Rated working pressure of detachable plate heat exchanger

Seal failure

1, sealing gasket material

Failure of gasket material is also an important factor. Mainly in the following ways:

When the rubber sealing gasket material is in contact with the fluid, when a fluid component is penetrated into the rubber, the soluble substances can be extracted from the rubber, and the swelling of the rubber sealing gasket can be generated;

The presence of halogen and the role of ozone to soften the gasket or to cause stress corrosion cracking.

Under some conditions, especially under high temperature, elastic materials will decompose and release of chemical substances, and these substances themselves will corrode the plate material, such as rubber FPM will release oxygen for assembling the heat exchanger, found the plate cold fluid end surface light, part of a small amount of black scale like, because of the board external corrosion. The leakage of the detachable plate heat exchanger. The number of corrosion pits is not penetrated, and there are black deposits in the corrosion pits, so it can be concluded that the corrosion of the gasket.

2, fluid pressure

Detachable plate heat exchanger in the rated working pressure when the use of leakage. The main water hammer, and the hammer with non normal impact load, in addition to the quality factors of equipment in the manufacturing assembly. This is not easy to observe the use of the phenomenon. Instantaneous peak pressure of shock caused by more often than the normal operating pressure is 1-3 times higher, which is mounted on the heat exchanger in the rubber sealing pad shift, resulting in seal failure due to the heat transfer element of the [2] equipment, stainless steel sheet manufacturing capacity (0.5-1.0mm thickness of the sealing was relatively poor and sealed around very long, so the impact pressure is far lower than that of shell and tube heat exchanger. The heat exchanger of non normal impact can provide basis for the transmission medium equipment to determine maintenance delivery for the lye found heat exchanger pump, pump shell in the presence of a small amount of honeycomb, shows the pump cavitation during operation; at the same time because around the plate in early leakage, a possible factor changes it can be inferred that the fluid pressure and leakage.

3, temperature

Rapid changes in temperature can also cause seal failure. When the temperature changes too fast. The sealing pre tightening force is decreased, and the linear expansion coefficient of the rubber gasket is not matched with the elastic deformation quantity and the seal pretightening force. The pressure bearing capacity of the equipment is lower than the rated pressure.

According to the working condition of the plate heat exchanger. Therefore can exclude. Temperature has little effect on it.

corrosion

The corrosion of plate heat exchanger is the main corrosion fingerboard tablets. Plate heat exchanger is mostly made of stainless steel sheet. However, after the passivation film is destroyed, the stainless steel sheet will be subjected to uniform or localized corrosion. The corrosion phenomenon of plate heat exchanger is mostly caused by Cl stress corrosion, stainless steel has excellent corrosion resistance. It usually occurs at the bottom of the sealing groove of the plate and the bottom of the dirt formed by the dirt:

1, stainless steel sheet by mechanical cold stamping, can not be prevented to a certain amount of residual stress of the surface, for molybdenum free stainless steel sheet, the appearance of residual stress is very difficult to eliminate.

2, the board after the formation of a multi slit structure, adjacent plate corrugated top cross each other to form a large number of contacts. There will be a gap in the cross contact, the flow of media in the gap is not smooth, so that the gap between the concentration of oxygen inside and outside the gap, resulting in crevice corrosion.

3, when the surface of the surface of the dirt is serious, the medium of corrosive elements (ClS, etc.) may be attached to a large number of dirt, and at the bottom of the scale gap enrichment.

4, seal groove bottom of harmful elements is often in adhesive in Cl by temperature instability analysis of the adhesive, such as neoprene series compressed asbestos pad (containing CaCl2 are often in the water and steam conditions, precipitation and enrichment of Cl and H + HCl to the bottom of the groove formed cracks occur serious stress corrosion cracking, check open board when found, hot fluid inlet side most plate crack, and no pre cleaning has a thick layer of dark brown deposits; plate heat fluid inlet side of Chevron bellows plate, the top adjacent chevron bellows at the top of the contact point, both appearance and damage the corrosion spots, surrounded by dark brown deposits. Each plate has a perforated corrosion 12, overlapping contacts are in corrugated near the top hot fluid inlet side of the local area, a pit, pitting corrosion. One side of the hot water side of the corrosion pit is more obvious, most of which are in the shape of cracks, and most of them have penetrated. Therefore, it can be concluded that the corrosion of the plate heat exchanger is a comprehensive reaction of various factors.

Analysis and discussion

Based on the above analysis and test results. The failure of the heat exchanger plate is mainly corrosion failure.

1, the heat exchanger herringbone corrugated sheet is formed by the deformation of a large number of martensite. To reduce the corrosion resistance of stainless steel. The residual stress after deformation, and the crystal is dispersed into the precipitated fine carbide. In addition, the force exerted on the plate assembly will result in greater stress at the top of the ripple, and promote intergranular corrosion.

2, containing a small amount of sodium chloride. Because of its strong penetrating ability, the plate gap contains a high concentration of Cl- ions. Damage or even penetrate the surface of the passive film, so that the matrix metal directly in contact with the media, causing corrosion and dissolution; S element may occur in the presence of certain sulfide, but also promote the occurrence and expansion of corrosion.

3, the heat exchanger uses three yuan ethylene propylene rubber as the seal pad. The S element in the plate contact pad and a sulfide, due to pressing force on the role of high inlet temperature. Promote the occurrence and expansion of corrosion.

4, the heat exchanger is composed of many plates alternately arranged and pressed together. The medium inside the gap is not flowing or the flow is not smooth, and the adjacent plates are corrugated with the top of the cross to form a plurality of contacts. There will be gaps in the cross contacts. The difference of the oxygen concentration inside and outside the gap, which results in crevice corrosion, causes the corrosion and dissolution of some areas in the gap, which is the main reason for the perforation corrosion at the contact point.