In fact, it’s a question my colleague David Sear posted in our Valve World LinkedIn forum around three months ago. At the time of writing the post had received 51 likes and 38 comments. It seems that if you’re to ask two different engineers you’re likely to receive two equally different yet acceptable answers. Whilst opinions will vary on the necessary considerations required to arrive at a definition, they will often include factors such as temperature, pressure, pressure drop, process material and cycles. Yet these are not the only factors—for example, should definitions vary according to each valve type? Should the frequency of repair be a consideration? What about criticality of the valve to overall plant uptime? Or does use of the word ‘critical’ only serve to confuse? Where questions arise, debate often follows, and whilst most agree the intended application is important, there is something left to be said for the individual user’s perspective. After all, since the end-user is responsible for the selection and installation of the valve, it is worth checking on their own definition and expectation. Perhaps this helps explain why definitions sometimes vary between projects (and regions).
Below are some of the opinions shared:
“Severe service depend project by project for the needs of a EPC/END USER”
End-user, United Arab Emirates
“I think there is no exact definition of severe service. The reason is that many parameters can make the service severe. These parameters could be corrosive elements such as H2S that makes the service Sour, Very dirty services (Particle Containing fluids), Very cold temperature services (Cryogenic), Very high temperature such as steam, etc. which affects the design of the valve in terms of material, sealing, type selection, etc.”
“The application plays a large part but the reason there is no single definition is because one users perspective differs from another. Great discussion to have and one that needs detailed discussions with the end user to find a solution that meets their specific needs.”
Director, Valve Manufacturer
“The term "Severe Service Valve" will always be subjective depending on the process involved. What might be considered as Severe Service by one user might be considered quite normal by another. For example, in my company we manufacture "standard" Gate Valves, but because they are generally made from Alloys (Alloy 20, Inconel, Monel, etc.) used in corrosive or toxic service, many users consider this Severe Service. On the other side, we also manufacture a true Severe Service Ceramet-Seated ball valve line that would be for another type of Severe Service entirely such as high temperature, high pressure, Hydrogen, solids / Slurries, etc. The people that use such Ball Valves would consider any gate valve a cheap commodity.”
President, US Valve Manufacturer
Finally, if you’re a magazine subscriber, be sure to have a look at this month’s issue in which Ross Waters (President, CGIS) advocates the importance to the industry of arriving at a definition in his article “Defining Severe Service Valves”.
Ross will also be presenting at the Valve World Conference in Düsseldorf this November—a great opportunity to discuss this topic further in person.