5520-SA – Spring, 5520, FS30, 17-7 STN.

The AqMatic 5520-SA Spring (FS30, 17-7 stainless) is a replacement compression spring used in 5520-series diaphragm valve assemblies, designed to maintain proper internal tension and valve response during operation.

This spring is manufactured from 17-7 stainless steel, a material commonly used in valve internals for its strength, corrosion resistance, and ability to maintain consistent performance under repeated cycling. It plays a critical role in diaphragm valve function by assisting with return force, positioning, or fail-safe operation depending on the valve configuration.

The FS30 designation corresponds to a specific spring profile used within 5520 valve assemblies. These valves are part of AqMatic’s thermoplastic and isolated bonnet platforms, where internal components like springs, diaphragms, and plates work together to control flow and sealing performance.

This component is typically replaced during valve rebuilds or maintenance cycles, especially in high-cycle systems where spring fatigue can impact valve timing, sealing, or responsiveness.