Application scope of bayonet connections
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In a certain project, I encountered extensive use of bayonet connections on site. Here comes the question: In instrumentation engineering, when and under what pressure levels should we use ferrule connections? Under what circumstances and under what level of pressure should we avoid using ferrule connections? What did all the fellow sailors do on site? Thank you all for actively sharing your on-site experiences!
Zero leakage is required; no card sleeve to be used. For instrument air pipes, especially those related to control valves, if a small amount of leakage is acceptable, or if the resulting loss is minimal and poses no hazard, or if the leakage does not affect the 6S standards, clamping sleeves can be considered.
Our company often uses ferrules; we have used ones with pressures of 35 MPa, 40 MPa, 55 MPa, 70 MPa, 100 MPa, and 150 MPa. Above 40 MPa, the design of the ferrules changes to a special high-pressure version equipped with reverse threads. The brands of ferrules we use include Swagelok, Parker, FESTO, etc., and there are almost no leaks – which is great! It is also used in low-pressure environments, but less often! :)
Clamshells are convenient, but with the money spent on importing such products, one can buy domestic alternatives that don’t use clamshell seals and still ensure zero leakage
Check if the contractor has the money; if they do, use card sleeves anyway – the brands listed for the 5th floor are all good options； If there’s a lack of money, just weld it!
For sizes below φ12, clamps are generally used; they are convenient for maintenance and installation. So far, no leaks have been observed due to the use of clamps.
Two sufficiencies: enough money and capable people
The pressure is too high, and the welding needs to be improved.
It mainly depends on the pipe diameter and pressure rating. In our company, for pipes with a diameter of 16 mm or less, clamps are not required for high-pressure applications. If clamps are used in high-pressure situations, then pipes of high precision must be selected as well. For high-pressure applications, our company usually uses imported welded fittings.