In the use of plate heat exchanger will also appear in such a dissolved phenomenon, although the general situation will not explode, but it will also cause the plate heat exchanger leakage to our production and life hazards.
We all know that the plate heat exchanger, with high heat transfer efficiency, material flow resistance loss is small, compact structure, sensitive temperature control, operational flexibility, easy to install and dismantle, long service life and so on, it is the most advanced high-efficiency and energy-saving heat transfer equipment. Has been widely used in metallurgy, mining, petroleum, chemical industry, electric power, medicine, food, chemical fiber, textile, paper, ships and central heating and other fields. And more and more types of plate heat exchanger, technical performance is getting better and better, the application range is more and more extensive. Rubber sealing gasket is plate heat exchanger is both very important, but also need to be demanding parts. Gasket not only to seal the medium so that it does not leak to the outside environment, but also to prevent the heat exchange medium between the intermixing. If the gasket appears to dissolve and lose its elasticity, it may lead to the heat exchanger can not operate normally.
Terminology
Dissolution and swelling of rubber
Unvulcanized rubber can be dissolved in solvents with similar solubility parameters. For vulcanized rubber, due to chemical cross-linking rubber macromolecules linked into a three-dimensional mesh structure, so in the solvent can only absorb the solvent gradually expand and reach equilibrium value (maximum swelling). This phenomenon is called rubber "swelling". The volume after swelling can be up to several times the volume of rubber. This is accompanied by a loss of mechanical strength. The maximum swelling of vulcanized rubber is related to its crosslink density. In the absorption of solvent, vulcanized rubber crosslinked network also swelled and produce the solvent will be extruded out of the network of elastic contraction force, when the solvent diffusion infiltration pressure and the crosslinked network of elastic contraction force is equal, that is, to reach the swelling equilibrium. As the depth of the liquid immersed in the rubber is a function of the square root of the contact time, therefore, even if the rubber on the liquid in contact with no special impedance ability, or the rubber product itself has a certain volume, but also on its service life will have a certain impact. In fact, the dissolution of the plate heat exchanger rubber sealing gasket is like a balloon meeting an orange peel.
Plate heat exchanger rubber sealing gasket swelling causes
1, the cause of the medium Working condition of the medium is not the same temperature, not the same concentration value, not the same medium will need to use different materials of the rubber gasket, such as high temperature thermal oil need to use acid and alkali NBR rubber strip, water to EPDM rubber strip can be, if high temperature thermal oil must use EPDM rubber strip, then the rubber strip swelling that is unavoidable, and therefore must be based on the media of different characteristics of selecting the appropriate gasket material. Therefore, it must be based on the different characteristics of the medium to select the appropriate gasket material.
2, improper selection of cleaning agents due to the plate heat exchanger heat transfer temperature is generally higher (especially vapor exchange), and its heat transfer efficiency is high, so it is very easy to scale. At the same time plate heat exchanger internal circulation aperture is small, after scaling the internal channel cross-section becomes smaller or even blocked, resulting in plate heat exchanger heat transfer efficiency is reduced, thus affecting the normal production and equipment safety. Plate heat exchanger must be regularly cleaned chemically, remove the dirt, in order to ensure that the plate heat exchanger efficient heat transfer and normal production. A lot of cleaning agent additives, containing the dissolution of dirt chemicals polyether amine PEA, has a very strong cleanliness and solubility, easy to cause the rubber sealing gasket swelling phenomenon. Remember to choose a cleaner that is not harmful to the rubber gasket.
Friendly advice
Rubber gasket used in benzene, ketone, ether and other organic solvents, easy to swelling, weight, softening, sticky phenomenon, resulting in seal failure. Generally, if the degree of swelling exceeds 30%, it cannot be used.
Rubber gasket once swelling, it is relatively lose the original physical and chemical properties, especially physical properties. Means that the structure of the rubber changes (aging), the loss of physical properties. Waiting to leave the solvent environment, swelling can not be restored, the rubber gasket is invalid, can not be reused!
