There’s an old adage that says “Cheap work isn’t good, and good work isn’t cheap”. Nowhere in the Canada Pipeline Accessories product line is that more apparent than when we debate the merits of our sonic nozzles versus orifice plates in restriction and overspeed applications.

While orifice plates are cost-effective, they often don’t perform as intended. When it comes to a solution that will last, function, and perform, a Canada Pipeline Accessories flow nozzle is the smart, sensible and quality choice, built on over 2 decades of experience and data. If you are looking for a product that will properly choke at a certain flow rate or velocity, only our Sonic Nozzles are designed for that kind of performance, which buys you reliability and peace of mind.

Why Sonic Nozzles? 

Sonic Nozzles work by creating a restriction in the pipeline. This restriction forces the gas velocity to increase at the throat of the nozzle. If the pipe flow rate gets high enough, the velocity at the nozzle throat reaches the local speed of sound. When this occurs, the flow is choked, and the mass flow rate through the nozzle cannot increase any further. A choked nozzle prevents the gas velocity in the pipe upstream of the nozzle from increasing as well. This condition protects anything installed in front of the nozzle, even if the downstream pressure continues to be reduced. The Canada Pipeline Accessories Sonic Nozzle must therefore be installed downstream of the pipe equipment it is meant to protect. The flow velocity in the pipe in front of the nozzle is limited, but high velocity flows will be possible downstream of the nozzle.

Use the Right Tool

Orifice plates are typically sized using ASME-3M/AGA3 differential pressure calculations (which don’t extend to choked, overspeed applications), or they are sized based on a correction of a sonic nozzles’ calculated dimensions. This kind of design is incorrect, and propagates the assumption that orifice plates behave like nozzles when fundamentally they do not. Only a properly designed ASME-7M critical flow nozzle will reach the designed choking point and won’t allow any further velocity increases, even as the downstream pressure continues to drop.

Orifice plates cannot regulate velocity increases, and will shoot past the target design point as the downstream pressure drops. Orifice plates are only effective at generating a differential pressure, where the nozzle is dynamically more efficient and generates a much lower permanent pressure drop when it is below the choking point.

The Geometrical Difference 

Sonic nozzles outperform orifice plates due to their very different geometry. Orifice plates have a very sharp inlet edge, while sonic nozzles have a very smooth, gradual inlet contour. Sonic nozzles can allow the proper development of a normal throat shock wave which allows the flow to properly choke. Orifice plates cannot do this, and instead generate oblique expansion shock waves off of the inlet edges.

Sonic nozzles offer guaranteed insurance where orifice plates cannot. Save yourself the time, headache and worry, and get the right product for your pipeline application, the first time. 

Contact our Team Today

Canada Pipeline Accessories provides accurate measurements, and unsurpassed products supported by verifiable proof from over 20 years of data collection. When we say our products are superior, it’s because we have the information, expertise and experience to know they are. We also provide more pipeline and measurement support than any other engineering company in the field. We help fix problems, solve measurement issues, and provide the innovative solutions your company needs. Contact us today to further discuss our products, their warranties, and how our engineers can achieve the flow measurement results you require.