EXPERIMENTAL EVALUATION 

 Wedge Ring Seal 



The seal was fabricated for the experimental evaluation program from 

 nylon and from brass. Its initial sealing depends on the wedging of the seal 

 between the end closure and the interior of the pressure vessel. This wedging 

 is accomplished by the weight of the end closure pressing upon the wedge, 

 which is restrained from moving by a lip protruding from the interior wall of 

 the vessel. Once the initial sealing is accomplished, hydrostatic pressure within 

 the vessel will tend to wedge the seal in further by pushing axially and radially 

 upon it. To make sure that the hydrostatic pressure acts on the wedge along 

 the vertical axis of the vessel, small serrations were provided on the base of 

 the wedge resting on the lip protruding from the wall of the pressure vessel. 



The experimental evaluation of the wedge ring seal has shown that it 

 is not very desirable for end closures that must be closed and opened often. 

 Its shortcomings are serious. First of all, it often fails to seal at low pressures 

 before hydrostatic pressure wedges it between the end-closure skirt and the 

 internal surface of the pressure vessel wall. Thus, to make the seal perform 

 at zero pressure, some force other than hydrostatic must wedge it between the 

 end-closure skirt and the vessel's interior surface. In the experimental evalu- 

 ation, this force was provided by the weight of the whole end closure pressing 

 against the wedge that rests on the circumferential ledge around the vessel's 

 circumference. In addition to the problems associated with sealing at low 

 pressures, the seal does not perform well at pressures above 5,000 psi. At 

 about that pressure, the plastic seal becomes forced completely into the 

 clearance between the end-closure skirt and the vessel wall; when the internal 

 pressure approaches 10,000 psi, it is forced completely through with an explo- 

 sive release of pressure. The high-pressure capability of the wedge ring can be 

 increased by substituting metal for plastic. With the metal seal, there is almost 

 no low-pressure sealing capability, as it is very difficult to apply enough force 

 to the metallic wedge at zero pressure to make it seal. 



0-Ring Seal With Continuous Antiextrusion Wedge Ring 



A marked improvement over the simple plastic wedge seal is a wedge 

 seal combined with an 0-ring (Figure B-4). The 0-ring acts as a seal at low 

 pressures (0 to 1,000 psi) since it is radially compressed even at zero hydro- 

 static pressure by the end-closure skirt and the vessel's interior wall. As the 

 pressure rises inside the vessel, the 0-ring causes the wedge to seat itself tight 

 and to keep the 0-ring from extruding into the radial clearance between the 



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