In process industry equipment. The plate heat exchanger is a piece of equipment that requires a high degree of safety. When the gasket is damaged. External dripping is visible. Heat exchangers. Heat exchangers, heat exchangers, etc. can initially show minor drips. In process equipment with high pressure shocks. Larger leaks can occur as a result of gasket damage.
Even in plate heat exchangers. Problems can occur during the course of a year. They need to be repaired. Especially its seals. It is important to see if it has come loose. In this article we will describe the considerations when maintaining a plate heat exchanger.
The plate heat exchanger is an important component of heat exchange technology in process industry equipment. The elastomeric gasket, which seals between the individual plate fins, is a wearing part. It is also a component that is susceptible to deterioration under natural conditions. Its service life has an important influence on the service life of the plate heat exchanger. If these seals harden thermally. They lose their elasticity. This can lead to the heat exchanger not working properly.
The following factors have an important influence on the service life of the elastic gasket.
■The mode of operation of the heat exchanger (continuous or discontinuous)
■The corrosiveness of the medium used for heat dissipation and the cleaning agent used
■The maximum working temperature
■ Maximum working pressure
■ high stresses on the elastomeric gasket due to excessive and uneven pressures
■ Natural ageing
The softening of the elastic gasket is pressure and temperature dependent. When the gasket loses its elasticity. The heat exchanger will drip. In some products. In order to solve the problem of dripping caused by the ageing of the gasket. It is permissible to adjust the sealing performance of the heat exchanger. This means that the bolts of the combined plate heat exchanger are tightened again. Adjust the pressure of the elastic gasket between the individual heat exchangers. Solve dripping problems. On the nameplate of heat exchangers with this function. The maximum and minimum permissible stresses are usually given on the nameplate of heat exchangers with this function. For new heat exchanger sets. The minimum permissible stress should be used to secure the connection. Depending on the number of heat exchanger plates in each group. The tightening force of the heat exchanger can be adjusted one or more times. Each time you tighten. The nut can be screwed in 3 mm and the stress on the adjusting piece should be observed throughout the tightening process. Furthermore. Only heat exchangers with no working pressure are permitted. Adjust the tightening force at room temperature. Prevent dripping.
For plate heat exchangers where the stress adjustment range is not given in the nameplate. Stress values are usually given in the parts drawing. When tightening such plate heat exchangers. The tightening torque should in no case be less than the value specified in the drawing. This is because it is related to the quality of the assembly of the plate heat exchanger. The deformation of the assembly is relevant. When the tightening torque has reached the required value. The elastic gasket can then be systematically replaced. For plate heat exchangers used in critical production facilities and in corrosive media. It is recommended to have a spare set of seals. At a warehouse temperature of 18°C. In transparent plastic packaging. The seals of the plate heat exchanger can be stored for about 3 years.
Fixing of the seals
In principle. The fixing of seals is divided into two categories: adhesive fixing and non-adhesive fixing. The shape of the gasket should be consistent with the shape of the plate heat exchanger seal. It must be noted that the adhesive fixing method does not have any effect on the sealing function.
Non-adhesive sealing
▪ Alignment: placing the seal in place
▪ Placement: the seal is correctly placed in the sealing groove
▪ Pressing: in the sealing groove. There are grooves of decreasing cross-section. to allow the seal to be positioned correctly
Bonded seals
Depending on the purpose of the gasket and the seal quality required. Depending on the purpose of the gasket and the quality of the seal required, a mix of sealants and non-mixing sealants from different manufacturers can be used. Prior to bonding. The adhesive and gasket residues should be thoroughly removed from the bonding surface using a steam stream. For blended sealant bonding. The residual adhesive and gasket must be removed by fire. When bonding large quantities. A pool of liquid nitrogen should be prepared to freeze the seals. Prepare the heating oven for drying the plate heat exchanger with gasket. The heating temperature should be 160°C. If available. Chemical cleaning of the plate heat exchanger should be carried out. This ensures that the gasket is completely removed from the bonded parts of the plate heat exchanger.
The correct installation of the gasket can be seen by looking through the beehive of the plate heat exchanger.
The joint surfaces of the plate heat exchanger should be cleaned with a chemical cleaner (e.g. with acetone). Likewise. The softeners and anti-adhesive coatings bonded to the gasket must also be removed with a chemical cleaner. The adhesive is applied to the middle of each bonding surface. Depending on the width of the gasket. The width of the adhesive is approximately the width of a match. The adhesive is then spread evenly over the entire bonding surface with a brush. The entire bonding surface is fully utilised. Depending on the type of adhesive. Allow a certain amount of time for the air to dry. The gasket is then placed. Place the individual plate heat exchangers on top of each other. Tighten with a tensioning screw. Alternatively, a weight can be placed on the stacked heat exchanger group. Depending on the type of bonding agent. The hardening time is approximately 8-20 hours. For blended adhesives. The hardening is carried out by screw tensioning and heating in the furnace.
