Just Ask Gus
Your motion control questions answered by the Neenah retail store manager, Gus Zielke. E-mail Gus your question.

Q: How do you help customers determine the right hose and fitting to use?
 
A: I use the acronym "STAMP," which stands for SIZE, TEMPERATURE, APPLICATION, MEDIA and PRESSURE.

I use a caliper - not a yardstick! - to measure the outside diameter of the male thread to determine SIZE. TEMPERATURE is always determined so the correct seal and fitting material is used. A discussion of APPLICATION is critical to avoid corrosion. Understanding the MEDIA conveyed through or around a component provides answers to what material should be used. Plastic fittings, tubing and hoses may hold up better than metal. PRESSURE should be equal to or higher than a system`s pressure.

Tube fittings, tubing and hoses are customarily rated at a 4:1 design factor, so a hose with a rated working pressure of 5000 PSI will have a burst/failure rating of 20,000 PSI. After the STAMP is discussed, I have the right solution for the hose and fitting challenge. 

Q: How do you properly preset a tube fitting?

 

Presetting can be accomplished by three different methods: in the fitting body, with a hardening presetting tool, and by means of a hydraulic or mechanical axial load. Do not use a fitting body for multiple presets and make sure the final assembly is made in the same body that was used for presenting.

 

Presetting in the fitting body is usually acceptable for smaller-sized fittings such as 20mm and below. The threads of the fitting body and other contact surfaces are lubricated prior to hand assembling the components in proper orientation (tube, nut, ferrule). Nuts should be tightened to manufacturer`s recommendation from the finger-tight position. You should mark the initial and final positions of the tube nut. After initial tightening, the nut is removed and the ferrule and tube are inspected for proper bite, tube insert and grip.

 

Presetting in hardened body is accomplished the same way as presetting in the fitting body. The advantage of the hardened tool is that it can be reused many times without excessive wear and expansion.

 

Presetting with hydraulic or mechanical equipment is preferred for large-sized fittings or large quantites.  The nut, ferrule and presetting die are assembled in the tube in proper sequence and orientation.  A hydraulic or mechanical axial load is then applied. 
Q: How do you properly inspect a preset fitting?

If there is a slight indentation around the end of the tube that indicates the tube was bottomed in the tool or fitting during the presetting. If evident of this complete contact is not visible, the ferrule may not be properly preset.

Steel ferrules should not be capable of moving back and forth along the tube beyond the bite area. A stainless steel ferrule will move more than steel because of its spring back characteristics.