System for loading and unloading fluid tanks containing hazardous fluids

A method for transferring a hazardous fluid product through a flexible hose assembly detachably coupled between a tank of a roadway vehicle and a fixed storage tank, one of said tanks having a gas operated product supply valve maintained in an open position for product flow to the other tank by pressurized gas during a normal transfer operation;

• said method comprising:
• providing a gas control valve for controlling the supply of pressurized gas to said gas operated product supply valve and movable between a supply position providing pressurized gas to said product supply valve and an exhaust position exhausting pressurized gas from said product supply valve, said gas control valve responsive to fluid pressure of the product flowing through said flexible hose assembly between said tanks;
• providing an external portion of a fluid sensing line for said flexible hose assembly for communicating fluid pressure from said flexible hose assembly to said gas control valve to maintain said gas control valve in a supply position when the fluid pressure in said flexible conduit is above a predetermined minimum and to exhaust pressurized gas from said product supply valve in an exhaust position when the fluid pressure in said flexible hose assembly is below a predetermined minimum to stop the transfer of product from said one tank;
• and
• positioning an internal portion of said fluid sensing line within said flexible hose assembly prior to coupling said flexible hose assembly between the vehicle tank and the fixed storage tank, said internal portion being a flexible tube extending longitudinally downstream along said flexible hose assembly toward said other tank for a majority of a length of said flexible hose assembly.

A system for transferring a hazardous fluid product between a tank of a roadway vehicle and a fixed storage tank, one of said tanks being unloaded and having a gas operated product supply valve maintained in an open position for product flow to the other receiving tank by pressurized gas from a gas source, said system including:

• a flexible hose assembly detachably connected between said tanks;
• a fluid sensing line in fluid communication with said flexible hose assembly for sensing the fluid pressure of product flowing between said tanks during a normal transfer operation;
• a gas control valve mounted between said gas source and said product supply valve to control the supply of gas to said product supply valve, said gas control valve having a body and a central bore therein, said body having an inlet port in fluid communication with said bore and said gas source, an outlet port in fluid communication with said bore and said product supply valve, and a sensing port in fluid communication with said sensing line;
• a piston chamber in said body having a piston mounted thereon and a piston rod received within said central bore, said piston chamber being in fluid communication with said sensing port;
• a vent from said central bore to atmosphere in fluid communication with said outlet port and normally closed by said piston rod from fluid communication with said outlet port;
• a member urging said piston rod to an open position of said vent to exhaust gas from said gas operated product supply valve for closing of said product supply valve;
• and
• said piston moving to an emergency position upon a reduction of fluid in said fluid sensing line and sensing port below a selected minimal fluid pressure, said piston rod moveable in the emergency position to an exhaust position to permit exhaust of gas through said outlet port and vent from said gas operated product supply valve for closing of said product supply valve.

A system for transferring a hazardous fluid product between a tank of a roadway vehicle and a fixed storage tank, one of said tanks being unloaded and having a gas operated product supply valve maintained in an open position for product flow to the other tank by pressurized gas from a gas source, said system including:

• a flexible hose assembly detachably connected between said tanks for product flow during a normal transfer operation;
• a gas control valve mounted between said gas source and said product supply valve to control the supply of gas to said product supply valve, said gas control valve having a body and a central bore therein, said body having an inlet port in fluid communication with said bore and said gas source, an outlet port in fluid communication with said product supply valve, and a sensing port in fluid communication with said flexible hose assembly;
• a piston chamber in said body having a piston therein in fluid communication with said flexible hose assembly, said piston chamber being in fluid communication with said sensing port;
• a vent from said central bore to atmosphere providing fluid communication with said outlet port in an exhaust position of said product supply valve;
• said piston moving to an emergency position for permitting fluid communication between said outlet port and said vent upon a reduction of fluid pressure in said flexible hose assembly below a selected minimal fluid pressure to exhaust gas through said central bore and vent from said outlet port and said gas operated product supply valve for closing of said product supply valve;
• and
• a flow restriction upstream of said central bore for the supply of inlet gas to said central bore at a rate less than a venting rate of said vent to allow said product supply valve to be closed while continuously supplying inlet gas to said system.

A gas control valve for mounting between a gas source and a product supply valve to control the supply of gas to the product supply valve, said gas control valve comprising:

• a monolithic body having a central bore therein, said body having an inlet port in fluid communication with said bore, an outlet port in fluid communication with said bore, and a sensing port;
• a piston chamber in said body having a piston mounted thereon and a piston rod received within said central bore, said piston chamber being in fluid communication with said sensing port;
• a vent from said central bore to atmosphere in fluid communication with said outlet port and normally closed by said piston rod from fluid communication with said outlet port;
• and
• said piston moving to an emergency position upon a reduction of fluid in said fluid sensing port below a selected minimal fluid pressure, said piston rod moveable in the emergency position to an exhaust position to permit exhaust of gas through said outlet port and vent for closing the product supply valve.