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8/1/1998 | 5 MINUTE READ

CPVC Piping System Prevents Corrosion

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At Delta Airlines, a new CPVC piping system has kept parts from piling up on the shop floor...


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From on-time arrivals and departures to friendly and courteous service, Delta Air Lines strives for excellence. The same holds true for Delta's Technical Operations in Atlanta, Georgia. At this facility, the landing gear of Delta's entire fleet is taken apart, cleaned, plated and reassembled to ensure that the equipment is constantly working beyond expectations.

Until about two years ago, a polyvinyl chloride (PVC) system serviced the ventilation needs in the facility's plating shop, which operated under high temperatures and corrosive conditions. When the system began to fail, Delta knew it had to be replaced by a stronger, more chemically resistant material that could withstand the facility's corrosive environment. The engineers found the solution to their problem in post-chlorinated polyvinyl chloride (CPVC) pipe.

"We needed the performance characteristics typically found in exotic materials, but at the same time our goal was to find the most effective material at the best price," said David Woods, manager, technical facilities, Airport and Corporate Affairs, Delta Air Lines. "Price and performance were the two main factors in selecting a replacement material."

That is when Lee Conner, project manager for Paul W. Heard and Co., Atlanta, Georgia, recommended that Delta talk with BF Goodrich, Cleveland, Ohio, the supplier of Corzan® CPVC. The excellent lifecycle economics, performance capabilities and material consistency of CPVC made it the preferred choice over more traditional alternatives, such as stainless steel and fiberglass. The material, which forms the 2.5 miles of duct, pipes, fittings and valves now in place at Delta's plating facility, has performed with zero rejections since its installation one year ago.

"This was a $3.9 million retrofit project," explained Mr. Woods. "Because of our previous experience with PVC, we wanted to guarantee that the new system would perform well, be cost-effective and not have to be replaced in two or three years. That is why we selected CPVC."

The Delta landing gear facility. Delta's plating facility has the capability to provide an excellent product, from removal through tear-down cleaning, rework, painting and rebuild. The company has worked to achieve a minimum turnaround time for various parts through the introduction of dedicated machining operations, a release priority scheduling system and an in-house plating facility.

At Delta's plating facility, CPVC piping and ducts are used to handle condensate return and tank ventilation, while CPVC-fabricated sheet is used in the chemical spill containment area. A combination of chromic, sulfuric and hydrofluoric acid, effectively handled by the system, is used in the various plating solutions in the rework of landing gear for Delta's aircraft. A wax mask able to withstand 220F protects portions of the parts that do not have to be plated.

At the facility, landing gear parts are stripped and replated to prolong the life of the equipment. Engine parts are broken down into pieces ranging from 1.5 to 3.75 inches for plating. Numerous parts used in Delta's airplanes are rebuilt not replaced, until the end of their usable lives.

Replacing PVC. Previously, PVC components serviced the plating facility's piping and ventilation needs. Approximately two-and-a-half years after its installation, the ventilation ducts became brittle and started to crack under the facility's extreme conditions. Condensate formed in the system's ductwork, causing it to leak at the joint welds. Delta, knowing the system had to be replaced, reviewed a variety of potential materials. PVDF, pure fiberglass, stainless steel, as well as Kynar with a fiberglass overwrap, were among the materials considered by the company.

Going for gold. "CPVC offers an excellent combination of corrosion resistance, mechanical strength and lifecycle economics, all of which are crucial to Delta," said Cornell Iacomi, the consulting engineer involved with Delta's retrofit project. "We knew the material was the perfect match for the needs of the plating shop."

Fiberglass-reinforced CPVC ducts efficiently handle high temperatures up to 148F, while CPVC piping services condensate return temperatures up to 180F. When steam is added to the equation, the material operates under temperatures from 215 to 230F. In addition to handling these high temperatures, CPVC proved itself to be resistant to the aggressive and corrosive chromic, sulfuric and hydrofluoric acid combination used by Delta in its plating operations.

"CPVC, a rigid thermoplastic, is also very corrosion resistant," Ms. Iacomi stated. "It has the structural integrity of metal and is less than half the weight. It was ideally suited for this type of application."

Installation is also faster with CPVC. "It is a lot easier to handle," said Gary Hopkins of Plastek Werks, Inc., the industrial fabricator/installer used for the retrofit project. "Two men can carry a pipe section, reducing the need for lifting equipment. That cannot be done with eight-inch stainless-steel pipe." This allowed Delta to realize additional savings through lower installation and fabrication costs. "Unlike steel, CPVC does not have to be threaded, and cementing sections together is a lot faster than welding," Mr. Hopkins stated.

CPVC components also provide the lower maintenance and cost-effectiveness Delta was looking for in its replacement material. "Knowing that this was a $3.9 million retrofit, we needed a product that would give us a lifespan of at least 10 years," indicated Mr. Woods. "Other materials may have lasted that long, but we couldn't justify the high replacement cost. The performance benefits we are realizing with CPVC thus far looks to more than cover our return on investment."

CPVC chemical containment area. CPVC sheet is also used in the facility's 5,600-sq-ft chemical spill containment area, which is located below the plating bath tanks. Given the aggressiveness of the chemicals used in the plating baths, deterioration was a major concern. Concrete was considered, but could not stand up to the harsh environment. Delta needed a material that could handle the chemicals' corrosive nature and prevent releases to the environment.

CPVC is used with an underlayment for cushioning to contain any spillage that might occur as parts are moved from one plating bath to another. It is also used in the unlikely event that there is a tank failure or rupture.

Teamwork gets the job done. The CPVC supplier confidently stands by its products. Right from the beginning of the project, the company's representatives were available to answer questions and offer assistance.

With a retrofit this size, getting the job done on budget and on time are of primary concern. Not only was the budget met, but the project was completed ahead of schedule. The project, scheduled to take up to 15 months to complete, took only eight.

"Achieving minimum downtime and increased operations can be challenging with systems such as ours, where corrosion can decrease equipment life, interrupt production and create potential environmental issues," said Mr. Woods. "Since installing CPVC components, our parts are cleaned and refurbished as scheduled, not backing up on the plant floor because the plating system doesn't work."