BACKGROUND

1. Field of the Invention

The present invention generally relates to well and expansion tanks and, more particularly, to fiberwound well and expansion tanks.

2. Description of Related Art

Many well and expansion tanks use a diaphragm or bladder to separate air from water. An air charge pressure on one side keeps the diaphragm/bladder at a distance away from the inside wall of the tank in the air dome. When the tank is installed onto a water system, the water system pressure pushes back against the diaphragm/bladder, compressing the air. The proper pre-charge will continue to keep the diaphragm/bladder away from the tank wall. If the pre-charge pressure is not enough to provide an air volume appropriate for the water supply pressure, the diaphragm/bladder will fill the air cell. If eventually the diaphragm/bladder “bottoms out” on the tank wall, the tank becomes ineffective in the function it has been design to provide. An example of a non-metallic conventional expansion tank assembly is provided in commonly assigned U.S. Pat. No. 7,216,673 to Gremour et al. Gremour et al. discloses a non-metallic, diaphragm-type tank assembly for use with a pressurized water system. The disclosure of U.S. Pat. No. 7,216,673 to Gremour et al. is incorporated by reference herein in its entirety.

One type of such tank is called a Type IV Fiberwound tank. The industry defines this tank as having a plastic liner with fiberwinding around the liner. Traditional Type IV fiberwound tanks have been considered satisfactory for their intended purpose, however, there is ongoing need in the art for improved Type IV Fiberwound tanks.

SUMMARY

A fluid tank includes polymeric liner comprising an upper wall and a lower wall. The upper wall and the lower wall define a cavity therebetween. A weld joint joins the upper and lower walls together.

In accordance with some embodiments, the fluid tank includes a backing ring inboard from the upper wall with respect to the cavity to provide support for the upper wall and the lower wall during welding. The weld joint can be an infrared (IR) weld joint. The upper wall can include an upper dome and a dome and/or cylindrical extension. The upper wall can include a second weld joint defined between the upper dome and the dome and/or cylindrical extension bonding the upper dome and the dome and/or cylindrical extension together. The weld joint can be defined on the dome and/or cylindrical extension of the upper wall.

It is contemplated that the fluid tank can include flexible diaphragm positioned within the cavity connected to an inner diameter surface of the lower wall. The diaphragm can separate the cavity into an upper portion and a lower portion. The upper portion of the cavity can be sealed to contain a pressurized gas and the lower portion can be sealed to contain a pressurized fluid. The fluid tank can include an inner hoop ring operatively connected to an inner surface of the flexible diaphragm to hold the flexible diaphragm in place against the lower wall. The lower wall can include a hoop groove that mates with the inner hoop ring to hold the flexible diaphragm therebetween. The fluid tank can include an outer band having a hoop groove operatively connected to an outer diameter of the lower wall. The hoop groove of the lower wall mates with the hoop groove of the outer band.

In accordance with some embodiments, the fluid tank includes a fiber winding layer around an outer surface of the liner. The fiber winding layer includes a preliminary fiber winding layer and an outer fiber winding layer. The preliminary fiber winding layer can be wrapped around the outer surface of the liner underneath the outer fiber winding layer to contain liner growth due to heat generated during wrapping of the outer fiber winding layer. The liner can define a longitudinal liner axis. The preliminary and outer fiber winding layers can be formed of fiber windings helically and circumferentially wrapped with respect to the longitudinal liner axis around the outer surface of the liner. The fiber winding layer surrounding the weld joint can be thicker than the fiber winding layer surrounding the remainder of the liner to reduce stress in the weld joint.

It is contemplated that the liner can include an opening with a connector positioned therein. The connector can include a connector housing having a central collar that defines a longitudinal axis and a skirt that extends radially outward therefrom. The central collar can define an axial passage and includes a circumferential groove around its periphery for receiving fiber windings during wrapping on to the liner. The connector can include a threaded member in the axial passage. The threaded member can project outward from a first side of the connector housing. The skirt of the connector housing can include an interface surface spin welded to an interior surface of the liner. The interface surface can include axially facing annular grooves defined therein configured to be spin welded to an interior surface of a fluid tank for added support of liner from internal tank pressure. The connector can include an annular ring with a combined diaphragm support and turbulator operatively connected to a second side of the connector housing opposite from the threaded member.

In accordance with another aspect, a connector for a fluid tank includes a polymeric housing, similar to connector housing described above, and a threaded member in the axial passage of the housing, similar to the threaded member described above.

In accordance with yet another aspect, a method for assembling a fluid tank includes overlapping surfaces of an upper wall and a lower wall to form a liner defining a cavity. The method includes joining the surface of the upper wall and the surface of the lower wall together by welding to form a weld joint between the upper wall and the lower wall. The method can include cooling the weld joint to control warpage of the liner at the weld joint.

In accordance with some embodiments, upper and lower walls are at least partially cylindrical. The respective surfaces of the upper and lower walls can each define a circular perimeter. The weld joint can be an IR weld joint. Joining the surface of the upper wall and the surface of the lower wall can include using an IR emitter to apply heat circumferentially around the overlapping surfaces of the upper wall and the lower wall. Using the IR emitter to apply heat circumferentially around the overlapping surfaces of the upper wall and the lower wall can include rotating the liner around its longitudinal axis relative to the IR emitter.

It is contemplated that the method can include wrapping the liner with the fiber winding layer around the outer surface of the liner. Wrapping the liner with the fiber winding layer can include flame treating at least one of the liner or the fiber winding layer. Wrapping the liner with the fiber winding layer can include applying an adhesive between the outer surface of the liner and the fiber winding layer to create a bond between the fiber winding layer and the outer surface of the liner. Wrapping the liner with the fiber winding layer can include wrapping the preliminary fiber winding layer around the outer surface of the liner to contain liner growth due to heat generated during wrapping of the outer fiber winding layer. Wrapping the liner with a fiber winding layer can include wrapping the preliminary fiber winding layer and the outer fiber winding layer helically and circumferentially with respect to the longitudinal liner axis around the outer surface of the liner. The method can include heat treating the polymeric liner assembly.

In accordance with another aspect, a fluid tank includes a polymeric liner comprising an upper wall and a lower wall. The upper wall and the lower wall define a cavity therebetween. The upper wall includes an upper dome and a dome and/or cylindrical extension to provide increased volume and structural support to the polymeric liner. An end of the dome and/or cylindrical extension of the upper wall is joined to the lower wall and an end of the upper dome of the upper wall is joined to the dome and/or cylindrical extension. In accordance with some embodiments, a weld joint joins the upper and lower walls together. The weld joint can be defined between dome and/or cylindrical extension of the upper wall and the lower wall. The upper wall can include a second weld joint defined between the upper dome and the dome and/or cylindrical extension bonding the upper dome and the dome and/or cylindrical extension together.

These and other features of the systems and methods of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the embodiments taken in conjunction with the drawings.

