che_december-2023 - 29

Feature Report
Part 2
Building Better Seal-Support
Systems for Pumps
Adhering to API 682 guidelines will create safe, efficient and effective mechanicalseal
supports in pumping systems
I
n the 1980s, mechanical seals became
the most frequently used sealing
technology in petroleum refineries and
chemical plants. The American Petroleum
Institute (API; Washington, D.C.;
www.api.org) responded by establishing a
committee to write standards for the components.
In 1994, API published guidelines
including API 682, Shaft Sealing Systems
for Centrifugal and Rotary Pumps, and
noted the following:
" This standard is designed to default to
the equipment types most commonly supplied
that have a high probability of meeting
the objective of at least three years of uninterrupted
service while complying with emissions
regulations. [1] "
The standard also included a stipulation
that facilities should default to technology
that has been proven to be safe and reliable
unless otherwise specified. Now in its
fourth iteration (published in 2014), API 682
remains the standard for mechanical seals
and their support systems.
Though API 682 remains primarily a mechanical
seal standard, it also provides guidance
on seal support systems (Figure 1) because
they are crucial to ensuring that a seal
and pump system operates properly. It is
important to understand whether your sealsupport-system
supplier adheres to the standards
laid out in API 682 4th Edition. These
best practices, outlined in this article, will
help to ensure seal support systems function
at peak performance. Following these guidelines
during system design and construction
can increase reliability and safety while
reducing costs.
Minimizing potential leak points
Much of the focus of API 682 4th Ed. is on
keeping potential leak points from occurring
through the reduction of seal-supportsystem
connections. To further emphasize
this point, the standard suggests avoiding
threaded systems, whether with welded
Brian Rudary
Swagelok Co.
IN BRIEF
MINIMIZING POTENTIAL
LEAK POINTS
DESIGNING SEAL
SUPPORT SYSTEMS
OPTIMIZED SEAL
SUPPORT SYSTEMS
FIGURE 1. The use of high-quality components can make
it much easier to maintain seal support systems and keep
them operating at peak performance, such as this API Plan 22
cooled flush system with a strainer
pipe or tubing. Since each connection may
leak if not properly constructed, reducing
the number of connections is essential. The
more connection points there are in any seal
support system, the greater the potential
to reduce its long-term reliability and result
in greater risk for asset damage, increased
downtime, environmental issues and
safety risks.
Historically, seal support systems used
pipe because it was the preferred method of
construction. Over time, however, that has
changed. Today, more seal manufacturers,
end users and pump manufacturers prefer
tubing rather than pipe because it has been
established as a more reliable option in multiple
crucial industrial applications. Though
many specifiers still opted for hard pipe, API
682 started endorsing tubing instead of piping
for many situations. In the current 4th
Edition, tubing and pipe are specified interchangeably
as preferred methods for seal
support systems.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
DECEMBER 2023
29
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