Previous posts have been focused on sanitary positive displacement pumps, specifically Waukesha’s External circumferential piston pumps, the Universal 1 and Universal 2. We’ve also spent some time discussing different valve types and functions. Today we will focus on sanitary relief valves, their purpose, and the products we offer.
What distinguishes a positive displacement pump from a centrifugal pump is the constant volume that a PD pump displaces, regardless of discharge conditions. PD pumps do not abide by the affinity laws. We do not see diminished output at increasing head pressures. Instead, when someone closes a valve downstream of a PD let’s, we see the pump continue to perform until something gives. In a sanitary piping system, this is often times sanitary flanges (if you’re lucky). Other components likely to fail include the pump itself. The high torque and differential pressures associated with dead heading a pump can get so high that the pump shafts can snap.
In order to protect a PD pump from dead heading, external over pressure relief valves are used. When a relief valve is used, if the pump discharge pressure exceeds the set cracking pressure, the valve will open to a relief path. The spring in the valve actuators are adjustable and users set the desired relief cracking pressure right at the valve by simply turning the adjustment screw.
The simplest way relief options are offered are with Waukesha’s 60R series of manual relief valves. These are “T” body valves with a manually adjusted spring. Seat metals include both Teflon and metal seats, with the ladder used at higher pressures. They are available with both 50 lb., 100 lb., and 300 lb. springs. The drawback to the manual 60R valve is the fine tuning that must occur to set the relief valve. Springs are not calibrated, so to set the relief pressure, one must tighten the spring all the way down and then carefully dial in the cracking pressure by adjusting the screw. Common orientations include the below diagram with the valve located at the discharge of a U1 Model 30 and piped back into the inlet.
While the 60R is the “Can Do” sanitary relief valve to be paired with the “can do” pump. Waukesha’s pneumatically actuated WR60 series of sanitary valves of the latest and greatest in sanitary relief valves. The WR60 valves feature an adjustable spring, maintenance-free actuator that are calibrated for easy setting of desired relief cracking pressure. They also feature piston actuators that allow users to bypass relief the pressure setting and fully open the valve for CIP cleaning without the need to over pressurize the valve. Multiple body styles also provide minimal dead leg relief configurations. Like all Waukesha W60 series seat valves, they are available with switch tops, solenoids, and proximity switches for feedback and automation.
One example on an application of the WR60 series valves is the WR63 valve with CD body and air-to-lower adjustable spring actuator. This valve configuration, as seen below, allows for free draining and minimal dead leg relief piping if the pump discharge pressure exceed the valve set cracking pressure.
By leveraging the different valve body configurations as well as taking advantage of well understood and quantified actuator sizing calculations available, we are not only able to protect expensive process equipment, but also minimize system dead legs and optimize cleaning. At Holland, we have trained sales engineers who can help select and size your next sanitary relief valve. Contact Holland today for more information.