IMO, it could be the mechanical integrity and strength concern related to the material and support of the equipment & equipment issues.

How about plant fire protection ?

What exactly is in the piping system that you wish to make this substitution ? Is it flammable or combustible ?

Composite Valves cannot be relied upon when external temperatures get too high ... SS body valves will retain their integrity at much higher temperature.

MJCronin
Sr. Process Engineer

Thank you for your answers.

Fluids are not flammable or combustible, by the way it is acceptable to have also the piping on FRP, but customer prefers Stainless 316, the point is that there will be more than 200 valves, and using FRP Ball valves vs. SS 316 makes a big price difference.

Thank again.

I have often stressed the importance of Drug testing for new clients .....

MJCronin
Sr. Process Engineer

Hi alprieto 2003,

The answer to your question involves a detailed analysis of all technical and economical questions related to the detailed application of all valves to find 'best cost over lifetime'.

Many engineers tend to forget that cheapest purchasing price could lead to higher operation and maintenance cost over time.

In your case all material combinations could be used. A lot more facts are needed to reach a conclusion. Anyway, the best material is SS, and the question of extra cost is often bound to contractual understanding.


Good luck!

Thank you for your input gerhardl, in the plants we had designed and built in the past we have used SS valves with SS piping and FRP valves with FRP piping (for example piping for seawater service). Now we are working on a larger project, with fluids for what SS316 or FRP piping is acceptable, the plan is to have most of the piping in SS, then we were wondering if FRP Valves may be acceptable to include on the SS piping class specification (I could not find an example including them, and I have examples from several companies on file). As it happens in many cases, some clients prefer to have the lower investment on the initial phase and keep improving the plant over the years.

Thank you

Hi,

Thanks for the information.

On a general basis the answer is that such combinations have been built and used.

The final answer must come from the persons/authorities responsible for the total safety/quality and detailed certifications necessary for the whole plant.

I worked in a new building where plastic valves were threaded onto copper chilled water pipes. The temperature changes along with different coefficients of thermal expansion caused the threaded joints to leak over time. The leaks were intermittent by zone by floor. The results was a lot of damage to computers, files, etc. in the offices, and a major expense to shut down the building and replace all the plastic valves.

You must consider all possible scenarios. Better yet, get verification of successful use in a previous facility. Mistakes like the case above can cost you your job.