Smokestack degradation: What causes it and how to stop it

What is a Smokestack?

A smokestack “is a structure that provides ventilation for hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere” according to a Wikipedia article. Smokestacks are generally vertical in order to release flue gases high enough to allow their dilution and reduced negative effects to the immediate environment.

Picture showing a Hamcock Crew working on a Goodyear smokestack in Port Elizabeth, South Africa

A Hamcock Industrial Access Crew Member working on a Goodyear smokestack in Port Elizabeth, South Africa

Complex Structures

Smokestacks are more complex than most maintenance managers may think. Usually, maintenance and plant managers tend to neglect smokestacks when they plan their plant shutdowns. The external appearance of smokestacks in some instances tend to give a false impression of their strength and current internal state. This usually results in the neglection.

The Need for Service

Maintenance managers understand that other plant equipment needs to be serviced. Boilers (which are attached to these industrial chimneys) are delicate equipment and as such, they are always maintained, on time without fail. This is not usually the case with smokestacks which are usually tall and hence introducing the component of working at heights that many maintenance managers are not comfortable to deal with.

Maintenance budgets

The degradation of a smokestack starts as soon as a smokestack is commissioned. It is therefore of uttermost importance that a smokestack maintenance regime is part of a proper plant maintenance budget. Smart plant managers know that they cannot ignore their smokestacks forever. Sooner or later, the “smokestack devil” will come knocking at the door of the ill-prepared maintenance manager and the costs are usually huge.

The main causes of smokestack deterioration

1. Poor construction techniques.

Poor construction techniques and poor smokestack designs cause smokestacks to deteriorate fast. It is very important for smokestacks to be built up using the latest and best designs possible. The quality of the construction materials also plays a very important role to ensure the steadiness of the smokestack.

2. The Boiler Fuel Quality and the Flue Gases

The quality of the fuel that is used in the boiler affects the rate of deterioration of the smokestacks. Fuels that have high sulphur (S) tend to causet in faster smokestack degradation. The sulphur in fuels is oxidised during the burning process to form sulphur dioxide. Sulphur dioxide is a gas that reacts readily with water or atmospheric moisture to form sulphuric acid. This sulfuric acid is a powerful oxidant that attacks the walls of the smokestacks thereby causing them to rust. As the walls of the smokestacks, rusts they start thinning down increasing the possibility of a smokestack collapse.

3. Liner Deterioration

Liner deterioration is caused by several operational factors in smokestacks. Both physical and chemical processes are to blame for liner damage. The speedy movement of flue gases containing some solid particles causes the liners to be physically damaged. This results in the thinning of the smokestack. The reaction of the flue gases with moisture, as mentioned above, also results in acids which in turn corrodes the liners thereby degrading the liners’ integrity.

4. Carbonation

The carbonation process starts immediately when concrete is exposed to air. When Carbon dioxide (CO2) penetrate the concrete through the pores on the surface of a concrete smokestack, it reacts with the calcium hydroxide and the moisture in the pores to form calcium carbonate. The carbon dioxide combines with the pore water to form a dilute carbolic acid which acts to reduce the concrete’s alkalinity. This is the start of the damage to the walls of the concrete smokestack.

5. Weather elements

Wind, rain, storms and lightning threaten smokestacks. The wind and storms introduce a lot of stress to the structure of smokestacks. This, in turn, causes the deterioration of the smokestacks. A lightning strike can cause a smokestack to collapse under the pressure of the high voltage that is introduced to its structure.

Thus said, it is therefore of uttermost importance for you to follow a regular smokestack maintenance regime in line with industry standards. A Smokestack maintenance contract will enable your boiler to keep on running when needed and your production manager happy.

Call Hamcock Industrial Access on 0127678643 or email us at info(at)hamcockaccess.co.za for a meeting to discuss your requirements.

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