Views: 9 Author: Site Editor Publish Time: 2022-10-12 Origin: Site
Heat exchangers are used to optimize heat transfer from one gas or liquid to another during processing and cleaning in place (CIP). Fouling or aging can result in degraded heat exchanger performance and additional operating and energy costs to compensate for the difference in target temperature. Therefore, the cleaning and maintenance of the heat exchanger are very important to keep the brewing equipment running efficiently. Regular maintenance keeps equipment in working order and helps prevent emergency maintenance. In addition, the cost of cleaning and maintaining a heat exchanger is small compared to the cost of unplanned downtime required for the heat exchanger.
Product or chemical deposits on the heat transfer surfaces can impair the heat transfer capability of the heat exchanger and must be cleaned regularly to maintain high-performance operation and prevent process interruptions. Heat exchanger fouling and unwanted deposit build-up on heat transfer surfaces can result in a variety of costs:
Production loss due to production stoppages
Maintenance costs to remove heavy dirt or deposits
Replace clogged equipment
How Do I Know When I Should Clean My Plate Heat Exchanger?
The frequency with which you clean your plate heat exchanger does not need to be based on a set schedule. When the heat exchanger fails to reach the correct product temperature for heating or cooling, you can tell when it is time to clean the heat exchanger, as the incorrect temperature is caused by fouling of the surface of the plates that reduce the temperature transfer.
Also, you may see a pressure drop higher than specified because dirt restricts the channel and increases fluid velocity. A good rule of thumb is to clean when the pressure drop on either side is 50% greater than the design pressure drop. If you do not know the design pressure drop, you should measure it immediately after cleaning and use these values to determine the next cleaning.
Ways To Clean A Plate Heat Exchanger
Compared to shell and tube heat exchangers, plate heat exchangers have grown in popularity over the past few decades. Generally speaking, plate heat exchangers have higher heat exchange efficiency and take up less space. These factors have helped spark brewery interest in plate heat exchangers as an alternative to shell and tube heat exchangers. There are two ways to clean a plate heat exchanger: cleaning in place (done by circulating chemicals through the channels of the plate heat exchanger) or manual cleaning (removing the plates from the frame and cleaning the plates individually using a pressurized water gun).
1.CIP Cleaning Method
This method allows a chemical solution to be circulated through the heat exchanger to dissolve and remove fouling from the surface of the plate. This method eliminates the need to separate the heat exchanger, simplifies the cleaning process, and reduces cleaning labor. Chemical cleaning is ideal because the corrugated plates clean turbulent liquids and help dissolve scale.
CIP cleaning method is a combination of time, temperature, and concentration. CIP systems provide chemical and mechanical cleaning of heat exchangers. If the brewery equipment prohibits CIP, the operator must perform manual cleaning.
Advantages of chemical cleaning with CIP:
（1）Faster cleaning process.
（2）Low labor intensity.
（3）Components that cannot be cleaned by mechanical cleaning can be cleaned.
Operators typically follow these four steps in the chemical cleaning process at CIP:
（1）Alkaline Cleaning: Removes build-up of organic matter.
（2）Rinsing: Usually done with a high-flow water rinser to remove loose debris and residual residue from the alkaline step.
（3）Pickling: Helps to dissolve and soften soiled materials at a deeper level.
（4）Final Rinse: Finally rinse the plate heat exchanger with clean water.
Manual cleaning is required to clean the plate heat exchanger if the heat exchanger does not support CIP cleaning.
Manual cleaning steps
The first step in maintaining the heat exchanger is to disassemble the plate heat exchanger, which requires professional mechanics to shut off all fluids entering and leaving the heat exchanger (need to ensure that lockout procedures are followed).
To be able to remove fluid from the heat exchanger, you need to release all pressure by opening the valve. You will want to finish cooling before the heat exchanger opens, to do this you will need:
Loosen the acid on the heat exchanger, about 1/4 ft. at a time, before moving the next bolt. To ensure effective bolt loosening, do not over loosen the bolt as it may damage the bolt head.
After removing the bolts, slide each removable head back to expose the hot plate pack.
To facilitate reinstallation, all boards need to be numbered in reverse order, and the number needs to be displayed on the top of each board.
（2）Clean the heat exchanger plate
Cleaning is included in the service plan of any good plate heat exchanger. Follow the steps below to make sure you don’t miss any steps:
First, remove the gasket. The gasket can be reused or not based on its current condition. To check if your gasket is still in pristine condition, just pinch it to know its condition. If you need to reuse the gasket, wash them with soap and water, then hang them in a clean, dry area.
If there is loose debris on the board, then it needs to be cleaned with soap, water, and a soft brush or pressure washer, not a grinder or a hard brush.
Clean the plate until all debris is removed.
The groove of the gasket needs to be very careful and in very severe cases hot acid and caustic need to be used to break down stubborn adhesives and buildup.
（3）Test the heat exchanger plate
During this inspection, it is critical to test and inspect your boards for cracks and pinholes throughout the facility.
Visually inspect the heat exchanger for defects, paying close attention to where the plates touch each other. You can use lights to aid visual inspection.
It’s also a good idea to perform a dye test to catch any pinholes missed by visual inspection. If more than 10% of the plate set contains defects, the plates must be replaced. If your plates pass the dye test, they can be cleaned and put back into service.
（4）Inspection and Reassembly
Before inspecting and preparing heat exchanger plates, the plate frame must be cleaned and prepared before reassembly:
Start by inspecting the nozzle area, paying close attention to weld areas where corrosion and defects may occur.
Check the straightness of the fixed head and movable head with a ruler. For painted and powder-coated carbon steel frames, the coating needs to be inspected to determine if it is in satisfactory condition.
Check the connection points of the upper and lower rails.
Polishing may interfere with serious defects in the sheet.
Once your heat exchanger is assembled, it is important to hydrostatically test your unit and check it for leaks.
Fill water through the system or other water source like a heat exchanger.
Let the water run for a while so it can remove the excess air.
Slowly restrict the outlet to increase the pressure, but do not exceed the design pressure.
Air-dry the outside of the heat exchanger to remove any residual water.
When the heat exchanger is under pressure, check the plate pack for water leakage.
What Additional Maintenance Is Required For Plate Heat Exchangers?
Use the isolation valve once or twice a year.
Check the filter and clean it as needed.
Check that the drains and vents are not blocked.
Check the pressure gauge and replace it as needed.
Top 10 Tips For Keeping Your Plate Heat Exchanger In Top Condition
Ensure that operating conditions (temperature and flow) meet design specifications.
Vent the heat exchanger at start-up, but open and close the valve slowly to avoid pressure fluctuations and water hammer.
Use upstream filters and strainers to remove particulate fouling and protect the heat exchanger.
Check daily for any changes in temperature, pressure, and any signs of external leaks.
Regularly keep the fastening bolts clean and well lubricated.
Use condition detection technology to avoid opening the plate heat exchanger for inspection.
Use clean-in-place (CIP) to avoid the need to open the heat exchanger for cleaning.
Always keep spare equipment clean and dry. If the heat exchanger is out of service, flush it with fresh water and drain it completely.
Protect the heat exchanger from water splashes and avoid exposure to UV rays and ozone normally generated by the power supply.
Only use original spare parts for plate heat exchangers to ensure equipment performance, reliability, and equipment life. Also, keep important spare parts in stock and follow storage instructions.