A Study on the power consumed in the drafting apparatus of a Ring Spinning Frame using pneumatic arm loading.
Prepared by J Venkatasubramanian, Research Engineer, Apex Precitech., Coimbatore
The objective is to find the load consumed for excess/ deficit loading of the bottom rollers by the loading arm of a pneumatically loaded drafting system. Another objective is to calculate the actual cost of such an increase for a mill.
The Rieter/ Lakshmi Rieter type of drafting with their current P 3-1 top arm is taken for analysis. Assumed is that one complete ring frame has 1008 spindles and the mill has 25,000 spindles.
The standard motor capacity is 45 KW and the percentage load consumed in the drafting is taken as 25 % i.e., 11.25 KW.
It is known from studies on P 3-1 top arms that the loading pattern from front to back roller of the drafting is as follows
Front- 16 kg Middle- 12 Kg Back 16 Kg.
For an optimum performance in cotton spinning conditions technicians keep these values. Also, at the recommended air pressure of 1.6 bar, only these values are recorded using Apex Top Arm Load Gauges. We can take a total load of 44 Kg for one top arm.
Total number of top arms – 504
Load per arm – 44 Kg
Total drafting Load – 44 X 504 = 22,176 Kg
Power consumed for one full machine = 11,000 watts
(11,000 watts are consumed by an exertion of 22,176 Kg.)
Therefore , for one Kg , the load consumed is = 11,250 / 22,176 = 0.507 watts
The P 3-1 top arm is centrally pneumatically loaded and the increase of air pressure fed into the machine will result in the increase of top arm loads in all the top arms. Another feature in the P3-1 top arm is that the increase of one kilogram of the front roller in the standard pin setting of the P3-1 top arm will result increase in other rollers too. The ratio (front: middle: back ) is 1 : 0.5 : 1
Hence, if we assume the front roller is loaded in excess of 1 kg (over the normal of 16 Kg) the loading pattern will be like 17 :12.5 : 17. The increase in load will be 2.5 Kg total. For 504 top arms the excess load applied = 2.5X 504 = 1,260.00 Kilograms.
Since we arrived at the power consumed per kilo as 0.496 watts, the total power for 1,260 Kilos of excess loading will be
= 1,260 X 0.507 = 638.82 watts.
For 24 hour running of the machine, the power consumed will be = 24 x 638.82
= 15,331.68 watts= 15.33 KW
Converting into energy units the 24 running consumes 15.33 kilowatt hour (units)
Calculating for 25000 spindles (25 machines) the excess energy consumed per day will work out to be = 25 x 15.33 = 383.25 units
For 365 days the calculation will be = 1,39,886.25 units
Considering Rs 7.00 as an average cost of a unit as in Tamil Nadu the Rupee equivalent of the excess energy consumed is = 1,30,886.25 x 7
= 9,79,203.75 Rupees per annum.
Since this cost is for unit increase of load , i.e., by 1 kilogram, for any further increase , the cost can be got by multiplying by the factor. For example , for 1.5 kilogram increase, the cost can be simply 1.5 multiplied by 9,79,203.75.
This can be used as an empirical method to calculate the costs for any increase or decrease of air pressure.