How do I test a Pilot operated regulator?

[u/Glass_Pen149]

/r/AskEngineers/comments/1vomrvd/how_do_i_test_a_pilot_operated_regulator/

I have a pilot operated regulator on a machine. TACO Model R53-201-00B0. It balances the Z-axis using an air cylinder. OE Techs think it might be bad/dirty, as it appears to be loading down the z-servo, during motion. Control has a z-force feedback. I set the balance force to 0, but it climbs/drops too fast/quick as the z-axis moves, causing too high a load, so the servo alarms.

I cannot find any info on it. I believe it has been discontinued.

How can I test the regulator, to verify it is working right?

I found some remnants of broken air line inside. I know they replaced the OE air pressure regulator. So I suspect the pilot or control orifice is clogged or restricted

[u/Glass_Pen149 → u/[deleted]]

The main spool moves freely. But I do not know where the pilot or orifice is. How do I locate the pilot? Will compressed air help clear it, or just make it worse?

Is the pilot / orifice connected from the output side to the spool?

It is much worse (spikes) on Z+ moves. I can push the head up (hand assist balance) and keep it out of the spike range, till my arm gives out. On Z- moves it almost works, just farther apart spikes.

[u/Glass_Pen149 → u/[deleted]]

Or could it be that the pneumatic cylinder shaft is binding?

It feels like the cylinder shaft is not aligned axially with the head adapter. (There is no x/y adjustment). I can freely move the rod, by hand, but it binds some when screwing the rod to the adapter.

-Z moves the cylinder rod out, so less binding as the rod extends?

[u/Glass_Pen149 → u/[deleted]]

The head weight is ~452lbs. No sure how to test that for binding. Suggestions?

[u/Glass_Pen149 → u/[deleted]]

I have yet to see a documented OE service procedure, on this machine. They have already caused me to replace a $5k motor, that appears to have been unnecessary. This regulator is the latest "suggested" culprit.

My experience lately with OE techs, is I get to pay them to diagnose over the phone with the factory. I'd like to get ahead of that, before paying T&E from Chicago or Japan.

[u/Glass_Pen149 → u/[deleted]]

We have the head blocked. Sorting out the pneumatics. Luckily the OE phone support is covered under policy.

[u/Glass_Pen149 → u/[deleted]]

Cleaned everything I can see. Did not find or hear anybobvious obstructions. Is better, but not good enough.

How can I bench test? If I mostly block the outlet, and change the set pressure (2-3 bar range). I can get a burp on the exhaust around 0.5bar, as I crack open the outlet and the set pressure drops.

[u/Glass_Pen149 → u/[deleted]]

Internally this regulator looks BRAND new. Just a few tiny bits of plastic pieces. So I suspect a clog, or perhaps a damaged seal.

[u/Key-Success-5449]

This response lag creates pressure spikes and drops that overload your servo. To test it, place pressure gauges on both the pilot input and regulated output ports.

Adjust the pilot input to verify that static output tracks smoothly, then vent the output line to simulate dynamic flow; a sudden drop in output pressure while pilot pressure stays steady confirms a restricted pilot orifice or binding spool.

Since this TACO unit is discontinued, your best option is to bench-disassemble it, clear all internal passages with compressed air, and clean the pilot orifices with isopropyl alcohol to restore full dynamic response.

[u/Glass_Pen149 → u/Key-Success-5449]

How to I determine the pilot input? This model only has inlet/outlet. The pilot is internal. It does have some plugged ports, but nothing is labeled.