Talking about steel-plastic composite steel barrel sealer
Nanjing Yangzi Barrel Factory Zhang Lianyuan
In recent years, the US-made PVF inner coating barrel has adopted a new steel-plastic composite closure. . This steel-plastic composite structure has attracted the attention of the domestic and international barrel industry. It not only meets the special requirements of some chemical products, but also expands the scope of use of the closure.
The steel-plastic composite closure has five distinctive features:
1. It can effectively protect PVF coating. In the past, when the inner coating barrel was produced, an anticorrosive coating suitable for the contents of the barrel was applied to the surface of the cock and the coil of the closure, and then locked in a conventional process. During the screwing and rubbing process of the steel cock and the screw thread, the sealer is severely corroded due to the crushing and falling off of the coating, which pollutes the contents of the barrel and even causes the barrel to leak. In order to solve this problem, the American sealer manufacturer developed a steel-plastic composite closure (registered trademark "Rieke"), the structure is shown in Figure 1. It can be seen from Fig. 1 that the cock of the steel-plastic composite closure is still made of steel plate, and the spiral ring is made of high-strength polyamide material (foreign name Polyamlde, commonly referred to as Nylon nylon). During the screwing process, the cock and the coil are changed from rigid friction to flexible sliding extrusion, and the elastic nylon ring effectively protects the coating between the cock threads from damage, thereby ensuring the corrosion resistance of the closure. .
Figure 1 closure assembly
2. The matching clearance is small. The fit of the steel-plastic composite closure cock to the nylon screw thread uses a minimum clearance of zero. This zero clearance fit has two advantages:
1 thread has sufficient contact height to compensate for the weaker mechanical strength of the nylon screw thread than the steel coil. In order to ensure the bonding strength of the nylon coil, considering the influence of the size error of the coil manufacturing and the temperature difference of the environment, there are dozens of expansion process holes in the nylon coil around the thread. When the thread is fitted with interference, the direction of the expansion process hole in the vicinity of the radial direction of the nylon screw thread is increased under the squeeze of the cock to ensure that the cock can be screwed in tightly and tightly.
2 Because the cock and the coil adopt zero clearance fit, the thread is tightly engaged, and the liquid in the barrel is difficult to pass, thereby improving the overall sealing performance of the sealer.
3. A new process of clamping and locking is used. Since the structure and seal of the nylon coil are different from the steel coils, the traditional locking process cannot be used. The United States has developed a clamp locking process. The working principle is similar to the locker anti-theft cover locking process. Design 16 R-shaped grooves on the outer circumference of the nylon coil, and punch out the flat boss on the top cover of the barrel, see Figure 2 and Figure 3.
Figure 2 Assembly diagram before the screw lock
Figure 3 nylon coil
When locking, put the coil of the elastic collar on the boss of the top cover of the bucket and lock it with the clamping device. Under the action of the clamping force, the boss of the top cover of the bucket shrinks into the annular groove around the coil. Due to the action of the R groove, part of the boss contracts into the R groove to form a concave ridge, and the boss without the R groove is subjected to the yoke. The blockage only causes the coil to be slightly elastically deformed and tightly wraps the coil. Due to the uneven force around the barrel boss, the outer circle is formed into a regular corrugated shape. When the cock is tightened, the ring R groove cannot be rotated under the prevention of the corrugated boss, and functions as a fixed coil. This kind of locking method has created a new way for the large number of non-metallic spirals in the future.
4. Change the double seal to a single seal. The traditional sealer seals are double seals, that is, one sealer has two sealing faces: one is that the screw ring and the top of the bucket are sealed, and the two are the coil and the plug seal. It is well known that the more sealing surfaces, the worse the reliability of the seal. In order to improve the sealing performance of the sealer, it is necessary to seal the two sealing faces reliably and indispensable. The US Rieke composite closure actually has only one sealing surface that plays a major role, ie the cock is sealed to the top of the bucket (see Figure 1). The sealing cock is directly pressed against the plane of the bucket boss by the washer by the tension of the coil. In actual use, there is a sealing gasket between the nylon coil and the bucket top boss that is elastically compatible with the contents of the bucket. Its main function is not simply to seal, it can also be used to adjust the tightness between the plastic coil and the top of the bucket, to ensure that the coil is not loose.
5. The line contact is a flat contact. The traditional cock press ring is narrow, only 2.5 mm wide, for line contact. It can only press a larger, smaller size polyethylene gasket. When the contents of the barrel have corrosion resistance requirements for the gasket, other corrosion resistant gaskets (such as fluororubber) cannot withstand the pressing force due to the low hardness, and are squeezed out of the sealing groove or twisted to lose the sealing effect. In order to solve this problem, the United States has changed the embossing edge from a narrow to a flat contact (see Figure 4) to meet the special requirements of the new corrosion-resistant gasket. In order to increase the faucet blanking force, the plate thickness is changed from 1.5 mm to 2.2 mm. In order to improve the working stability of the gasket and eliminate the radial scratches that may occur in the squeezing process, they designed two V-shaped grooves on the plug sealing surface to cut the radial scratch channel of the cock. When the cock is pressed, the elastic deformation of the rubber gasket is used to fill the small unevenness on the sealing surface to prevent leakage.
Figure 4 cock
From the above analysis, we can see that the steel-plastic composite closure has a certain positive effect on chemicals with special requirements. At present, no one has heard of domestic production. In the future, we can learn from it and produce a steel-plastic composite closure suitable for China's national conditions.
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