In part 1 of our series on how to CIP your PD pump, we focused on pump features and options. In part 2, we’re going to take a look at piping considerations and what you should consider when you place the pump into the process line. In addition to the pump features we talked about (make, flat body profile, and “Full” CIP features), there are a few system design features we want to keep in mind when designing for a pump that will be cleaned in place.
First, let’s talk about the start of a cleaning cycle. You don’t wash your dishes with cold water, so it makes sense that CIP solution is usually hot- much hotter than what we are running process at. In order to avoid temperature shocking the pump after introduction of hot CIP fluid, stop the pump after filling with CIP fluid. Once the hot CIP fluid has filled the pump head, allow up to 15 minutes for the pump fluid components to thermally expand, then re-start the pump.
Once we get started with our cleaning cycle, we want to ensure that the velocity of CIP solution through the pump is adequate to clean the entire circuit (downstream of the pump as well). For most applications, this is a flow velocity (not rate) of 5 feet per second. To do this, we need to make sure that the pump drive can run fast enough and has enough horsepower to overcome downstream friction losses. Because we usually run pumps slower than this for process, this can mean the installation of a downstream bypass or a bypass loop using a WR63 valve with CD body configuration and the use of a separate CIP supply pump (or a Universal Twin Screw pump that can better handle both duty points).
Next, we want to make sure we’re creating a differential pressure across the pump head. The differential pressure will push CIP solutions through close-clearance areas of the pump, resulting in better cleaning action. Typically, we aim for 30 psi differential, though this may be higher for hard to clean products. The easiest way to achieve this is the use of a restriction orifice (such as an orifice plate gasket) on the pump bypass line or by pulsing a valve downstream.
And if the above didn’t make it clear, we need to run our Universal 2 or Universal 3 pump during CIP. This is needed to create turbulence and cleaning inside the pump as well as to maintain downstream line velocity to clean the rest of the pump.
In sum, the ability to be able to consistently CIP your PD pump is the result of properly specified equipment and piping best practices. Not only do we need to make sure we’re using a Universal 2 or Universal 3 positive displacement pump, but we also need to make sure we have a flat body profile and possibly drilled rotors and body hubs. But that is only half the battle. We also need to make sure we don’t thermal shock the pump, select an appropriate supply pump, bypass if necessary, and always make sure we’re creating differential pressure to “scrub” the pump clean. That’s all there is to it. If you have any questions about how to CIP your sanitary PD pump, please contact a Triplex Sales Engineer today!