Texas
Slam Dance! - New Valve Technology Eliminates Valve Slam
By:
Val-Matic
System
operators have their work cut out for them when the pumping
applications deal with high head, surge tanks, or multiple pumps.
A North Texas Wastewater treatment plant was learning
this first hand. The North Texas utility serves four
cities, the largest having between 70,000 and 80,000 people.
It's
lift station contains four 8 in. vertical centrifugal sewage
pumps that feed a 600 ft. long, 48 in. diameter force main.
Online since 1987, the station was equipped with traditional
weight and lever air cushioned swing check valves .
"The
check valves were breaking down. We repaired them, but
they kept breaking internally. We were getting a lot
of water hammer. This station takes a lot of flow, so
it was hampering us. The station was down until we could
get parts in or have them machined," said a system operator
for the plant.
The
existing valves, from multiple manufacturers, were unreliable
and it was difficult to find something to fit the unique circumstances
of a vertical application. The existing air-cushioned
swing check valves had to be rigged with additional external
springs and cables in an attempt to combat slamming.
The valves were closing hard, and a 1-year old replacement valve
had just broken a shaft pin. The installation was too
dynamic for an ordinary check valve. The tall vertical
run of pipe after the pumps created extremely fast flow reversals
and water hammer after power failure. The existing valves
had weighted levers with cables and springs anchored to the
floor which made for a dangerous situation
"This
is one of the biggest suppliers of water in North Texas and
the largest processor of wastewater," noted John Bolender, President
of Valve and Equipment, Huffman TX, a manufacturer's representative.
"They came to me looking for replacement valves that
could replace slamming cushion swing check valves."
Enter
the Val-Matic SURGEBUSTER! Check Valve. Specifically
engineered to handle high head applications, multiple pump systems,
and systems known to surge, the SURGEBUSTER was designed to
handle extreme applications.
The
SURGEBUSTER achieves a rapid closure through a short disc stroke
of 35° and still maintains a 100% flow area. What
makes the SURGEBUSTER unique is the patented Disc Accelerator,
the next generation in valve technology. The Disc Accelerator
is a precision formed stainless steel mechanism that closes
the disc rapidly, avoiding any slamming by flow reversal while
also allowing the disc to be stabilized under flow conditions.
The accelerator is fully enclosed and out of the flow
path. The valve fully meets ANSI/AWWA C508.
"When
they told me about their application, I suggested the Val-Matic
SURGEBUSTER. I knew they hadn't seen anything like it,"
said Mr. Bolender.
"We
saw the valve and thought it was a good design," the system
operator explained.
The
SURGEBUSTER was installed in place of the traditional swing
check valve after a vertical elbow on the vertical discharge
of an 8" pump. The results were so quiet, the flow could
only be heard by placing your ear against the valve.
The only way to tell that there was flow through the valve was
by the top mounted valve indicator.
The
traditional weight and lever swing check valves are now being
phased out of the facility, and the Val-Matic SURGEBUSTER check
valve has proved to provide some unexpected benefits.
All SURGEBUSTER valves come with a fusion bonded epoxy coating
on both the interior and exterior of the valve which is highly
resistant to the corrosion sometimes associated with wastewater
applications. And, due to the fact that there is no external
weight and lever on the valve, the external moving hazard was
eliminated making for a safer working environment.
"We
were amazed at how quiet it was! After that we were pretty
much sold. Another valve went down and I replaced it
[with a SURGEBUSTER]. As the other 2 go down I will replace
those as well," the system operator declared.
For
more information on the SURGEBUSTER and to view tests conducted
with the valve, contact valves@valmatic.com
. Copies of the test are currently available on CD-Rom,
DVD, and VHS.
Mission:
Possible
Using
Glass Lined Plug Valves to Tame Struvite
By:
Val-Matic
Your
system was running like clockwork. The pressure and flow
are normal and everything is moving smoothly. You are
about to leave for the night, when you start to notice the flow
rate dropping. The back pressure starts increasing while
your flow is steadily decreasing. Getting concerned,
you check on things and find that the flow rate has all but
slowed to a trickle.
It
is a quick search, and when you locate the problem it is not
what you want to hear. Struvite. Also known as
magnesium ammonium phosphate, Struvite can develop quickly and
its crystals can grow like weeds until it all but shrinks your
flow area to nothing.
A
common occurrence in wastewater treatment plants, Struvite can
quickly get out of control. When the conditions are right,
the Struvite will rapidly form crystals that spread throughout
a pipeline forming a concrete-like crust. It is most
commonly a problem in dewatering filtrate or lagoon decant and
in spots with local turbulence, such as pipe elbows, mixer blades,
and pumps [1] .
The
Madison Metropolitan Sewerage District in Madison, WI was well
acquainted with Struvite. A large plant, the Nine Springs
Wastewater Treatment Plant treats over 40 million gallons of
wastewater per day, and serves over a quarter of a million residents
in Madison and the surrounding townships. It's sprawling
compound is fed by 120 miles of interceptor sewers and force
mains, and it boasts over 100 pumping stations [2]
.
"We
have a problem with Struvite forming in digested sludge lines.
We've also seen it in plug valves," said Jeff Brochtrup, Director
of Administration, formerly Project Manager for digestion improvements
project at the Nine Springs Wastewater Treatment Plant.
To
combat the Struvite problem, the Madison Metropolitan Sewerage
District partnered with engineering firm Black and Veatch along
with mechanical contractors J.F. Ahern Company.
"Madison
has had a significant history of Struvite accumulation within
their digesters and associated digested sludge piping and valves,"
said Scott Fronek, Project Engineer with Black and Veatch.
Struvite
can become debilitating if left unchecked. Like cholesterol
coating the walls of vessels and arteries, Struvite can reduce
flow area significantly, severely restricting flow and reducing
pressure. Its effects aren't only felt there.
Struvite
can damage equipment, especially valves. "Struvite
becomes a problem with valves because when the valves close,
the Struvite rips the rubber faces of the plugs. It not
only reduces flow, but you lose the ability to close the valve
snugly," commented Jeff Brochtrup of Madison Metropolitan.
It
also requires frequent, laborious maintenance, as the employees
at the Nine Springs Wastewater Plant learned. "Madison has
experienced some maintenance issues as a result of Struvite
accumulation. Struvite would normally build
up on the inside of piping and valves, causing a reduction
in flow. This necessitated disassembling the piping system
to chisel the Struvite from the piping and valves," said Fronek
of Black and Veatch.
The
proposed solution: install glass lined plug valves. The
glass lining provides a smooth, non-stick surface that helps
to prevent the collection of elements that lead to a Struvite
build up in a location that is known to be a likely problem
area.
"Most
plug valves are provided with a fairly rough epoxy
lining to which Struvite can attach. Glass lined
plug valves were chosen because they provide a smoother interior
surface and will reduce Struvite accumulation on the plug
valves," commented Fronek.
Though
not readily available as a coating option, glass lining plug
valves in a Struvite-prone environment has a number of benefits
in addition to Struvite reduction. "Part of the decision
to go with glass-lined plug valves is to cut down on friction
loss, " said Bart Barthaly, Assistant Project Manager with J.F.
Ahern Company.
To
find the glass lined plug valves, they turned to Val-Matic Valve
and Manufacturing Corporation.
"Glass
lining is a highly specialized option. Val-Matic is one
of the few manufacturers who provide glass lining for all sizes
of plug valves," said Carl Smith, Director of Sales for Val-Matic.
So
far, the Nine Springs Wastewater Treatment plant has installed
nearly 20 Val-Matic glass lined plug valves.
There
are other methods of Struvite removal. Some utilities
depend on a variety of chemical control methods. Though
these methods can be effective, they can also be costly and
would be an indefinite expense in order to keep the problem
in check. By choosing to glass-line the plug valves,
an area particularly prone to Struvite growth, there is only
the upfront cost to consider.
Madison
Metropolitan Sewerage District is one of a number of utilities
making the switch to the installation of glass lined plug valves
to alleviate their Struvite problem. No longer will they
have to waste valuable man-hours chiseling out inches of Struvite
in order to get their pipeline flowing again, or have their
system running below capacity due to a build up of Struvite.
Will you?
[1]
Some information for this article was gathered from an
article by Mario Benisch, Daniel Clark, Robert G. Sprick, and
Rob Baur in the August 2002 WE&T Magazine entitled, "Struvite
Deposits: A Common and Costly Nuisance."
[2]
Information about the Madison Metropolitan Sewerage District
can be found on their website at www.madsewer.org.
These
pictures show the glass-lined plug valves installed in the Madison
Metropolitan Sewerage District, and a look inside an unfinished
casting of a plug valve that has been glass-lined.
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