**Introduction:
**Blow room is the first stage of spinning where opening, cleaning, mixing, and blending are done. The quality of yarn largely depends upon this stage. It also affects the CV%. Here trash content is also important. So, we have to know the calculations of blow room as well as the formulas. Some Important formulas for the blow room section are given below.

**Some important formulas for blow room section**

…………………………………………………………………..Amount of trash removed

1. Cleaning efficiency of blow room section = …………………………………………. X 100

………………………………………………………………………Total amount of trash

……….Amount of trash in raw cotton – Trash in lap

= ……………………………………………………………………….. X 100

…………………Amount of trash in raw cotton

……………………………………………………….Amount of trash removed

2. Cleaning efficiency of carding (%) = ………………………………………. X 100

…………………………………………………………………Trash in lap

……..Amount of Trash in lap – Amount of trash in Carding

= ……………………………………………………………………………………… X 100

…………………………….Amount of Trash in the lap

…………………………………..The trash in carded sliver (%)

3. Trash in lap (%) = ……………………………………………………X 100

………………………………………100 – Cleaning eff. (%)

………………………Lap length (in gauge)…………Unit of weight

4. Lap hank = ………………………………….. X ……………………………….

………………………..Unit of length…………………..Lap weight (Lbs)

……Lap length (in gauge)………………….1 lb

= ………………………………… X ……………………………………

……………840 gauge…………………Lap weight (Lbs)

5. Blow room production per hour = Surface speed of calender roller (inch/min)

………………60

X ………………………….. X Eff. % X Waste% X No. of scatcher

…..36 X 840 X Hank

6. Lap length constant = Lap length X Change pinion

………………………………..Lap length constant

Or, Change pinion = …………………………………..

……………………………………….Lap length

7. Lap length = Surface speed of bottom calendar roller (In gauge)

= Circumference of bottom calendar roller (gauge) X Speed of bottom calendar roller

= (πD/36) X N Gauge (here, D= Dia of bottom calendar roller and N = Speed)

………………………Knock off wheel……………Warm wheel

= (πD/36) X ……………………………….. X ……………………….. (Gauge)

………………………..Change wheel……………..Single warm

8. Lap length constant (%) = Surface speed of bottom calendar roller (In gauge) X Speed from knock off wheel to bottom calendar roller

………………………Knock off wheel………..Warm wheel

= (πD/36) X ……………………………. X …………………………

…………………….Change wheel …………….Single warm

**Conclusion:**

The delivery product of blow room is lap which is used in carding as feed material. So to make it faultless we have to know the calculation and its formulas.

Author of this Article:Md. Abu SayedFounder of Textile Apex Pabna Textile engineering college, Pabna, Bangladesh Email: [email protected] Cell : +8801745214773