Importance of Maintenance
Plate heat exchangers have rarely experience failure or problem.
However, long periods of use can lead to defects such as deteriorated plate gaskets, scale adhesion, and penetrating cracks.
- For sound operation of production lines
- When a heat exchanger is used and/or stored for a long period of time, the components will deteriorate over time.
-
- Deterioration of
seal materialLeakage - Damage/corrosion on
heat transfer platesMixture of
two fluids - Accumulation of
dirt inside equipmentFluid at the
temperature required for
plant operation
cannot be supplied - Reduced production volume
- Operation stoppage
- Production lines stop!!
- Aiming for a higher heat recovery rate
- Equipment that affects the manufacturing process is under control, so it is easy to notice a decline in capacity. The heat recovery unit is difficult to notice even if the recovery rate decreases, and it may not be able to recover useful energy.
- *Heat recovery = Use of energy that would normally be discarded, to control the temperature of processes at low cost
- Initially: 40°C→80°C
Over time: 40°C→50°C - Initial performance can be achieved by performing maintenance
- Steam expense
- A difference of 13 million annually!
- *This is only one example.
- Click here for details.
If maintenance is neglected for a long time...
Visual confirmation of cracks on the heat transfer area (left)
Cracks found during a penetrant test (right)
Heat exchanger on which gaskets were not replaced (left)
Crevice corrosion that occurred in the gasket line (right)
- What if there is leakage, mixture of fluids, or no cooling in quenching tanks, plating layers, and aquariums for living things?
- What if there is leakage, mixture of fluids, or no cooling in the coolers for building air conditioning units?
- What if there is leakage or no cooling of the cooling water for the control panels of electrical equipment?
Heat exchangers are not equipment that is operated.
They are silent equipment that does not generate abnormal noise or odors.
When recovering heat from concentrated waste fluid
- Operation conditions
- Initially
Heating of waste fluid under the conditions of 40[°C] -> 80[°C], 10 [m3/h]
Heat recovery = (80[°C] - 40[°C])x10 [m3/h]x1000 [kg/m3]x1 [kcal/kg･°C] = 400,000 kcal/h
- Performance drops
over many years
of operation ... - After continued operation
Heating of waste fluid is only up to 40[°C] -> 50[°C], 10 [m3/h]
Heat recovery = (50[°C]40[°C])x10 [m3/h]x1000 [kg/m3]x1 [kcal/kg･°C] = 100,000 kcal/h
- Steam amount(Calculated with steam latent heat = 550 [kcal/kg])
- Initially
- 400,000 [kcal/h]/550 [kcal/kg] = 727 [kg/h](0.72 [ton/h])
- Performance drops
over many years
of operation ... - After continued operation
- 100,000 [kcal/h]/550 [kcal/kg] = 181 [kg/h](0.18 [ton/h])
Due to reduced performance, 0.72 [ton/h] - 0.18 [ton/h] = 0.54 [ton/h] more steam is required than initially.
Assuming that steam is 3000 [yen/ton], 8000 [h] of operation annually, and no change in performance a steam expense of 0.54 [ton/h]x3000 [yen/ton]x8000 [h/year] = 12.96 [million yen/year] is required.
Steam expense can be reduced by performing maintenance to keep the PHE in proper working condition.
Heat exchangers in operation
When servicing a plate heat exchanger, it is important to find the cause of any defect.
Please check the following items regarding heat exchangers that are currently in operation.
ProblemCauses and Measures
The heat exchanger is not performing as expected.
The specified flow rate is not flowing through the plate heat exchanger.
The concentration and composition of the fluid being used are impure (two fluids are mixed).
Fluid leaks out between the S. frame and D plate.
Fluid is leaking outside from the plate side.
What emergency actions should be taken when fluid leaks to the outside?
How can we tell if fluids have mixed?
How can we improve the performance of the heat exchanger?
ProblemCauses and Measures
The heat exchanger is not performing as expected.
Are the heat transfer plates dirty?
If you think that performance is slowly decreasing, the heat transfer plates might be dirty.
If the heat transfer plates are dirty, scale that has adhered to the heat transfer surface will cause heat transfer resistance, reducing the performance of the heat exchanger.
Even with water for industrial use, dirt might accumulate on the surface of heat transfer plates This will result in the formation of a layer of scale that is sufficient enough to reduce performance.
You will need to disassemble the equipment, check for dirt, and clean the heat transfer plates.
*Recommended replacement parts
-Plate gaskets
Are the pipes connected as shown in the drawing?
The performance of a plate heat exchanger varies depending on how the fluid flows.
The design for a plate heat exchanger includes piping connection positions (fluid inlets and outlets). Therefore, models that are designed with opposite flow will not achieve sufficient heat transfer performance when connected to a parallel flow. Check the piping positions and make necessary adjustments.
Refer to the assembly drawing for the piping positions.
Are the heat transfer plates arranged correctly?
-If there is an E plate (a plate without holes) in middle position
Heat transfer plates after the E plate cannot be used effectively.
Check the element configuration diagram and set the E plate in the correction position.
-If special hole plates are not in the correct positions
Some equipment might include special hole plates (which do not have four holes) among the other heat transfer plates.
If these heat transfer plates are not arranged in the correct position, the heat transfer performance will be affected.
Check the element configuration diagram and set the special hole plates in the correction positions.
-If there is a mixed arrangement
f a mixed arrangement is not performed correctly, the heat transfer performance will be affected.
Check the element configuration diagram and perform the mixed arrangement correctly.
Are the target performance and design conditions the same?
Heat exchangers are designed according to the original specifications.
Check the operation conditions against the specifications on the element configuration diagram.
ProblemCauses and Measures
The specified flow rate is not flowing through the plate heat exchanger.
Are the heat transfer plates dirty (or blocked)?
A gradual reduction in the flow of fluid could be caused by dirt.
If a large amount of scale or sludge accumulates in the heat exchanger, a sufficient fluid flow might not be ensured between the heat transfer plates.
Disassemble the heat exchanger and clean the heat transfer plates.
*Recommended replacement parts
-Plate gaskets
Are the heat transfer plates arranged correctly?
If the flow rate suddenly drops after the heat exchanger is assembled, the plate arrangement might be wrong.
Check the element configuration diagram and arrange the plates correctly.
ProblemCauses and Measures
The concentration and composition of the fluid being used are impure (two fluids are mixed).
Is the fluid on the primary side flowing into the secondary side?
If the fluid flows from the high pressure side to the low pressure side, the heat transfer plates might be damaged.
Perform a crack confirmation test on the heat transfer plates to check if they are damaged. Replace any damaged plates with new ones.
If you do not have a spare units for replacement, remove A plate and B plate as one set, and then reassemble while paying attention to the tightening dimensions.
*Recommended replacement parts
-Plate gaskets, heat transfer plates
If it is unclear whether the fluid on the opposite side is flowing into the equipment
For a special hole plate, contact HISAKA for assistance.
s fluid leaking from the heat exchanger?
Deterioration of the sealing properties of plate gaskets might cause fluid to leak to the outside.
Generally, two fluids will not mix when a plate gasket deteriorates. However, if two gaskets deteriorate at the same time, the fluids might mix.
This could happen if a leak is left uncorrected for a long time. Be sure to replace deteriorated plate gaskets.
*Recommended replacement parts
-Plate gaskets
ProblemCauses and Measures
Fluid leaks out between the S. frame and D plate.
Is the D gasket installed correctly?
When looking through the nozzle on the equipment, if the D gasket appears to be protruding, open the heat exchanger and make sure that the plate gasket is securely on the seal line.
Unlike other heat transfer plates, fluid does not pass through the surface of the D plate (the side that is in contact with the (S. frame)).
Make sure that all four of the portholes are aligned.
Has the D gasket deteriorated?
If there is deterioration in the D gasket, the sealing properties of the D plate and the S. frame could drop and cause leakage to the outside.
Replace the D gasket.
*Recommended replacement parts
-Plate gasket
Is the D plate corroded or damaged?
If the D plate is damaged, the fluid flowing on the surface of the second plate will penetrate to the surface of the first plate. Fluid does not flow along the surface of the first plate. Therefore, if it is not sealed, fluid will leak out of the heat exchanger.
Replace the D plate.
*Recommended replacement parts
-D plate
Is a piping gasket being used with a rubber boot?
Deformation can occur in heat transfer plates that have both a rubber boot and a D plate.
Disassemble the equipment and check for deformation in the heat transfer plates.
Remove the piping gasket.
Is there deterioration in the rubber boot?
If the equipment uses a rubber boot, the part of the S. frame that is in contact with fluid is covered by the rubber boot. If the rubber boot deteriorates, the sealing properties will drop and fluid might leak out through the S. frame.
The rubber boot needs to be replaced.
*Recommended replacement parts
-Rubber boot
-Plate gasket
*Click here for details about how to confirm the model of the equipment.
Is there deterioration in the tube flange or metal boot?
If the equipment uses a tube flange or a metal boot, part of the S. frame that is in contact with fluid is covered by metal.
If that metal is penetrated due to corrosion, fluid might leak out through the S. frame.
The tube flange or metal boot needs to be replaced.
*Recommended replacement parts
-Tube flange, metal boot (Contact HISAKA for assistance when replacing these parts.)
-Plate gasket
*Click here for details about how to confirm the model of the equipment.
Is there deterioration in the S. frame?
If the S. frame deteriorates, the sealing properties will drop and fluid might leak out.
If there is any noticeable deterioration in the S. frame, it needs to be replaced.
*Recommended replacement parts
-S. frame (Contact HISAKA for assistance when replacing these parts.)
ProblemCauses and Measures
Fluid is leaking outside from the plate side.
Is there deterioration in the plate gaskets?
Plate gaskets are consumable items that deteriorate if used for a long time.
Replace the plate gaskets.
The cycle for replacing plate gaskets is shown in the following table.
| Operating temperature | Estimated replacement period for gasket |
|---|---|
| Hot water of 100°C or hotter | 1 to 3 years |
| Warm water of 30°C to less than 100°C | 5 to 7 years |
| Water of less than 30°C | 7 to 10 years |
*Recommended cycle will vary depending on usage conditions and fluids.
Are the tightening dimension within the specified range?
When tightening the plate heat exchanger, refer to the tightening dimension on the nameplate.
If the tightening dimension is greater than the MAX dimension, tighten to the specified dimension range.
If leakage does not stop at the MAX dimension, check the conditions throughout the range, all the way down to the MIN dimension, and gradually tighten.
Are the thickness and number of heat transfer plates as indicated on the nameplate?
The tightening dimension for the equipment is determined according to the thickness and number of heat transfer plates. If the thickness/number of heat transfer plates is thinner/fewer than indicated in the design, tightening to the tightening dimension indicated on the nameplate will cause looseness throughout the entire equipment, and fluid will leak out.
Make sure that the thickness and number of plates are as indicated on the nameplate.
Are the heat transfer plates arranged correctly?
Arrange the heat transfer plates so that the A plates and B plates alternate.
An arrangement of A/A or B/B plates will cause a drop in seal properties.
If any heat transfer plates are in the reverse orientation, turn them around so they are arranged correctly.
Is there any foreign matter caught in the equipment?
If any foreign matter such as gravel or dust get between a plate gasket and a heat transfer plate during disassembly or assembly, the fluid might leak.
Use a cloth to gently wipe off the sealing surface of the plate gasket.
Are any plate gaskets falling off or dropping out?
When looking through the heat exchanger from the side, if a plate gasket is protruding farther than the others, that plate gasket might fall off.
Install the plate gasket correctly.
ProblemCauses and Measures
What emergency measures should be taken when fluid leaks to the outside?
Although it depends on how the fluid is leaking, one method is to retighten the components.
Tightening the heat exchanger within the range of MAX - MIN dimensions indicated on the assembly drawing or nameplate might reduce the amount of leakage.
ProblemCauses and Measures
How can we know if fluids have become mixed?
If you see a tendency of the mixture of two fluids in piping or other areas, use this method to check for plate damage.
ProblemCauses and Measures
How can we improve the performance of the heat exchanger?
If there is scale build up in the heat exchanger
Scale can interfere with heat exchange and reduce the performance of the heat exchanger. Disassemble the equipment and remove the scale.
If there is no scale in the heat exchanger
You can arrange the performance of a plate heat exchangers by disassembling the equipment and adding plates or replacing parts. Contact HISAKA for details.
For details about equipment other than heat exchangers that are in operation, click here.
