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What Does a Sanitary Flow Orifice Do?

May 16, 2014

At Holland, we take pride offering unique solutions to complex process problems. One problem we kept seeing in sanitary process systems was finding a way adjust flow rates and equalize backpressures in a sanitary manner that fully drains and allows for complete recovery of valuable product. To address this problem, we introduced are fully machined sanitary HOMM fitting. This post will take a look at what a fixed flow orifice does and the sanitary orifice types that are offered.

Holland Sanitary Orifices

Holland Sanitary Orifices

To begin, an orifice is a small hole in the middle of a larger plate. It is placed in a pipe through which fluid flows. In a sanitary process system, when flow reaches the orifice plate, it is forced through the hole and converges. The point of maximum point of contraction actually occurs shortly downstream of the physical orifice and is known as the vena contracta. As the fluid converges on itself, the velocity and pressures changes. One of the most fundamental laws of fluid mechanics- Bernoulli’s Equation- tells us that as fluid velocity increases, pressure decreases. This creates a differential pressure across the orifice (a higher pressure before and a lower pressure after the orifice).

This pressure reduction effect can be useful for a variety of purposes in a sanitary application. A flow orifice, while traditionally used as a flowmeter, also allows us to adjust our process flow rate, balance backflow and equalize pressure. Balancing backpressure is useful in SIP and CIP applications where the pressure is needed to create the turbulence necessary for cleaning. Flow orifices can also be used to check excess flow from a system header. A flow orifice could also be used to check a centrifugal pump, providing the back necessary to prevent the pump from running to far left on the curve causing starvation, cavitation, and possibly causing the pump motor to overload and kick out.

So now that we know what a flow orifice is, what makes one sanitary? Traditionally, a sanitary flow orifice has been a plate gasket with a hole drilled in it. There are a few problems with this. First and foremost, it won’t fully drain. While special conically shaped flow plates have been developed for vertical flow installations, there are still other limitations. With orifice plate gaskets, you are limited to the gasket materials available from the manufacturer. This also means that when the gasket fails, you must throw the entire assembly away. Labeling and identifying an orifice plate gasket is also a challenge. While they do make tabbed orifice plate gaskets, you’ll need a special clamp- and those are cheap.

To address these issues, Holland introduced our HOMM fitting. This inline fitting features machined full radii that allows full draining. It does not incorporate a gasket as an integral part of the orifice so you can use any gasket material you’d like. We can pin stamp and tag the orifices with any identifier you’d like. Our in-house machining and polishing capabilities allow us to offer these with pristine surface finishes (15 Ra or better), as well as electropolished. Holland HOMM’s are subject to the same strict quality standards all other materials are and ship complete with MTRs and even optional surface finish reports. They are generally offered with TC ends, however we can work with you on any connection type (including DIN and metric sizes and styles). We even offer eccentric flow orifices.

So for your next sanitary pressure reduction application, contact a Holland sales engineer today. We have proprietary software that allows us to size an orifice for your application. We have the tools to drive the high quality standards you demand.

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