Question about Ingersoll Rand Stationary Air Cooled Rotary Screw Compressor 10 Hp, 35 Cfm At 125 Psi, Model# Ep

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SSR-EP10 37CFM 10HP Keeps venting air at air filter after 125PSI shutoff. Compressor keeps cycling between 100-125psi within a few minutes. After I shut off the power, it vents till pressure is below 50PSI then it stop venting and hold at about 48psi. I had traced the air hose and think the 1SV and 3SV are ok; since, I disconnect the air hose from the Separator Tank into the SV1, screw drive would not engage and no pressure build up, reconnect, drive engaged and pressure goes up. On 3SV, when power is on, valve energized (closed) no air coming thru and air is being sucked in thru air filter, when power is off, air venting thru filter. I believe something inside the Separator Tank keeps venting it until pressure is below 50psi. Air is being teed of from Separator tank to 1SV and 3SV. Is there a check valve I should check? and where is it located? Thanks

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  • ISayGLD Mar 16, 2011

    Thank you for answering my question.
    This MPRV, is it also called Orifice, Check Valve P/N: 39303219 ? Flow direction is from the top of Separator Tank down to the bottom of the AIR END? Does this MPRV have any control on the air that's going into the 1SV that's venting? Also, when the machine is idle, does the motor slow down to a slower RPM? Reason is it's a bit loud.

    The last owner used Kaeser Sigma lubricant M-460, I looked it up and said it's compatible with IR Ultra coolant, is this ok? Thanks again.

  • ISayGLD Mar 19, 2011

    First I'd like to say THANK YOU for the to the "straight to the point answer". You are a true IR Guru.
    I followed your instruction and removed the MPRV from the machine; Removed the AL cap then knock the piston lightly from the other side. It was full of gunk on one side and inside it was another brass piston with a smaller spring, it was also full of gunk. I tried to clean it with soap, and other solutions but couldn't remove much. I then put it on a scotch-brite wheel and was able to clean both the small

  • ISayGLD Mar 19, 2011

    I did it per your instruction and it is now running. THANK YOU! You are a true GURU.
    It pumped up to 125psi then hissed and stop at 120psi. If there's no activities, the machine shut down till pressure dropped below 110psi then it fire up again to 125psi then hissed then stop at 120psi. Is this how it should behave? Or is there anything that I need to fine tune? The instruction manual does not say much.
    I'd like to send more reward but don't know how. Maybe a PP account?
    Again, thank you!



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You have a minimum pressure check valve (MPRV) leaking by. Depending on year model the mprv may be back in the cabinet. However based on previous experience i think your mprv is located near the separator tank top. Their should be an elbow out of the top of the separator tank,a short line then the mprv.It will probably have an aluminum cap. Some models you will have to replace the entire valve while others will have a repair kit available.If it has an aluminum cap, disconnect from power supply,bleed off all air pressure and remove the cap from the mprv. Their will be a spring,a piston with an o-ring on it, a small spring,a stem with a teflon seat. After removing the cap remove the large spring and if necessary use needle nose pliers to pull the piston out. This may prove to be be difficult because the piston may be stuck due to rust,dirt,rolled o-ring or all of it. I have had to remove the mprv and knock out the piston. if this is the case stop and just replace the whole mprv. If it comes out easily make sure you remove the small spring,stem with teflon seat next. Inspect the teflon seat for cuts tears etc. If good clean everything up especially the piston. Make sure not to damage the o-ring on the piston as they are hard to find unless you purchase a rebuild kit from IR.Next use a small cylinder hone and clean the bore where the piston travels. After all items are cleaned honed etc lube everything up with sil-glide. Assemble the mprv. your problem should be gone. Note: sometimes cleaning and lubricating is not enough and the mprv will need to be replaced

Posted on Mar 15, 2011

  • elunsford Mar 16, 2011

    I've never hear it called an orffice. Most of the time it's called a check valve or most techs call it the minimum pressure valve. This valve is set by spring pressure to hold air pressure in the separator tank. These units do not have oil pumps so the oil is moved thru the system by the air pressure. This valve typically is set to lift and let air into the system/tank at about 65 psi. Part # I found is 39490693. Beware, to make sure you have the correct part or kit you will need the model and serial #. There can be big differences between 1 year model like a 99 vs 2000.The flow direction is from the top of the separator tank to the after cooler if so equipped then to the receiver tank.This should not cause air to blow from the 1sv. The motor should not slow down. The sound will change between loaded and unloaded. While loaded the load of the compressor may slow the motor a few rpm's but it should not be that noticeable.I don't like to mix lubricates but as long as it's a polyglycol base it will be OK.

  • elunsford Mar 19, 2011

    No that's the way it should run. At set pressure it should unload. It should not start up until the pressure has dropped then again start back up. Please note that if the unit shuts down completely (motor stops) to many times in a 1 hr period the motor can be damaged due to heat . It will not have enought time to cool between starts. The motor should be able to handle 8 or less starts per hour. If I can answer any other questions just email back.



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