Views:4 Author:Site Editor Publish Time: 2021-04-26 Origin:Site
The plate heat exchanger is a new type of high-efficiency heat exchanger made up of a series of metal sheets with a certain corrugated shape. Thin rectangular channels are formed between the various plates, and heat exchange is carried out through the half plates. Plate heat exchanger is a device for liquid-liquid and liquid-vapor heat exchange. It has the characteristics of high heat exchange efficiency, low heat loss, compact and lightweight structure, small footprint, convenient installation and cleaning, wide application, long service life and so on. Under the same pressure loss, the heat transfer coefficient is 3-5 times higher than that of the tube heat exchanger, the floor space is one-third of the tube heat exchanger, and the heat recovery rate can be as high as 90% or more. As a kind of compact and efficient heat exchange equipment, plate heat exchanger has been widely used in many industrial fields in our country and has achieved huge economic benefits. However, the failure of the plate heat exchanger also causes certain economic losses to our users. The main reasons are sealing failure, fouling, clogging and corrosion, making the heat exchanger unable to function.
Cause analysis of seal failure and related preventive measures
The main causes of seal failure are pressure, temperature, time and operating conditions.
The plate heat exchanger types are detachable and sealed. For example, when the plate heat exchanger is used under the rated working pressure, leakage occurs. In addition to the manufacturing quality of the equipment, it is mainly related to the abnormal impact load in the system. , This is a phenomenon that the operator is not easy to find. The impact causes an instantaneous pressure increase, and the pressure may be 1 to 3 times higher than the normal pressure, causing the sealing gasket installed in the plate heat exchanger to shift, resulting in sealing failure. And because the heat transfer elements of the equipment are made of thin plates at one time, with a thickness of 0.5 to 0.8 mm, the rigidity and bearing capacity of the seal are relatively poor. Moreover, some heat exchange plates have a long periphery and relatively poor impact resistance.
In this regard, corresponding preventive measures should be taken: depending on the operating pressure, increase the design pressure of the equipment to 1.5 to 2 times the operating pressure; try to avoid impact in the system during use; take measures to increase the thickness of the plate under special circumstances.
The rapid change in temperature also causes the seal to fail. When the temperature changes too fast, the expansion coefficient of the gasket does not match the elastic deformation and the pre-tightening force of the seal, which reduces the pre-tightening force of the seal, causing the equipment to withstand lower than the rated working pressure.
The following measures should be taken to solve this problem: the pressure rise and temperature rise should be as slow as possible when operating the equipment; a compression pre-tightening spring is designed on the clamping bolt to compensate for the change of the pre-tightening force.
Plate heat exchanger's use time problem, as the use time increases, the material of the sealing gasket will also deteriorate. Causes the sealing effect and affects the sealing effect of the plate heat exchanger.
In this regard, according to the characteristics of the material, the sealing gasket of the appropriate material should be selected, and different sealing gaskets should be used according to the different conditions of use.
1.4 operating conditions
Different process media conditions can also cause seal failure. As the supersaturated steam of temperature will cause the sealing sheet to fail in a short time. The saturated steam at the same temperature can form a water film on the surface of the gasket, which can protect the gasket.