Fastener selection (11): Selection of sealing fasteners

The selection of sealing fasteners is as follows:

(1) Flat pad seal

The flat-pad type seal is a mandatory seal. A soft material or a gasket made of metal is placed between the joint surfaces. Under the pre-tightening force of the bolt, the unevenness of the contact surface (that is, the gap or the hole through which the medium may leak) is The plastically deformed gasket material is filled after extrusion, thereby achieving the purpose of sealing.

In order to improve the sealing performance, one or two triangular cross-section grooves can be opened on the sealing surface, the groove depth and the groove width are each 1 mm, and the centers of the two grooves are 5 mm apart. This type of sealing is generally only used on small and medium-sized high-pressure vessels that are not hot. The structure is simple, the sealing is reliable when the diameter is small, the pressure is not high, the gasket and the sealing seat are easy to process, and the experience is more mature. However, when the diameter is large, the pressure is high, the temperature is high (above 200 ° C) or the temperature and pressure fluctuate greatly, a large bolt pre-tightening force is required, and the sealing performance is relatively poor. Since the bolt load is proportional to the static pressure of the medium and the area of ​​the gasket. Therefore, when the pressure is high and the inner diameter of the device is large, the bolt size is relatively large, so that the size of the flange and the top cover is increased, the structure is cumbersome, and the loading and unloading is inconvenient.

(2) Kazari seal

Kazari seal: This is a forced seal with externally threaded kazari seals, internally threaded jammed seals and modified kazary seals. Among them, the external threaded cardary seal is used most, and its gasket is a soft metal mat with a triangular cross section, made of copper or aluminum. The barrel flange of the container is connected to the end cap by a threaded sleeve, and the sealing is achieved by tightening the pressing bolt to force the pressing ring to press the gasket. The advantage of this structure is that the connecting bolts of the end of the cylinder and the end cover are omitted, and the disassembly is convenient, belonging to the quick release structure; the area of ​​the gasket can also be small, so the required pressing force and the diameter of the pressing bolt are also Smaller; reliable seal, suitable for containers with large temperature fluctuations. However, the structure is complicated, the number of sealing parts is large, the precision is high, and the processing is difficult. This sealing structure is often used for large diameter, high pressure, pressure vessels that require frequent assembly and disassembly and require quick opening.

The internal threaded kazarid seal works in the same way as the external thread, except that the threaded end cap is screwed directly into the end of the internally threaded barrel. The sealing gasket is placed at the junction of the end cover and the end of the cylinder body, and has a pressing ring thereon, and the inner side surface and the bottom surface of the sealing gasket are respectively adhered to the side surface of the end cover and the end surface of the cylinder body by pressing the bolts. seal. It omits a threaded sleeve which is more difficult to machine than the external threaded zipper seal. The structure is simpler, but its end cover needs to be thickened, which occupies more pressure space. The thread is easily corroded by the medium, and the assembly and disassembly are not Convenient and poor working conditions. Generally used only on small diameter high pressure vessels.

The modified Kazar-in sealing structure does not require a threaded sleeve to connect the end cap to the barrel, but instead is bolted, and the others are the same as the externally threaded inner seal. There are no significant advantages, so it is rarely used.

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