Dynamic Pressure Relief Seal for Pressure Vessels

FIG. 1 is an elevational view of a pressure tank according to one aspect of this invention, with portions broken away for clarity;

FIG. 2 is a fragmentary, cross-sectional view, the plane of the section being indicated by the line 2--2 of FIG. 1;

FIG. 3 is a fragmentary, cross-sectional view similar to FIG. 2, but showing the pressure seal in an exaggerated, deformed condition caused by excessive pressures;

FIG. 4 is a cross-sectional view similar to FIG. 2, but showing one aspect of the invention employed as a seal for a metal tank; and

FIG. 5 is a cross-sectional view similar to FIG. 4 showing a further aspect of that embodiment.

Referring to the drawings, and particularly to FIGS. 1 through 3, there is illustrated a pressure tank 10 having upper and lower container sections 12 and 14, respectively. Each container section is cup-shaped, having a cylindrical wall portion 16 and oblate, ellipsoidal end sections 18. The illustrated pressure tank has particular utility as a tank which serves as a swimming pool filter, such as that described in U.S. Pat. No. 3,774,772.

Since it is necessary to permit access to the interior of the pressure tank for servicing the filter elements, it is necessary that the pressure tank be capable of being disassembled. Therefore, the container sections 12 and 14 are assembled together for disassembly and to define a pressure-retaining joint between the sections 12 and 14. The pressure-retaining joint is formed by identical portions of the container sections 12 and 14 at the open ends of the cylindrical portions 16, and includes an annular flange portion 20 defined by a cylindrical outer wall 22, an angularly related wall 24, and an end wall 26. An O-ring groove 28 is formed in each end wall 26 and an O-ring 30 is sealingly positioned in the O-ring grooves 28. For reasons which will hereinafter become apparent, a plurality of passage-defining notches 32 extend between the O-ring groove 28 and the cylindrical surface 22.

The separable container sections 12 and 14 are mechanically coupled by a clamping band 34, which is preferably fabricated from stainless steel and includes a cylindrical portion 36 which encircles the cylindrical portions 22 of the flange 20 and angularly related portions 38 which engage the angularly related portions 24. The clamping band 34 is tightened around the flange 20 by bolts 40 which are adjusted to a predetermined torque to apply sufficient pressure on the flange portions 20 to compress diametrically opposed portions of the O-ring for proper sealing of the pressure tank. A properly sealed condition of the pressure tank is illustrated in FIG. 2.

If the pressure tank should become overly pressurized, such as, for example, by connecting the tank inlet to city water pressure at, for example, 60 psi, the tank sections 12 and 14 will distort, as is shown in FIG. 3, to cause the pressure-retaining joint to assume the position illustrated therein. According to prior art practices, such distortion would not necessarily affect the efficiency of the seal, since the O-ring 30 would merely move and distort to the position illustrated in phantom outline in FIG. 3. This distortion may cause the tank sections to separate explosively. The provision of safety relief valves has been found to be an unacceptable solution, since large amounts of water must be exhausted to attain a safe operating pressure.

According to this invention the O-ring is prevented from attaining an unacceptable secondary sealing position by providing outlet passageways from the interior of the tank which would prevent resealing of the O-ring. To this end, there is provided a plurality of passageways 32 between the interior of the tank and the exterior. When the tank is in a proper sealing condition as illustrated in FIG. 2, leakage cannot occur therethrough, since the O-ring is sealed at the bottom of the O-ring grooves 28. Upon distortion of the tank sections 12 and 14, as illustrated in FIG. 3, water will flow through the passageways 32 as soon as the O-ring is removed from its seats in the groove 28. The area and number of passageways 32 are selected so that the pressure built up in the tank may be quickly relieved to a safe operating pressure of, for example, less than 35 psi. When the pressure is relieved, the tank sections will return to the condition illustrated in FIG. 2, with the O-ring in its proper sealing position. As long as the improper pressurization of the tank exists, the tank will continue to cycle between the positions illustrated in FIGS. 2 and 3 to give a visual indication of an anomalous condition without separation of the tank sections.

Referring now to FIG. 4, there is illustrated a metal pressure tank having upper and lower tank sections 50 and 52. A pressure-retaining joint is formed between the sections by an arrangement which includes a circumferential channel member 54 welded to a portion of the lower tank section 52 and a radially extending lip 56. The mouth of the container section 50 forms a cup 58 which is defined by a radially extending flange 60 and a cylindrical portion 62. The cylindrical portion 62 serves to cover the channel 54 and provide a sealing surface for an O-ring 64.

The tank sections 50 and 52 are mechanically coupled by a plurality of rigid shoe clamps 66 which are held in position by a clamping band 68. As may be noted in FIG. 4, a compliant pad or cushion 70 is provided between the clamp 66 and the radially extending portion 60. The cushion 70 acts as a spring to absorb upward movement of the tank section 50 as the tank is pressurized. Overpressurization of the tank will compress the pad 70 to such a degree that the circumferential wall 62 will increase the gap 72 between the channel 54 and the cylindrical portion 62 to such a degree that the O-ring 64 will be blown through the gap, thus relieving the pressure in the tank in a safe manner. If the O-ring is blown out of the tank, the tank must be disassembled to properly reseat the O-ring.

The arrangement illustrated in FIG. 4 may be constructed so that it will cycle in the manner discussed with reference to the embodiment shown in FIGS. 1 through 3.

The embodiment shown in FIG. 5 is similar to that shown in FIG. 4, and identical components have identical reference numerals. The pressure-retaining joint illustrated in FIG. 5, however, includes a cylindrical portion 62a having a plurality of notches 72a. Upon overpressurization of the pressure tank, the notches 72a will prevent the O-ring 64 from maintaining a seal so that water will flow through the notches 72a. The O-ring 64, however, is retained within the channel 54 by the cylindrical portion 62a so that the O-ring does not escape from the channel 54 and so that the seal will cycle between a proper sealing condition and a leaking condition, to give a visual indication of an improper seal.

Although the preferred embodiments of this invention have been shown and described, it should be understood that various modifications and rearrangements of the parts may be resorted to without departing from the scope of the invention as disclosed and claimed herein.