Temperature fluctuations causing flange leakage

DataTime:[2024-5-1]

Early last Wednesday morning to see the customer returned to the analysis of the report of the comments, read the comments have the urge to vomit blood; the feeling is not to write an analysis report, is to write a tutorial or to participate in the analysis of the defense, and the project is responsible for communicating with the clarification of the matter. I heard that the customer site has a heat exchanger leak, to give ideas to solve the leakage problem!

First, a brief introduction to the heat exchanger: seven or eight years ago, the owner of a replacement heat exchanger, the use of a few years of leakage two or three times, the recent leakage is a bit serious (clamped U-tube heat exchanger, equipment flange and tube plate connection position leakage, gasket many years ago with asbestos gaskets, seven or eight years ago, to replace the heat exchanger with a modified PTFE gaskets). When the design gave the conditions, there was no mention of pressure or temperature fluctuations; this time it was clear that the temperature from 0 to 180 ℃ every four hours on the cycle. In fact, the manufacturing plant design and manufacture of some of the equipment is actually a cycle of conditions, but the owner of the conditions did not say, with the problematic design conditions can be designed and manufactured very good products that is strange!

The reason for the leak is estimated to be the gasket resilience decline, bolts in the repeated warming and cooling process and the flange deformation is not coordinated.

Solutions:

1. To the nut below the increase in disc springs.
2. change back to better elasticity of the gasket, the recommended wave tooth gasket (but the equipment flange involves the calculation of the problem, to calculate whether it can be); if the wave tooth gasket calculation flange is not qualified to consider PTFE covered gaskets. Each overhaul for a new gasket, regardless of whether leakage occurs! If it is not possible, I personally think that the effect of using two PTFE gaskets will be good.

Wave tooth gasket

PTFE covered gaskets

Some gasket manufacturers recommend PTFE wrapped pads, personally I think it is not very suitable, wrapped pads of the resilience of the general, in the case of temperature fluctuations is said to be very fast decline in resilience. Winding pads need to be too large preload flange calculation is difficult to pass, preload is too large flange is easy to screw the deformation.

Slightly explain why the proposed solution: change back to a good elasticity of the gasket and add disc springs. From the role of gasket and disc spring to explain.

Gasket in the role of the sealing system:

1) to compensate for the unevenness of the flange.
2) to compensate for the flange sealing surface of the microscopic porosity.
3) to compensate for the flange and bolt changes in the operating conditions (pressure and temperature).

Disc springs are conical washers to put it bluntly. Since it is called a disc spring actually also has the characteristics of a spring, subdivided into disc springs can be divided into preloaded disc springs and tension disc springs. Disc springs in the pressure vessel industry are generally used in high-temperature conditions; in fact, it should be accurate to say that the use of preloaded disc springs, preloaded disc springs installed in the flange connection of the bolt, to compensate for the operation of the bolt due to thermal expansion and contraction and other factors caused by the loss of the preload force. When the bolt is tightened, the absorption of mechanical energy into potential energy (actually conical deformation) stored in the disc spring, when the equipment due to temperature changes, pressure changes or mechanical vibration caused by the bolt pre-tensioning relaxation, the release of the potential energy converted into mechanical energy, the bolt preload compensation, so that the bolt pre-tensioning force is always maintained in the range of pre-tensioning force required for the sealing of the gasket.

There are temperature fluctuations in the equipment in the gasket selection and washer selection should pay attention to; personal advice to be equipped with disc springs!

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