Industrial timber treatment regulations
26 Feb 2014
Natural wood needs protection from the elements and from infestation whether it is used in construction, building panels, playground, kitchen appliances or heat treated pallets.
The risks of infestation and deterioration are greater if the wood is used outdoors and has to survive constant contact with moisture, heat, cold and insects. This is particularly the case with low durability softwoods that are used for budget garden furniture as well as industrial pallets.
High pressure impregnation
Protection for timbers is provided by high pressure impregnation. This provides a coating around the cell walls and cavities that make up the wood structure. The process works though a combination of vacuum and pressure. Air is removed from the cavities by the vacuum and is replaced by a wood preservative.
The International Standards for Phytosanitary Measures No 15 – ISPM 15 – are regulations that address the heat treatment of industrial timber of thicknesses greater than 6mm.
This treatment is carried out in a pressure vessel called an autoclave. Regulations on timber treatment not only stipulate the design and construction of the pressure vessel, but its operation, maintenance, the risks associated with its safeguarding and the training of personnel involved in the treatment process.
Treatment plant regulations
British health and safety laws require that industrial timber treatment plants comply with:
Employers are required to take all practical steps to ensure that the treatment processes are safe and do not endanger the health and safety of employees. Appropriate instruction, training, supervision and staff welfare should be provided. This includes changing facilities, a deluge shower to wash any possible of whole body contamination.
The operation of autoclaves is governed by:
• Provision and Use of Work Equipment Regulations
• Pressure Systems Safety Regulations (PSSR)
The main risks arise from the:
• Vessel components
• Pressuring medium
• Vessel contents
The treatment plant operators have to determine the following:
• Key issue risk factors such as operation and control, loss of power, pressure and over temperature, inadvertent pressurisation and depressurisation, vessel location and the possibility of vessel lids opening violently
• Some autoclaves are large enough for a person to enter inside. In this case, they should be provided with safety alarms or pull cords that will execute an emergency stop
Additional safety devices include:
• Only one of the autoclave blowdown valves should be in an open position at any time in order to avert an pressurisation blowdown
• In smaller autoclaves, the door seal may crack and open the door violently under pressure. Pressurisation should not be possible in the vessel unless the door is closed
• Nil pressure should be verified before the vessel is opened
The PSSR regulations stipulate that any significant repairs should be communicated to a competent person. Arrangements have to be made that the vessel is properly maintained. In addition, preventative maintenance should be carried out by experienced people and this should form the basis of a maintenance programme
There should also be frequent check of the equipment for any build ups of waste materials or other detritus. Bolts and welds should be checked regularly for cracking.