Rapid Search

Find SPIROL products fast.

Optimal Application Engineering

Design the most cost effective fastening solution.

Your Location

For best online service, please change location if not correct.

Your Language

Please select your preferred language.


Figure 1. Center component friction-fit hinge design. (A Lever, free-fit. B Rod, friction fit.)

Figure 2. Center component free-fit hinge design. (A Lever, friction fit. B Rod, free fit. Pin can expand. Expansion helps lock pin in place.)

Coiled Spring Pins
Application: Pressure Relief Valve

SPIROL 420 Stainless Steel Coiled Spring Pins are used in pressure relief valves to secure lift levers relative to pull rods.  These valves are used to regulate temperature and pressure in residential water heaters and storage tanks.

The flexibility of the Coiled Pin enables a friction fit engagement with the rod and a free fit with the lever.  Since the rod provides more engagement length than the lift levers, it is better suited to be used as the friction fit portion of the hinge (Figure 1).

When properly employed, this spring feature of the Coiled Pin can be used to design better free-fit and friction-fit hinges as well as improve retention and reduce the incidence of lateral movement.  This not only provides the proper “feel” of the hinge, but can also help ensure that the pin stays in place due to the “ballooning effect,” as shown in Figure 2.

In addition to excellent balance of strength and flexibility, another benefit of SPIROL’s Coiled Pins that is essential to many pressure relief valves, is that they come standard in various types of stainless steel.  This provides the necessary corrosion resistance required by many pressure relief valves since they are can be exposed to water.

Even though the pin is often one of the smallest and least expensive components in an assembly, it is critical to design in the optimal pin configuration to ensure proper operational and functional excellence at the lowest installed cost.  With over 65 years of technical expertise related to joining and assembly, SPIROL is well positioned to assist with design of the pin to ensure our customers’ parts go together and stay together for the intended life of the assembly.

Our staff of engineers will review your application needs and work with your design team to recommend the best solution.  One way to start the process is to select Pinning Applications in our Optimal Application Engineering portal.