Semi-welded plate heat exchanger services

In most cases loose materials as organic compounds, gathered on the surface of the plates can be removed by inverting the flow or with back flow washing with warm water or cleaning medium.

A = Danfoss Heat Exchanger	1.1 – 1.2 = System shut off valves
B = Heat or Cold Consumer	2.1 – 2.2 = Shut off valves for cleaning system

Warm water or cleaning medium is flushed with high speed on the brine side in the opposite direction than during normal operation. The valves in the connection pipes must be closed and the drain valves mounted on the pipelines opened. The dirty medium must be discharged, collected and discharged in accordance with local requirements.

Example of backwards cleaning procedure:

• Close valves 1.1 and 1.2. The recommended temperature of heat exchanger should be between 10-30C
• Drain off the liquid from the brine side by opening valve 2.1
• Connect a hose to valve 2.1
• During 10-15 minutes cleaning medium should flow through heat exchanger
• Check if organic compounds and dirt are removed
• Stop the water flow by closing valve 2.1
• Fill the heat exchanger with system liquid in accordance with start-up procedure, close valve 2.2

In order to achieve a good cleaning result, the cleaning agent is to be chosen based on the dirt and impurities in the process and/or heat exchanger. The use of unsuitable cleaning agents may result in worsening of the impurity problem.

The cleaning process should involve the use of common cleaning agents which contain additives that reinforce the effectiveness of the cleaning procedure and at the same time is compatible with the materials of the heat exchanger.

Remarks:

• Before cleaning the heat exchanger with chemicals, check resistance of all materials to the cleaning agent
• After chemical treatment the plates must absolutely be flushed carefully with clean water
• When during cleaning on the coolant side a high temperature can occur in heat exchanger. Be sure that the pressure on the refrigerant side will not increase to high
• Before cleaning remove the refrigerant or be sure the refrigerant is not trapped

A = Danfoss Heat Exchanger	1.3 – 1.4 = System shut off valves
B = Heat or Cold Consumer	2.3 – 2.4 = Shut off valves for cleaning system
C = circulating tank	3 = Pump for chemical tank

Example of CIP cleaning procedure:

1. Close the valves 1.3. and 1.4. The recommended temperature of heat exchanger should be between 10-30C
2. Connect the hoses of cleaning system to the valves 2.3. and 2.4
3. Fill the tank with the chemical solution
4. Switch on the Pump (3) and let it run during 30-40 minutes. Check during cleaning at certain intervals the concentration and activity of chemicals at inlet and outlet. Stop the process if there is no changes (inlet vs. outlet)
5. If dirt has been removed, drain the chemicals from the heat exchanger and tank. Contain and remove used chemicals according to local regulations
6. Flush the heat exchanger plate pack by using clean water under backflow
7. Fill the heat exchanger with system liquid in accordance with start-up procedure

For Semi-welded plate heat exchangers it is possible to clean the plates manually on the gasketed side, however it requires that the heat exchanger is opened to get access to the plate surface.

Semi welded cassettes are only manually cleanable on the outside. If needed the cleaning agents may be used.

Consult a cleaning specialist for choosing a suitable cleaning agent. Ensure that all agents are compatible with the plate/cassette and gasket materials.

Plates do not need to be removed from the heat exchanger during cleaning.

1. Start cleaning when the heating surface is still wet and the plates are hanging in the frame
2. Remove deposits using a soft brush and running water
3. Rinse with water using a high pressure hose

If above procedure does not remove the dirt, next step is to add a cleaning agent to the process.

1. Brush with cleaning agent using a soft brush
2. Rinse immediately with water