Wood Kiln Heat Exchanger Uses Victrex PEEK Pipe
Marwood division Cape Cod Wood Sidings has selected Victrex PEEK pipe for its wood kiln heat exchanger system to enhance performance and extend service life. The stainless steel fittings used to install the Victrex PEEK pipe are coated with Vicote coatings, based on Victrex PEEK polymer, to protect the metal from external corrosion. The coating is said to offer good wear resistance, high temperature performance, strength and durability.
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. Doug Creelman, managing director of Marwood, said: 'In the kiln environment, external corrosion is a major factor. '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.
'During the drying process, the pipe carries steam to the heat exchanger and condensate away from the heat exchanger. '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,' Creelman added. Regulating the temperature and humidity of the circulating air is a major factor in successful kiln drying. Creelman said: '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,' he added. In addition to offering corrosion resistance on both the outer diameter and inner diameter, Victrex PEEK pipe has the advantage of being lighter and easier to work with for the installer. Creelman said: '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,' he added.
Installers can use standard threaded off-the-shelf fittings, making installation easier and faster. Victrex PEEK pipe is available in 12.19m (40ft) joints, which could eliminate the need for multiple connections when compared with systems that require welds every 3.04 to 6.10m (10 to 20ft). Fewer joints allow for faster and more efficient installation, less hydraulic friction, and fewer opportunities for leakage. '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 20ft) to connect the heat exchangers along the length of the kiln,' Creelman said.
However, the 12.19m (40ft) lengths could be of advantage in a range of other markets such as oil and gas, and aerospace. Victrex PEEK pipe successfully completed all 4,000 hours of steam service without any leaks or other failures.
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. Doug Creelman, managing director of Marwood, said: 'In the kiln environment, external corrosion is a major factor. '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.
'During the drying process, the pipe carries steam to the heat exchanger and condensate away from the heat exchanger. '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,' Creelman added. Regulating the temperature and humidity of the circulating air is a major factor in successful kiln drying. Creelman said: '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,' he added. In addition to offering corrosion resistance on both the outer diameter and inner diameter, Victrex PEEK pipe has the advantage of being lighter and easier to work with for the installer. Creelman said: '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,' he added.
Installers can use standard threaded off-the-shelf fittings, making installation easier and faster. Victrex PEEK pipe is available in 12.19m (40ft) joints, which could eliminate the need for multiple connections when compared with systems that require welds every 3.04 to 6.10m (10 to 20ft). Fewer joints allow for faster and more efficient installation, less hydraulic friction, and fewer opportunities for leakage. '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 20ft) to connect the heat exchangers along the length of the kiln,' Creelman said.
However, the 12.19m (40ft) lengths could be of advantage in a range of other markets such as oil and gas, and aerospace. Victrex PEEK pipe successfully completed all 4,000 hours of steam service without any leaks or other failures.
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