It is generally possible to find out if a heat exchanger seal is out of action by dripping during the cold movement of the plate heat exchanger or dripping during parking and cooling, but some plate heat exchangers now have a re-adjustable function, which means that the heat exchanger group can be screwed together twice in the event of a small drip, to achieve an increase in stress between the gaskets and effectively solve the drip phenomenon in a short time. In newly assembled heat exchangers, larger combination length sizes can be used and when dripping occurs, the groups of plate heat exchangers are then tightened. The maximum and minimum combination length sizes are generally found on the heat exchanger nameplate. It should be noted that the minimum combination length should not be less than the minimum combination length size. When the combined heat exchanger reaches the minimum combination length size and still drips, it means that the gasket must be replaced. Important factors affecting the service life of the rubber gasket are the way the heat exchanger works, the corrosive nature of the media and cleaning agents used, the maximum working temperature, the maximum working pressure, the high stress on the elastic gasket due to excessive and uneven pressure, and natural ageing. These should be maintained and serviced or replaced in good time.
The main steps for the reuse and replacement of rubber gaskets are
A, heat exchanger plate back to use before the inspection and cleaning:
1、Check the wall thickness of the heat exchanger and pipes in case of suspected corrosion.
2, remove aging seals, according to the different dirt, using acid and alkali for chemical cleaning, the surface of the cleaned parts will not be corroded by chemical media.
3、After the chemical cleaning, use the high pressure blowing device to thoroughly remove the chemical media remaining on the surface of the plate heat exchanger and in the pipeline.
4. The heat exchanger plates are coated with a fluorescent testing agent and checked for small cracks and corrosion holes under UV light and cleaned again.
5, also focus on checking the condition of the sealing groove, if necessary to trim.
Second, the heat exchanger sealing gasket back to use before the inspection and cleaning:
1, check whether the surface of the gasket is stuck with any impurities other than rubber, if there must be clear off, and shall not have the slightest damage to the gasket;;
2, observe whether the gasket has obvious indentation, or the local thickness is obviously thinner than the overall thickness, if such phenomenon is found, please reject all;
3、Compare the gasket with the gasket slot, observe whether there is a short length of more than 8mm, or a long length of 3mm out of the gasket slot, if you find such phenomenon, please reject all of them.
4、For adhesive gaskets, the residual material will be thoroughly removed and re-bonded using a blended adhesive. The reassembled heat exchanger set will be clamped in a special fixture to cure the adhesive and heated in a heat preservation oven to achieve the best adhesive effect.
Third, reassemble the heat exchanger unit.
In process industry equipment, the plate heat exchanger is a piece of equipment with high safety requirements and when the gasket is damaged, external drips are visible. Reuse performance of Heat exchangers are initially subject to minor dripping and in process equipment with high pressure shocks, larger leaks can occur due to damage to the gasket. The reason for this is that under strong pressure shocks the gasket can sometimes break out of the correct plate gasket groove of the plate heat exchanger, or in severe cases even come right out of the heat exchanger.
In such cases, the heat exchanger must be shut down immediately and allowed to cool down to room temperature without pressure. If a gasket that has been subjected to a strong pressure shock has been permanently deformed, then the gasket cannot be restored to its original shape and size and loses its sealing properties, in which case it must be replaced with a new gasket.
If no spare gasket is available, the temporary emergency measure is to remove the damaged gasket from the entire plate heat exchanger plate set and the adjacent plate (two plates in total), check all gasket surfaces to confirm that there are no defects affecting the seal such as impurities, cracks etc. and then install the remaining heat exchanger plates according to the examples in the operating instructions. To ensure that the heat exchanger can be used for short term emergencies, it is necessary to ensure that there is sufficient sealing force. This is done by recalculating the exact clamping dimensions. The general empirical values are
Clamping size = (plate thickness + gasket thickness) x number of plates x 0.72
