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Flushing of heat exchangers

Специалисты АСГАРД-Сервис занимаются очисткой теплообменника

Currently, heat exchange equipment is used in all areas of human activity. These are engineering systems of buildings (heating, cold supply, hot water supply), technological processes in the production of goods, food products, large industrial energy: oil refineries, large factories, thermal power plants, nuclear power plants and so on.

Cold tap water in most Russian regions has hardness, which leads to the appearance of various deposits, limescale in the heat exchanger, etc. The internal surfaces of pipelines that have been in operation for ten years are clogged by more than sixty percent. During operation, any unit is contaminated, and as a result – deterioration of heat exchange and the passage of heat carriers / product through a heat exchanger occurs. All this leads to loss of heat or disruption of technological processes, which, in turn, leads to high energy costs and loss of quality or quantity of the product produced. At the same time, the cost of cleaning or repairing the unit is one order less than the losses that a faulty machine can cause and even more so the need to replace the equipment partially or completely.

The frequency of flushings is determined by the design of the units and the area of its application (for example, in the food industry this procedure has to be carried out very often). A flushing method is determined by the design features, the degree and type of contaminants. On average, equipment should be flushed once or twice a year to keep equipment in good condition. The choice of flushing technology is made by experts and depends on the design features of the unit and its technical characteristics.

In-place flushing of heat exchangers

Объект, на котором проводились работы по очистке теплообменников

In this case, in-place flushing of heat exchangers is considered an effective method. The plate, brazed and welded heat exchanger is particularly in need of such flushing. Cleaning of the heating plates in this case occurs without disassembling the structure and replacing the seals. Special installations including a pump and a tank for chemical solutions, as well as a system of filters and hoses are used. The reagents are selected individually, and they contain inorganic or organic acids, which can clear the unit not only from lime, but also from biological organisms. All chemical reagents are certified by sanitary and epidemiological authorities.

In practice, heat exchangers are often flushed with special compositions developed by manufacturers or specialized organizations, which quickly dissolve carbonates and iron oxides.

In-place flushing and cleaning of the unit is carried out in compliance with the technical safety rules, because there is a danger to get personnel not only chemical but also thermal burns. High temperature of flushing chemical solutions is important for effective procedure.

After chemical flushing, the plate heat exchanger completely restores its working capacity, therefore in-place flushing replaces the capital repair procedure, although it costs several times less.

The in-place method is inexpensive, fast and simple, as well as suitable for all types of unit (plate, welded, etc.).

Advantages

  • cost is cheaper, especially on large units;
  • less time consuming, which reduces the time in some cases, especially on large heat exchangers;
  • no need to change seals in plate heat exchangers.

Disadvantages

  • in some cases it does not completely remove deposits, especially mechanical inclusions and scale after installation.

Folding flushing of heat exchangers

Attention! Folding cleaning of heat exchanger is available only for plate and shell-and-tube products. Welded and soldered units can not be disassembled due to design features. The specialists of ASGARD-Service will offer various types of in-place cleaning for them.

Работы по очистке пластинчатого теплообменника

Folding cleaning of contaminated plate heat exchanger is carried out as follows:

  • removal of the movable plate, then the plate pack is removed;
  • plates are treated with a special high-pressure unit and are placed for some time in a special chemical solution that eats away the dirt, but spares the metal;
  • plates are mechanically cleaned – service engineers for cleaning remove stuck dirt that is not amenable to chemical treatment;
  • after the end of processing, the plates are installed in the same place, the unit is assembled and undergoes a crimping procedure, which guarantees its tightness.

If necessary, pre-reagent processing of the plates is used. As a rule, if the heat exchanger is less than 8 years old, there is no need to replace the seals. The cost of seals, as a rule, is 4-5 times higher than the cost of the rinsing itself. During the inspection or in the course of the work, our specialists can advise on the residual life of the seals and the need for replacement.

Folding hydrodynamic cleaning of plate heat exchangers:

  • plates are removed from the heat exchanger;
  • then they are thoroughly cleaned with a high pressure water jet;
  • then they are mounted back into the unit.

The advantage of the method is its environmental friendliness, while in-place hydrodynamic cleaning is quite effective for many types of pollution.

Folding flushing of shell-and-tube heat exchangers is carried out as follows:

  • covers / rolls are removed to access the pipe space.
  • with the help of high-pressure unit and special nozzles, each pipe is cleaned separately.
  • if it is necessary to clean the annular space, the tube bundle is taken out and is cleaned from the outside using a high pressure unit.
  • after hydro-mechanical cleaning is completed, all parts of the unit are installed in the same place, the heat exchanger is assembled and undergoes a crimping procedure, which guarantees its tightness.

The best time to clean the heat exchangers from scale is the period of scheduled maintenance or emergency repairs of the main equipment. In addition, there are cases when the capital cleaning of the unit is carried out in the process of technical improvement of equipment (power increase).

Folding method

Advantages

  • 100% result of cleaning plates / tubes, removal of all insoluble deposits.
  • It is possible to revise the plates / tubes for corrosion and damage.

Disadvantages

  • Price is usually higher than in-place flushing, especially for large heat exchangers.
  • It may be necessary to replace the seals for the plate-type units, which will increase the cost of servicing the heat exchanger.

Объект заказчика, на котором проводила работы компания АСГАРД-Сервис

Selection of cleaning chemicals for heat exchangers cleaning depends on the type of sediment.

In the process of applying methods of chemical cleaning of heat exchangers by ASGARD-Service, certified cleaning products are used, they are chemical reagents based on various acids with the addition of surfactants, corrosion inhibitor and chelating agents, diluted with water in the required proportion. The purpose of adding a complex of the above additives is to increase the effectiveness of the reagent effects on deposits that contaminate the internal surfaces of the unit, while at the same time reducing the corrosivity of the metal from which these surfaces are made.

Since acids react with different types of deposits to various extents, it is recommended to select reagents depending on the type of deposits detected on the internal surfaces of the heat exchanger being cleaned.

The data in the table below are prepared on the basis of information from Alfa Laval Company, as applied to the flushing of heat exchangers.

 

Type of sedimentComposition of sedimentComposition of sediment
Corrosion productsCalcium carbonateNitric acid
Metal oxidesCalcium sulfateSulfamic acid
SlimeSilicatesMechanical impact
AlumineSilicatesMechanical impact
Diatomic organismsSilicatesComplexing agents, sodium polyphosphates
Biological fouling – slimeBacteriaCaustic soda
Biological fouling – slimeNematodesSodium carbonate
Other contaminationsFuel oil, asphalt, greaseSolvent based on paraffin oil fractions (kerosene)

 

We draw your attention to the fact that the following solutions are prohibited to apply:

  • ketones (for example: acetone, methyl ethyl ketone, methyl isobutyl ketone);
  • esters (for example: ethyl acetate, butyl acetate);
  • halogenated bicarbonates (for example: chlorophene, carbon tetrachloride, freons);
  • aromatic compounds (for example: benzene, toluene).

It is also not allowed to use hydrochloric acid-based cleansing agents to remove deposits from surfaces and parts of stainless steel structures.

Truly effective cleaning of the heat exchanger significantly increases its performance, and in fact reduces the frequency of the necessary cleaning, keeping the heat exchange equipment in a constantly working state. ASGARD-Service Company has a proven methodology leading to impressive results when using any option of cleaning of heat exchanger components (plates, tube plates, channels, casings, ducts and radiator grilles), either hydrodynamically or chemically, or its combination.

Our company performs all services related to the recovery of heat exchangers, namely:

  • flushing of heat exchangers of all types – plate and shell-and-tube
  • repair of heat exchangers of all types:
  1. replacement of seals, plates in plate units, diagnostics of work of plate heat exchangers, plate troubleshooting, crimping;
  2. replacement of tube bundles in shell-and-tube units, troubleshooting and crimping of the tube bundle;
  3. assembly / disassembly and replacement of all types of heat exchangers.

Оборудование компании АСГАРД на объекте заказчика

Selection of reagents is carried out for each case individually. Ideally, if there are sediment samples, then it is possible in practice to choose the optimal composition and technology of flushing (time and temperature conditions). Chemical reagents do not affect metal or bar-to-bar seals.

Our company has a large number of pumping installations, both for flushing of small plate-type units of individual heat points and boiler stations, and for flushing of large shell-and-tube heat exchangers of large technological enterprises.

In addition, the scientific and technical association conducts research methods and technologies for reagent cleaning of heat exchange equipment.

The company has its own production base for the creation of high-tech flushing equipment for the individual needs of the customer.

In any case, after talking with the Client, our specialists will help you choose the optimal type of flushing both in terms of quality and prices. Visit to inspection is free.