[ Return ]
Log vats condition Neson Pine peelers
National Forests & Timber March/April 2002
"An overhead gantry crane is used to load the vats and a second crane unloads the vats.The vats are covered when full and hot water is circulated through heat exchanges to maintain the temperature," Rick Herd, General Manager, Nelson Pine New Zealand.Nelson Pine Industries in New Zealand has recently commissioned a new laminated veneer lumber (LVL) manufacturing facility.
"We heat logs to get a better quality veneer," explained Rick Herd, general manager of Nelson Pine. "We find that the veneer produced from these conditioned logs has a smoother finish and giver better glue adhesion between the laminate LVL panels eventually."
"We have been producing veneer since last October, and although we are currently exporting our product, ultimately, we intend to use it in the production of LVL."
"We contracted Southern Cross Engineering to do a turn key project to design, build and install the vats as well as the materials handling system into and out of the conditioning vats.
From an existing debarker, logs, on an average at 300 to 400mm but sometimes up to 800mm are cut into 2.4 and 2.74 metre (8-9ft) blocks on a bank of five saws.
These blocks are swept into bins from which they are retrieved. One overhead gantry crane is used to load the vats and a second crane unloads the vats. The vats are covered when full and hot water is circulated through heat exchangers to maintain the temperature," Rick explained.
In addition to their range of specialised materials handling equipment, the New Zealand company Southern Cross Engineering also sell and install cranes for a range of end uses.
"When the blocks are conditioned, they are placed on a central transfer which feeds via a log singulator onto a 65 metre log conveyor into the veneer mill.
"The 550 cubic metres of water in the closed system is circulated through the five heat exchangers of a megawatt capacity each which are heated using excess process steam from the heat plant that energises the veneer dryer. The system is designed to cut and condition 830 cubic metres per day."
The advantages of conditioning logs before peeling or slicing are well known. For many years soaking ponds were the way to go. Due to energy consumption, waste disposal and various other issues alternative methods including steaming chambers have been tried.
Today, with the advent of modern controls, monitoring systems and improved manufacturing techniques, log vats offer many advantages over steaming or water spray systems.
Advantages of the new Southern Cross Engineering log conditioning system are:
- Less land required as marshalling space for log carts is not required
- Less energy costs as the current site energy plant can work with water in the system to create a "heat battery" whereas steam chambers require a constant and consistent energy source
- Transfer of heat to the log is more efficient when it is soaked in water the modern heat exchanges are designed for effortless mechanical cleaning on the rare occasions it is required.
- Lower running costs as log loaders are not required
- The heavy concrete construction is extremely thermally efficient and more robust that aluminium chambers
- The vats never require cleaning as draining in normal operation removes almost all debris, whereas steam chambers need regular cleaning due to the build up of debris on the steam generator can affect efficiency
- All log-conditioning systems must deal with waste water that contains tannins etc from the logs
- The vat system allows for monitoring and control of water volume (temperature, pH etc)
- The discharge of waste can be at a rate consistent with the ability of the site effluent plant
- Steaming chambers often provide an environment conducive to fungal growth.
Management personnel at Nelson Pine say that to date they are all very pleased with the mill's new end product and the efficient log conditioning and block handling system as the initial component of their LVL plant.
[ Return ]