Eucalyptus Poles- The Process of CCA Pressure-Treatment

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Eucalyptus poles are used in the construction of many structures and buildings. These poles are strong and offer good value for money. Eucalyptus poles can be used in a variety of applications. The pressure-treated gum poles offer resistance to insects and harsh environments. Pressure-treated wood poles have a greenish appearance and are safe for use in any building project (including erecting jungle gyms for children).

What is the green look on Eucalyptus poles?

When you touch a greenish pole as you step outside on a veranda overlooking the wide bushveld – have you ever wondered about the pole?  Why is it green?  And what is the process to get it to have the greenish look?  What is the pole called?  And can it be stained or painted?  What is the lifespan of the green poles?

Before answering any of these questions, we must first understand the processes that poles must undergo to become a pole that’s got a green colour!

Understanding the process before CCA pressure-treatment of eucalyptus poles

Sustainable forest management plays a central role in our future, so to ensure the best quality poles we have checks and balances in place from the day that a seedling is planted until it is in our customer’s yard.  It is our passion at Sabie Poles to manage our plantations in such a way that nature is not harmed in any way.  This will ensure that our children have a future!

When trees are harvested in the plantation the best quality eucalyptus poles are graded for the treatment plant.

Operators and other team players in the plantations are equipped with all the necessary Personal Protective equipment that they will need to keep themselves safe while they go about harvesting and grading for the Pressure-treatment plant.

Chainsaw operators will cut down a tree, and once it lays on the ground, and it is safe for people to work in the vicinity of the fallen tree, the bark strippers will move in to remove the bark from the logs.

Manual debarking is normally performed with a sharpened hatchet. The bark is detached either as long or short strips or small plates.  Debarking spuds (a hoe-type piece of equipment) and shaped spades can also be used to debark.

Once the pole is cut into the required length it is ready to be transported to the Sabie Poles CCA pressure treatment plant.

Our quality control team makes sure that only the best eucalyptus poles are accepted at our Treatment plant.

Poles arriving at our CCA pressure treatment plant go into our grading and quality control system.

Once we have picked the best of the best we get the poles ready for treatment, by stacking them into the trolleys. Once they are filled to the required capacity they are winched into the pressure vessel and everything is sealed air-tight. The pressure treatment process will now begin. Now the High pressure is used to force the chemicals into the wood, leaving the wood a greenish colour afterward.

Our CCA CLASSES

H2 CCA Class
  • Internal Applications like structural timber, flooring, panelling and more
H3 CCA Class
  • External Above Ground applications like fencing bearers, steps and cladding.
H4 CCA Class
  • In Ground Contact applications like Fencing poles, playground structures and decking
H5 CCA Class
  • Wet Soils or In-Water applications like retaining walls, jetties and walkways.
  • SABS inspects each individual order.
H6 CCA Class
  • For application in Sea Water like jetties, walkways and retaining walls.
  • SABS inspects each individual order

Grading criteria before eucalyptus pole treatment 

Drying is a key step in the process. Optimal drying before treatment is necessary to allow maximum absorption of the CCA chemicals. 

  • Poles must be straight
  • Poles must have the correct diameters
  • No cracks/splits
  • Knots should be tight and not protruding
  • No wane/bark is allowed
  • Poles must not have dents.

All our eucalyptus poles are SABS certified

Understanding What Timber drying Is?

Drying is a process in which moisture is removed from saturated porous materials. Wood is a material that, in addition to being porous, is considered to be nonhomogeneous, hygroscopic, and anisotropic (Jankowsky and dos Santos 2005). Log drying plays an important role in adding value and quality to poles.

However, wood drying can potentially cause degradation (Kollmann and Côté Jr. 1968). During this process, defects can occur in wood, such as end splits, collapse, warp, surface cracks or checks, and internal cracks (honeycomb), among others (Forest Products Laboratory 1999; Tenorio et al. 2012), especially in Eucalyptus wood (Yang and Liu 2018).

Most of those defects are caused by the deformation of the wood tissue. Drying stresses and shrinkage are the main causes of rupture because they can exceed the strength of this material. Those phenomena are influenced by the moisture content in the wood, which can be observed in the two main forms of water, namely free water and bound water.

Two types of Timber Drying Methods.

At Sabie Poles, we make use of airdried material for our pressure-treated eucalyptus poles and kiln-dried timber for all our construction-grade timber.

Air Drying Eucalyptus Poles

To stack pole/logs with spaces in-between each other – usually, the first layer will be stacked from north to south and the next layer from east to west.

Air-drying times vary widely from 2 weeks to several months depending on species, dimensions, local weather conditions, and time of year when the material is stacked.

Rainfall, temperature, radiation, and relative humidity all contribute to the wetting/drying process of woodpiles. Also, species exhibit a fivefold range in drying times, and water loss slows down as wood water content decreases. Additionally, different log diameters and lengths, debarking, and piling specifications may strongly affect air-drying rates.

CCA Laths
Finished Stack of CCA Pressure Treated Laths (Air Drying)

Kiln Drying Eucalyptus Poles

In specific cases, kiln drying prior to preservative treatment is the prescribed method of utility pole seasoning in South Africa. The slow drying nature of Eucalyptus Grandi’s poles makes rapid kiln drying potentially detrimental due to the development of defects such as excessive surface checking, honeycomb, and collapse.

Once the poles are dry enough (measured with a moisture meter) they are taken to the pressure cylinders where they are put into the chambers and securely closed.   In the pressure treatment process, a solution of CCA is applied using a vacuum and pressure cycle, and the treated wood is then stacked to dry. The primary advantages in the use of CCA-treated wooden poles are that it produces no smell or vapor and its surface can be easily painted. The drawbacks of the wood are a strong green color at high retention values. It should not be used in applications where it is in contact with food or drinking water.

CCA treated wood is highly resilient against attack from biological decay and organisms if correctly applied and used in accordance with the required hazard classification, ranging from H2 (dry interior above ground) to H5 (heavy wet soils and freshwater), and for H6 (Marine contact) when used as a dual treatment with creosote.

Preservation of logs is far more cost-effective and easier than treating logs with decay problems afterward. An attack of dry rot, wet rot, or woodworm can be prevented by using efficient wood preservers on logs.

Poles are also fitted with end plates to limit end splits and cracking. www.sabiepole.co.za

Can you build with wet CCA pressure-treated Eucalyptus Poles?

Wet pressure-treated wood expands and is not very great when used for construction in that state.

To prevent things such as warping, you must allow your wood enough time to dry. It might take a very long time of up to several weeks before the wood is finally dry and ready for your projects. Your local climate will affect how fast or slow the treated wood will take to dry.

It’s a big YES, you can build with wet treated wood, the only drawback about this type of wood is that they contain so many moisture components. Therefore, they are heavy and would take so much effort when lifting from one place to another.

Should I dry the Eucalyptus Poles before building?

it is the most advisable thing to do- allowing your CCA pressure-treated wood to dry. Kilns help in the faster drying of timber, and if you have one, it will be an added advantage in trying to get your lumber to dry for the various building projects.  If you do not have a kiln – you can always air dry your poles!

Advantages of using dried timber/poles

  1. Dried timber is lighter, and the transportation and handling costs are reduced.
  2. Dried timber is stronger than green timber in most strength properties.
  3. Timbers for impregnation with preservatives have to be properly dried if proper penetration is to be accomplished.
  4. In the field of chemical modification of wood and wood products, the material should be dried to a certain moisture content for the appropriate reactions to occur.
  5. Dry wood generally works, machines, finishes and glues better than green timber (although there are exceptions; for instance, green wood is often easier to turn than dry wood). Paints and finishes last longer on dry timber.
  6. The electrical and thermal insulation properties of wood are improved by drying.

Your building project might call for stained or painted or varnished poles.  Our CCA pressure-treated poles from Sabie Poles can be stained and painted to your heart’s desire.  Call our experts at Sabie Poles to assist you with the correct stains and varnishes.

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