Question

A vertical vessel a nominal capacity of 5000 gal. is to be mounted on four electronics shear-type load cells. the system is designed so that in extreme case, three of the four loads cell can carry the entire weight. The liquid specific gravity is 1.15. The tare weight of the empty vessel is 5380. shear type load cell are available in the following range 2000lb, 5000lb, 20,000lb, and 30,000lg 1- select a measurement range from the weight system. 2-The electronic load cell readout has four active digits to display the weight. what is the smallest weight that can be display. 3-given a accuracy of 0.1% what is the maximum inaccuracy in lb when the tank is full? 4- given an accuracy of 0.1% what is the maximum inaccuracy in lb wen the tank is 10% full?

Answer 1

Empty weight of vessel = 5380 lb

volumetric capacity of vessel = 5000 gal, mass capacity of vessel = volume*sp.gravity = 5000*1.15 = 5750 lb

At any time total weight of vessel = empty weight of vessel + liquid filled in vessel.

1) measurement range = 0 to (2000+5000+20000+30000) = 0 to 57000 lb

2) Minumum weght displayed will be when vessel is empty. At that time, weight displayed would be the weight of vessel = 5380 lb

3) when tank is full, ttal weight to show = vessel weight + liquid weight filled in vessel = 5380+5750 = 11130 lb.

now accuracy =0.1 % = (displayed-atual value)/100 =( displayed -11130)/100 = 0.1

or displayed value = 0.1*100+ 11130 = 11140

thus inaccuracy = error = displayed-actual = 11140-11130 =10lb

4) when tank is 10% full, mass of liquid in tank = 10% of 5750 = 5750*10/100 = 575 lb

Now total weight of vessel +liquid in vessel = 5380+575 = 5955 lb

now accuracy =0.1 % = (displayed-atual value)/100 =( displayed -5955)/100 = 0.1

or displayed value = 0.1*100+ 5955 = 5965

thus inaccuracy = error = displayed-actual = 5965-5955 =10lb