Double walled tanks with internal containment chambers
A double-walled above-ground storage tank includes a primary tank and a secondary tank, and an interstitial space; an containment chamber formed by a primary chamber wall and a secondary chamber wall, forming a chamber interstitial space therebetween, and an exterior door assembly; and at least one pipe and valve assembly wherein the pipe originates in the tank interior volume and the valve is disposed within the chamber.
1. A double-walled above-ground storage tank comprising:
(a) a tank roof, a tank floor, a primary tank and a secondary tank, which together define a tank interstitial space therebetween, wherein the primary tank and the tank floor together define a tank interior volume;
(b) a main containment chamber formed by a chamber wall;
(c) an ancillary containment chamber formed by an ancillary chamber wall, wherein the ancillary containment chamber is above and contains the main containment chamber, and both the main and ancillary containment chambers are disposed within the tank interior volume;
(d) a high level shutdown pipe which extends between a freeboard portion of the tank interior volume and the main containment chamber, passing through the ancillary containment chamber, and comprising a high level shutdown valve disposed within the main containment chamber, wherein the high level shutdown valve comprises a fluid sensor and a switch operative to stop inflow into the tank, or signal an alarm or both.
2. The tank of claim 1 , wherein the ancillary chamber wall extends from the tank floor to the tank roof.
3. The tank of claim 1 wherein the high level shutdown pipe comprises an overflow valve which allows fluid into the ancillary containment chamber.
4. The tank of claim 3 wherein the primary tank defines an overflow opening providing fluid communication between the ancillary chamber and the tank interstitial space, the opening positioned at or near the top of the ancillary chamber.
5. The tank of claim 4 further comprising an interstitial connect disposed within the chamber, providing a fluid connection between the tank interstitial space or the chamber interstitial space, or both, and the high level shut down valve.
6. The tank of claim 5 wherein the interstitial connect is transparent or translucent to allow visual confirmation of the presence of absence of fluid in the interstitial connect.