A Pulp & Paper Canada Special ReportEurocan Pulp & Paper, a unit of West Fraser Mills, manufactures more than 400 000 tonnes per year (t/y) of unbleached sack kraft and liner board and employs more th…
A Pulp & Paper Canada Special ReportEurocan Pulp & Paper, a unit of West Fraser Mills, manufactures more than 400 000 tonnes per year (t/y) of unbleached sack kraft and liner board and employs more than 500 people at its Kitimat, BC, mill. After nearly 30 years of operation, the facility’s brine and caustic lines were in need of replacement, as evidenced by the build-up of crystalline deposits where threaded joints had leaked.
The mill pumps water from the nearby Kitimat River through 36-in. seamless welded steel pipe to a treatment plant where it passes through pressure filters. Filtered water is then pumped to a demineralization plant where generator banks add a 5% caustic solution and brine to adjust the pH level for boiler make-up. Raw water is piped directly to the press sections of the paper machines and for general plant use.
The caustic solution and brine used for regeneration in mixed beds are pumped from their respective tanks through two lengths of 2-in. pipe off the pumps that reduce to 1.5 in. to build pressure to 45 psi. The caustic line was threaded stainless steel, the brine line threaded black steel, both Schedule 40. Yet another line was used to feed caustic solution to the water treatment plant.
Eurocan decided to replace this piping with a pressable Schedule 5 316 stainless steel system provided by Victaulic Company of Canada, Rexdale, ON. The pipe was supplied by Westlund Industrial Supply, which stocks several hundred feet of each size up to 2 in.
“We wanted a stainless steel system because of the corrosive nature of the media,” said Scott Campbell, the mill’s steam and recovery maintenance supervisor.
“At first, we were leery about using Schedule 5 pipe,” he explained. “But the manufacturer demonstrated that threading Schedule 40 pipe actually leaves less wall thickness at the joint than Schedule 5 pipe that has been assembled using the Pressfit system. Its simplicity also reduces the manpower required to install it.”
Originally introduced for use with lightweight Schedule 5 carbon steel pipe, the system is based on technology that has been used in Europe for more than 30 years. Its speed and ease of assembly provide significant savings. And since it does not require welding, threading or flanges, the system eliminates the use of flame and resulting pipe distortion. Also eliminated are cutting oil, chips and extensive pipe preparation. Assembly simply involves cutting the pipe to size, marking it, inserting it into a coupling, and pressing the coupling into the pipe with a special handheld electric or hydraulic tool.
Made of Type 316/316L stainless steel, the couplings incorporate precision-molded synthetic rubber O-ring seals. They also contain internal pipe stops to assure uniform take-out from overall centre-to-end or end-to-end dimensions for simplified fabrication. The jaws of the assembly tool engage the entire circumference of the coupling and compress it uniformly to indent the pipe providing a mechanical bond between pipe and fitting. In the process the tool also compresses the seal against the outside diameter of the pipe and the inside of the coupling to create a permanent leak-tight seal.
The system includes couplings, elbows, tees, reducers, and adapters to facilitate field make-up of fitting combinations for reduction and connection to threaded or flanged components.
In the process of replacing the existing piping, the caustic line broke, the result of years of deterioration. Mill crews ran 150 ft of pipe in just four hours, averting a shutdown of the water treatment plant, according to Campbell. “The system is quite easy to use and eliminates a lot of welding time on the elbows and fittings,” he explained. “Plus there are no leaks. Caustic and brine find their way through threads.
“Just two people were needed to install the system, one to level the pipe and another to operate the pressing tool. Although the components are somewhat more expensive than conventional systems, you more than make up the difference in labor savings.”
Eurocan used Pressfit flange adapters coming off the pumps. However, instead of using Pressfit valves, the company opted for standard ball valves with threaded adapters, all of which leaked, according to Campbell. “The leaks stop after they crystallize,” he joked, “but the next time we’ll use Pressfit valves as well.”
The “next time” in this case is already completed, a new $35-million pulp washing line that was installed using the stainless steel Pressfit system. Although he did not know the details, Campbell noted that another major Canadian pulp and paper mill is planning to use Pressfit.P&PC
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