Metal, plastic and rubber safe general purpose lubricating oil?

It appears as though my Husky 20-gal air compressor is leaking through the pressure regulator. I've pulled the knob assembly apart, and there was a fair bit of grit and grime in there, so I've cleaned it all off. I do have some general purpose household oil, however it does not specify whether it is plastic and rubber safe, and I've learned the hard way about making sure lubricants ARE indeed plastic and rubber safe if I need to use them on such materials. I have two o-rings, a plastic part, and plenty of metal that are all in contact with each other inside of this pressure regulator assembly.

I've been around town, and have not been able to find any lubricating oils that actually state they are plastic and rubber safe...outside of silicon based products, however I've read too many things about how bad silicon can be if it gets into the fibers of your wood grain. It never comes out, and wreaks havoc with finishes. I've successfully managed to keep silicon OUT of my shop thus far.

Does anyone know of any particular brands of general purpose oil that is indeed guaranteed safe on plastic and rubber? This is after all the pressure regulator on an air compressor that can support up to 90 PSI...a degraded seal would be bad news. I have an Ace all purpose household oil, but it does not list any of the materials it is safe to use on. For some reason, none of the Home Depots or Lowes carry any of the general purpose oils anymore (only the mostly silicon-based spray solvents and lubricants). Ace has some, but none of them specify the materials they are safe on...

Thanks!

I just had to deal with a similar situation. Restoring an old device with plastic, brass and steel. I found a product called Tinkseal. It's a white grease. It will allegedly leave a nanofilm of lubrication on the metal or plastic. I found out about it from a friend that makes 3D printed gears. As I was researching Tinkseal, I found that is recommended for motorcycle wheel bearings. Usually find a rubber or plastic seal next to the bearing.

I suggest getting air compressor oil. It is normally safe for o-rings (neoprene) which the compressor uses. I got mine from Princesses Auto, a Harbor Freight or Tractor Supply type place. Probably overdue to do the compressor anyway.

Thanks @carlmorrell and @Curly. I should have thought of air compressor oil! Oh well. I guess since this is an oilless one, I haven't needed to do that.

Regarding Tinkseal...being a grease, I assume it is thicker than oil? I do have some synthetic SuperLube grease, but I was wary of using that as I wondered if it would make any moving parts harder to move. I also just found a bottle that I have of SuperLube O-ring oil. Its compatible with plastic, rubber, metal, etc. I don't even remember buying this, and it may be a bit old (it wad buried in a box in a corner of a closet in my craft room) but...I think for now it will do. I am curious about the Tinkseal though...I have other use cases where that might be just the ticket.

I used it where there was previously grease. Not an expert at all. I needed it on a long steel rod, with a brass sleeved plastic transport for a linear tracking turntable. I also used it where I would normally use oil, with the expectation that it would not be reoiled for another 40 years!

It reminded me of some lithium grease I've had for years to lube up r/c transmission gears. Perhaps only because of the color. Definitely not like the mobil-1 grease use for engine assembly (motorcycles). Never had an issue with bearing seals using M1. But who knows what I will use next time I need to pack bearings.

Yeah, I guess if you only need to do it every 40 years or so...

Alrighty! Pressure regulator fixed! Seems to work better than it ever did now...it used to be a bit hard to dial in a particular pressure, but now it seem to work like a charm, very smooth and precise. Who knows how long this superlube o-ring oil will last. Its a bit thicker than normal household oil, but it seemed to do the trick. Probably not 40 years good, but I'm back in business at least.

Well, I guess none of that worked. Initially, when I add pressure to the output side, I hear a hiss until the pressure normalizes, then no more hiss. The problem I am having now seems to be that after I've reached the nominal pressure, the hiss stops for a short while, then slowly pressure from somewhere hisses out through the regulator exhaust port. Over time, if I don't do anything about it, that his gets louder and louder until its quite loud. I don't know where the pressure that is driving this hiss is coming from...but, the problem seems to be fairly severe now. I used to think it was my lines leaking, and I did fine a couple of swivel joints that were problematic. But, this is definitely a hiss through the regulator assembly...

Well, it seems as though all the seals are good. From what I can determine, the air is leaking through the pressure release path. The way this regulator is designed, the assembly with the pressure gauges has a central part with a rubber membrane. When the regulator assembly is tuned to higher pressure, a pointed nozzle in the center of the plastic part that contains a pressure sensitive o-ring pushes on that rubber membrane. So long as the pressure is at the regulated setting, then the nozzle and membrane seem to maintain good contact, and pressure is maintained. When you back off the pressure regulator, the pressure in the outflow side is higher than possible given the pressure of the nozzle on the membrane, and air passed through a hole in the center of the nozzle until equalization again. It seems, that even AT the nominal pressure, I have a small leak through that nozzle... The flow through that nozzle eventually exits through a small hole in the housing of the regulator assembly (behind the knob, with the knob is attached.)

It starts out slow. Then the flow seems to grow until its a rather loud hiss. As far as I can tell, the nozzle is undamaged. I've done what I can to clean off both the nozzle and the membrane. There was some very fine wood dust in there originally, but now it seems to be quite clean.

Don't know if anyone has any experience here. Any ideas, before I replace the whole regulator?

A year or two ago I replaced my entire compressor because of something like this. Mine had developed a problem with the Check Valve / Unloader which was an integral part of the regulator assembly. To replace it was going to cost me more than 80% of the cost of a whole new compressor, so I went that direction. I hope you can fare much better than I did. Best of luck - Dave

egnald said:

A year or two ago I replaced my entire compressor because of something like this. Mine had developed a problem with the Check Valve / Unloader which was an integral part of the regulator assembly. To replace it was going to cost me more than 80% of the cost of a whole new compressor, so I went that direction. I hope you can fare much better than I did. Best of luck - Dave

Click to expand...

Man, I hope that is not the case. This one set me back $375 only a little over two years ago...

I found a number of the regulators for Husky compressors on the home depot site. They ranged in price but were around $50-75. Problem is they don't seem to carry the one for this compressor. It also seems as though I may have to buy the entire manifold assembly to replace the regulator, as the membrane part is in the manifold...

I don't even understand why it is leaking. None of the parts appear to be damaged...but, within a few seconds of settling at my chosen pressure, I can start to hear a hiss, and within a minute or so its quite loud.

Is the hole in the regulator assembly housing a deliberately designed in , one , or is it just porosity in the casting ? Many years ago , the cheap pressure pot I bought leaked air in several places through the porous casting . Some thin CA blocked the holes , and it has been fine ever since .

1080Wayne said:

Is the hole in the regulator assembly housing a deliberately designed in , one , or is it just porosity in the casting ? Many years ago , the cheap pressure pot I bought leaked air in several places through the porous casting . Some thin CA blocked the holes , and it has been fine ever since .

Click to expand...

The hole is designed. It is part of how pressure is equalized when you back off the pressure, say from 70 to 60 psi, this hole is where excess pressure on the outflow side escapes until reaching equilibrium again. I guess I should take some photos. I had to deal with a couple of other things the last few days, but now that I'm back to it, the problem seems to persist. It is obviously worse at higher pressures, but even at low pressures, say 30 or 40 psi, I can still hear the hiss, so air is still escaping even at lower pressures.

Here is the whole manifold, with the regulator (sans knob) in the center.


The regulator screwed into place:


In the manifold is the "membrane" as I've called it. Pressure from the tank (inflow side) is held behind this, and the regulator's nozzle pushes it inward to allow airflow:


The regulator assembly removed. There is a small hole on one side that you can see here, which is where excess pressure from the outflow side is released when you back off, or reduce, the regulated pressure to the lines:


The housing with the spring that maintains (or at least, is supposed to maintain, maybe this is the problem) a reverse pressure on the nozzle part:

The nozzle part. There are several rectangular notches that allow pressure within the regulator assembly and outflow area to fill a groove in the o-ring here. So as the regulated pressure is increased, the pressure pushing the o-ring into the inner wall of the regulator assembly housing ALSO increases. I have not noted any leakage through the o-ring here...the o-ring seems to work fine, and the pressure-dependent nature of it seems to work fine (so long as the groove in the o-ring is facing the right direction, which should be to wards the manifold.) This is the part that has a nozzle that presses up against the "membrane" in the manifold assembly, with a hole in the center that I believe is where excess outflow pressure backflows when you reduce pressure:


Sorry for the potato quality, was having trouble holding my phone here (I think I had it on macro zoom, which exaggerated any motion). A top-down view of the hole in the nozzle that presses up against the membrane to release pressure from the tank, into the outflow (which connects to up to two different hoses). The hole is by design, IMO, as its where excess pressure from the outflow area is released when the regulated pressure is reduced:


A view of the back side of the same part above. The larger circular part in the middle, fits perfectly inside of the spring that resides in the regulator housing:


Air flowing through the hole here, then escapes the hole in the side of the regulator housing as shown in an earlier photo. I've simply arrived at the function of how this regulates pressure by examining all the various parts, as I've spent a good while now trying to figure out WHERE the hiss was coming from, and how and why the air was escaping. I'm pretty sure its the front of the nozzle where it contacts that membrane. I think air is escaping from that...interface, of plastic to rubber. It seems to happen regardless of pressure (unless the pressure is around say 25psi or less)...but, at higher pressures (say 100psi) then the problem is certainly worse, the hiss is definitely louder.

The odd thing is, when I first choose a pressure by turning the knob (which moves the white plastic part here, with the grooved o-ring, in and out of the regulator housing...I guess I didn't show it, but below the spring is a small metal plate with a dome in the middle, and behind that plate is the screw that attaches to the knob. Twisting that screw/knob moves the plate in and out, thus moving the plastic part with the nozzle in or out of the manifold housing...which of course pushes that green membrane further in or out.) Anyway, when I first set my pressure, there is no hiss, and it seems stable. It can take anywhere from a few seconds to a minute or so, before I start to hear a hiss, and that hiss progressively gets worse and worse, until its loud enough for me to hear over some other tools in my shop, including turning on my lathe. The shop vac covers the hiss, but almost always now when I turn the vac off, I hear that hiss of air escaping through the regulator. I've been trying to turn without air...which is actually surprisingly challenging!! I never knew quite how much I relied on having pressurized air to clean up my workspaces and all.