I have questions regarding throttle orifice plates
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New member reporting in – I have a question. A set of standard orifice plates is installed on the pipeline to measure the water flow rate. The operating conditions are a pressure of 3 MPa, a temperature of 120°C, and the typical flow rate is around 1000 t/h. What material should be used for the gasket inside the orifice plates? The manufacturer provided asbestos gaskets, but the client said those are not acceptable and requested graphite gaskets instead. Is this really necessary?
The type of gasket to be used must be determined based on the characteristics of the medium (temperature, pressure, etc.).
Asbestos gaskets – Low-pressure asbestos gaskets: These gaskets are made from white chrysotile fibers and are suitable for most applications involving low temperatures and low pressures. They are primarily used for sealing in systems involving steam, water, gases, oils, and non-corrosive media. Medium-pressure asbestos gaskets: mainly used for sealing steam, hydraulic fluids, gases, oils, and non-corrosive media. High-pressure asbestos gaskets: mainly used for sealing steam, hydraulic fluids, gases, oils, and non-corrosive media. Oil-resistant asbestos gaskets: mainly used for sealing steam, hydraulic fluids, gases, oil-based solvents, and non-corrosive media. Main technical parameters of asbestos gaskets: Models XB150, XB200, XB250, XB300, XB350, XB400, XB450, XB510. Tensile strength: 5MPa, 6MPa, 8MPa, 9MPa, 11MPa, 18MPa. Temperature range: +150°C, +200°C, +250°C, +300°C, +350°C, +400°C, +450°C, +510°C
3MPa at 120 degrees – asbestos should be fine; of course, using graphite would be even better
It is best to use asbestos-wrapped gaskets for easier replacement in the future. Ordinary asbestos gaskets are difficult to replace.
Your asbestos pad also meets the requirements, but the manufacturer used it to save costs; as a result, it becomes difficult to remove and clean the pad when maintenance is needed in the future.
Thank you to the brother upstairs for his helpful answer! ! ! There is another issue: by adding a tee on the positive pressure side of the differential pressure measurement and connecting a pressure transmitter to it, will this affect the accuracy of each other? I saw it connected like this at the factory
It should not affect the measurement accuracy, but it is better not to install it in this way as it will impact future maintenance; it is preferable to install the pressure tap separately.
There should be no problem. I really don’t understand why you’re applying positive pressure; what’s the point of doing that?
There’s nothing wrong with it; the asbestos pad meets the requirements! If Party A does not agree, then switch to a PTFE gasket or a graphite wound gasket; it is best to choose a graphite wound gasket.
There is no need for replacement; pressure measurement is still possible, and accuracy is not affected, but it will make future repairs more difficult.