Pressure retention valve and integrated valve for tank system

1. A pressure retention valve with integrated check valve comprising:

a housing having an upper portion, a wider lower portion, and a shoulder between the upper portion and the lower portion;

an outer piston positioned in the housing;

a main seal between an outwardly extending flange on a bottom of the outer piston and the shoulder of the housing;

an inner piston positioned in the outer piston, the inner piston having a bore containing a check valve;

a seal between a top of the inner piston and an underside of a top of the outer piston;

a seal between a bottom of the inner piston and a bottom of the housing;

a spring between the housing and a top of the outer piston;

an adjusting screw extending through the housing and contacting the spring;

an ambient bore in the upper portion of the housing above the main seal;

an outlet in the lower portion of the housing below the main seal; and

a vessel connection in the housing adjacent to the bore of the inner piston.

2. A method of supplying fuel to a gas consuming system comprising:

providing a tank vessel, the gas consuming system connected to the tank vessel by a pipe, a refueling line connected to the pipe between the tank vessel and the gas consuming system, and a pressure retention valve with integrated valve connected to the pipe between the tank vessel and the refueling line connection, the pressure retention valve comprising:

a housing;

an outer piston positioned in the housing;

a main seal between the outer piston and the housing;

an inner piston positioned in the outer piston, the inner piston having a bore containing a valve;

a spring between the housing and a top of the outer piston;

an ambient bore in the housing above the main seal;

an outlet in the housing below the main seal; and

a vessel connection in the housing adjacent to the bore of the inner piston;

selecting a minimum operating pressure for the tank vessel;

when a tank vessel pressure is greater than the minimum pressure, the tank vessel pressure lifting the inner piston from a bottom of the housing and opening a path from the vessel connection to the outlet, a top of the inner piston remaining in contact with the outer piston and lifting the outer piston, and supplying fuel to the gas consuming system; and

when the tank vessel pressure is less than the minimum pressure, the tank vessel pressure being insufficient to lift the inner piston from the bottom of the housing or being insufficient to maintain the inner piston in the lifted position, closing the path from the vessel connection to the outlet, the top of the inner piston remaining in contact with the outer piston, and ending the supply of fuel to the gas consuming system.

3. The method of claim 2 further comprising:

when the tank vessel pressure is less than the minimum pressure, connecting a refueling supply to the refueling line, an outlet pressure being greater than the tank vessel pressure, the outlet pressure lifting the outer piston from the top of the inner piston while the inner piston remains in a lowered position so that the path from the vessel connection to the outlet is closed, opening a refueling path from the outlet between the top of the inner piston and the outer piston and through the bore in the inner piston to the vessel connection, and refueling the tank vessel.

4. The method of claim 2 wherein the pressure retention valve further comprises an adjusting screw extending through the housing and contacting the spring, further comprising adjusting the adjusting screw.

5. The method of claim 2 wherein the minimum pressure is a sum of a force of the spring, ambient pressure, and a pressure of the main seal.

6. A pressure retention valve with integrated valve comprising:

a housing;

an outer piston positioned in the housing;

a main seal between the outer piston and the housing;

an inner piston positioned in the outer piston, the inner piston having a bore containing a check valve;

a spring between the housing and a top of the outer piston;

an ambient bore in the housing above the main seal;

an outlet in the housing below the main seal; and

a vessel connection in the housing adjacent to the bore of the inner piston.

7. The pressure retention valve of claim 6 wherein the main seal comprises an o-ring.

8. The pressure retention valve of claim 6 further comprising an adjusting screw extending through the housing and contacting the spring.

9. The pressure retention valve of claim 6 wherein the check valve comprises a spring and ball.

10. The pressure retention valve of claim 6 further comprising a seal between a top of the inner piston and an underside of a top of the outer piston.

11. The pressure retention valve of claim 10 wherein the seal between the top of the inner piston and the underside of the top of the outer piston comprises an o-ring.

12. The pressure retention valve of claim 10 wherein the seal is in the top of the inner piston.

13. The pressure retention valve of claim 6 further comprising a seal between a bottom of the inner piston and a bottom of the housing.

14. The pressure retention valve of claim 13 wherein the seal between the bottom of the inner piston and the bottom of the housing comprises an o-ring.

15. The pressure retention valve of claim 13 wherein the seal is in the bottom of the inner piston.

16. The pressure retention valve of claim 6 wherein the housing has an upper portion, a wider lower portion, and a shoulder between the upper portion and the lower portion.

17. The pressure retention valve of claim 16 wherein the main seal is between an outwardly extending flange on a bottom of the outer piston and the shoulder of the housing.

18. The pressure retention valve of claim 16 wherein the ambient bore is in the upper portion of the housing.

19. The pressure retention valve of claim 16 wherein the outlet is in the lower portion of the housing.