Cut-away of Vanton Chem-Gard®
polypropylene pump with PVDF impeller
and PVDF thick sectioned shaft sleeve.
These horizontal centrifugal pumps
helped solve the severe
corrosion/abrasion problem created by
the pumping of an etching solution of
hydrofluoric acid and a proprietary
powder compound. Both metal and FRP
pumps previously specified for this
service resulted in repeated failures
and costly maintenance.
Wheaton Glass Products
CHEM-GARD Horizontal Centrifugal Pump
Reprinted from CHEMICAL PROCESSING
By Brayton O. Paul, Technical Editor
Plastics, alloys meet challenges of hydrofluoric acid
Wheaton Glass doubles production without speedup, reduces rejects
to almost zero.
The Decora Division of Wheaton Glass Products, a division of Wheaton
Industries in Millville, NJ, eliminated downtime, doubled production and
reduced its output of rejected product to almost zero by eliminating
slurry settling and hydrofluoric (HF) acid corrosion problems in its
The frosting department was having difficulty using a slurry of HF acid
and solids to etch designs onto glass bottles. The content of the
proprietary gritty solid compound was between 30% and 50%. If the
slurry stagnated, abrasive particles settled out of the solution to form a
concrete-hard solid. But Wheaton Glass Products' larger problem was
"When I transferred from corporate engineering in 1984, I was told the
problem in the frosting department was solids settling out of
suspension in the etching tanks. As I started to investigate, I found
settling was only part of the problem; corrosion was a major issue. I
had to solve the whole problem," says Peter R. Shadinger, P.E., project
manager for the Decora Division.
Production: out of control
Every two hours, operators of the two existing lines — one manual and
one automatic — needed to stop production to stir the HF slurry with a
wooden paddle. On the manual production line, operators briefly
immersed 30 to 50 bottles for frosting in the vat. On the automatic line,
which resembled the manual line, the bottles were attached to a
stainless-steel chain. Neither the wood nor the carbon vat, both of
which were about 2 cu. ft., had sufficient space for agitators. Production
personnel also experienced problems with a new glass formula that
would not frost properly.
Before Shadinger became project manager, one ½-hp plastic circulation
pump with stainless internals operated adjacent to each of the two vats.
Each vertical centrifugal pump was too small to keep the vat agitated.
After about two months of continuous service, the stainless-steel
internals within the preserved plastic casing would corrode, resulting in
the need to replace the pump. These frequent replacements continued
for three years.
"The process was out of control. Production had no temperature or
solids-mixing controls. Sometimes production stopped for hours
because the temperature was wrong." Glass does not frost below 70°F,
and HF acid fumes above 90°F.
System redesigned with plastics
"Someone before me had purchased a 3-½-hp plastic pump with
120-gpm capacity. There were no provisions for its use or process
modifications. I had to redesign the whole system before I could install
"First, I redesigned the vat on the manual line." The vat's pump handled
the corrosive nature of the slurry, but its capacity was undersized.
Shadinger designed a holding tank to feed the pump. The pump
discharge went to the existing vat and then overflowed into a new
This system was a significant improvement because the operators only
needed to stir the slurry once during each eight-hour shift, rather than
every two hours. (The vat still had to be cleaned weekly.)
Next, Shadinger redesigned the vat, adding a mixer. After the redesign,
the operators needed to stir the vat only once a week.
Shadinger tested many materials to handle the severe corrosive nature
of the HF acid slurry. Originally, he specified only polyvinylidene
fluoride (PVDF), but he found that some components of the system
were unavailable in that material. Then, he tried polypropylene, which,
at half the cost, has become the preferred material of construction for
the vats and pump casings. The pump impellers are still specified in
PVDF. To maximize corrosion resistance, the pump design eliminates all
metal contact with the slurry. The stainless-steel shaft is isolated from
the fluid by a thick-sectioned PVDF sleeve. The mechanical seal is
reverse-mounted, so metal components are outside of the wetted area.
Shadinger replaced the original corroding stainless-steel pipe with new
schedule 80 polyvinyl chloride (PVC) glued and backwelded pipe and
Stainless-steel immersion heat exchangers were installed to control the
temperature to ±2°F. "They cost a fortune, and they didn't last long." To
save money, the plant eventually replaced the original heaters with
units made of standard freon-grade copper tubing assembled with 45%
silver brazing alloy.
The chain on the automatic line rides on a metal angle about 1 in.
directly above the acid vat. Splashing corroded the original ¼ x 2 x 2
stainless-steel angle continuously, necessitating its annual replacement.
Shadinger replaced the stainless steel with a nickel-based-alloy
The chain's original stainless-steel sprockets also needed frequent
replacement. Four years ago, Shadinger replaced them with sprockets
made from ultra-high molecular-weight polyethylene (UHMW-PE).
No more paddles
Today, the tanks are twice their original size and the pumps three times
the original capacity. The polypropylene pumps with PVDF impellers are
driven by 7-½-hp electric motors at 1,750 rpm and are rated at about
300 gpm. At about 200-gallon slurry volume in the tanks, the turnover
rate is 1.5 per minute. "We eliminated the hand paddle," Shadinger says.
"Originally, we stirred the vat four times per shift with a wooden paddle.
We drained it every weekend. After the larger pump was installed, we
didn't use the wooden paddle, but we still drained the vat every
weekend. Now we don't do anything, we just run it. We haven't drained
the tank in six or eight months, and there is zero settling in the bottom."
Shadinger says that production has increased 10% per year since 1989.
Water consumption is down 10-fold. The increase in production is the
direct result of keepinq the production line operating without shutting it
down for stirring or temperature control. There is no unscheduled
Before Shadinger's transfer, 5% held ware (rejected product) was the
target production standard, although 20% was common. Today, the
product is more uniform. Held ware, which is near zero, is no longer
Changes in materials of construction have reduced maintenance. Neither
the nickel-based alloy angle that conveys the production chain above
the automatic system vat nor the polyethylene sprockets for the chain
have been replaced since installation four years ago. Shadinger says
each copper heat exchanger lasts for several years. The only problem
the plant is having with the pump is that the seal lasts only about one
year, but Shadinger says, "We are really happy with that."
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WHEATON INDUSTRIES 100TH ANNIVERSARY
Wheaton Industries celebrated its 100th anniversary in 1988. The
company began as T. C. Wheaton Co., when Dr. Theodore C. Wheaton,
a pharmacist and practicing physician in Millville, NJ, purchased a
fledgling glass company after having loaned it money. T. C. Wheaton
Co. became nationally recognized as a manufacturer of drug and tablet
vials. The company provided glass products to scientific laboratories,
pharmacists, physicians, manufacturing chemists and perfumers.
Today, Wheaton Industries is still a privately held firm.
Wheaton Glass Products, a division of Wheaton Industries, produces
containers for the pharmaceutical, health-care, cosmetic fragrance,
personal care, beverage, food and household industries. In addition to
the manufacturing plant in Millville, NJ, Wheaton Glass Products, which
has 3,400 employees, comprises five companies with 19 plants in the
United States and Puerto Rico. The company specializes in executing
challenging glass container designs.
In the 1950, Vanton developed a revolutionary all-plastic pump for use in conjunction with the first heart-lung device. The design limited fluid contact to only two non-metallic parts: a plastic body block and a flexible liner. This was the birth of our Flex-I-Liner rotary pump. Its self-priming sealless design made it an industry standard for the handling of corrosive, abrasive and viscous fluids as well as those that must be transferred without contaminating the product. Vanton now offers the most comprehensive line of thermoplastic pumps in the industry.
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Vanton Pumps (Europe) Ltd.
Unit 4, Royle Park
Congleton CW12 1JJ