SM 11 the back pressure Error is preventing me from starting

by Josh
(Australia)

SM 11

SM 11

SM 11
SM 11 gauge closeup
SM 11 air compressor
SM 11 gauge and plumbing

Hi Carl these are the Picture of the unit im having trouble with

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Kaeser SM11 Back pressure error

Kaeser SM11 compressor with dryer on a tank

Kaeser SM11 compressor with dryer on a tank

Can I get some help on what to look for to solve a problem with my SM11. When I turn the compressor on it starts up then stops, gives a back pressure error, then goes to idle.

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Sep 13, 2015
Venting
by: Carl

Ive only just seen this problem on here so I may be a little late but for future reference, the back pressure fault occurs when pressure in the separator tank (where the oil goes) doesn't vent, or doesn't vent quickly enough.
There can be a few reasons for this..

1. The vent valve does not activate and holds pressure inside the separator (look at the pressure gauge that should be on the sep tank to see if it is holding pressure or just slowly going down). Either replace the vent valve (Brass valve with solenoid attached, on top or on the side of the sep tank)

2. The above solenoid I mentioned above, is the more likely fault, replace the complete solenoid to fix

3. Inside the vent valve the diaphragm can inflate and stop air from venting (This happens very rarely though). This diaphragm can also perish and cause the compressor to constantly vent. Either way its worth replacing)

4. MPV (Minimum Pressure Valve) could be sticking open, service kit is available for this. PLEASE GET A QUALIFIED ENGINEER TO REPLACE THIS, THEY CAN CAUSE SERIOUS HARM IF DISMANTLED INCORRECTLY!

Hope this helps

Carl

Oct 11, 2014
seperator?
by: Anonymous

Looks like you can get to it from the top - it's hinged on the large air filter side.

Not positive, as I don't have a manual.
You should have one - if not I suggest you get one.

Oct 10, 2014
Think you are right
by: Jay

The compressor needs a good maintenance. Had to break down and call in a service company. I think you are probably right, it's a filter. How do you get to the separator filter?

Oct 10, 2014
Back pressure error
by: Anonymous

I am having the same problem. But the filters haven't been chancged for 9-12 months.

Oct 10, 2014
back pressure
by: Doug in s.d.ca

Not much to go on.

Sounds like a separator or filter problem.

Have you been doing regular service?

Do you have the manual?

How long has it been in service?

New or second-hand?

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SM 11 has back pressure Error

by Josh
(Australia )

I have an SM 11 And the back pressure Error is preventing me from starting.

I have bought this second hand and it was running fine when i picked it up when i get home the error comes up as soon as i turn the power on.

I have changed the 3 phase around to change direction with no difference

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Oct 08, 2015
Fault code
by: Carl

Actually, thinking about it, i cant see the number on the bottom line of the screen? What number or letter is it showing when you turn the power on?

Oct 08, 2015
Controller
by: Carl

Hi again,
Thanks for the photo. Sorry, i may have misunderstood, it looks like, as you said, the back pressure fault is as soon as you turn the power on, not when you press the start button. I can see on the screen of your Sigma basic controller the bottom line is illuminated.
Does it let you reset this by pressing the reset button (reset button is the red "Stop" button) if if it doesnt let you reset then i havnt seen that before, are all the electrical connections in properly? The connection into your vent valve? (Brass component attached to the separator with a hose going to the air filter) if all these connections are ok then you may have a problem with the controller itself which could mean you may need an HPC engineer to come along to look at it to "K-load" it which mean taking all software off and putting back on again. Or a new controller.
Let me know how you get on
Carl

Oct 04, 2015
Vent
by: Carl

Hi,
Im guessing you have a sigma 1 controller fitted and it has the words "back pressure" on the screen as opposed to a number on the bottom row of the screen as you would with a sigma basic controller?

Either way, the back pressure error is indicating that you have pressure in the separator tank (where the oil is).

Do you have a pressure gauge on this tank? If so then it should read zero on start up.

Attached to the separator tank is a combination vent valve where you should find a little ball valve which is used for keeping pressure in this tank and firing out the oil when you have an oil change.

Check that this valve is open or you will get the back pressure error.

Secondly, inside that brass vent valve i mentioned is a rubber diaphragm, it has been known for this to inflate so will not let the separator vent, replace the diaphragm (it comes in an intermediate service kit along with air filter, oil filter and filter mat)

Finally, again with the vent valve, do you have an electrical connection to it? Make sure you have voltage going to it?

How old is your machine? If you could post a few photos of the machine and the vent valve/separator it would help a great deal.

Try all the above and reply to this post to let me know if it fixes it.

Many Thanks

Carl

(To add pics to this post, start a new thread in this forum, and tell me to add the pics to this one: SM11 has back pressure error, and I will do so. Bill)

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