dropping in the ball chamber it allows the diaphragm and spring pressure to move the ball off its seat allowing air to bypass the ball seat where it vents out of the muffler. (Figure 5) Figure 5 System Air Pressure System Air Pressure Mechanical Force. Additional Serch Terms: Oil out the exhaust, oil out the muffler, Sintered muffler, Sintered exhaust.