Help: Can anyone share how many different ways there are to connect pressure transducer tubes in chemical process instrumentation, and which method is the most reliable?

Selection of instrument pressure guiding tubes – Regarding the choice of pressure rating: The pressure ratings for flanges and pipes in use today are available in both metric and imperial units. Given the current production situation of materials used for instrument installation in China, and in order to reduce the variety and specifications of such materials while adhering to the common practice in piping engineering of using nominal pressure grades, for operating pressures ≤ 16.0 MPa, the nominal pressures PN63 and PN160 are employed ； Under operating conditions with a pressure > 16.0 MPa, nominal pressures of Class1500 and Class2500 are used. Regarding the selection of tubes: Tube (abbreviated as T-tube) has more advantages over Pipe (abbreviated as P-tube). For example: it is easy to install using a socket connection, offers a high strength-to-weight ratio, is easy to maintain, is available in metric and imperial versions (P-tubes are only available in imperial), which facilitates selection. It is actually recommended to use stainless steel T-tubes. Selection of tube wall thickness: Generally, it is recommended to use stainless steel tubes with a wall thickness of 1.5–2 mm when the design pressure (i.e., the maximum allowable operating pressure) is below 16 MPa; for socket weld connections, a wall thickness of 3 mm is used ； When the design pressure is between 16 and 25 MPa, stainless steel pipes with a wall thickness of 2 to 2.5 mm are used (3 to 4 mm for socket weld connections) ； When the design pressure is between 25 and 42 MPa, stainless steel pipes with a wall thickness of 3 to 4 mm are used (4 to 5 mm for socket weld connections). When selecting the wall thickness of the tube, the effect of the process medium temperature on the pressure resistance of the pressure guiding tube should also be taken into account. Selection of pressure guide tube diameter: When a ferrule connection is used, it is recommended to use stainless steel tubes with a diameter of Φ12 ； When using a butt-welded connection, it is recommended to use stainless steel pipes with a diameter of Φ14 ； When using the socket weld connection method, it is recommended to use Φ18 stainless steel pipes for the pipe diameter.

Thank you. I would like to ask if there are any pictures showing how the ends of the pressure guiding tube are connected to the flanges and instruments; I’d like to take a look to see which type of connection is more reliable!

All of them are reliable; they are designed based on specific conditions. When the temperature of the material is not very high, double-flange capillaries are generally used. Steam is used as a condensation tank from which pressure is taken; there are also direct pressure tapping pipes for liquids or clean gases. Pressure tapping pipes are generally fitted with clamps, and welding may be used when necessary – this is mainly to consider weight distribution and support

Connection methods include welding, which encompasses butt welding and socket welding； Threaded connection ； The lock nut fits with the connector. The above connection methods usually rely on connectors for linking.

This post was last edited by HEJIYUER on 2020-9-14 at 22:59. For taking pressure readings from process media, it is recommended to use the \"pressure pad-type with butt welding\" method; threads can be used at the meter location. ANSI 150/300/600 pipes, 12x 1.5 pipes ； 900/1500 uses 14x3 ； 2500 uses process pipes directly. Casing products are highly constrained by the level of processing/construction. The butt weld is defective; it’s a problem with the quality of construction ； The card sleeve is leaking; the instrument is involved in this.

I would like to ask about the pressure range applicable to flared connections