Wistrand is specialized in chemical cleaning and pickling of the water and steam system on large recovery boilers and power boilers. Our customers are scattered throughout the world and consist mainly of actors in the pulp and paper industry, power plants, refineries and pharmaceutical industry — all with high quality demands.
Wistrand also work with chemical cleaning of other types of boilers, heat exchangers and piping systems.
“Wistrand shall perform the chemical cleaning ordered by their customers in the fastest, safest and most cost efficient way, with the highest consideration for internal as well as external environment.”
– The optimal technical solution for your chemical cleaning
– Clean metal surfaces, tight protective films and pure steam
– Shortest possible production break and consequently the least production loss
– A professional workmanship
A chemical cleaning of a new boiler is called pickling, pre-commissioning- or pre-operational chemical cleaning. The purpose of a pickling of a steam boiler, before it is taken into operation for the first time, is to achieve the purity requirement for water and steam in the shortest possible time, and to form a protective oxide layer. A pickling makes the exposed surfaces clean, in order to form a comprehensive, compact and protective layer of magnetite when the boiler is put into operation. The quality of this protective layer and its ability to resist corrosion is critical for the lifetime and availability of the boiler.
A pickling shall remove impurities such as rust, shale, fat, sand, slag and other foreign objects, which originates from the manufacturing of the boiler.
How and if a boiler should be cleaned before commissioning is determined by a variety of factors such as heat flux density, pressure, demands on steam purity etc. Economic factors such as the cost for the cleaning and waste treatment, as well as savings through a technically less complicated and faster start-up of the boiler, must also be evaluated.
Wistrand generally perform pickling according to the standard VGB-S-513-00-2014-07-EN Internal Cleaning of Water-Tube Steam Generating Plants and Associated Pipework, modified according to local conditions.
In addition to the implementation and execution of the pickling, Wistrand also provides consultations within the field.
Operational chemical cleaning normally means to clean a boiler that has been in operation. The need of a chemical cleaning depends on several factors. Just one factor is usually not crucial and the appropriate time for a chemical cleaning shall be assessed on a case-by-case-basis.
Decisions regarding chemical cleaning shall be based on the chemical composition and thickness of the deposits and the operation time since the last chemical cleaning. Observations from the latest inspection and tube samples shall also be considered. The main reason to remove deposits is because they significantly reduce the heat transfer and thereby the cooling of the tube material leading to greater risk of failure.
The result of a successful chemical cleaning, with the subsequent start-up of the boiler, will lead to a clean boiler with a thin compact and protective oxide layer. In addition, all parameters for water and steam quality will reach desired levels within the shortest possible time.
After a chemical cleaning it is important to start-up the boiler with careful control of the water chemistry and other operation conditions. A successful chemical cleaning followed by a start-up that is performed under incorrect conditions can lead to a situation where the goal for the chemical cleaning is not achieved.
Wistrand generally perform chemical cleaning according to the standard VGB-S-513-00-2017-07-EN Internal Cleaning of Water-Tube Steam Generating Plants and Associated Pipework, modified according to local conditions.
In addition to the implementation and execution of the cleaning Wistrand also provides consultations within the field of chemical cleaning.
Besides chemical cleaning Wistrand also work with consultation in the area of boiler feedwater, steam and water treatment. During a number of years we have been active at different power plants and pulp mills all over the world.
The work has included chemical cleaning supervision, chemical cleaning planning, survey and examination of tanks and the feedwater treatment, sampling and analyses of water and steam in the boiler system. By a close co-operation with the staff responsible for operation and analyses we have achieved good results during our work of improving and simplifying feedwater treatment, analyses and methods of analysis. As a result we can both solve existing challenges and prevent future problems at the plant.