Comparison of the C20 and C60 Pressure Regulating Valve Designs

Wanner^® builds sealless positive-displacement pumps - Wanner Hydra-Cell Pro^® - from a fraction of a GPH to more than 150 GPM at 30 to 5,000 PSIG. A pressure regulating valve is the usual accessory so discharge pressure cannot exceed the pump or piping rating. This article compares the two Wanner^® designs: C20 and C60.

Pressure Regulating Valve Design

These valves keep a positive-displacement pump from exceeding the maximum discharge pressure you set. Wanner valves have three ports: inlet, outlet and bypass. Inlet and outlet are 180° apart (in-line). Bypass is 90° off that line. The valve can sit in horizontal or vertical pipe. Normal flow is inlet to outlet, with little or no flow out the bypass.

A plunger is held on a metal seat by spring load, so the bypass stays shut. When system pressure is high enough, that load compresses and the plunger lifts, sending liquid out the bypass.

The plunger only lifts far enough to pass the excess and hold the set pressure. “Regulating” and “relief” get used as if they were the same part. A relief valve usually means it opens fully at the set point and dumps the whole flow.

All but one Wanner model uses stacked spring discs — slightly concave washers — instead of a coil spring. That stack gives a steadier adjustment and lasts longer. Pressure range is set by how many washers you stack, the order, and the thickness.

C20 was the first Wanner regulating valve. C60 is the later design, introduced a little over 20 years ago. Both give an adjustable range, immediate response and chatter-free bypass.

C20 Series

C20 valves use O-ring seals on the plunger so liquid cannot get into the washer stack at the top of the body. Those rings wear with cycle count and with abrasives in the liquid. Leakage then weeps out the top of the valve.

The plunger and seat also wear and will eventually leak through the bypass. Both parts are available in erosion-resistant materials.

On high-pressure water, oversizing pump flow by about 10% keeps the plunger slightly off the seat. That cuts metal-to-metal wear and knocks down the spike that occurs when the plunger first lifts. On abrasive liquid it is usually better to size the pump with no bypass in normal running, and let the valve move only on upsets or cyclic pressure changes — a plugged spray nozzle, for example.

Bodies are oversized to keep pressure drop — and wear from abrasives — down. When the liquid is very abrasive, install the valve off-line: tee the discharge, pipe the tee branch to the valve inlet, and plug the valve outlet. Liquid then goes through the valve only when system pressure exceeds the set point.

C60 Series

C60 valves work on the same three-port, spring-disc principle. The difference is the plunger seal and a simpler parts list.

Look at the two exploded views. The layout is the same except the C60 uses a diaphragm seal and the plunger guide is part of the plunger, so there are fewer pieces to wear or replace.

The diaphragm is the same idea as a Hydra-Cell Pro diaphragm: a built-in convolute lets it rise and fall with the plunger without fatigue cracking. The outer edge is clamped between the upper and lower body halves — a static seal — so abrasives do not cut a leak path the way they do on a C20 O-ring. On a C20, hard particles get between the O-ring and the plunger guide sleeve and cut the ring.

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