Taper-Tank Design from Weld-It Provides More Domelid Protection
Nov 1, 1997 12:00 PM
AN ACCIDENT can be a powerful motivator for design innovation, especially in the tank truck industry. Problems are clearly highlighted, and carriers have a strong incentive to find a means of preventing future incidents.
During accident investigations over a number of years, Paul Schulz, vice-president of fleet maintenance at Beneto Inc, had noticed that marginal protection was provided for tank hardware between the overturn rails on petroleum units. He approached several cargo tank manufacturers, looking for ways to provide better protection for the domelids and other hardware on top of the tanks. Severalapproaches were attempted but weren't satisfactory to Beneto.
A workable solution came from Weld-It Company in Los Angeles, and Beneto has purchased two truck-and-trailer combinations built to the new design. Additional vehicles are being considered, and other West Coast petroleum haulers are showing an interest.
"This is a premium product because it takes extra labor and a lot more expertise during assembly," says Ray Schaffer, Weld-It co-owner. "We think Beneto is an outstanding company because they want to do what is right, not what is cheapest."
Weld-It started with its basic West Coast tanker design. In the new configuration, the tank truck has a 13,820-lb tare weight and carries 4,400 gallons. The two-axle full trailer weighs 7,350 pounds and holds 5,400 gallons.
Top Radius In modifying the basic design, Weld-It decided to lower the domelids and other hardware below the top radius of the tank. While that sounds relatively simple, it has increased the amount of time and skill needed to fabricate a petroleum tank.
Baffles and interior heads were cut down to lower the top radius of the tank by six inches. The front head is six inches smaller than the rear head, resulting in a single-taper design for the truck tank. Loss of capacity due to the lowering of the top means that the double-taper pull trailer had to be extended by two feet. The drawbar was shortened to 7 1/2 feet.
"We're hearing from Beneto that the extra trailer length has improved the trailer ride," Schaffer says. "We also think that stability might have been improved."
The top of each tank is water-level, which ensures adequate drainage from the spill dam area. Spill dam drainage is through a two-inch pipe that runs through the tank. This is a standard arrangement on Weld-It tanks.
With the design changes, the truck tank now slopes from front to rear, which has improved drainage. In addition, Beneto requested that the truck tank be fabricated with full-length drain troughs for even faster product flow. The trailer has a double-taper design that is common on the West Coast.
Beneto specified the new tanks with Dwyer over-pressure switches that will shut down loading operations if increasing pressures are sensed in the vapor-return lines. Typically used in industrial applications, the Dwyer sensors are tied in with the Scully IntelliCheck overfill system.
Among other top-mounted hardware are Knappco domelids, Bayco inward-opening mechanical pressure-relief vents, and Trucknology aluminum vent hoods. Underneath are Betts internal emergency valves and butterfly-valve outlets and Emco Wheaton bottom-loading adapters.
Freightliner Truck The truck tank has a single compartment, while the trailer is built with three, each separated by a single bulkhead. The truck tank is mounted on a Century Class Freightliner conventional with aluminum frame rails for lower tare weight.
The two-axle trailer has a Hutchens 9700 suspension with composite springs. Timbren helper springs ensure a better empty ride. Both the truck and trailer have Rockwell WABCO antilock braking and 19 1/2-inch radial tires on aluminum disc wheels.
Like many West Coast fleets, Beneto specified LED marker and signal lights on the new trailers. Schaffer says the LED lights are popular because theyare brighter than typical bulb-type lights and require less maintenance. The Pe terson lights selected by Beneto also come with a lifetime warranty.
Tank polishing was contracted to Caliva's Truck Polishing in Montebello, California.
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