best option for a ball valve seats

I would like to know the best scenarios to use Nylon and PTFE as ball valve seats.
I know the different temperature range of both of them but, what about corrosion?, are good enough to use them in ball valves installed in lines with oily water as fluid?.
Thanks for all of your collaboration and best regards,
Jorge

 

[pittguy727]

Nylon is usually used for Toluene, Benzene, etc... and Teflon can be used for almost anything except these. It will rub away if the valve body is SS, so I would recommend using PP bodies on them. Can you tell us alittle more specifics about this application and what you are looking to use the valve for?

 

Hello pittguy727,
First of all, thank you for your answer.
The valve will be installed in a drainage line of a vessel at 650 psi.
This line comes from a separation vessel which separates water from oil. The composition of the water is:
Cations (mg/l):

Ca ++ 14,428.8
Mg++ 3,769.60
K+ 1,100
Na+ 21,550
Fe++ 271.21

Anions (mg/l)

Cl- 73,573.28
SO42- 237.85
HCO3- 32.33

pH = 4.6

Chlorides in NaCl = 121.395 g/l

About the body will be in a-105 but the trim will be in SS316. Do you agree with that configuration?. The next question is about the seats, Nylon or PTFE?

Thank you again for your collaboration

Jorge