Valve selection for NGL service

[Rakesh2560]

Greetings All,

I am new in the field of valve selection and am looking for information related to selection of valve .We are looking to purchase a 24" , 300# Emergency isolation valve for one of our plant we have received offer from different vendors however i have a few questions The service is clean hydrocarbon non Nace

(1) For ball valves is bearing material SS 316 with PTFE coating acceptable ? i think we can select this upto 150 deg C but not sure where to find the reference for this ?

(2) For big size ball valves are sealant injection points for steam and the seat mandatory ?

(3) Most vendors are offering ball material as eg A350 LF2 + 75 m ENP + 150 m TCC ,A182 Gr F6A cl 2 , A217 CA 15 + TC , F6A + TCC i am not sure about A217 CA 15 and its performance in comparison to others any guidance about this will be helpful.

(3) Need information regarding 75 m ENP + 150 m TCC what does 75 micro m ENP +150 micro m TCC mean ?

(4) Can the ball material be same as the trim material ? Eg if ball is A350 LF2 + 75 m ENP + 150 m TCC then the trim material can be A350 LF2 + 75 m ENP + 150 m TCC ? I am confused as the same material will lead to no difference in hardness and with the time damage to both seat and the ball will ocurr i assume here ball should be more harder the seat as seat can be replaced when needed.

Thanks well in advance for all those who provides their valuable time and guidance for my post.

Regards,
R

 

[SPDL310]

Rakesh,

I don't have definitive answers to you questions, as isolation valves and their specifications are outside of my expertise.

(1) In absence of a standard reference which precludes it I can't say one way or another, but the limitation is likely for the PTFE coating. While it may not become fully plastic at that temp the high loading from trunnion to bearing friction may lead the coating to peel/degrade early.

(2) Once again it may depending on the valve standard, but as the bore/stem grow in size the amount of leakage past the packing/ball and seat will increase exponentially leading to sealant injection ports being highly desirable. Considering that this is an emergency safety device the injection ports may very well be required. This may also factor into or be required by the SIL rating of the valve.

(3) I have nothing to say about the merits of one ball material over another. The 75 micron ENP is electro nickel plating with 150 microns of tungsten carbide coating. This is done to increase surface harness as well as offer increased corrosion/erosion capabilities.

(4) I don't believe that you will be seeing a field replacement of a seat on a large bore meatal seated ball valve. It is my understanding that these types of ball/seat combos are lapped together in order to form a seal. When that lapped surface degrades the injection ports are there to assist with continued sealing until a replacement ball/seat is available. If this is something you are concerned about it is best to inquire with you vendor out their track record with similar service, as well as seat replacement procedures.

 

[mk3223]

The material of the valve and trim my be based on your piping spec as a minimum requirement. The Vendors may provide the proposal to match the your spec or equivalent.
Also, you may confirm with the Vendors if the proposed ball valve meets your Spec and operating process. If having any doubt, you may request the Vendor to provide the supporting document and reference to prove the vale is suitable.