Common Forms & Causes of Industrial Chimney Degradation PT 1

Common Forms & Causes of Industrial Chimney Degradation PT 1

Industrial chimneys and smokestacks are generally exposed to severe environmental conditions like high wind loads, vibrations, chemical attack, high operating temperatures, rapid heating and cooling, and hot & cold extremes due to change in seasons & weather. These environmental conditions combined with operation conditions like fuel switching, duty cycling, and structural modifications can cause distress and deterioration over time. It’s important for facility managers to recognize early signs of distress to ensure that problems can be taken care of immediately. Significant and unplanned expenditures for repairs can often be mitigated by regular maintenance and inspections that are performed in a timely manner.

Here is a look at some common forms & causes of degradation in the important components of an industrial chimney or smokestack:

Concrete Shell
Cracking & spalling causes by external stresses, thermal stresses, and corrosion of rebar are a sign of degradation on the concrete shell. The shell itself is also affected by chemical attacks caused by carbonation that triggers corrosion of the rebar. Sulfate and acid attack can cause surface soften and erosion of the concrete shell over time.

Steel Stacks
Steel stacks are subject to corrosion and loss of thickness due to atmospheric and flue gas corrosion. If the structure is under-designed for wind load, it can experience excessive deflection. Excessive cross-wind motion or fatigue is a sign of inadequate design for vortex shedding.

Independent Brick Liners
Structural and thermal stresses and stresses that are concentrated at corners can cause cracking in an independent brick liner. Years of use, acid condensation, and change in operation can cause the mortar and brick to soften, making the brick liner vulnerable to cracks or leaks. Scrubber operation, salt grown, moisture penetration, and over/under or opposite breeching can cause leaning which may cause problems with hood and interior platform alignments. If the independent brick liner is suffering from excessive wetness, very low operating temps and high moisture content within the scrubber may be the cause.

Corbel Supported Brick Liner
Penetration of flue gases through cracks in the air space can cause acid attacks on these types of brick liners which can lead to mortar and concrete erosion.

Steel Liner
Steel liners are susceptible to impact damage at bumpers due to improper sliding of the bumpers or too many bumpers causing over stressing. A steel liner may also show signs of corrosion or loss of thickness due to flue gases that eat away at the structure. Structural damage like buckles and ripples may be causes by explosion or unexpected high temperature excursions.

Fiber Reinforced Plastic (FRP Liner or Stack)
Fatigue, overheating, and corrosion can all cause cracking, wicking or blistering of an FRP liner which will need to be addressed quickly to ensure further expensive damage to the stack or chimney is averted.

Gunite Lining
Gunite linings are subject to spalling, cracking, and erosion caused by age, service related wear and tear, and even improper material selection.

Lightning Protection System
Years of use, ice load, movement of a chimney relative to a liner with a tight jumper cable, and stack work /construction can all cause corrosion, broken anchors, or broken connections on a lightning protection system. Repeated lightning strikes are also of concern since they can cause deteriorated lightning points, air terminals, & ground path.

These components are just a few of the elements that need regular maintenance on industrial chimneys and smokestacks. Stop by the blog next week to see the second post in this series on Common Forms & Causes of Industrial Chimney Degradation. Our experts will discuss maintenance for the rest of the components found on your industrial chimney and stack.

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