What would actually happen if teflon tape flaked off into the hydraulic system?

Magicman710 · Feb 26, 2018

I know that teflon tape is a general "no no" when it comes to hydraulic fittings.

Nevertheless, I know several implements that I have came from the factory or dealer with teflon tape used on the fittings for various implements. Usually, if I have to install or repair a fitting, I use Rectorseal which I always have on hand. I've always assumed that a pipe dope like rectorseal wouldn't cause as much of a problem if it was to get into the system, since it is more of a thick pliable paste than a solid piece of tape.

I guess my main question is what exactly would happen if some of that tape did ever break off? I usually hear that it would "damage the pump" or that "it would block a passage in the spool valves". I'm not very familiar with the precise inner workings of a hydraulic system, so I don't really know what all of that means. How would you know if it did happen? Would you have a reduction in pressure? Overheating fluid? The 3 pt or SCV's not working?

Does anyone have any first hand experience?

BHD · Feb 26, 2018

most of the time if teflon tape does cause a problem is not the first use but when something has been taken apart and reassemble, the tape shreds in to threads and bits, and can get in to the system if not careful,

most of the time it will block a port or jam a spool, and usually a real B$%h to find and to remove, the tolerance in a lot of hydraulic systems is only a few thousands most of the times there are not rings or seals in the system just very very close fit of parts in pumps and valves,

for the fun of it: take a (not in system) but a fitting and tape it up and then assemble it, disassemble it and reassemble ti and see what the old tape does, just do this on some spare fittings on the bench, and get some hydraulic oil on the tape, when you disassemble it,

ultrarunner · Feb 26, 2018

The first serious problem I encountered with Teflon was a neighbor had just picked up his car from having it dealer serviced...

Gasoline was pouring out everywhere as the carb float was stuck OPEN

The dealer had wound the tape the wrong way and enough of it got into the fuel bowl to prevent the float valve from closing.

I was around 17 at the time and fixed it for him... having seen what can happen it made me more meticulous in my work.

Still amazed a New Car Dealer Service Department could send this out the door.

IceStationZebra · Feb 26, 2018

What can happen all depends on the system. I simple system like an old tractor with open center valves and a forgiving gear pump probably wouldn't even notice. And if it is on an implement the oil normally has to go thru a return filter and will get cleaned out before it get to the vital parts. But take a late model system with a variable displacement pump and electronic valves and you are asking for trouble.

My practice and recommendation is avoid pipe fittings except for some large return lines. It is difficult to tell a customer how tight to tighten pipe fittings, much less taper thread like NPT. Plus you can't clock elbows. If you look at a product from a top tier OEM like Deere or Case you will be hard pressed to find any NPT fittings except maybe grease lines or engine sensors.

And just put enough sealant on to fill the threads and leave the first one dry. If you have so much on you are getting globs inside the system you have way too much. NPT threads form a metal-on-metal seal, the sealant or tape just makes up for any imperfections.

And if you have to use tape make sure you wrap it clockwise when viewing the fitting so it wraps tighter when you assemble the joint. Otherwise you get the same situation Ultrarunner ran into were the tape unwrapped.

ISZ

MHarryE · Feb 26, 2018

Prior to production release I had 30 pilot machines running with customers. Had a 70% failure rate of the steering units - leaking, small leaks but on pilot production any leak needs to have cause determined and solution validated prior to full production. Drove us crazy as one failed 3 units. Supplier tear down found they all had small pieces of Teflon in the steering wheel shaft seal. Then try to determine where the Teflon originated which meant visiting every component supplier. No luck. Finally go to our assembly line and have a sit down with our assembly mechanics. They told me an industrial engineer trying to cut assembly time came up with the Teflon tape idea for the single pipe thread fitting in the system. I had a sample of the tape they used sent to our lab - spectrograph analysis proved it to be a match for the material stuck in the seals. The 3 failure machine - once in the system there's virtually no way to get it out.

LD1 · Feb 27, 2018

Lots of small passages, metal to metal seats, reliefs, load checks, etc that tape can foul up.

If it hangs in the seat of the pressure relief valve....your tractor won't make rated pressure and hydraulics will be weak.

If it hangs in a spool valve, it can cause cylinders to drift under gravity (like a worn valve would) or can completely jamb it up where it won't move. Because spools are usually clearances not in thousandths of an inch, rather tenths of thousandths.

Threads can also foul up the couplers and have them leak when not in use.

Loader valves have load checks to prevent dropping loads when feathering. Have a load on the loader and want to raise real slow....feathering the valve.....with a sticking load check instead of going up slowly....the load goes down quickly

dannoGT · Feb 27, 2018

I would agree with LD1 with comment on valves most late model machines have valve spools that are machined to extremely tight tolerances and they just cannot handle any foreign objects in the oil

Thomas · Feb 27, 2018

If you really...really need to use Teflon start 3 threads back wrap darn good in tight.
Teflon in spool etc.equals bad headache.

LD1 · Feb 27, 2018

dannoGT said:
I would agree with LD1 with comment on valves most late model machines have valve spools that are machined to extremely tight tolerances and they just cannot handle any foreign objects in the oil

Yes.

Human hair is about three thousandths. (0.003")

A three ten-thousandths clearance (0.0003")....that's one tenth the size of a human hair.

When people complain about their loader drifting down.....there are no seals in the valve. This very tight tolerance.....metal to metal.....is the only thing sealing the oil. So yea....a small shard of Teflon stuck in a .0003" clearances bore....causes problems.