Tuning Synthetic Grease for Air tube/bottle threads

[dutoitk]

Decided to start a new thread with relation to this topic

https://www.airgunnation.com/topic/do-not-use-superlube-grease-for-pcp-handpump/

I had been using Superlube multi purpose grease with PTFE (21030), but stopped after I read about the original posters issues with his Hill Pump.

I sent an email to Synco technical support and they recommended not using it with high pressure.



What I have picked up from there Technical data sheets and SDS.

21030 Multi purpose with PTFE: Fire rating 1. Not for pure oxygen environments. For use in almost all applications including metal to metal and orings.

92003 Silicone with PTFE: Fire Rating 1. Less applications. Mostly plastic, rubber and metal to plastic.

93003 Oring Silicone grease: Fire Rating 1. Orings, seals etc.

The fire rating of these worries me.



What type of synthetic grease can one use on the threads of air tubes and buddy bottles to prevent damage or premature wear of the threads. If not lubricated, the threads take a lot of wear when changing air tubes or bottles.

From personal experience, I now know that silicon grease does not work as it causes seizing. Is there a non-flammable product on the market that can safely be used on threads in high pressure areas.



Thanks

Kevin

 

[nervoustrig]

Krytox or Ultimox. I see in the other thread you’ve already ordered some.

Silicone-based lubricants are great for where plastic or elastomers run against metal but nearly worthless for metal-on-metal, so I’d skip those types. Even ones that are blended with something that’s supposed to make it a “do everything” lube. Invariably the result is a compromise and performance is sacrificed for convenience.

 

[dutoitk]

Just ordered KRYTOX 205. Looks like it will do the job.

Now for the wait. Mail order goods from America to South Africa take weeks to get here.

That is if someone does not help himself to it when it arrives at customs.

 

[elh0102]

For those specific threads, clean and dry is fine, no lube needed. That advice comes from a well regarded high end rifle maker.

 

[bchannell]

Although I do use SuperLube syn grease for the threads on my air cylinder, I'll probably stop after seeing this. The threadds are outside the high pressure area of the gun, which is sealed via an oring on the tip of the threaded stub, but still it just doesn't seem like a great idea. I will be ordering some Krytox for that. However, I know that not lubing, "at least the threads on some guns" bottle threads can lead to ruined threads, (don't ask how I know this), so I will be lubing them with something.

 

[Airgun-hobbyist]

For those specific threads, clean and dry is fine, no lube needed. That advice comes from a well regarded high end rifle maker.

After having discovered through error that silicone grease will seize high pressure threads, I like reading this advise.

 

[nervoustrig]

An open flame test confirms the Super Lube #21030 will indeed ignite and sustain a flame.



The annotated photo explains my observations compared to a basic silicone dielectric grease.



Bear in mind this is a deliberate apples and oranges comparison. The silicone grease is worthless as a metal lubricant. And the fact this particular flavor of Super Lube will burn is not a knock against it, just an observation that it should be used with caution if a source of ignition or extremely high temperatures are present. Per the technical data sheet, it has a flash point >428F (220C) and a fire point >572F (300C).

How or why any of these conditions would exist in a high pressure pump or PCP is beyond me. Years ago, before I knew any of this, I used it in a Benjamin pump rebuild. It gave me no issues, working until the final stage O-ring gave up the ghost. I didn't use it again for this purpose, not because of the flammability concern but because of its viscosity. I spoke to Duane Sorenson of Sun Optics who advised cleaning out all the old lube and using a good synthetic motor oil. In other words, the guy who designed the pump said use a lubricant with virtually the same flammability ratings as the Super Lube synthetic grease. So I did and I had no problems associated with the lube.

That's not to say I think either of them are great choices for that application, just that the technical data and my experiences do make me wonder if we are missing a critical piece of information when someone says they had a hand pump ignite. Granted, nowadays I only use 30W silicone oil in hand pumps or any dynamic O-rings in an air rifle. It works well, lasts a long time, and won't ignite. Good enough for me. For static O-rings, I use the dielectric grease above. Cheap and effective.