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Dear JohnLL Trunnion mounted ball valves are always DBB, no matter if self relieving or double piston. Usually if you choose self relieving seats the overpressure is discharged in both sides of the valve. Ciao

Check www.rmtvalvomeccanica.com

Dear Gregorio, I work in a ball valve company and we produce also fully welded. For big size of course the problem is not so big as the distance from the welding area to seats is more that enough to prevent any damage. For small sizes is a more complicete. Anyway you should ask the company owner...

All the explanation are right and complete. Just want to add that in both configuration, single and double piston, the valve (trunnion) is always double block and bleed. API 6D rules the construction of these valves. Ciao

Gerhardl is right. A control valve should be more appropriate for this service. Regards

Dear Dan, AISI 4140 has a higher yield strenght value. If you need to use a SS material you have to change from SS 316 to 17-4PH or F51. Ciao

Dear Sam have a look at it. ciao http://files.engineering.com/getfile.aspx?folder=94dadbde-8534-4b6e-8855-845e1528d441&file=GS_EP_PVV_142_Rev05_du_10_2009.pdf

Dear Sam, regarding point 1, if you are going to overaly the ball with inconel, then why you use F6 as base material? You can easily use carbon steel which is less expensive. Regarding point 2, I do not have evidence to send you but I suggest you to check TOTAL specification PVV 142 on the...

Sam, if you have particles coming from the well that damage the surface of the ball, you will not solve the problem by changing the base material in inconel. If you have this kind of problem stellite is even worst!!!! Anyway, I remain with my suggestion of CS trim + ENP + TC coating. Ciao

If you want the most cost-effective solution you can do like TOTAL requires i.e. Carbon steell trim + 75 microns ENP + 400 microns of tungsten carbide coating. Doing that you avoid the use of expensive materials and you have a corrosion and wearing protection on the trim. Ciao

Dear Sam, the issue is not due to the service. The real problem of applying stellite on the ball is that it gests exfoliated after a while. For this type of application on ball valves Tungsten carbide coating, applied with HVOF method, is technically better. But if the service is really highly...

As far as I know on trunnion mounted ball metal seated valves a leakage is always allowed as stated in API 6D. Reference norm is ISO 5208 rate D. With great effort is possible to reach rate B, but rate A remain almost impossible to achieve. Don't know if floating ball valve follow the same...

The answer of camvalve is exhaustive except for one point. In fact a SPE valve is not unidirectional as both seats are designed to release the overpressure. On the contrary if a ball valve is designed with one seat SPE and the other seat DPE, then the valve becomes unidirectional as the...

If you are looking for a TSO valve, a ball valve with metal to metal seats (tungsten carbide coated) will never be tight but will admit a leakage according ISO 5208 rate B as maximum sealing, more often it will be ISO 5208 rate D. Temp/pressure is important to know ehter you can use cast...

Hi, this is a typical "trick" that usually valve manufacturer play to follow the specification. As general rule when we speak about this type of valve we intend that primary sealing (valve under pressure) is metal to metal, and secondary (valve not pressurized) is soft (basically with Viton...