Inside
Insights
How I Saved the
World and Then
Woke Up:
The importance of safety
relief valves
Steve Tredinnick, PE, Vice President of Energy Services, Syska Hennessy Group
Editor’s Note: “Inside Insights” is a column designed to address ongoing issues
of interest to building owners, managers
and operating engineers who use district
energy services.
Itruly hope your summer has been fantastic. Mine has. Along with getting
sunburned and working hard at my
new job, I have seen a bunch of movies:
“Spiderman 3,” “Fantastic Four: Rise of
the Silver Surfer,” “Pirates of the Caribbean:
At World’s End,” “Harry Potter and the
Order of the Phoenix” and more. I just
love movies, but I’ve seen so many that
I’ve started to have weird dreams – really
weird ones that combine my own version
of the movies with features from work.
Take this dream for example:
I am miniaturized and in a mini-sub like
the one in “Fantastic Voyage” (but without
Raquel Welch). The sub is called the Black
Pearl, and I am getting pushed along by
system flow alone (got to conserve energy
with the price of diesel these days!) in the
world’s largest district cooling water pipe
system. (I must be in Dubai!) My job is to
troubleshoot any problems and look for
maintenance issues. It is a really exciting
pipe layout with many bends, like the water
parks in Wisconsin Dells, but on steroids
(once again think Dubai). Yeehaa! My
external sensors indicate that the water
conditions are 42 degrees F and 100 psig.
Cool – everything is normal, and we are
flying like the Silver Surfer.
All of a sudden, the water flow terminates, and I coast to a stop. Hmmm....
The temperature is still steady at 42 F, but
the pressure has dropped to about 50 psig.
Either I ran out of quarters or the pumping
system has been shut down by the dreaded
Sandman! As I get my bearings, I discover
that I am in a plate heat exchanger (PHE),
and the isolation valves are closed so I am
not going anywhere. I am trapped!
After about an hour of cruising around
the herringbones of the PHE looking for
an exit, I notice my external temperature
sensors are slowly rising from the standard
42 F to past 45 F. Curious, but I am nice
and comfy in the Pearl, so I do not give it
another thought. After a while, however, I
am bored silly of flying like I am in a Quidditch match, so I do the natural thing when
the going gets tough: I take a nap to
recharge. (Hey, Quidditch is hard work!)
Several hours later, I am jolted awake by
the pinging and popping of the Pearl. I check
the instruments, and the water temperature is up to 60 F. Great Caesar’s ghost!
What’s happening out there? The pressure
gauge is reading over 400 psig! How did
that happen? My sub is only designed for
500 psig, so I have to work fast.
Bringing up the system schematics quickly
on the graphic display, I see that I am close
to where a safety relief valve (SRV) between
the PHE and the isolation valves should be.
Why hasn’t it popped yet? Navigating to the
SRV location, I see that it has been removed
and replaced with a cap. Foiled again by my
arch enemies! But in an inspiration, I take
out my magic wand and mutter “alhamora”
and the cap opens! I am purged out of the
system like a slug coughed up by Ronald
Weasley.
Floundering on the wet energy transfer
station room floor, I utter another hex,
“Engorgio,” and once again I am full-sized.
I pocket my trusty wand and review what
just transpired. After a moment, it comes
to me… Of course! This is exactly what
they teach at the ITT Fluid Handling Little
Red Schoolhouse – even a small increase
in temperature will increase the system
pressure dramatically. Those SRVs are really
worth their weight in gold!
I reinstall the SRV and save the world…err,
at least the chilled-water system. Just then
Sue Storm of the Fantastic Four materializes
out of thin air and is going to give me a
congratulatory embrace, but then I wake
up. (Dang!) I guess I have either been out
in the sun too long, or I really have seen too
many movies. However, within all these
extremely corny babblings is a real live story.
Unlike me, SRVs are really the ultimate
pessimist. They just sit around and wait for
things to fail, but before the system reaches
that critical point they spring into action to
save the day. Not only are SRVs critical to
protecting piping systems and equipment,
but more important, they protect the safety
and well-being of operating personnel.
It is true that a minor increase in tem-
perature may create more extreme increases
in pressure. That is exactly why the SRV is
Not only are SRVs critical to
protecting piping systems and
equipment, but more impor-
tant, they protect the safety
and well-being of operating
personnel.
located between the isolation valve and the
PHE connection. Even a small movement
of the safety valve will relieve a great deal
of pressure. One article I came across lately
used an example of where trapped water
