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Wood preservation facilities, general recommendations: chapter A, table 20

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Table 20. Recommended Operating Practices for Process Systems (All Preservatives)

Routine checks

Objective: Define procedural practices that will enhance environmental and worker safety.

Operation Recommendation
Worker safety
  • Follow the personnel safety precautions for all procedures from Tables 6 and Table 8.
  • Procedure for operating practices should be available to workers.
Work solutions
  • Regularly check and record quantities of treatment solution in storage.
  • Test and record solution strengths at regular intervals.
  • Take necessary measures to prevent solution contamination.
All process components
  • Condition wood adequately to minimize after-bleeding.
  • Visually check the complete system for leaks: take immediate action to stop leaks.
  • Check sludge levels in retorts: clean out as appropriate, in accordance with facility policy, observe personnel safety precautions.
Tank vents
  • Test tank vents to ensure they are not blocked (suggest once/year).
Charges
  • Secure loads to avoid uncontrolled floating and jamming.
  • Stack loads to allow good drainage of preservative from all wood surfaces after treatment.
Treating cylinder
  • Check door seals for damage and wear: replace door seals at regular intervals or as required if damaged or worn.
  • Check cylinder doors for proper seal after loading charges: ensure that all bolts on doors are securely fastened or that the hydraulic collar has moved to its regular endpoint.
  • Recommend that a final vacuum process be applied after completion of the pressure cycle.
Recycle systems
  • Check filters: clean or replace if necessary.
Trams
  • Clean soil and debris from trams to prevent contamination of the preservative.
  • Use tram design that will facilitate ready drippage during “drain” stage.
  • Thoroughly clean trams before alternative preservative treatments are used.

Checks during treatment

Objective: Monitor the treatment system to quickly identify potential/actual problems.

System integrity
  • Process controls should be installed, maintained and calibrated in accordance with the proper standards and/or the supplier directions.
  • Closely monitor process systems for leaks during initial stages of treatment.
  • Check for leaks or abnormal conditions throughout pressurized system at least once per shift or once per charge (whichever is more frequent).
  • Frequently inspect and test all safety shutoff valves and other fire safety devices.
  • Compare recording instrument readings with indicating gauges and thermometers.
  • Note malfunctions of recording devices, thermometers, gauges (including level floats) and arrange for prompt repairs.
  • Carefully observe pressures during treatment to make certain that maximum limits are not exceeded (maintain records of treatment cycles, tank gauge readings and chemical consumption).
  • Define (in writing) operator actions for abnormal situations of concern (e.g. response to equipment breakdown).
Treatment cylinder
  • Recommend that a final steaming/vacuum process be applied after completion of the pressure cycle to equilibrate internal wood pressure and to cool the wood.
  • Keep net retentions as close as possible to specified levels.

Post-treatment checks

Objective: Prevent worker contact with treatment solution and with freshly discharged loads.

Operation Recommendations
Retort opening
  • Ensure that retorts cannot be opened when liquid and/or pressure remains.
  • Avoid breathing preservative mists or vapours (see PPE in table 8).
Charge removal
  • Pull charges only when the superficial excess preservative has sufficiently drained and the charges are essentially drip-free.
  • Consider accelerated fixation or stabilization methods to reduce potential for transfer of preservative solution to the environment.
Load jams
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