Murphy’s Law, that is typically stated, says: ”Anything that can go wrong will go wrong”. Guess what: Explosions in recovery boiler operations are not a modern fairy tale, they happen in reality. And you don`t want to bear the consequences, which are very high damage to the boiler with long shutdown times needed to bring the boiler back into daily operations.
Continue quality assurance is the key to avoid unplanned downtime, as well as the associated costs. So let`s discuss these three critical spots in a recovery boiler, which must be checked regularly:
1. Superheater corrosion
High wear on super heaters can have several reasons. The main reason is mostly the reaction between deposits and the material accelerated by the high temperature stresses. They are caused by the combustion in the boiler. The check of the material thickness as well as a visual check of the superheater material should be done in predefined cycles. This can help to prevent problems in advance as well as react and plan maintenance for the next shuts.
2. Floor bends
Floor bends are critical areas in the boiler. They have high thermal stresses due to smelt as well as the combustion which takes place in the lower furnace. They are flown through by water, therefore they are critical areas for leakages. When a leakage occurs at these areas the possibility for a smelt-water explosion is high. For that reason, a careful inspection with thickness measurements, check of pipe cracking as well as a total and careful visual inspection of welds must be done.
3. Primary air ports:
Primary air ports are the most important air suppliers in the recovery boiler. They are directly related to the reduction degree and the combustion temperature as well as the flue gas emissions as NOx and CO. They are often protected by casted inlays. Due to high thermal stresses, they have a tendency to microcracking. Visual and penetration testing is a must for this area.
Which test methods are used to check these three critical issues?
By means of a visual testing (VT), it is possible to detect errors such as e.g. mechanical damage, deviations in colour and lustre, or even open cracks. Based on the penetration testing (PT), surface cracks and pores, which are invisible to the naked eye, can be perceived through fluorescent and colour penetrants. Magnetic particle testing (MT) is a method for identifying cracks in or near the surface of ferromagnetic materials. Ultrasonic testing (UT) is an acoustic method for detecting material errors by means of ultrasound. The Radiographic testing (RT) is an imaging method for fault detection in the interior of components.
Professional quality assurance is always an investment in the future to secure:
- Projectable maintenance costs
- Compliance and improvement of operational safety
- More effective use of plants and machines
- Reduction of costly downtime to the minimum
- Continuous monitoring of critical pressure-bearing components
Only through a professional quality assurance it is possible to carry out a maintenance and thus to determine or create a specific quality plan. This is the only way to ensure the effective and economic use of plants and machines in the future.
Our focus in the field of measurement and testing technology is on boiler construction, pressure vessel systems and pipe heat exchangers.