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Boilers and heating exchangers after being used for a period of time need to be descaled to ensure efficient heat exchange. So, how to clean the boiler and other heating exchangers? What chemicals should be used? What to keep in mind when doing this? Let’s find out more details through the article below for cleaning boiler and also cleaning other industrial systems!

1. Why need to clean boilers and other equipment?

  • Remove dirt, grease, and oxidation layer, welding slag when manufacturing, processing, transporting and installing to avoid any problems during operation.
  • Remove the deposit layer to increase the efficiency of heat transfer, avoid overpressure causing unsafety.
  • Wash the oxidized layer, the corrosion layer before remediating such as painting or replacing to avoid leakage and unsafety.
  • Remove deposits to avoid corrosion caused by aerobic microorganisms in cooling water systems.

However, the best water treatment and maintenance are required to limit the repeated descaling of the boiler and other industrial machines which will shorten its life

For boilers, periodically need to be inspected (normally, boiler over 10 years old, no more than 2 times / year, less than 10 years old, no more than 1 time / year) and open boiler to check the actual situation of deposits , corrosion to adjust the treatment plan or descale the boiler.

2. Plan an effective, safe and fast cleaning

Inspecting of exisiting condition of equipment, properties of deposits (silica residue, hardness due to heavy metals, grease, etc.) to choose a suitable descaling chemical and appropriate cleaning process, refer to here. : https://uce.com.vn/cleaning-chemical-service-package/

Plan early to do:

  • Prepare well for occupational safety.
  • Prepare enough replacement materials, chemical, tool and labor.
  • Prepare adequate supply water, safe discharge water, avoid affecting biological or chemical wastewater system
  • If it is a boiler, it is necessary to cool down with allowed speed.

Operate immediately after cleaning to see if there are leaks or problems was born during cleaning.

3. Basic procedures to clean boiler and industrial equipment

3.1. Basic steps for de-scaling boiler

Descaling diagram for boiler

Diagram to clean boiler

Depending on kind of each scale that the chemical and process will be different, here are the basic steps for reference. The general time to clean Silica residue is 2-3 days, other residues will be from 1-2 days.

1- Cool down boiler if hot.

2- Open main holes to see the internal condition and deposits (photography, endoscopy, ultrasound of metal thickness ).

3- Connect an external chemical pump to circulate water through boiler.

Boiler bottom valve → Cleaning chemical tank → Circulation pump → Upper main holes

4- Test runing the pump with water.

Step 2: Clean with boiler descaling chemicals

(The parameters of pH, iron, TDS… need to be checked many times in this step)

1- Pumping anti-corrosion chemicals first or can be mixed together with cleaning chemical (15-30 minutes).

2- Circulate cleaning solution, then soak for about 2 – 4 hours without Silicat scale, 10-15 hours withi Silicate scale.

3- Continue to add other chemicals to neutralize, circulate for 2-6 hours to ensure discharge pH (or separate this step into a separate cleaning step).

4- Discharge all.

Vệ sinh lò hơi

Cleaning boiler

Cleaning boiler

Cleaning boiler

Step 3: Clean inside of boiler with a high-pressure pump

Use water flow with high flow and pressure to clean the inside, especially at the corners, and check the cleaning results (photography, endoscopy, metal thickness ultrasound).

Close the oven, pump make up water with passivation chemical, check for leaks.

Flushing with high pressured water

Flushing with high pressured water

35 Ton/h Food boiler after cleaning

35 Ton/h Food boiler after cleaning

Step 4: Passivate to metal surface (pH = 10.5 – 12.0 is best) or dry with a desiccant

  • Recirculate with passive chemicals, then dis-connect circulation pump, cleaning site work, collect equipment and material
  • Increase boiler pressure slowly to monitor, open the exhaust valve before using steam, then increase to operating pressure to prepare for production.
  • Finish boiler cleaning work

Step 5: Monitoring the condition and quality of boiler water after cleaning

  • Use of maintenance chemicals is necessary.
  • Increase blow down rate, if still high impurites then may replace boiler water for 1 time
  • More checking boiler water quality in the first 1-2 weeks until it reaches a stable state.

3.2. Cleaning the condenser or chiller


Condenser is copper material, weak, easy to damage during cleaning, so it is necessary to clearly determine the condition by:

  • See if this has happened in the past.
  • Compare the difference temperature (Approach) and increased pressure to estimate deposit thickness.
  • Refer to the water parameters to guess the composition of the residue (CaCO3, CaSO4, Silicate, Biofilm…).
  • Open to check reality, sample to test is the best.
  • Check inside by endoscopy through camera, store images.

Main Process

  • Connect the chemical pump to the equipment carefully calculated before.
  • Use chemicals suitable for scale, such as ND-HF701 (Silicate residue), ND-L701 (CaCO3 residue), ND-H701 (Biofilm residue)… If not clearly defined, use ND-SM10.
  • The amount of chemical used 15 – 25% depends on the type of residue.
  • Circulatory 30 – 90 minutes depending on the case. The pH should be checked after 15 minutes
  • If too thick, scale it can be cleaned a second time or repeated but with a different chemical (please contact us for more informaiton)

Connecting diagram for cleaning condensor

Connecting diagram for cleaning condensor

Note: Mechanical cleaning can be combined by connecting a suitable brush head, rotating by machine or by hand to further remove residue in undissolved areas.

Combine brushing to remove all undissolved scale

Combine brushing to remove all undissolved scale

3.3. General cleaning of heat exchanger


  • Similar to cleaning the condenser, but with copper, aluminum, stainless steel, and titanium heat exchangers, the distance between of heat exchanger plates or the unit diameter of the heat exchanger needs to be clearly defined.
  • See if this has happened in the past.
  • Check inside by endoscopic camera, store images
  • Compare the difference temperature (Approach) and increased pressure to estimate deposit thickness.
  • Refer to water parameters to guess the composition of scale (CaCO3, CaSO4, Silicate, Biofilm…).
  • Open to check reality, sample to test is the best.

Main Process

Similar to cleaning the condenser, but using a brush ratation will be difficult, so it can be checked by monitoring chemical indicators, cleaning solutions and testing heat transfer and operating pressure before and after cleaning

Check the inside by endoscopic through the camera, record the image.

Cleaning of  plate heating exchanger

Cleaning of  plate heating exchanger

3.4. Cleaning the heating coil unit

Heating or cooling coils are used a lot, from air chiller systems to equipment in production.

Most these Coils are weak metals such as copper and aluminum, so cleaning needs to be done with caution.

Most of the Coils often dirty with dust (dust from the soil, production environment such as Silicon dust, fine cloth, wood …), oil clinging…

This is the type of cleaning the outside of the plate, so you can choose 1 of 2 ways:

  • Mix CoilCleaner-100 with water, spray on Coil unit, wait for the reaction to occur and spray again with water. Depending on the fact, it is possible to repeat.
  • Remove Coil Units, soaking in the chemical according to the ratio, then bring it out to use the high-pressure pump to spray. This option would be better, but the implementation is not easy and takes a lot of effort.

Steps to clean Coil Unit

Steps to clean Coil Unit

4. List of boiler cleaning chemicals and some other practical works

For detailed information on chemicals used for descaling boilers, cleaning industrial equipment, please see here.

5. Reasons to choose UCE Co., Ltd to descale boilers other industrial equipment

For many years, UCE Co., Ltd has always been the first choice of enterprises when they have demand for descaling boilers as well as cleaning other industrial equipment. We always bring 100% satisfaction to your company because:

  • This is our expertise.
  • Experienced in cleaning more than 300 different projects.
  • There is a laboratory to support the analysis.
  • Having a team of professional, responsible and well-trained engineers.
  • Fully equipped with testing tools.
  • Support analysis, check after completion.

We will bring Safety – Efficiency – Fast to your company. Please get in touch for more details.