Wistrand is specialized in chemical cleaning and pickling of large water and steam system on recovery boilers and newly built power plant boilers. The customers of Wistrand are scattered throughout the world and consist mainly of pulp and paper industry, power plans, refineries and pharmaceutical industries, all with high quality demands. We also work with chemical cleaning of other types of boilers, heat exchangers and piping.
“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
When a chemical cleaning of a new boiler is performed it is called pickling. 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 time as possible. Also 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 comes 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.
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, the time for a chemical cleaning shall be assessed on a case-by-case-basis.
The decision of chemical cleaning shall be based on data of the thickness of the deposits, chemical composition 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 these deposits is because they reduce the heat transfer and thereby the cooling of the tube material.
The result of a successful chemical cleaning with the subsequent start-up of the boiler shall lead to a clean boiler, with a thin, compact and protective oxide layer. In addition, all parameters for water and steam quality is reaching its limits within the shortest time as possible.
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 cause that the aim with the chemical cleaning isn’t 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.
Besides chemical cleaning of steam boilers Wistrand work with consultation in the area of boiler feedwater treatment. During a number of years we have been active at different power plants and pulp mills both in Sweden and abroad.
The work has included a survey and examination of 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. By solving existing problems and preventing future problems in the plant.