Steam is the working fluid of a garment washing plant — used in the tunnel finisher, steam ironing, drying tunnels, and some washing processes. The boiler that generates this steam is also one of the largest energy costs in the plant. Understanding how to calculate steam demand and match it to boiler capacity — and what it actually costs in fuel — is essential for both plant sizing and cost control.
Steam Consumption by Process
Different processes in a washing plant consume steam at different rates. The tunnel finisher is typically the largest steam consumer, followed by drying and ironing.
Typical Steam Consumption by Process
| Process | Steam Consumption | Notes |
|---|---|---|
| Tunnel finisher (per unit) | 1–3 kg steam/garment | Depends on fabric weight and cycle time |
| Steam ironing (per garment) | 0.2–0.5 kg steam/garment | Varies by garment type |
| Drying tunnel (per kg fabric) | 2–4 kg steam/kg fabric | Depends on initial moisture content |
| Washing machine heating (per kg fabric) | 0.5–1.5 kg steam/kg fabric | For hot wash processes |
Calculating Boiler Capacity Requirement
To size a boiler or verify whether your existing boiler meets demand, you need to estimate total steam consumption per hour at peak load.
Total steam demand (kg/hr) = Sum of all process steam consumptions at peak Example: Washing plant processing 3,000 garments/8-hour shift Hourly throughput = 3,000 / 8 = 375 garments/hr Tunnel finisher: 375 × 2 kg/garment = 750 kg steam/hr Ironing: 375 × 0.3 kg/garment = 112 kg steam/hr Washing (hot processes): 375 garments × 0.4 kg fabric × 1.0 kg steam/kg = 150 kg steam/hr Total = 750 + 112 + 150 = 1,012 kg steam/hr Add 20% safety margin: 1,012 × 1.2 ≈ 1,214 kg steam/hr Boiler capacity needed: at least 1.2–1.5 tonnes/hr
Fuel Cost Comparison: Gas vs HFO
Most washing plants in Bangladesh use either natural gas (where available) or heavy fuel oil (HFO). Gas is significantly cheaper per unit of heat generated and burns more cleanly, but supply can be unreliable. HFO is widely available but costs more and requires heating before pumping.
Approximate Fuel Cost Comparison (Bangladesh, 2026)
| Fuel Type | Calorific Value | Approx. Price | Cost per 1,000 kg Steam |
|---|---|---|---|
| Natural gas | 8,500 kcal/m³ | ৳12–16/m³ | ৳1,800–2,400 |
| HFO (furnace oil) | 9,800 kcal/kg | ৳65–80/litre | ৳4,500–6,000 |
| Diesel (emergency use) | 8,800 kcal/litre | ৳109/litre | ৳8,000–10,000 |
Tip
Boiler efficiency matters as much as fuel price. A well-maintained boiler operates at 80–85% efficiency; a poorly maintained boiler with scale buildup, air leaks, and no blowdown management may run at 60–65%. At that level, you are burning 25% more fuel for the same output. Annual boiler inspection and tube cleaning pays for itself within weeks.