Corrosive service valves are often identified by applications that challenge the valve’s ability to survive, but the term SSV can mean different things to different people. In the past, defining Corrosive service valves had little, if any, global agreement or common recognition. That is about to change as the Manufacturers Standardization Society (MSS; Vienna, Va.; www.msshq.org) has accepted an application to produce a standard practice document to define them.
Within these challenging applications, the
conditions that make the service severe are being analyzed, quantified and
qualified. From this effort, it is expected that objective and repeatable
definitions will arise, along with guidance to improve the performance of SSVs,
reduce unnecessary costs, provide longer service life and process runs, improve
safety and reduce environmental issues.
This blog provides information about the selection
of Corrosive service ball valves in all chemical process industries (CPI), but
focuses on metallurgical processes and applications, and offers examples to
illustrate both the successful and unsuccessful use of this type of valve. The
intent of the article is to raise the awareness of SSV considerations for all
industry stakeholders, including suppliers and manufacturers, specifies and
users, as well as owners. The article also supplies tools to better understand
where and why Corrosive service valves should be categorized separately from
commodity or general purpose valves (GPVs).
Corrosive service ball valves can be found throughout the
CPI. However, certain industry sectors have many more SSV-related challenges
than others. For example, municipal water treatment will have fewer SSV
opportunities or needs than the mining or chemical industries.
In general, valves have two basic uses; they either
control a process variable (like pH), or they isolate the process. No matter
what type of valve — ball, butterfly, check or globe — all fit somewhere into
the basic role of control or isolation.
