Vacuum seal closures

Although slip lids are also used on rectangular drawn containers, the geometry of the two components does not allow as tight a fit as is possible with round lids. Hence moisture sensitive tablets or pastilles are better packed in round containers. Alternatively a slip lid of the type commonly used on both round and rectangular tobacco containers can be used. This is usually referred to as a vacuum sealed lid but is more accurately described as a differential pressure lid. The lid itself incorporates a flowed-in PVC or EVA gasket to form a closure with the upper rim of the base. 

Bag closure and sealing of vacuum and injection channels Resin injection and curing... 

The reactor was made from a 304 stainless-steel cylinder 69.8 mm in diameter and 50.8 mm in length. The catalyst pellets were placed in seven 9.53 mm in diameter holes in the cylinder and were retained by screens. The two end closures were sealed by standard copper vacuum gaskets which were gold plated. 

Figure 19 illustrates one type of compression mold suitable for molding lip type shaft seals with a metal outside diameter (O.D.). Figure 19a shows the compound preform resting on the shelf and the mold beginning to close. The mold continues to close until it gets to the position shown in Fig. 19b. Finally, the mold opens as shown in Fig. 19c. It can be seen that this molding technique produces a molded lip seal with the flash already removed. In general, when using a vacuum chamber on the press, to ensure that all the air and/or gases are evacuated from the mold after closure, one or...

Bottles and vials are not subjected to such a vacuum test because of the flexibility of the rubber closure. However, bottles that are sealed under vacuum may be tested for vacuum by striking the base of the bottle sharply with the heel of the hand to produce a water hammer sound. Another test is the spark test, in which a probe is applied outside the bottle. When it reaches the air space of the bottle, a spark discharge occurs if the headspace is evacuated. 

In production the filled container—with the lid loosely applied—is fed into a vacuum chamber where a vacuum is first applied followed by a top loading to force the lid into intimate contact with the container rim. When the external pressure is restored to atmospheric, the vacuum within the container maintains the seal. The effectiveness of the closure can be checked visually or automatically by observing a depression in the lid due to the pressure differential. The container is opened by releasing the vacuum with the aid of a coin slot built into the base. Both container and lid are constructed of tinplate rather than aluminium and in a fairly thick gauge in order to withstand the pressures applied. 

Steam condensate removal is most commonly achieved by traps—devices that, in efFea, are very simple level controllers. Many plants have experienced the need for high maintenance with these. Sometimes enough steam leaks through to impair the accuracy of steam-consumption estimates based on steam flow metering. In addition, as pointed out by Mathur, a rapid closure of the steam valve may cause a vacuum in the shell and pull back condensate through the trap with possible hammering and vibration in the shell. As a result, some reboilers, particularly large ones, are now equipped with condensate seal pots. These pots then have conventional level controllers. 

A Pyrex Schlenk tube equipped with a stir bar and PTFE closure was flame dried under vacuum. The tube was backfilled with Ar and charged with [HPPhjKBF ] (525 mg, 1.5 mmol, 1.5 equiv) and PPhj (262 mg, Immol, 1 equiv). The tube was evacuated and backfilled with Ar. The solids were dissolved in CH Clj (10ml). The substrate (Immol) was added in one portion. The Schlenk tube was sealed and placed in the photobox for 24h. The solvent was removed from the reaction mixture via rotary evaporation to afford the phosphonium salt (95%). 

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