Can a high-pressure threaded flange be replaced with a flange having an RF seal surface?
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Our company has a Class III vessel with a design pressure of 10 MPa. The safety valve connections on this vessel use flanges in accordance with HG/T20592 standards, and the sealing surface is of the RF type； However, the safety valves provided by the valve manufacturers come with JB2769 threaded flanges and are sealed using lens gaskets. Is there a way to modify the flange on the safety valve to an RF sealing surface? I would appreciate it if the experts could give me some advice. Thank you.
Based on your description, high-pressure threaded flanges and RF-sealed flanges are different types. High-pressure threaded flanges are sealed using lens gaskets, whereas RF-sealed flanges are sealed with flat gaskets. To replace the threaded flange on a safety valve with a flange featuring an RF seal surface, the following steps are generally required: 1. Determine whether the container and the safety valve permit the use of a flange with an RF seal surface. You can review relevant standards and specifications or consult professionals to ensure that the modification meets safety and regulatory requirements. 2. Remove the existing threaded flange, clean it, and inspect the threads and sealing surfaces to ensure they are undamaged. 3. Select an appropriate RF-sealed flange, ensuring that it meets the requirements of the container and safety valve, including material, size, and pressure rating. 4. Install the new RF seal flange, ensuring proper connection and tightening of the bolts. Note: Before making any modifications, be sure to consult relevant professionals and follow the applicable safety regulations and procedures. .
You can add a section of pipe in between; one end of the pipe is welded to a flange with an RF seal surface to connect with the equipment, while the other end with an RJ surface is connected to the safety valve. I mean, isn’t a root valve needed to be installed between the safety valve and the equipment?
Safety valves usually don’t come with valves attached; they also require lead sealing, must be reported, and need additional inspections – it’s too troublesome
The safety valve flange cannot be modified; only a safety valve that meets the flange standards can be replaced. It is possible to install overly short pipes, but adding more sealing points is not the best option.
Replace the safety valve; follow what’s specified on the container
If we ignore the management and design aspects. Simply put, there is only this one option: first, check the outer diameters of the two flanges as well as the distance between their eyes, and the width of the sealing surface. If the dimensions are appropriate, the threads can be moved in the direction of the safety valve, leaving enough thickness for the lens pad to make contact; the flange and the inlet pipe of the safety valve should then be spot-welded together. On a lathe, a corresponding RF plane can be machined. If the material of the threaded flange is different from that of the threaded pipe, and corrosion is a concern, cladding can be applied prior to machining. Given the high pressure, composite wave-patterned gasket made of flexible graphite can be considered.
There are two different connection methods using RF surfaces; it is necessary to consider whether they are feasible and cost-effective.