Lending A Hand
An important piece of equipment in the propane-railcar unloading process is the compressors that are used to remove the propane from the tankers and transfer it into the storage tanks.
"We've got four compressors total, which are good for unloading two railcars at a time," McClelland said. "What they're doing is hooking up the railcars, using the compressors to unload the liquid and perform vapor recovery. The terminal runs all the time, and with those compressors they can turn their 1.5 million gallons of storage, fill it and pump it out, all in 24 hours. They can offload 16 cars in only six or seven hours."
The compressors, which feature 30-horsepower motors and a mounting configuration that includes pressure gauges, a structural steel base and welded or flanged piping, are ideal for the Alliance terminal's needs because they provide single-stage, oil-free operation and have been designed specifically for propane transfer and vapor recovery with flow rates up to 125 standard cubic feet per minute (212 cubic meters per hour, 935 gallons per minute).
Design features of the compressors include high-efficiency valves, ductile-iron pistons, self-adjusting piston-rod seals, head and cylinders sealed with O-rings, heavy-duty crankshaft, pressure-lubricated bearing, pressure-assisted piston rings and wear-resistant crosshead assemblies. They also feature American Society of Mechanical Engineers liquid traps, which have a mechanical float to protect the compressor by preventing liquid from entering.
"Our compressors have to be operating in all weather conditions at all times and be fail-safe with no problems. If we're shut down, we've got a line of trucks that are waiting, and that just can't happen," said Johnson, who likes that the products are American-made. "I'm very pleased with the product. They're very quiet, they run amazingly; we haven't had any problems. I like them because I push the button—it's almost like the commercial, 'Set it and forget it.' That's what it reminds me of. You push the button, and it's going to work all day—no problem."
With the compressors playing a prominent role, the operation has been so successful already that Alliance has purchased additional land around the 17-acre facility with an eye toward eventually adding more track to handle more railcars and building additional storage tanks. Any unloading rack or storage additions would also increase the need for compressors.
There's no question that the propane-supply market in Minnesota was knocked for a loop in 2012 when Kinder Morgan announced that the Cochin pipeline would no longer be used to deliver propane. But great change can bring with it great opportunity. Alliance Midstream recognized this and immediately responded by finding a solution to what could have been an overwhelming challenge.
The solution—converting the Benson propane terminal into a rail-supplied facility—was a smart move, but the plan could only work if all of the facility's components were operating to their full effectiveness and reliability. That includes the compressors that must operate on a 24/7 basis.
"This is the largest propane facility in three states, so everything needs to be state-of-the-art," Johnson said. "To operate at the level that we are going to operate at, we need top-of-the-line equipment, and they spared no expense when they bought those compressors. There's no way they're going to let us down."