LIGHTWEIGHT, CORROSION RESISTANT VICTREX® PEEK™ PIPE FEATURED IN WOOD DRYING APPLICATION

Manufacturing wood siding from a raw piece of wood to a finished product allows Cape Cod Wood Sidings to control the quality at each stage of production. A critical stage in that process is kiln-drying the lumber after it has been sawn into boards. One of the inherent problems in wood drying is external corrosion of the piping in the kiln’s heat exchangers. Seeking a corrosion-resistant solution, the company decided to install two types of pipe in the kiln to compare which one would perform better. One was VICTREX PEEK pipe, a thermoplastic polymer-based pipe, and the other was Super Duplex, a corrosion-resistant alloy pipe. The trial was based on the successful completion of 4,000 hours of steam service.

“In the kiln environment, external corrosion is a major factor,” explained Doug Creelman, Managing Director of Marwood Ltd. “Chlorides and pH can cause rust and stress corrosion pitting of the pipes. Due to the corrosive environment carbon steel pipe lasts approximately six months and the stainless steel option is expected to last approximately up to two years, while the VICTREX PEEK polymeric pipe is not susceptible to corrosion, and is expected to surpass and outlast both systems providing advantages with lower operational reliability and reduced maintenance costs.

During the drying process, the pipe carries steam to the heat exchanger and condensate away from the heat exchanger,” explained Creelman. “The steam heats the kiln and provides a controlled humidity level. The objective is to remove moisture from the wood, which prevents shrinkage and warping after the siding is installed on a building.” Regulating the temperature and humidity of the circulating air is a major factor in successful kiln drying. “Because the VICTREX PEEK pipe has lower heat transference than steel pipe, it provides for a more even steam temperature throughout the run of the pipe, and reduces heat loss. This translates into delivering more efficient heat transference,” said Creelman.

In addition to offering corrosion resistance on both the OD (outer diameter) and ID (inner diameter), VICTREX PEEK pipe has the advantage of being lighter and easier to work with for the installer. “This is an added benefit,” explained Creelman. “The heat exchangers are located near the roof of the kiln, in line with the circulation fans. The fact that the VICTREX PEEK pipe is lighter allows for less weight hanging from the wood frame structure, and can reduce the overall structural stress.”

Installers can simply use standard threaded off-the-shelf fittings, making installation easier and faster. Bill Pernice, Pipe Market Leader at Victrex explained, “Installing VICTREX PEEK pipe is simple because the fittings can be installed by a regular operations team, whereas Super Duplex requires hiring a capable certified welder.”

VICTREX PEEK pipe is available in 12.19m (40 ft.) joints, which could eliminate the need for multiple connections when compared to systems that require welds every 3.04 to 6.10m (10 to 20 ft). “Fewer joints allow for faster, more efficient installation, less hydraulic friction, and fewer opportunities for leakage,” said Pernice. “The availability of VICTREX PEEK pipe in specific lengths was not an issue in this particular kiln design because we need to make a connection every 3.04 to 6.10m (10 to 20 ft) to connect the heat exchangers along the length of the kiln,” said Creelman. However, the 12.19m (40 ft.) lengths could be a significant advantage in a range of other markets such as Oil and Gas, and Aerospace where the combination of VICTREX PEEK polymer properties makes the pipe technically attractive and cost effective.

Commenting on the outcome of the trial, Creelman said that the failure identified prior to the completion of the 4,000 hour steam test was “…improper welds on the Super Duplex pipe connections.” VICTREX PEEK pipe, on the other hand, successfully completed all 4,000 hours of steam service without any leaks or other failures.