Inert gas fill nozzle and pressure relief valve

#This invention relates to a nitrogen or other inert gas distribution nozzle for insertion within a fuel inlet aperture of a tractor trailer fuel transport tank, and more particularly to a nitrogen distribution nozzle functioning as a pressure relief valve for the prevention of overpressurizing of such fuel transport tanks formed of lightweight metal such as aluminum.

#Tractor trailer fuel transport tanks and fuel storage tanks in general employ pressure relief valves for preventing overpressurization of the tank, particularly when employing an inert gas under light pressure to purge oxygen from an empty tank and prior to filling of the same with a liquid hydrocarbon fuel. The presence of significant oxygen content within the tanks at the time of filling of the tank with the liquid hydrocarbon fuels significantly increases the possibility of an explosion occurring, particularly where, due to the chemical makeup of the fuel or other combustible liquid being carried by the tank, there is a buildup of static electricity capable of igniting the fuel or like liquid during filling of same. Typical trailer fuel transport tanks formed of stainless steel plate are rated for 25 psi. In contrast, the aluminum trailers which have come into vogue such as those referred to as MC306 carry a rating of 3 psi. While the aluminum trailer tanks carry the liquid hydrocarbon at atmospheric pressure, in order to purge the aluminum trailer tanks with an inert gas such as nitrogen, to reduce oxygen content substantially below 9%, with below 7% being preferred and below 5% being most preferred (all contents by volume), with the oxygen escaping the interior of the aluminum trailer tanks via one or more vapor recovery units within the tank wall, there is a high potential for potential damage to the trailer should the tank become pressurized. Whether such trailer transport tanks are of stainless steel or aluminum, the tanks carry pressure relief valves to prevent overpressurization. While most trailers are equipped with a vapor recovery system which includes means for relieving the pressure and preventing overpressurization of the trailer transport tank, such pressure relief vapor recovery system often fails. Where the trailer transport tank or the like is formed of aluminum, it imperative that while purging of the tank with an inert gas such as nitrogen, the tank pressure be relieved at 1.5 psi or near that value.

#Therefore, it is a primary object of this invention to provide a nitrogen distribution nozzle for effectively diffusing the nitrogen gas under pressure throughout an aluminum trailer transport tank or the like, which performs a pressure relief function as low as 1.5 psi, which is of simplified structure, which is projected within a tank inlet aperture and gravity maintained therein; and which is physically raised under gas pressurization of the tank during nitrogen purging to prevent overpressurization of the tank during purging to self pressure relieve, which is of low cost and which is highly reliable.

#FIG. 1 is a partial schematic side elevational view of a rear end of an aluminum tank trailer for use in transport of flammable liquids such as gasoline carrying a weighted nitrogen distribution nozzle forming a preferred embodiment of the invention.

#FIG. 2 is an enlarged side elevational view of the weighted nitrogen distribution nozzle of FIG. 1.

#FIG. 3 is a front elevational view of the upper end of the weighted nitrogen distribution nozzle of FIG. 1.

#Referring to the drawings, a preferred embodiment of a weighted nitrogen distribution nozzle, which is gravity mounted to an inlet aperture or opening within the top of a trailer indicated generally at 12 and constitutes the movable member of a pressure relief valve 8 when the tank 12 is purged of air through a vapor recovery system or unit 6, which is mounted to the tank 12 in the illustrated embodiment at the top and in fluid communication with the tank interior 14A via a vapor recovery port or nipple 4. To one side of the vapor recovery unit 6, the pressure relief valve 8 utilizes a nipple 18 which is sealably coupled to the top of the tank 12 and whose bore forms an aperture 2, with the nipple 18 constituting the fixed component of the pressure relief valve 8 as will be described in detail hereinafter.

#Due to the flammable nature of liquids typically carried by the trailer 12, it is necessary to purge oxygen from the interior 14A of the trailer tank 14. Such is achieved by flowing an inert gas such as nitrogen (N.sub.2) at a given flow rate, as for instance 600 SCFM in the instant embodiment at a pressure above atmospheric such as 17 psig through a hose or other conduit 20. A hose end 20A remote from the source 22 is coupled via a quick disconnect female coupler 28 to the upper end 30A of the weighted nitrogen distribution nozzle 10. The lower end 30B of the weighted nitrogen distribution nozzle projects downwardly into the interior 14A of tank 14 and carries a plurality of diametrically opposite circumferentially spaced diffusion openings or slots 48 within the side of the nozzle. To purge the tank, it is necessary that the inert gas, preferably nitrogen, be slightly above atmospheric pressure within the tank. The invention is particularly applicable to trailer transport tanks manufactured of aluminum such as aluminum trailers designated as MC306 trailers and the like, which are only rated for 3 psi gas pressurization. As such, the nozzle 10 provides a reliable pressure relief valve for such aluminum trailers during purging with an inert gas such as nitrogen. While most trailers are equipped with a vapor recovery system or unit such as unit 6, which normally relieves pressure, the vapor recovery system or unit 6 often fails. The aluminum tank 14 of trailer 12 is mounted on wheels 16, shown schematically, for transport by a tractor (not shown) after loading at a loading station constituting a source 22 and which includes the hose or like conduit 20 terminating in the quick disconnect female coupler 28. In the embodiment of the invention, the nipple 18 defining an inlet opening or aperture to the interior of the tank 14 is a three inch diameter nipple, i.e., one having a nominal three inch internal diameter.

#Turning to FIG. 2, the weighted nitrogen distribution nozzle 10 is formed principally of a two inch diameter schedule 10 stainless steel tube having a bore 32 slightly less than the two inch outside diameter d3 of the tube. The first, upper end 30A of tube 30 terminates in a two inch SST quick disconnect male coupler 40 having an internal bore 40A corresponding to and acting as an extension of the tube bore 32. The open end 34 of the male disconnect coupler 40 opens to the interior of the hose 20 leading to the nitrogen source 22 via quick disconnect female coupler 28. A sealed snap fit is effected between the quick disconnect female coupler 28, which receives the quick disconnect male coupler 40, with an end face of the quick disconnect female coupler 28 remote from the hose 20, abutting a radial flange 40B of the male disconnect coupler 40. The male disconnect coupler 40 is shown in FIGS. 2 and 3 as having an annular semi circular cross section groove or recess 38 effected by deforming the tubular body of the male disconnect coupler inwardly that circumferential recess or groove. A member or members of the quick disconnect female coupler 28 physically lock the couplers 28 and 40 together. Such coupler system employing the male and female components 40, 28 is commercially available under the trade name Kamlock.RTM. coupling, MIL-C-27487.