Installing a heat exchanger correctly is only the beginning.

A heat exchanger can lose performance over time because of fouling, scaling, incorrect flow conditions, gasket problems, corrosion or poor maintenance.

For this reason, operators need to understand three basic procedures:

Heat exchanger installation

Heat exchanger cleaning

Heat exchanger maintenance

This guide explains the practical points to check during each stage, with a focus on plate heat exchangers.

1. Heat Exchanger Installation: What Should Be Checked First?

Before installing a heat exchanger, confirm that the equipment matches the application.

Check:

• Heat duty
• Fluid type
• Flow rate
• Inlet temperature
• Outlet temperature
• Operating pressure
• Design pressure
• Operating temperature
• Connection size
• Connection location
• Installation orientation
• Available maintenance space

Do not install a heat exchanger only because the connections appear to fit.

The selected unit must also meet the required thermal and hydraulic conditions.

The manufacturer’s installation instructions should always take priority over a general installation guide because the allowable operating conditions and assembly requirements vary by design.

2. Leave Enough Space for Maintenance

One of the most common installation mistakes is leaving insufficient service space.

For a gasketed plate heat exchanger, the plate pack may need to be opened for inspection or manual cleaning.

Before installation, consider:

• Plate removal space
• Bolt access
• Crane or lifting access
• Cleaning equipment
• Drainage
• Venting
• Pipe removal
• Gasket replacement

If the exchanger is installed in a location where the plate pack cannot be opened, future maintenance can become unnecessarily expensive.

Maintenance access should therefore be considered during installation, not after the first failure.

3. Check the Piping Before Connecting the Heat Exchanger

The connected piping should not place excessive mechanical loads on the heat exchanger.

Check:

• Pipe alignment
• Pipe supports
• Connection orientation
• Expansion
• Vibration
• Valve location
• Drain points
• Vent points

Do not use the heat exchanger connection as a structural support for heavy piping.

The piping system should be independently supported.

For larger equipment, thermal expansion and vibration should also be considered.

4. Install the Correct Flow Direction

Flow arrangement directly affects heat-transfer performance.

Depending on the application, the heat exchanger may be designed for:

• Counter-current flow
• Parallel flow
• Multi-pass flow

For most liquid-to-liquid heat exchanger applications, counter-current flow is commonly used because it can provide a favorable temperature approach.

Before connecting the piping, confirm the inlet and outlet markings on the equipment.

Do not assume that the connection arrangement is interchangeable.

Incorrect flow direction can reduce thermal performance even when the heat exchanger itself is correctly sized.

5. Install Isolation, Drain and Vent Valves

A practical heat exchanger installation should allow the unit to be isolated and serviced.

Depending on the system, consider:

• Isolation valves
• Drain valves
• Vent valves
• Pressure gauges
• Temperature sensors
• Flow meters
• Differential-pressure measurement

These components make troubleshooting much easier.

For example, if the heat exchanger begins to underperform, operators can compare:

Inlet temperature

Outlet temperature

Flow rate

Pressure drop

before deciding whether cleaning is required.

6. Clean the System Before Commissioning

New piping systems may contain:

• Welding debris
• Metal particles
• Rust
• Sand
• Construction dirt
• Sealant residue

These contaminants can enter the heat exchanger.

A suitable flushing and filtration procedure should therefore be considered before normal operation.

This is particularly important for plate heat exchangers because the flow channels can be relatively narrow.

A clean heat exchanger cannot compensate for a dirty upstream system.

7. Commissioning: Start Slowly

Do not immediately expose the heat exchanger to full operating conditions.

A controlled startup helps reduce the risk of thermal shock and pressure surges.

A practical sequence is:

Check valves

↓

Check connections

↓

Confirm correct flow direction

↓

Open the system gradually

↓

Remove trapped air

↓

Increase flow gradually

↓

Monitor temperature and pressure

↓

Check for leakage

↓

Reach normal operating conditions

The exact startup procedure should follow the manufacturer’s instructions.

Sudden pressure peaks during startup or shutdown can damage a heat exchanger designed for lower transient loads.

8. Check for Leaks After Startup

After commissioning, inspect:

• Connections
• Gaskets
• Plate pack
• Welded areas
• Valves
• Pipe joints

For gasketed plate heat exchangers, leakage may indicate problems such as:

• Damaged gasket
• Incorrect gasket installation
• Uneven compression
• Plate deformation
• Excessive pressure
• Thermal or chemical damage

Do not simply tighten everything when a leak appears.

First determine the cause.

Over-tightening a plate heat exchanger can create additional problems.

9. Heat Exchanger Cleaning: When Is It Necessary?

A heat exchanger does not need to be cleaned simply because it has been operating for a certain number of months.

Cleaning should be based on operating conditions and performance.

Typical warning signs include:

Reduced Heat Transfer

The outlet temperature no longer reaches the expected value.

Increased Pressure Drop

The pressure difference across the exchanger increases.

Reduced Flow

The system cannot maintain the required flow rate.

Higher Energy Consumption

More pumping power is required to maintain operation.

Visible Fouling

Scale, sludge, biological deposits or process residue are found.

Manufacturers recommend monitoring operating temperatures, flow and pressure conditions and using changes in performance to determine when service is required.

10. Common Causes of Heat Exchanger Fouling

Different fluids create different deposits.

Common fouling types include:

• Mineral scale
• Calcium carbonate
• Rust
• Sediment
• Biological growth
• Oil deposits
• Organic residue
• Process chemicals
• Suspended solids

Fouling creates an additional thermal resistance between the fluid and heat-transfer surface.

As fouling increases:

Heat-transfer performance decreases

while

Pressure drop may increase.

This is why regular monitoring is important.

11. How to Know Whether Fouling Is the Problem

Do not immediately open the heat exchanger when performance decreases.

First compare current operating data with the original commissioning data.

Check:

Flow rate

Hot-side inlet temperature

Hot-side outlet temperature

Cold-side inlet temperature

Cold-side outlet temperature

Pressure drop

Pump operating condition

If flow has changed, the problem may not be fouling.

If temperatures have changed, the problem may be upstream.

If pressure drop has increased while operating conditions remain similar, fouling becomes a stronger possibility.

Diagnosis should come before cleaning.

12. Cleaning a Plate Heat Exchanger: Two Main Methods

For gasketed plate heat exchangers, the main cleaning approaches are:

Cleaning in Place — CIP

The exchanger remains closed while a suitable cleaning solution is circulated through the channels.

Manual Cleaning

The heat exchanger is opened and the plates are cleaned individually.

CIP is generally useful when routine fouling can be removed without dismantling the unit.

Manual cleaning provides direct access to the plates and allows inspection at the same time.

Manufacturers commonly describe both methods for gasketed plate heat exchangers.

13. CIP Cleaning: When Is It Useful?

CIP can reduce downtime because the heat exchanger does not necessarily need to be opened.

A typical CIP process involves:

Isolate the exchanger

↓

Drain or prepare the circuit

↓

Connect the CIP system

↓

Circulate the appropriate cleaning solution

↓

Monitor the cleaning process

↓

Flush with clean water

↓

Return the exchanger to service

The cleaning chemical must be compatible with:

• Plate material
• Gasket material
• Deposits
• Operating temperature
• Cleaning concentration

The wrong chemical can damage the heat-transfer surface or gasket.

Alfa Laval specifically recommends cleaning before complete fouling causes process problems and identifies CIP as a method for cleaning gasketed plate heat exchangers without dismantling them.

14. Do Not Choose a Cleaning Chemical by Guesswork

Different deposits require different cleaning approaches.

For example:

Mineral scale

may require an appropriate descaling solution.

Oil contamination

may require a different chemical treatment.

Biological deposits

may require another cleaning strategy.

The chemical must also be compatible with the plate and gasket materials.

Do not assume that a strong acid or alkaline cleaner is automatically better.

A cleaning solution that removes scale effectively can still damage the equipment if the chemistry, concentration or temperature is inappropriate.

When uncertain, consult the heat exchanger manufacturer or a qualified cleaning specialist.

15. Manual Cleaning of a Gasketed Plate Heat Exchanger

If CIP cannot remove the deposits, the plate heat exchanger may need to be opened.

Before opening:

Stop the equipment

Isolate both circuits

Depressurize completely

Allow the exchanger to cool

Drain the fluids

Only after the exchanger is safely isolated should internal maintenance begin.

Manufacturer manuals specifically require the unit to be depressurized and cooled before opening.

16. Measure the Plate Pack Before Opening

For gasketed plate heat exchangers, record the original plate-pack compression dimension according to the manufacturer’s instructions.

Also consider:

• Marking the plate-pack position
• Recording plate sequence
• Recording gasket orientation
• Photographing the assembly

This makes reassembly easier.

Plate arrangements can affect the flow channels.

Incorrect plate orientation can change the flow path and affect heat-transfer performance.

17. Remove and Inspect the Plates Carefully

When plates are removed, inspect them for:

• Scale
• Corrosion
• Pitting
• Cracks
• Deformation
• Erosion
• Gasket damage

Plate heat exchanger plates can have sharp edges, so appropriate protective gloves should be used during handling.

Do not bend plates during removal.

A damaged plate may cause leakage or alter the designed flow channel.

18. Use the Right Tools for Manual Cleaning

For manual cleaning, use methods recommended for the specific heat exchanger.

Depending on the manufacturer’s instructions, this may include:

• Clean water
• Soft brush
• Nylon brush
• Approved cleaning solution

Avoid abrasive tools that can damage the heat-transfer surface.

Steel brushes, aggressive scraping and unsuitable chemicals can damage plates or their protective surfaces.

Danfoss, for example, recommends soft-brush cleaning and warns against abrasive methods and incompatible cleaning agents.

19. Be Careful With High-Pressure Water

High-pressure water can be useful, but it must be controlled.

Do not place the nozzle too close to:

• Plates
• Gaskets
• Coatings
• Frame components

Excessive pressure or incorrect technique can damage the equipment.

The exact pressure and distance should follow the manufacturer’s instructions for the specific heat exchanger.

Do not assume that a pressure washer that is safe for industrial equipment in general is automatically safe for heat exchanger plates.

20. Inspect the Gaskets During Cleaning

Cleaning is an ideal time to inspect the gaskets.

Look for:

• Cracks
• Hardening
• Swelling
• Deformation
• Chemical damage
• Loss of elasticity
• Separation from the gasket groove

A gasket that looks acceptable may still have lost its sealing ability.

If the gasket has deteriorated, replace it with the correct material and profile.

The gasket material must match the application.

21. Reassemble the Plate Heat Exchanger Correctly

After cleaning:

Inspect plates

↓

Clean sealing surfaces

↓

Check gaskets

↓

Install plates in the correct sequence

↓

Close the plate pack

↓

Tighten according to manufacturer requirements

↓

Check final compression dimension

↓

Pressure-test if required

↓

Return to service gradually

Correct plate arrangement and gasket positioning are critical to sealing and flow distribution. Manufacturer manuals specify checking plate order, gasket position and sealing surfaces during reassembly.

22. Do Not Over-Tighten the Plate Pack

Tightening bolts are not simply a matter of:

“Tighter is better.”

Excessive compression can damage:

• Plates
• Gaskets
• Frame components

Insufficient compression can result in leakage.

Use the manufacturer’s specified closing dimension or tightening procedure.

Do not rely on visual judgment alone.

23. Pressure-Test After Maintenance

After major maintenance, verify that the heat exchanger is safe to return to operation.

Depending on the equipment and site procedures, this may include:

• Leak testing
• Pressure testing
• Visual inspection
• Connection inspection

The test pressure, medium and procedure must follow the manufacturer’s instructions and applicable site or regulatory requirements.

Do not improvise a pressure test.

24. Heat Exchanger Maintenance: What Should Be Checked Regularly?

A basic maintenance program should monitor:

Temperature

Compare actual inlet and outlet temperatures with expected values.

Flow

Monitor whether the required flow is maintained.

Pressure Drop

Track changes across the heat exchanger.

Leakage

Check connections, gaskets and the frame.

External Condition

Look for corrosion, damage or abnormal conditions.

Bolts and Frame

Inspect the mechanical condition according to the manufacturer’s maintenance instructions.

Gaskets

Check condition when the exchanger is opened.

Regular service guidance from Danfoss includes checking temperatures and flows against commissioning data, inspecting for leakage and checking the general condition of the unit.

25. Keep a Heat Exchanger Performance Record

One of the simplest ways to improve maintenance is to record operating data.

For example:

A single measurement tells you little.

A trend over time is much more useful.

If performance gradually deteriorates, maintenance can be scheduled before the exchanger causes a major process problem.

26. Cleaning Frequency Depends on the Application

There is no universal rule saying:

“Clean every six months.”

The correct interval depends on:

• Fluid quality
• Fouling tendency
• Operating temperature
• Flow velocity
• Water treatment
• Process conditions
• Heat exchanger design
• Previous cleaning results

Clean fluids under stable conditions may require less frequent intervention.

Dirty or severe operating conditions may require much more frequent inspection and cleaning.

Manufacturer maintenance schedules similarly distinguish between normal and severe operating conditions.

27. How to Reduce Heat Exchanger Fouling

The best cleaning strategy is to reduce fouling before it becomes severe.

Depending on the system, consider:

Water Treatment

Control scaling and corrosion in water systems.

Filtration

Remove suspended solids before they enter the heat exchanger.

Correct Flow Velocity

Avoid operating conditions that encourage excessive deposition.

Proper Temperature Control

Avoid unnecessary overheating that can accelerate scaling.

Regular Monitoring

Detect changes in pressure drop and heat-transfer performance early.

Planned Cleaning

Clean before deposits become difficult to remove.

Cleaning should be part of a larger operating strategy rather than the only response to fouling.

28. Cleaning a Brazed Plate Heat Exchanger

Brazed plate heat exchangers are different from gasketed plate heat exchangers.

They normally cannot be opened in the same way as a gasketed unit.

Therefore, cleaning is generally performed through the connected piping system using an appropriate CIP procedure.

The cleaning solution must be compatible with:

• Stainless steel plates
• Brazing material
• Process fluid
• Deposits

If performance cannot be restored through appropriate cleaning, replacement may need to be considered.

Do not attempt to mechanically open a brazed plate heat exchanger unless the manufacturer specifically provides a method for that design.

29. Cleaning a Shell and Tube Heat Exchanger

Shell-and-tube heat exchangers require a different maintenance approach.

Depending on the design and fouling condition, cleaning may include:

• Mechanical tube cleaning
• Chemical cleaning
• Tube-side flushing
• Shell-side cleaning
• Tube inspection
• Tube plugging
• Tube replacement

The correct method depends on:

• Tube material
• Tube diameter
• Deposit type
• Shell design
• Access
• Fluid chemistry

A cleaning procedure suitable for a plate heat exchanger should not automatically be applied to a shell-and-tube exchanger.

30. Common Heat Exchanger Maintenance Mistakes

Mistake 1: Cleaning Only When Performance Is Already Very Poor

Heavy fouling may require more downtime and more aggressive cleaning.

Mistake 2: Using the Wrong Chemical

An unsuitable chemical can damage plates or gaskets.

Mistake 3: Using Abrasive Tools

Aggressive mechanical cleaning can damage heat-transfer surfaces.

Mistake 4: Ignoring Pressure Drop

A rising pressure drop may indicate developing fouling or blockage.

Mistake 5: Reassembling Plates Incorrectly

Incorrect plate arrangement can alter flow paths.

Mistake 6: Reusing Damaged Gaskets

A deteriorated gasket can cause leakage after reassembly.

Mistake 7: Ignoring the Manufacturer’s Manual

Different heat exchanger designs have different operating and maintenance limits.

31. A Practical Heat Exchanger Maintenance Workflow

For a gasketed plate heat exchanger:

1. Monitor performance

↓

2. Identify abnormal temperature or pressure-drop changes

↓

3. Confirm operating conditions

↓

4. Determine whether fouling is likely

↓

5. Choose CIP or manual cleaning

↓

6. Isolate and depressurize

↓

7. Clean the exchanger

↓

8. Inspect plates and gaskets

↓

9. Reassemble correctly

↓

10. Test for leakage

↓

11. Restart gradually

↓

12. Record the new operating data

This creates a repeatable maintenance process rather than relying on guesswork.

32. Heat Exchanger Installation, Cleaning and Maintenance Checklist

Installation

☐ Correct heat exchanger selected

☐ Heat duty confirmed

☐ Flow rates confirmed

☐ Pressure and temperature confirmed

☐ Correct flow direction

☐ Piping properly supported

☐ Maintenance space available

☐ Isolation valves installed

☐ Drain and vent provisions available

☐ System flushed before operation

Cleaning

☐ Performance deterioration confirmed

☐ Fouling type identified

☐ Cleaning method selected

☐ Cleaning chemical compatibility confirmed

☐ Both circuits isolated

☐ Pressure released

☐ Equipment cooled

☐ Plates cleaned without damaging surfaces

☐ Gaskets inspected

☐ Heat exchanger correctly reassembled

Maintenance

☐ Temperature monitored

☐ Flow monitored

☐ Pressure drop monitored

☐ Leakage checked

☐ Gaskets inspected

☐ Plates inspected

☐ Frame condition checked

☐ Maintenance records updated

33. When Should You Contact a Heat Exchanger Manufacturer?

Contact the manufacturer when:

• Heat transfer suddenly decreases
• Pressure drop increases significantly
• Leakage continues after normal inspection
• Plates are damaged
• Gaskets repeatedly fail
• Corrosion is suspected
• The fluid has changed
• Operating pressure has changed
• Operating temperature has changed
• The heat exchanger needs to be resized
• You need a replacement
• You need a different material
• You need a larger capacity
• You need an OEM replacement

Do not assume that changing operating conditions is harmless.

A heat exchanger is designed around specific thermal, hydraulic and mechanical conditions. Significant changes should be reviewed before operation.

Heat Exchanger Video Tutorials: Learn the Procedure Before You Start

A good heat exchanger maintenance video should show the actual equipment rather than simply explain the theory.

Useful video tutorials should cover:

Heat exchanger installation

Piping connection

Startup and commissioning

Plate heat exchanger disassembly

Plate cleaning

Gasket inspection

Gasket replacement

Plate inspection

Plate pack assembly

Tightening procedure

Leak testing

CIP cleaning

Heat exchanger maintenance

A complete visual demonstration can make complicated maintenance procedures easier to understand. Heat exchanger manufacturers and service companies commonly organize maintenance training around disassembly, cleaning, inspection, gasket installation, reassembly and testing.

Need Help With Your Heat Exchanger?

If your heat exchanger has:

Low heat-transfer performance

High pressure drop

Scaling

Fouling

Repeated leakage

Damaged plates

Gasket problems

Corrosion

Cleaning difficulties

or if you are planning a new heat exchanger installation or replacement, provide the operating information to the manufacturer before choosing a solution.

Useful information includes:

Heat duty

Fluid

Flow rate

Inlet temperature

Outlet temperature

Operating pressure

Allowable pressure drop

Material

Existing heat exchanger model

Drawing or photos

A manufacturer can then evaluate whether the problem is related to selection, fouling, operating conditions, maintenance or equipment condition.

Install it correctly. Clean it before fouling becomes severe. Monitor its performance. Maintain it according to the manufacturer’s requirements.

That is the simplest way to keep a heat exchanger operating reliably and efficiently over its service life.