Thinking about the subject to write my blog, I remember about a discussion that I had a few years ago, when I was taking my certification in valve automation, this was in TYCO FLOW & CONTROLS (this company was bought by a huge conglomerate).
In this capacitation we had to choose the right valve, then we proceed to sizing the actuator to operate the valve that we selected.
We have an exercised with the follow information: the fluid was diesel, also they give us the diameter, inlet pressure and the pressure differential.
One of my classmate was trying to find the right valve, but also he was thinking in the price to, he select a resilient seat valve, with the seat made for a plastic who can handle with the hydrocarbon.
My mate select a resilient seat valve with fail closed pneumatic actuator, he was initiating in the valve them and he wasn’t a dude with experience.
In my case, my experience wasn’t big to, I had one year working with valves, but I remember when my trainer was teaching me when I just starting to work with ECN, he told me about this application and he show me about it in the field, the risk to buy something “cheap” trying to save some moneys of you budget.
Taking notice of this, I selected a High Performance Valve with metal/metal seat (Fire Safe Trim) and fail closed pneumatic actuator.
Our trainer said the correct valve to handle with diesel is the high performance valve with metal/metal seat and fail closed pneumatic actuator, and this is for the follow things.
When you have a risk fluid and it is flammable, in case you have a fire in you plant, a resilient seat valve even it’s closed, because the heat it going to have a great leak, and the risk for a bigger problem is huge; remember a good seal in the resilient seat valve depends in the interaction between disk and seat, and the high temperature reach in a fire is going to destroyed the seat and loos you seal.
The fire safe trim valve doesn’t have plastic in the seat, this help us to isolate our fluid and closed our system.
The fail closed actuator is going to close our valve when you don’t have air in the system and the actuation is going to be using springs.
We have to said, the actuator size is not the same even if the valves are in the same diameter, the high performance fire safe trim valve, required a bigger torque for closed in case of accident, because of that you have to calculate the force necessary to open or closed.
As you see, a correct selection of valve and actuator can help you to save money in case of accident in our process.
I hope this information help you.