TYPES OF PRESEVATIVES.

The customer needs to determine which the best suitable preservative based on availability of the preservative and the specific area where the wooden pole will be in use.

Currently in Africa the customer has an option of the following.

1. Creosote
2. CCA
3. Copper azole compounds (CuAz).
4. Alkaline-copperquaternary compounds (ACQ).

The selection of what type of treated wood pole to use in a particular utility system is an issue of paramount attention and deliberation. While the relative percentage of each of the above preservatives used in utility treated wood transmission and distribution structures varies, each preservative plays a unique and critical role in the overall ability of utilities to provide reliable and cost-effective electrical service to the public.

Each preservative has unique characteristics that are evaluated by utilities in determining which preservative is best suited for use in a particular region of the country. These decisions are based on a variety of factors, including the physical and performance characteristics of the preservative, the location of the service area, and the associated environmental, climatic and developmental (urban versus rural) characteristics of the service area. In circumstances where one preservative may serve as effectively as another in any particular setting (e.g., the use of creosote-treated wood poles in hot, dry climates), other variables such as costs, supply and worker acceptability (e.g., utility linemen may prefer working with one treated wood pole over another) are important factors in selecting the type of treated wood used in a particular setting.

In short, there is not a one-to-one “substitutability” between the above preservatives; rather, each preservative is selected for use by utilities depending on a variety of unique preservative characteristics and the individual needs of each utility.

Currently in Africa the customers are predominantly using creosote or CCA for electrical and communication lines.

CCA.

Although CCA also has an excellent track record regarding its performance as a heavy duty wood preservative, it is a water-based

formulation as opposed to the “oil”-based creosote and therefore does not afford any water repellency or “lubricating” properties to the treated timber. Surface checking and end splitting of CCA-treated Eucalyptus poles as a result of drying stresses are therefore experienced, especially when poles are stored and used under hot, dry conditions soon after treatment. The treated poles should either be properly conditioned and/or dried after treatment to the prevailing relative humidity and resultant wood moisture content before being used in order to avoid any unacceptable surface checking and end splitting.

Drying stresses in poles are caused by moisture differentials, also known as the moisture gradient between the outer layers and the inner core of a wooden pole. When the inner core of the pole is still in a swollen state as a result of high moisture levels and the

outer layers start to dry out and shrink, high stress levels occur on the outside of the pole causing the wood fibres to separate and form surface checks that may extend deep into the pole. Rapid loss of moisture from the end grain of poles is further responsible for very high drying stresses to develop in these areas, resulting in end splitting during storage. It is therefore important reduce these moisture differentials between the outer layers and the inner core of a wooden pole as well as at the pole ends to a minimum, especially after treatment with water-borne wood preservatives. This can be done by either controlled drying/conditioning or application of a water repellent post treatment that retards moisture loss after pressure impregnation with water-borne wood preservatives.

Many end users such as farmers using fencing and vineyard poles and also electricity supply companies utilizing large quantities of wooden utility poles prefer creosote as a preservative treatment because of its oily nature. Not only is creosote resistant to fires but it also provide a great deal of water repellency to the treated timber at the same time it “lubricates” the wood. This ensures that creosote-treated poles, especially those obtained from Eucalyptus species, resist surface checking and end splitting to a large extent when exposed to conditions that cause drying stresses in the timber.

CCA – Circumstances Where the Use of CCA-Treated Poles Is Specified Over the Use of Creosote-Treated Wood Poles

CCA-treated poles are specified for locations where a dry, residue-free surface is required (United States Department of Agriculture, Forest Service (USDA), and/or odours are not acceptable, including, for example, in urban areas where sidewalks are common and poles are set through the sidewalk into the ground. In this setting, CCA-treated poles are frequently specified as the best choice because creosote-treated poles sometimes “bleed.” Bleeding causes oily staining at the base of a pole. Use of CCA is also specified frequently for residential areas, where contact with the wood surface is more likely than in rural areas and where staining/odours may be a concern.

In areas with high soil moisture, where the water table is high, or water is perched at a shallow depth, CCA-treated poles are specified over creosote-treated poles because the CCA preservatives are “fixed,” or chemically bonded within the wood. Proper fixation minimizes the risk of leaching. Long-term subsurface saturation is less likely to deplete the CCA preservatives, shortening service life, and increasing the risk of early pole failure and unplanned electrical outages.

CCA-treated poles are also specified in areas that experience occasional freshwater flooding, because the CCA is fixed and thus helps ensure a longer service life. Further, in these “flooding” environments, creosote poles may cause an unacceptable sheen in the water.

Creosote.

Creosote – Circumstances Where the Use of Creosote-Treated Poles Is Specified Over the Use of Penta- or CCA-Treated Wood Poles

From an operational and functional perspective, one of the highest-valued uses of creosote-treated wood poles is along coastal areas. Creosote -treated poles also repel salt water better than CCA. Use of creosote-treated poles in this environment ensures the reliable and cost-effective delivery of electricity to the public.

From an operational perspective, creosote-treated wood poles are also specified for use by utilities in hot and dry environments. Creosote is a better choices as preservatives in these environments over CCA because the carrier oils keep the wood “lubricated” and “soft.” As such, there is less splitting/cracking/checking than typically occurs with CCA poles in this environment.

Creosote-treated poles may have greater flex (due to the “oil” content) than CCA-treated poles, which are dry and stiffer. Creosote may be specified in areas prone to impact loads such as ice and/or wind.

In coastal settings, where poles may experience occasional flooding, creosote poles are more effective at preventing marine borer damage.

ROLE OF THIRD-PARTY CERTIFICATION.

The inspection of a batch of poles is not sufficient. It is important for the customers and the industry that all poles supplied are through a certification mark scheme.

Key benefits of third-party certification body.

1. Ensure the quality and quantity of the
2. Ensure the marking and product as per buyer
3. Ensure the material is genuine and as per specified

A certification body is a third party and an independent inspection agency which provides facilities in the different type of field without discriminatory decisions. In the wooden pole market in Africa third party inspections can play a very important role in ensuring the wooden pole remains the preferred transmission and telecoms utility pole over the concrete and steel poles.

Improved product quality

One of the most important benefits of third-party inspection for suppliers is the quality improvement that often results. Sometimes inspection reveals a product defect that’s easily preventable. Regardless of whether the defect is major, minor, or critical, knowing about it before shipping helps the supplier address the root cause to correct the underlying problem.

What is a product certification scheme?

As products are designed, produced, distributed, used and ultimately disposed of, they can give rise to concerns with purchasers, users and society in general. Such concerns could relate to safety, health or environmental impacts, durability, compatibility, suitability for intended purposes or for stated conditions.

Generally, these concerns are addressed by specifying the required product attributes in a normative document such as a standard. The supplier of the product then has the task of demonstrating that the product conforms to the requirements of the normative document. It might be sufficient for the supplier to assess and declare its product’s conformity, but in other cases the user or a regulatory authority might require that conformity be assessed by a competent and impartial third party.

Assessment and impartial third party attestation that fulfilment of specified requirements has been demonstrated for the product is referred to as product certification.

Conformity assessment is done by an accredited Certification Body which acts in the interests of a fair deal between the first and second parties. The Certification Body acts as a third party between producers and end-users or between government and suppliers.

How does a third party become a certified mark scheme?

Certification is part of conformity assessment, the process whereby an independent neutral body confirms that a product or service complies with any national standard.

Not any organisation is declared an independent third-party conformity assessment provider. First, it must be declared competent to provide the service: it must be accredited. In South Africa, accreditation is provided by the South African National Accreditation System (SANAS).

SANAS is one of 3 bodies in Africa responsible for carrying out accreditations in respect of conformity assessment. These includes accreditation of-

• calibration, testing and verification laboratories;
• certification bodies;
• inspection bodies;
• rating

This accreditation confirms that the Certification Body is technically competent to fulfill its function, that its results are impartial and that it can be trusted by all parties.

The Certification Body, however, also acts as a third party between e.g., South African manufacturers and East African end-users or between East African manufacturers and South African customers.

This phrase “Certification Body approved” refers only to products which have attained the Certification scheme mark, a product certification scheme offered by the Certification Body. A product is certified when it has been assessed by an independent third party to the requirements of a specification such as a national standard. The product is then certified if it meets the specifications.

To attain the Certification Body Mark Scheme, the product must meet the specifications of the national standard applicable to it. The Certification Body will also inspect the product manufacturer’s production facility to determine whether it has adequate quality assurance systems in place (e.g., ISO 9001) to ensure continued and consistent quality. The Certification Body will then conduct

ongoing audits of the quality management system, as well as regular tests of product samples (obtained from both market outlets or from the factory) to verify that the product still meets the required national standards or specifications.

National Specifications and Standards

All specifications and standards in any country need to address the following criteria in order for poles to last 40 years. Below is a comparison of Eskom standards and the rest of Africa.