Why do people keep torqueing spark plugs dry on turbine engines

I pulled six plugs out of a PT6 last week that were so seized I had to helicoil two holes. Stop using anti-seize on turbine plugs, the torque spec already accounts for a dry thread. Has anyone else seen this cause more damage than it prevents?

2 comments

2 Comments

the_amy5d ago

Dry torque spec is the spec, plain and simple. Anti-seize throws the friction value off and you end up clamping way tighter than intended, which is exactly how you get galling or cracked holes. Just run them clean with a tap first and follow the manual, saves everyone the helicoil headache.

max8085d ago

Take that same logic to something like putting new lug nuts on with a torque wrench you trust, the difference between dry and lubed threads can be 20% or more on the final clamp load. I've seen guys snap studs just because they put a dab of grease on the threads thinking it helps, when really it just makes the torque reading lie to you. Same goes for head bolts on older engines where the manual actually specifies oil on the threads, you follow what they say and don't get creative. It's like anything else, stick to the standard method unless the engineer wrote a different one for a good reason.