In the world of pumps, valves, and fluid control systems, every connection counts. The right fasteners, coatings, and sealants can make the difference between a leak-free assembly and costly downtime. In this edition of Ask the Expert, Endries engineers address some of the most common questions from pipe and valve OEMs—from torque specs and sealant selection to corrosion prevention and vibration resistance—helping manufacturers build reliable, high-performance systems designed to last.

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Is there a recommended torque specification for connecting pipe fittings?

There is a common misconception that, like other threaded hardware, there’s a specific tightening torque, or that because you’re trying to contain liquids and gases, tight is good but tighter is better; that’s not how pipe threads are designed.  The general rule is to tighten the fittings by hand to “snug”, then use a wrench for another ¼ to ½ turn (potentially 1-2 turns for black pipe or similar connections).  It is suggested to use a thread sealant product, like PTFE tape, liquid sealants applied at the time of assembly, or pre-applied options.  It is also suggested to use a second wrench to prevent the rest of the assembly from spinning.

What types of thread sealants are available for PVF connections?

Thread sealants vary based on temperature, pressure, and chemical exposure. Common options include:

• PTFE tape: Ideal for low-pressure systems and easy to apply.
• Anaerobic liquid sealants (e.g., Loctite): Excellent for high-pressure and vibration-prone environments.
• Pipe dope compounds: Useful for metal threads in high-temperature applications.
• Loctite Vibra-Seal Orange:  Common pre-applied sealing compound, resistant to various chemicals and temperatures.
• Nylok Precote 5:  Pre-applied sealing compound, comparable to PTFE tape.
• ND Industries Sealant Options:  ND Industries has several pre-applied sealing options that range from the ST-3 series that’s comparable to PTFE tapes, to reactive options that mix together upon assembly to create high pressure seals for gas and fluids.

Our team can help you select the right sealant based on your specific operating conditions and materials.”

How do I prevent galling when using stainless steel fittings?

Galling is a common issue with stainless steel, caused by the breakdown of the outside oxide layer due to friction/heat. To prevent it:

• Use a lubricant during installation.  Most PTFE tapes, liquid sealants, and pre-applied sealants have a lower coefficient of friction to resist galling. 
• Avoid over-tightening; follow proper assembly tightening.
• Slow down.  Hand tighten the fittings and use a hand wrench to finish tightening. 

We offer pre-applied sealants, that will not only seal the connection, but decrease the thread friction.

Are there specific coatings or platings that improve corrosion resistance for fasteners in wet or chemical environments?

Yes, coatings play a crucial role in extending fastener life. Some popular options include:

• Zinc plating: Economical and suitable for mild environments.
• Hot-dip galvanizing: Great for outdoor or submerged applications.
• Xylan or PTFE coatings: Provide chemical resistance and reduce friction.
• Nickel or chrome plating: Used for aesthetic and corrosion-resistant purposes.

We can help you choose the best coating based on your environment and budget.

What are the best practices for selecting fasteners for high-vibration applications like pump and valve assemblies?

In high-vibration environments, fasteners can loosen over time. To mitigate this:

• Use lock washers, nylon-insert lock nuts, or prevailing torque nuts.
• Consider pre-applied thread-locking adhesives for added security.
• Opt for flanged bolts to distribute load and reduce loosening.

Our engineers can assist with vibration-resistant fastener suggestions tailored to your assembly needs.