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Title / Pressure treat wood using waterborne preservatives
Level / 4 / Credits / 35
Purpose / People credited with this unit standard are able to: demonstrate knowledge of the principles of pressure treatment processes using waterborne preservatives; demonstrate knowledge of the operation of pressure treatment plants for waterborne preservatives; demonstrate and apply knowledge of preservative formulations and treatment specifications; identify, explain and apply safety and security requirements for pressure plants; assess treatment suitability of wood and estimate solution absorption; prepare and check the wood preservative solution; operate the wood treatment plant and monitor charge and plant performance; assess and confirm wood treatment performance and identify complying product; complete documentation and records and analyse records to improve productivity; apply maintenance requirements for pressure treatment plants.
Classification / Solid Wood Manufacturing > Timber Drying and Treatment
Available grade / Achieved
Entry information
Recommended skills and knowledge / Unit 21758, Explain wood drying, determine wood moisture content and establish equipment correction factor; Unit 155, Demonstrate knowledge of the characteristics of wood; Unit 156, Demonstrate knowledge of phytosanitary standards in the solid wood manufacturing industry; Unit 159, Demonstrate knowledge of environmental issues in wood manufacturing industries; Unit 8339, Demonstrate knowledge of the principles of wood preservation and antisapstain treatment; and Unit 16240, Interpret legislative requirements and workplace compliance relating to wood preservation operations.
Explanatory notes
1 This unit standard does not apply to the preservation of wood using light organic solvent preservatives (LOSP).
2 Definitions
Biological degradation refers to products affected by insects, mould, sapstain, decay fungi, internal brown stain.
Efficacy is defined as being capable of or successful in producing an intended result; effective.
Empty Cell includes but is not limited to: Lowry, Tan dry, Drip free, Lite and Fast treatment processes.
Worksite documentation refers to instructions to staff on policy and procedures (including the application of legislation to worksite situations), which are formally documented, and are available for reference at the worksite. Examples are standard operating procedures, specifications, manuals, and manufacturer's information.
3 Evidence of the outcomes of this unit standard must be presented across the following contexts:
a Treatment processes include but are not limited to: Bethell, empty cell, Q-method, alternating pressure method (APM);
evidence is required of two charges treated to two different hazard classes.
b Evidence is required of 12 recently completed charge records.
4 References
Competence in this unit standard requires knowledge of the following:
a NZS 3640:2003A1 Chemical Preservation of Round and Sawn Timber Amendment 1. This is referred to below as ‘NZS 3640’, and is available from Bennett’s Government Bookshops or online at http://www.standards.co.nz.
b New Zealand Timber Preservation Council, Timber Preservation Quality Manual (Wellington, 2005).
This is referred to below as the ‘TPQM’.
c Best Practice Guideline for the Safe Use of Timber Preservatives and Antisapstain Chemicals (Wellington, 2005).
This is referred to below as the ‘Guideline’.
These last two references are available through the New Zealand Timber Preservation Council, Wellington or online at http://www.nztpc.co.nz.
5 All evidence requirements must be demonstrated and assessed in accordance with the reference text: Pressure Treat Wood (Auckland: Competenz, 2002) and available from Competenz, PO Box 9005, Newmarket, Auckland 1149.
6 The following apply to the performance of all outcomes of this unit standard:
a All work practices must meet recognised codes of practice and documented worksite health and safety and environmental procedures (where these exceed the code) for personal, product and worksite health and safety, and must meet the obligations required under current legislation, including the Hazardous Substances and New Organisms Act 1996, the Health and Safety in Employment Act 1992, the Resource Management Act 1991, and their subsequent amendments.
b All work practices must meet documented worksite operating procedures. This includes the recording (by electronic or non-electronic means) of activities, events, and decisions.
c All evidence of communications gathered in relation to this unit standard must be in accordance with worksite procedures for content, recipient, timing and method.
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of the principles of pressure treatment processes using waterborne preservatives.
Evidence requirements
1.1 The principles and purpose of treatment processes and their effect on wood impregnation are explained in terms of treatment phases, cycles and sequences in accordance with the reference text.
Range Bethell, Alternating Pressure Method, Lowry.
1.2 Advantages and limitations of each pressure process are described in accordance with the reference text.
1.3 Other treatment methods are identified and their treatment principles explained in accordance with the reference text.
Range evidence is required of three.
1.4 Species that are approved for pressure treatment are identified in accordance with the TPQM.
1.5 Types of biological attack are differentiated in terms of their visual appearance and their degrading effect on wood.
Range incipient decay, surface mould, sapstain fungi, decay fungi, internal brown stain.
1.6 The effect of surface mould and sapstain fungi on preservative uptake are explained in accordance with the reference text.
1.7 The influence of moisture content and moisture gradient on treatment effectiveness is explained in accordance with the reference text.
Outcome 2
Demonstrate knowledge of the operation of pressure treatment plants for waterborne preservatives.
Evidence requirements
2.1 The role, scope and responsibilities of the preservation plant operator are described in accordance with worksite documentation.
2.2 Operating parameters, capability and capacity of pressure treatment plants on the worksite are defined.
Range may include but is not limited to – plant design and layout, preservative types, maximum/minimum charge volumes (sawn timber and round wood), packet build and length, treatment methods and schedules, throughput capacity, preservative storage capacities.
2.3 Factors for consideration when scheduling charges to optimise production throughputs are explained.
Range may include but is not limited to – priority order timetabling, species and product suitability and availability by Hazard Class requirement and charge lots, type of treatment, specification requirements, anticipated charge duration, charge batching and succession, preservative stock levels (bulk and in solution), solution status (formulation balance).
2.4 Operating components of the pressure treatment plants are identified, and their function and sequence of operation are explained in accordance with the Guideline and worksite documentation.
Range may include but is not limited to – plant design and layout, treating cylinder and door safety mechanisms, storage tanks, agitation methods used, pumps, valves, pipe work, linkages, filters, sight tubes, flow meters, control panels, automatic and manual control systems, pilot lights, sequence controllers, isolating and reset controls, warning devices, check gauges, solution containment safeguards, product handling systems.
2.5 Plant control and product testing equipment is identified, serviceability checked, and their use explained in accordance with the TPQM and worksite documentation.
Range equipment may include but is not limited to – increment borer, moisture meter, refractometer, titration equipment, chemical reagent viability, pH test equipment, X-ray fluorescence, spot test solutions and chemical viability, vacuum and pressure gauges or certification, sensors, metric ruler, calibrated sight tubes.
Outcome 3
Demonstrate and apply knowledge of preservative formulations and treatment specifications.
Evidence requirements
3.1 Waterborne preservatives suitable for pressure applications are identified in accordance with the reference text.
3.2 Preservative types used at the plant are identified and their properties and uses are explained in accordance with the reference text.
3.3 The efficacy of copper chrome arsenic (CCA) preservative formulations is explained in terms of chemical components, ratios, and balance parameters.
3.4 Influence of treatment process, temperature and product condition on formulation balance and viability is explained.
Range processes – Bethell, Empty Cell, Alternating Pressure Method;
product condition – steam conditioned, air and kiln dried product.
3.5 Causes of solution imbalance are identified and explained in accordance with the reference text.
3.6 Preservative formulation balance and viability is monitored and prevention or corrective measures are explained and applied in accordance with worksite documentation.
3.7 Treatment specification requirements are referenced and explained in accordance with the TPQM, NZS 3640, and worksite documentation.
Range may include but is not limited to – pre-treatment condition, species, preservatives, hazard class, process requirements (pressure, duration, vacuum), quality checks (retention and penetration), product branding or labelling, out-of-specification product, environmental considerations;
evidence required of three levels of treatment, two preservative types and two process methods (one of which must involve dry timber).
3.8 Documentation and charge sheet record requirements are identified and their use explained in accordance with the TPQM and worksite documentation.
Range may include but not limited to – charge sheets, reconciliation statements, sampling summaries, production log books, analytical records.
Outcome 4
Identify, explain and apply safety and security requirements for pressure plants.
Evidence requirements
4.1 Hazardous areas on the treatment site, their safety and security measures are identified and risks explained in accordance with the Guideline requirements and worksite documentation.
Range may include but is not limited to – warning signs and symbols, authorised access areas, chemical storage areas, vacuum exhaust vents, automatic remote control mechanisms, vapour suspension in confined spaces, loading and unloading mechanisms, chemical handling and mixing areas, storage and handling of treated products.
4.2 Risk factors associated with preservative formulations used on the worksite and the safeguards required are explained in accordance with Material Safety Data Sheets (MSDS) and the Guideline.
Range formulations include but are not limited to – copper chrome arsenic (CCA), Tanalith E, Boron compounds, ammoniacal copper quarternary (ACQ).
4.3 Safe operating and housekeeping requirements are explained in accordance with the Guideline and worksite documentation.
Range includes but is not limited to – safe operating practices, codes of conduct and personal hygiene, appropriate personal protective clothing and equipment, chemical and product handling, Material Safety Data Sheets (MSDS) for each preservative type, eye wash, emergency shower, first aid facilities, emergency procedures.
Outcome 5
Assess treatment suitability of wood and estimate solution absorption.
Evidence requirements
5.1 Pre-treatment suitability of the product is assessed and confirmed, and non-conforming product is removed in accordance with the TPQM.
Range includes but is not limited to –
product factors – approved species, product characteristics, surface condition, moisture content and moisture gradient, dimensional thickness, biological degradation, pre-cutting, machining;
production factors – strapping tightness, packet build and length, treatment identification (branding), product/unit identification.
5.2 Required holding period for steamed product is confirmed against steam records and product marks in accordance with the TPQM.
Range Alternating Pressure Method, Q Bethell process.
5.3 Solution absorption is estimated for air and kiln dried product for Bethell and empty cell treatments.
Range may include but is not limited to – product source, species, size variations and quantities, sapwood and exposed heartwood ratios, moisture content, wood density, surface condition, historical charge data;
evidence is required of a practical demonstration plus reference to five recent charge sheet records.
Outcome 6
Prepare and check the wood preservative solution.
Evidence requirements
6.1 Pre-test checks are undertaken on solution testing equipment and test chemicals in accordance with worksite documentation.
Range may include but is not limited to – cleanliness, suitability, correction factors, preparation of chemical reagents and viability checks, refractometer condition, X-ray fluorescence.
6.2 Factors affecting the accuracy of solution concentration measurements are identified and corrective action is taken in accordance with worksite documentation.
Range may include but is not limited to – operator technique, solution contaminants, aerated solution, inaccurate instruments, correction factors, equipment cleanliness and calibration, incorrect references, pH, efficacy of titration reagents.
6.3 Representative solution samples are taken at predetermined times and solution concentration is measured and calculated in accordance with worksite documentation.
Range prior to, during and on completion of treatment process; accuracy parameters in accordance with worksite documentation; and comparisons between operator and laboratory analysis determinations.
6.4 Solution concentration and volume is adjusted in working tanks to meet charge requirements in accordance with worksite documentation.
Outcome 7
Operate the wood treatment plant and monitor charge and plant performance.
Evidence requirements
7.1 Operational steps for treating wood are demonstrated in accordance with worksite documentation.
Range evidence is required of two charges treated to two different hazard classes.
7.2 Critical factors influencing successful charge performance are explained and applied in accordance with the process requirements.
7.3 Pre-start-up preparations appropriate to the process are demonstrated in accordance with worksite documentation.
Range may include but is not limited to – solution concentration confirmation, working tank levels, solution agitation, control panel settings, sequence controls, sump levels, charge sheet entries, product pre-treatment condition, loading, door seal.
7.4 Charge and plant performance are monitored and corrective action taken in accordance with worksite documentation.
Range may include but is not limited to – pressure relief valve and gauges, vacuum intensity, cycle duration, cylinder leakage, solution concentrations, charge absorption, working tank levels, final rate of flow monitoring against charge requirements.
7.5 Equipment faults and malfunctions in the process cycle are identified and corrective action is taken in accordance with worksite documentation.
Range may include but is not limited to – electrical, hydraulic, mechanical, chemical leakage.
7.6 End point of the treatment process is determined and all working solutions are returned to storage and final solution measurements are taken in accordance with worksite documentation.
7.7 Environmental measures are observed for the treated product in accordance with the TPQM, the Guideline, and worksite documentation.
Range includes but is not limited to – use of approved drip areas, drip time allowance according to process type, CCA treated wood product holding times, spillage clean up and disposal.
Outcome 8
Assess and confirm wood treatment performance and identify complying product.
Evidence requirements
8.1 Treatment compliance is determined from charge sheet results and product testing in accordance with the TPQM and worksite documentation.
Range may include but is not limited to – charge sheet compliance parameters, correct product sampling prescription applied, valid test samples collected and prepared, correct interpretation of spot test results, accurate results determination and recording, charge samples batched, labelled and held for audit purposes as required.