**Introduction**

The section, where the supplied compressed bale is turn into a uniform lap of a particular / specific length by opening, cleaning, mixing and blending is called **Blow Room section**. It is the first step of spinning. Blowroom consists of a number of machines used in succession to open & clean the cotton fiber to the required degree and 40-70% trash is removed in this section. Calculations play an important role during the process. Some important Blow Room production calculations with example are mentioned in the following article.

**Some Important Conversion Factors for Blow Room Production Calculations:**

- 36 inch = 1 Yard;
- 1 Lea = 120 Yards;
- 1 Meter = 1.09 Yards;
- 1 Pound(lb) = 453.6 Gram = 16 Oz;
- 840 Yard = 7 Lea = 1 Hank;
- 1 Pound (lb) = 7000 Grains;
- 1 Meter = 39.37 Inch;
- 1 KG = 2.205 Pound (lb)

Hank or count means the number of 840 yards length that weigh exactly one pound.

Lap Hank Ranges: 0.0012, 0.0013

**Blow Room Production Calculations Formula with Example:**

**Formula 1: Cleaning Efficiency % = (Waste% in Input – Waste% in Output) / (Waste% in Input)**

**Example:** The trash content of a cotton as fed to beater 3.2%. The waste extraction is 1.6% of which 80% is trash. What is the cleaning efficiency?

**Solution:**

Of the 1.6% waste extraction,

Trash = (80/100) x 1.6 = 1.28% of the trash has been taken out by beater.

3.2 – 1.28 = 1.92% waste remains in the material delivered from the beater.

Here, waste% in Input = 3.2%

Waste% in Output = 1.92%

Cleaning Efficiency = (Waste% in Input – Waste% in Output) / (Waste% in Input)

= (3.2-1.92)/3.2 = 40% **(Ans.)**

**Formula 2: Beats/inch = (Beater RPM x No of Striker) / (π x Feed Roller Dia x Feed Roller RPM)**

**Example:** Find out Beats/inch from the following

- Beater RPM = 720
- No of Striker = 16
- Feed Roller RPM = 26
- Feed Roller Dia = 3”

**Solution:**

Here, Beats/min = Beater RPM x No of Striker = 720 x 16

Surface Speed of Feed Roller = π x Feed Roller Dia x Feed Roller RPM = 3.1416 x 3 x 26

Beats/inch = (720 x 16)/(3.1416 x 3 x 26) = 47.011 ≈ 47** (Ans)**

**Formula 3: Waste% = Waste x 100/Input**

**Example:** 80 Bales of cotton each of 167kg are being fed daily in a 2 scutcher blow room line. Actual production per 2 scutcher per day is 12000 kg. Calculate the total quantity of waste throughout whole blow room line & waste%.

**Solution:**

Here, Input = 80 x 167 = 13360 kg

Output = 12000 kg

Waste = 13360 – 12000 = 1360 kg

Waste% = 1360 x 100/13360 = 10.18% **(Ans)**

**Formula 4: No of Bales/Day Fed = (Input (kg/day)) / (Wt. of per bale (kg))**

**Example:** The production per scutcher per hour in a 2 scutcher blow room line is 325 lbs. Waste from whole blow room line is 700 kg/day. Calculate the no of bales required per day for given blow room line. (1 bale = 167 kg)

**Solution:**

Here, Waste = 700 kg

Output = 325 x 2 x 24/2.205 = 7076.4 kg/day

Input = 7075.4 + 700 = 7776.4 kg/day

No of bales/day fed = 7776.4/167= 47 bales. (Ans)

**Formula 5: Production Per Scutcher per Day = (Output (kg/day)) / (No of Scutcher)**

**Example:** 65 bales of cotton are being fed daily in a blow room line consisting of 2 scutchers. The blow room is to be kept stopped for one hour after each shift for maintenance, if waste% is 6%, then what will be the production per scutcher in a day (in kg/hour), while 1 bale = 165 kg.

**Solution:**

Input = 65 x 165 = 10725 kg.

Waste% = 6%

Waste = 10725 x 6/100 = 643.5 kg

Output = 10725 – 643.5 = 10081.5 kg/day

Production per scutcher per day = 10081.5/2= 5040.75 kg **(Ans)**

The machine keeps running = 21 hour

Production in kg/hour = 5040.75/21 = 240.03 kg/hour **(Ans)**

**Formula 6: Blow Room Production Per Hour = π x D x G x Efficiency x Waste%**

**Example:** Calculate the machine production. Here, scutcher m/c RPM is 300, Roller diameter is 8” and m/c efficiency is 80% within waste% = 5. [Lap Hank = 0.0012]

**Solution:**

Here,

- Machine RPM, G = 300
- Roller Diameter, D = 8”
- Efficiency = 80% =80/100
- Waste loss = 5% = (100-5)/100
- Lap Hank = 0.0012

M/C Production = π x D x G x Efficiency x Waste%

= {3.1416 x 8 x 300 x 80 x (100-5) x 60} / (100 x 100) inch/hour

= (3.1416 x 8 x 300 x 80 x 95 x 60) / (36 x 840 x 100 x 100) yards/hour

= (3.1416 x 8 x 300 x 80 x 95 x 60) / (0.0012 x 36 x 840 100 x 100) lbs/hour

= 9474.67 lbs/hour **(Ans)**

**Formula 7: Lap Hank = (Length in Hank) / (Weight in Pound)**

**Example:** If lap weight is 15 oz per yard. Find out the lap hank.

**Solution:**

We know, Length in hank = (Length in Yard) / 840 = 1/840

Weight in Pound = (Weight in (oz)) / 16 = 15/16

Lap Hank = (1/840) / (15/16) = 0.0012 **(Ans)**

**Formula 8: Production Per Shift = (π x D x G x Efficiency x Waste% x No of Scutcher machine x 60 x shift) / (36 x 840 x Hank)**

**Example:** Calculate the production of Blow room with 2 scutchers if

- Calendar Roller Dia = 7”
- Calendar Roller RPM = 10
- Efficiency = 60%
- Wastes = 4%
- Lap Hank = 0.0012
- Shift = 8 hour

**Solution:**

Here,

- Calendar Roller RPM, G = 10
- Calendar Roller Diameter, D = 7”
- Efficiency = 60%
- Waste loss = 5%
- Lap Hank = 0.0012

Production Per Shift =(π x D x G x Efficiency x Waste% x No of Scutcher machine x 60 x shift )/(36 x 840 x Hank)

= {3.1416 x 7 x 10 x 60 x (100-4) x 2 x 60 x 8} / (36 x 840 x 0.0012 x 100 x 100) lb

= 3351.04 lb **(Ans)**

**Formula 9: Production Per Shift = π x D x G x Efficiency x Waste%**

**Example:** Bottom calendar roller diameter = 7”, RPM of B.C.R = 10, weight of every yard lap is 12 oz, efficiency = 75% and waste% = 5%. Find out the production of B/R per shift. [Shift = 8 hour]

**Solution:**

Here, B.C.R dia, D = 7”

B.C.R RPM, G = 10

Efficiency = 75% = 0.75

Waste = 5% = (100-5)/100 = 0.95

Weight of every yard lap = 12 oz, i.e., 12 oz/yard

Production per shift =π x D x G x Efficiency x Waste%

= (3.1416 x 7 x 10 x 0.75 x 0.95 x 2 x 12 x 60 x 8 ) / (36 x 16 ) lb

= 1566.88 lb **(Ans)**

**Formula 10: No. of Laps Per Day = (Output Lap(kg/day)) / (Weight of One lap (kg))**

**Example:** 80 bales of cotton are being fed in a blow room line daily. If the pure weight of cotton per bale is 170 kg and waste% of blow room line is 5%. What will be the weight of cotton lap received per day from scutcher? Calculate the no of laps prepared per day if the weight of one lap is 20 kg.

**Solution:**

Input = 80 x 170 = 13600 kg

Waste% = 5% = 0.05

Waste = 13600 x 0.05 = 680 kg

Output = 13600 – 680 = 12920 kg/day (This is the cotton lap received per day)

No of Laps/Day = (Output Lap(kg/day)) / (Weight of One lap (kg))

= 12920/20 = 646 Laps **(Ans)**

**Conclusion:**

I have tried to explain the formulas with examples of different production calculations of blow room through this article. Hope this article will be helpful for those who are new to the factory or those who are students.

**Author of this Article:**

Md. Imran Hossain

B.Sc. in Textile Engineering

Shahid Abdur Rab Serniabat Textile Engineering College, Barisal.

Email: [email protected]

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