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Calibration of pressure vessel load cells

Calibration of pressure vessel load cells

Calibration of pressure vessel load cells

(OP)
At our facility we have ten 3750-liter pressure vessels. Each has 4 legs which in turn rest atop 4 load cells. Currently we have Mettler Toledo calibrating these load cells, but at $18-20K per tank x 3 visits a year this has become far too expensive. The brass has asked what it would take to do the job in house.

As it happens we recently hired a mech that worked at Mettler Toledo's main competitor. He came with with an idea and I thought why not float it here to see if anyone thinks it may or may not fly, and if you have any other possible alternatives.

His idea is as follows:

-Attach a chain to the vessel's lifting lugs. There are two lugs per vessel, each 180* apart. If you were to view the vessel from above the legs would be every 90*, and the two lugs at the 45* and 225* mark.
-Midway down the chain would be a come-along, followed by some more chain, a turn buckle, more chain and then a 'S' type load cell. This load cell would be attached to a display which would show each S load cell's reading plus the overall.
-After the load cell another small length of chain would take you to a metal ring which two more chains of equal length are attached. These two chains are then attached to a metal bar. The bar will be anchored to the concrete floor with redhead anchors, or equivalent. Three anchors, one on each end and one in the center, will be used for each bar. Each chain will then be attached to the bar between one end anchor and the one in the middle to distribute the pull evenly. This arrangement from lug to floor is identical on both sides of the vessel.
-Once everything is installed the operator would crank down on each come-along, always watching the display to ensure the pull is being administered evenly. When it reaches close to 1000 lbs he will then tighten up the turnbuckle to get the fine adjustment. He will then check to see if the vessel's built-in load cells register the same reading, and adjust accordingly if needed. He then continues in 1000lb increments until he reaches 5000lb per side, which is our overall target.

So, does anyone see any potential problems with this arrangement, or have an even better idea? All suggestions welcomed.

Thanks

RE: Calibration of pressure vessel load cells

Yeah, I see a potential safety problem.  The original lift lugs are not normally designed for in-service conditions.  They are typically designed to safely handle an empty vessel.  Be sure not investigate the lug capacity.

Joe Tank

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