Regardless of the industry or type of application, differential pressure (DP) transmitters are can be found throughout process plants. With dozens of possible configurations, they are the do-everything instruments able to measure pressure, level and flow. The Rosemount 3051S is probably the finest example available today for a long list of reasons.
One of the things that makes this Swiss army knife versatility possible are manifolds. Yes, those gadgets able to provide mechanical support and easier process connections are the true unsung heroes. Chris Selle and Logan Woolery give manifolds their props in their article in Process Cooling magazine in July 2018: Manifolds Extend the Utility of Differential Pressure Transmitters.
As the numbers of electronic pressure transmitters began to grow, especially in flow-metering applications, users pressed vendors for different inlet configurations to satisfy more complex applications. One frequent complaint addressed the complexity of impulse-line configurations with demands for multiple fittings and tubing sections. If other accessories such as shut-off valves or isolators had to be added, they created additional connections where leaks could form. The early biplanar clamping flanges separated into two parts, making the impulse lines and accessories easy to displace during disassembly. These maintenance headaches caused users to look for better solutions.
So there you have the story—as users find new applications for basic products, Emerson responds with solutions to solve those problems, making life easier for engineers in the field.
Modern transmitter/manifold combinations are designed for versatility and user convenience. Many configurations with threaded or flange-faced inlets are available to accept piping from any direction. These options provide the means to make all process connections via the manifold. If the transmitter needs to be removed, it can be unbolted without disturbing any of the impulse piping. This basic concept of ease of assembly and maintenance is the primary advantage of manifolds.
Manifolds go well beyond simply providing the hooks and handles necessary to get things put together. One of the common applications for DP transmitters is measuring flow, and in a lot of situations these are DIY lash-ups created in the maintenance shop. While these can work remarkably well when built around a transmitter like a 3051S, all the required piping and valves can add to maintenance intensity. Using a pre-assembled unit, such as the Rosemount 3051 SFP Integral Orifice Flow Meter, can avoid a lot of problems.
Traditional DP flow measurement configurations use impulse lines from the taps on either side of the restriction device — typically an orifice plate or a pitot tube — to convey high and low pressure readings to the transmitter. These impulse lines normally require multiple fittings, and often they end up being leak prone. Modern designs replace the impulse piping with a small number of cast or welded components with a matching interface to the differential-pressure manifold. With all the elements bolted together, the assembly is robust, compact and leak proof.
The article goes into more detail on design interchangeability, how to minimize work in the maintenance shop, tricky installation/commissioning jobs and more—so it’s well worth a full read. You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Pressure Group and other specialty areas for suggestions and answers.
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