The high-pressure hydrogenation heat exchanger is generally used at the
Reactor outlet, where the reactor product and the mixed hydrogen feedstock are the main
Heat Exchangers. High temperatures and pressures are therefore required. There are basically two forms of high pressure heat exchangers in use, a flange type and a threaded locking ring type.
1, flat pad structure.
Tube box flange and tube box side flange between the two sides of the tube plate with a metal flat pad.
Advantages: simple structure, easy to manufacture. When the flange and gasket thermal expansion coefficient is different, more favorable, especially in large diameter conditions.
Disadvantages: Gasket compensation for axial rebound is very small, once the main bolt and the flange have a certain temperature difference, when the thermal expansion of the flange is greater than the main bolt, the elongation of the main bolt exceeds its own elastic deformation length, and is in the process of cooling down the conditions, the leakage will occur.
Adopted countermeasures: shorten the length of the main bolt to change the sealing effect, that is, as far as possible to use planted wire bolts, but this has a greater difficulty for the maintenance and disassembly.
2、Octagonal pad structure
Due to the flat pad rebound is small, in order to solve this problem using octagonal pad form, is widely used, but when the diameter of the heat exchanger is larger, also found the leakage problem.
Octagonal pad material is often different from the flange material coefficient of linear expansion, when the temperature is relatively high, the diameter is large, because there is a large expansion difference system, it is likely to leak. And often found octagonal gasket sealing surface on the wrinkle deformation, flange sealing surface groove with indentation. This is the overhaul must be repaired sealing surface, replace the octagonal gasket.
3、Ω-shaped structure
Factory production, such as foreign leakage will produce greater damage to the environment and personnel bring great danger, so people use Ω ring structure.
Advantages: reliable sealing, not prone to leakage, this structure has a large rebound compensation, when the main bolt is stretched longer, beyond the elastic deformation and can not compensate when the Ω-shaped can be opened, there is a relatively large compensation capacity, edible and safe.
Disadvantages: disassembly is very troublesome, maintenance will first Ω-shaped seal along the centre line cut, back to install when re-repairing the broken mouth after welding. An Ω ring can not be used more than once, otherwise it will reduce the reliability of the Ω ring
Second, the thread locking ring heat exchanger
1, structure and interrelationship of components
It has a complete shell, that is, the tube process and shell process with the same barrel, one end of the barrel body welded head, the other end of the threaded pressure ring and a gland composition immediately attached to the sealing plate, sealing plate around the metal pad seal and the outside world away from the outside to prevent leakage. The tube bundle is placed inside the barrel and the tube plate on the bundle is gasketed to the inner step of the barrel to separate the tube course from the shell course. The part of the tube plate adjacent to the side of the tube box is close to the inner sleeve, the other end of the inner sleeve is top pressed by a bolt, the top press bolt is set on a snap ring, the snap ring is placed in a groove in the inner wall of the tube box, the snap ring is designed in several divisions for easy installation, tightening the top press bolt on the snap ring, through the inner sleeve, transmits the force to the gasket at the tube plate to compress it.
A compression ring is set on one side of the snap ring and it is attached to the sealing plate on the other side. The ring has two roles, one is to limit the position of the gland to prevent damage to the sealing plate during transport and the other is to transmit the compression force of the inner ring bolt on the threaded bearing ring. If a gasket leak is found on the side of the pipe plate during process operation, the inner ring bolt can be tightened directly and the internal leak can be eliminated at any time.
When tightening the inner and outer ring bolts on the threaded ring, the inner compression rod is first pressed, which is longer and acts as a spring after compression to compensate for the lack of gasket rebound.
The inner sleeve is divided into two semi-circular cylinders from the middle with a spacer, one of which is closed with a semi-circular cover so that the inlet and outlet of the tube box are completely separated. In order to prevent short-circuiting, a sealing mechanism is set up in the other semi-circular cylinder and fixed to the inlet of the tube box to prevent short-circuiting from the annular gap between the inner sleeve and the cylinder body.
2、The role of the main components
The sealing mechanism prevents short-circuiting of the inlet and outlet. The inner sleeve transmits the compression force so that the tube plate gasket is compressed and the other role separates the inlet and outlet of the tube course. The sealing disc transmits the compression force of the threaded bearing ring, and the compression gasket acts as a seal. The inner compression rod transmits the bolt compression force and has the ability to spring back. The threaded pressure ring and the gland bear all the internal pressure load and the gasket pressure together.
3. Some requirements to be noted in the use of the equipment
The timing of the use of the inner ring bolt on the threaded ring is very important, it can only be tightened when the temperature reaches its maximum and an internal leak is detected.
When starting work it is necessary to open the silk plug in the observation hole of the pipe course part to observe whether there is external leakage.
When inspecting and assembling back, pay attention to replacing the seals on both sides of the tube bundle to prevent a short circuit in the shell course.
When inspecting and dismantling the heat exchanger, be careful not to damage the large threads, tighten the inner and outer bolts in strict accordance with the drawing requirements of the upper tighteni
ng force, in order to prevent the upper tightening is not in place can refer to the positioning to increase the torque.
Source: Reprint
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