TL-115

 

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.

Thermoplastic Pumps

INDUSTRY:

ENTITY:

SOLUTION(S) PUMPED:

PUMP TYPE(S):

Chemical

Wheaton Glass Products

Hydrofluoric acid

CHEM-GARD Horizontal Centrifugal Pump

Reprinted from CHEMICAL PROCESSING

By Brayton O. Paul, Technical Editor

 

Plastics, alloys meet challenges of hydrofluoric acid

etching

 

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

frosting process.

 

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

corrosion.

 

"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

the pump.

 

"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

holding tank.

 

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

fittings.

 

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

fabricated angle.

 

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

downtime.

 

Improved quality

 

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

recorded.

 

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.

Copyright 2016 - Vanton Pumps (Europe) Ltd - All rights reserved

About Us

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.

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UNITED KINGDOM

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