Stainless steel fittings exhibit many desirable properties, but a common problem is seizing or pick-up on assembly or disassembly, also known as galling.
Galling is thought to be caused by cold welding of the high points of clean, oxide free metal left when the oxide film is dislodged by surfaces rubbing against each other, especially when threading mating parts of the same grade and surface hardness.
Due to the extreme hardness of stainless alloys and the issues regarding galling, the sealing of stainless steel threaded connections can be much more challenging than when working with brass and or bronze alloy fittings.
In this blog, we have included information that will help greatly reduce the problems and frustration that first-time users of stainless fittings and accessories sometimes have.
The information below explains the issues with sealing stainless to stainless thread connections, and will greatly reduce the learning curve, ensuring a smooth transition into using stainless steel products.
There are specialty tapes and thread seal compounds that must be used to avoid galling or seizing of the threads caused by oxidation. The use of both together is a proven technique for a leak-proof connection.
Gray Stainless Steel PTFE (Polytetrafluoroethylene) Thread Seal Tape
PTFE tape has been a fixture in many tool boxes for years. It continues to be a very reliable thread sealing solution for water systems and many other plumbing applications.
Specially formulated tape is required for sealing NPT thread connections, gray in colour, a nickel pigment is added for use on all stainless-steel fittings. It is specially designed to prevent galling, seizing and corrosion.
A quality tape with a high-density rating makes this tape an excellent product for sealing coarse stainless steel pipe threads.
For more information on different thread sealant tapes, check out our blog, Thread Sealant Tape: Where and How to Properly Use it.
DIRECTIONS FOR USE:
- Use ½" wide tape dope.
- Place the end of the tape on the first thread, do not extend past the end of male pipe thread. Hold the end in place with your thumb and wrap the tape in the opposite direction to the direction the male pipe thread will be turned into the fitting. Make sure to keep the tape under tension as you are wrapping so it molds itself into the root of the thread.
- When using 3.5 or 4.0 mil tape, wrap three revolutions, A thinner 3.0 mil tape may need four to five full wraps around the pipe.
- Make up joint in a normal manner.
Note: If the threads are damaged or poor quality, it may require more than three wraps of PTFE tape.
Gray Magic Pipe Thread Compound
This thread compound is an all purpose, non-seizing, industrial grade thread sealing compound that produces a leak-proof seal on all types of plastic and metal including stainless steel threaded connections having superior anti-galling properties.
This slow drying, soft settling, non-hardening pipe thread compound is lead free, non-toxic and used for sealing threads on all types of metal. Ideal for stainless steel threads which are more difficult to seal but can also be used for sealing plastic pipe fittings including ABS, PVC, CPVC, Poly and Nylon.
DIRECTIONS FOR USE:
- Wear gloves and eye protection.
- Clean dirt, grease, excess oil or any foreign material from threads (Gray Magic adheres to oily threads).
- Stir well before using.
- Brush liberally onto male threads.
- Make up joint in a normal manner.
NOTE: Store in a cool, well-ventilated place. Keep container tightly closed.
In Conclusion:
To ensure leak-proof connections in stainless steel it has been proven and is highly recommended that the installer first wraps the pipe threads with two or more thicknesses of Gray Stainless Steel PTFE Thread Seal Tape then apply Gray Magic Pipe Thread Compound over the tape. This is a practice that is necessary on large diameter stainless pipes 4" and up. It has been proven to be very effective in preventing leaks in all sizes of stainless steel threaded connections!
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