Waukesha U2 Pump with Water Jacket Mounted on a Skid. Note the Extended Length of Straight Piping on the Inlet Side of the Pump
One thing people will often lose sight of when going through the process of specifying a pump for a sanitary application is what to do after they get the pump on site. The reality is that there are several good piping practices that should be kept in mind when designing your next system that will help maximize pump service life and return on investment. This post will focus on good sanitary pump piping practices and things you should keep in mind for your next sanitary PD pump install.
When installing a sanitary pump, it is of the utmost importance to allow 4-6 tube diameters of straight inlet tubing into the pump. This continuous length of inlet allows for laminar flow to develop into the pump. By preventing choppy, turbulent flow- which greatly increases air entrainment in product- we reduce the risk of pump cavitation. As we’ve discussed in the past, cavitation is a killer of pump efficiency in both sanitary centrifugal and PD pump applications. We have similar recommendations for flow meters- just remember, the smoother the flow, the less transition, the better the performance.
Here’s an obvious one we’ve touched on in previous posts- piping support. When sanitary tubing is full of fluid it can be pretty heavy. Ten feet of 3” sanitary tube can hold about 4 gallons of fluid. Based on water, that’s about 33 pounds. That’s a lot of weight to hang off the end of the pump. It’s important that we distribute this weight and strain independently of the pump through the use of hangers or other supports. The use of hangers will also come in handy for some of our other tips as well. All of this weight can cause misalignment of the motor and pump shafts. This can lead to shaft deflection and catastrophic pump failure. Excess strain can also compromise system seals, allow air into the process.
Piping slope is important in a sanitary system for a few reasons. The first is to help systems drain when we run a cleaning cycle. The second is to prevent air pockets in the suction line. Again, mixing of fluid and air can lead to pump cavitation and a loss of efficiency. For this reason, while horizontal lengths are acceptable, it’s important to minimize line high points where air can accumulate and to slope piping upward toward the inlet of the pump.
Strainers and Traps
Strainers and traps not only protect the product, they also protect the pump. Inlet side strainers and traps can be used to prevent pump damage from foreign matter. When specifying a mag trap or strainer for the pump inlet, be cautious- clogging or restricting the pump inlet can cause cavitation and flow stoppage.
As we’ve talked about in previous posts inlet and discharge gauges are helpful in identifying and diagnosing pump problems. Gauges are the easiest way to identify changes in pump, product, or system condition. See our post in pump pressure gauges for more on this.
There are three primary types of valves we like to see in a good pump set up- check or foot valves on the inlet side to maintain a liquid leg in the suction side of the pump, isolation valves, and relief valves. Check valves help us to keep the pump primed and prevent backflow. Isolation valves allow us to maintain and safely remove the pump from the system without emptying the entire line. And relief valves, as we have also discussed previously, protect the pump and piping system again excessive pressure.
To conclude, successful sanitary pump application in multifaceted. It starts with identifying the best technology for your specific application. Then we need to properly size and select a motor and drive. Once we get the pump on the base, also a challenge, we need to make sure we install it in a manner that provides system feedback and enables long life. If you have questions about any of these pumping challenges, contact a Holland Sales Engineer today.