Chemical Engineering June 2017 - 52

Feature Report
Getting the Most from
Severe Service Valves
Severe service valves (SSVs) differ from general purpose valves in important ways. Presented
here is guidance on how to increase service life, reduce costs and improve safety and
environmental performance of SSVs
Flowserve
Ross Waters
CGIS Canada
IN BRIEF
SEVERE SERVICE
CONTROL VALVES
SEVERE SERVICE
ISOLATION VALVES
VALVE SELECTION DATA
CHALLENGES
DIFFERENTIATING GPVS
FROM SSVS
DEFINING SSVS FOR
CHEMICALS
SSVS IN PULP AND
PAPER
LESSONS LEARNED
FUTURE OUTLOOK
S
evere service valves
(SSVs) 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
SSVs 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 article provides information about the
selection of SSVs 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,
specifiers and users, as well as owners.
The article also supplies tools to better
understand where and why SSVs shoud be
categorized separately from commodity, or
650
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10
52
Sulfuric acid
isocorrosion chart*
Zr
N-7M
CW-6M
CN-7M
CD-4MCu
CH-6M
CF-8M
20
*20 mils/yr lines
30
40
50
60
70
CN-7M
CW-6M
DCI
WCB
CF-8M
80
90
100
wt. % H2SO4
FIGURE 1. This sulfuric acid isocorrosion chart depicts corrosion performance of
several materials
general purpose valves (GPVs).
SSVs 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.
Severe service control valves
The dilemma facing all users of SSVs is for
the valves to remain in service providing their
singular functions while performing at the
basic level required by the process. Severe
services challenge both performance and
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JUNE 2017
HSI
350
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250
200
150
100
50
Degrees (oF)
OLEUM
CN-7M
Degrees, ˚C
CW-6M

http://www.msshq.org http://WWW.CHEMENGONLINE.COM

Chemical Engineering June 2017

Table of Contents for the Digital Edition of Chemical Engineering June 2017