Full Service Cleaning, Stripping and Powder Coating

Article From: Products Finishing, , from Products Finishing

Posted on: 9/1/1996

Vance Darlage was set for life.

Vance Darlage was set for life. He worked in the family agricultural business, made a decent living, started a family and planned to "grow old" in his hometown of Seymour, Indiana (pop. 15,576). However, this enterprising young man was not content to simply follow the road map placed before him.

A street rod enthusiast, Mr. Darlage occasionally took his car parts to a local company for stripping and derusting. After a while, however, he decided to do it himself. Although he retained his job at the fertilizer manufacturing company, he took a chance and opened a paint stripping and derusting business in 1989.

The 8,000-sq-ft shop in downtown Seymour had two vats, a fork truck and one employee, not Mr. Darlage. After a year Mr. Darlage could no longer work one job and run Metal Prep, so he quit his job at the agricultural company and worked for his own company full time.

In 1992 the business moved from the small downtown shop to a larger, 30,000-sq-ft building just outside of Seymour. By May, 1995, Metal Prep added 23,000 sq ft of manufacturing space. It was no longer a two-dip operation. It currently has almost 50 employees and more than 100 customers in 12 states.

The company now boasts three automated turntable washers, blast cleaning, bake-off ovens, vibratory equipment as well as three powder coating lines and a fleet of trucks.

Before parts are stripped, cleaned or derusted, the type of material and coating to be removed must be determined. An MSDS on the coating to be removed is reviewed to comply with EPA regulations and company environmental policy. After that, the most effective removal method is applied. Three Proceco turntable washers and the bake-off ovens do the majority of the work at Metal Prep; however no system is ever idle long.

The automated washers handle large, heavy parts, such as engines for large generators and mining trucks. The engines are shipped to Metal Prep for cleaning and degreasing prior to rebuilding.

Two of the washers are stationed approximately 30 ft apart with an overhead hoist system running between them. This is used to load the heavy engines and other parts onto racks. The racked parts are then positioned in the nine ft tall washers. The five ft wide turntables have a capacity of 5,000 lbs.

Inside the systems the wash manifold and V-jet spray nozzles provide fan-shaped, high-velocity, high-impact cleaning spray from the top, bottom and sides. The turntable rotates on permanently lubricated ball bearings. An adjustable roller chain permits slippage when falling parts obstruct free rotation.

The control system features a cycle timer that allows operators to set individual cycle times for wash, rinse, fresh water rinse, blow-off and exhaust stages. Control cycles are programmed into the system so that each time a part arrives at Metal Prep the cycle is simply called up and run without reprogramming.

The washers also feature an automatic sludge removal and grease skim conveyor that automatically scrapes sludge from the tank bottom and skims floating grease from the solution surface.

Parts as large as car bodies and many smaller ones are stripped in burn-off ovens, including some that are subsequently sent to the washers. Metal Prep has four bake-off ovens. The smallest oven is 10-by-8-by-10 ft and the largest is 10-by-10-by-18 ft.

The ovens are used to strip paint, adhesives and other substances from a variety of parts. Stripping paint and powder coatings requires approximately two to four hrs, depending on the amount and type of coating and the oven temperature. For example, if 100 fixtures are cleaned each hr, then the oven used is one sized for 250 to 450 parts. A space is allowed that is equal to one diameter between fixtures for hot gas and cooling water spray to circulate.

When parts are in the ovens, sufficient space is allowed for hot gases to circulate between parts. An oven load of parts and/or fixtures requires five to eight hrs, depending on processing temperature. Some of the large engines are baked to remove adhesives and other materials prior to washing in the turntable washing system.

The ovens also have a fire prevention system. Ovens do not actually burn off the coating or other contaminants, since this could cause the parts to become extremely hot and warp or melt. Instead, the ovens thermally decompose the solids into a combustible vapor in a low-oxygen atmosphere to inhibit combustion and then destroy the vapor in an afterburner.

The dynamic response system in Metal Prep's ovens monitors the combustible vapor concentration and controls it at a safe level. The system responds to the load and does not require operator intervention.

The ovens use a rate-of-change control system, which is a factory programmed system that continuously monitors the heat-up rate of the oven chamber and the afterburner. If either heats up too rapidly, the load is cooled until the heat rate is acceptable. If water systems fail to cool the load, the primary burner automatically shuts off to stop the process.

The oven also has an automatic cycle timer that senses when the oven is no longer producing combustible vapor and is up to the pre-selected temperature. This indicates that the oven can be safely shut off without releasing smoke to the atmosphere. A second thermocouple in the coolest part of the oven assures that parts are uniformly heated before shut-off.

Once parts are baked they go through a chemical process for derusting and ash removal.

Another method of metal cleaning at Metal Prep is plastic shot blasting. This is done largely on aluminum substrates, such as wheels and the aluminum pieces on engines. Metal Prep also has a small vibratory system for deburring smaller parts.

In addition to all this metal cleaning, derusting and preparation, Metal Prep can also powder coat parts. It has one manual batch coating line and a conveyorized line. All lines are manufactured by Nordson Corp.

The conveyorized line has heavy I-beam conveyors to hang parts up to 400 lbs. It can accommodate parts with dimensions up to two and a half by four and a half by five-ft one-inch. Prior to powder coating, parts go through a five-stage pretreatment system. The sequence is cleaner, rinse, iron phosphate, rinse, rust preventive and sealer. The iron phosphate from the pretreatment line is used to lower the pH in wastewater treatment. Parts are then dried in a direct-fired, forced-air oven. The conveyorized powder coating system features a polypropylene powder coating booth with a three by five ft vestibule opening. A powder reclamation device is inherent to the system. Six automatic reciprocating Versa-Spray guns and two manual guns are used to spray the variety of parts. Colors primarily used are black and white, but a number of colors are used regularly. Parts are cured using gas-fired ovens.

The powder coating batch line handles parts six-by-six-by-15 ft.

Metal Prep's quality assurance includes a continuous improvement program. "We are becoming more automated," noted Mr. Darlage. "Automation helps with quality control, production and safety. We only
have one caustic dip tank left, and we would like to eliminate that." The company uses no chlorinated solvents. All chemicals used for stripping and derusting are biodegradable.

Metal Prep can provide transportation using trucks ranging from one ton to 48-ft tractor/trailers, ensuring timely pickup and delivery.

The chance Vance Darlage took in 1989 has paid off. He attributes the growth to total communication with his customers, providing the best service and a commitment to environmental safety by not using cold strippers and adhering to EPA prescribed disposal methods. Not only is Mr. Darlage running a successful business, he was named 1996 Small Business Person of the Year by the Seymour Chamber of Commerce.

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