NEWS

6/29/12

Reprinted with permission from June 2012 issue of CryoGas International

BREAKING INTO THE BREAK-AWAY MARKET

Macro Technologies Introduces Break-A-Way LNG Hose Coupling Fittings

By: Keith Hall

With all vehicular fueling, the possibility of a “drive-away” situation exists. This dangerous issue has been addressed by fueling dispenser manufacturers with use of “break-away” hose coupling devices. Designed to be the weak link in the fuel delivery system, such devices provide a predictable load-limiting mechanism to minimize the damage to the fuel station’s dispenser and to the vehicle involved.

Macro Technologies LLC of Kirkland, WA (www.macrotechnologies.com) has introduced a new coupling solution to the LNG fuel station drive-away problem. Howard Konishi, Vice President of Engineering for Macro Technologies, informs us that the "break-away coupling" is engineered to automatically shut-off the flow of liquid natural gas from both sides of the broken joint in the case of a vehicle drive-away while the fueling hose and nozzle are still connected. The break-a-way coupling serves to prevent the associated spillage that would otherwise occur, and prevents extensive damage to the liquid natural gas fueling station and its customers if the cryogenic hose and LNG fueling nozzle are forcefully pulled away.”

Designed specifically for LNG refueling applications, the 50 GPM (gallons per minute) rated device will separate with a 300–400 pound pulling force if the one-inch diameter cryogenic hose is pulled at 90 degrees to the break-a-way coupling. The coupling also comes with a blanked-off air pressure fitting. This can be used to shut-down the fueling station's pumping system if a pneumatic pressure switch is employed in the Emergency-Stop electrical circuit. “Particular attention needs to be given to the mounting of the break-a-way coupling,” cautions Konishi. “The dispenser structure and piping runs, as well as the vehicle fuel tank and receptacle mounting, must be able to withstand breaking loads that can exceed 700 pounds of force without damage. The coupling should be installed so that the pulling loads are directed between 45 to 90 degrees to the axis of the breaka-way coupling.”

If the break-a-way coupling is broken, a positive flow shut-off is accomplished from both the dispenser side and the hose end of the intended breaking and separation point. The two internal opposing check valves, one on each side of the break-a-way joint, shut-off the flow of product. On the hose side of the break, liquid or gas is checked to also control spillage and to minimize hose whip caused by pressurized liquid and rapidly expanding gases. An internal relief system is incorporated into the design to prevent over-pressurization of the hose due to the phase change of trapped liquid to gas (thus there is some minimal amount of methane present in the air during a drive-away incident).

Macro Technologies’ Break-A-Way coupling has a service pressure rating of 500 psi and all materials of construction are compatible with liquid and gaseous natural gas. The coupling also comes with a blanked-off air pressure fitting. This can be used to shut down thefueling station’s pumping system if a pneumatic pressure switch is employed in the Emergency-Stop electrical circuit. As you can see in Figure 2, a small threaded plug is attached to a ring that rotates around
the end of the break-a-way fitting. A piece of pneumatic tubing coming from a pressure switch can be attached to the plug. Should a driveaway situation occur, the plastic tubing would also be sheared off causing an air pressure loss, which would trip the pressure switch causing an Emergency-Stop of the dispensing pump’s control system.

The break-a-way can be equipped with virtually any end fitting for hose attachment. Macro Technologies currently offers the coupling in a one-inch pipe size; a half-inch version is in development for 10 GPM liquid with LNG vent return line applications. Delivery is scheduled for mid-year 2012. The use of the break-a-way coupling is not limited to LNG applications. Macro Technologies couplings are also used in other cryogenic service and gas applications, such as for delivering liquid nitrogen, liquid oxygen, and liquid argon.

How the Break-A-Way Coupling Works 

Macro Technologies’ Break-A-Way Coupling

Keith Hall is the Engineering Manager of INOXCVA’s Cryogenic Vessel Alternatives’ LNG/Specialty Products Division in Mont Belvieu, TX, and can be reached at khall@cvatanks.com.

 

The author gratefully acknowledges the assistance and contributions to this article from Howard Konishi, VP Engineering at Macro Technologies LLC. He can be reached at HowardK@macrotechnologies.com.

 


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