# How much furnace oil does better insulation save on a galvanizing furnace?

Canonical: https://senseible.earth/answers/galvanizing-furnace-insulation-oil-saving

About 9,900 litres of furnace oil a year, 9.4% of a 105,000 litre unit, in BEE's Howrah report. Most of it comes from the drying bed at 200 C, not the zinc furnace walls. Cost Rs 3.01 lakh, saving Rs 3.37 lakh, payback under 11 months at 2010 prices.

## Where the heat leaks, face by face

- Drying bed and duct: 9.49 m2 at 200 C, losing 30,097 kcal an hour; 2,123 at 60 C.
- East furnace wall: 4.8 m2 at 121 C, 5,358 kcal an hour; 961 at 60 C.
- North wall 92 C and south wall 69 C: small areas, small gains.
- West wall already at 54 C: nothing to gain.
- The drying bed alone is 84% of the rupee saving.

## The sum and the cost

- 12 hours a day, 240 days: 2,880 hours.
- All faces brought to 60 C save Rs 336,704 a year at Rs 34 a litre: 9,903 litres.
- Cost: Rs 1.90 lakh insulation, Rs 0.80 lakh fitting, Rs 0.31 lakh tax and other: Rs 3.01 lakh.
- Payback: 3.01 / 3.37 = 0.89 years. The report allows 16 days of downtime.

## Measure before you pay

1. Shoot every face with an infrared gun at full fire and write down the temperature and area.
2. Start with anything above 150 C; the drying bed and ducts usually lead.
3. Ask for a finished surface of 60 C or less, the touch temperature the report uses.
4. Re-measure in the same shift after the work, and compare litres a month on your oil bills.

## The report's CO2 is a little high

It states 31,492 kg, applying 3.18 kg of CO2 per kg of oil to litres. At 2.97 kg a litre the saving is about 29.4 t a year.

## The drying bed alone

- Now: 30,097 kcal an hour / 10,500 / 0.92 = 3.12 litres an hour
- At 60 C: 2,123 kcal an hour = 0.22 litres an hour
- Saved: 2.90 litres an hour x 2,880 h = 8,352 litres
- Whole job: 9,903 litres x 2.97 = 29.4 t CO2 a year

Oil at 10,500 kcal a kg and 0.92 specific gravity, as in the report. Furnace oil at 2.97 kg CO2 a litre, an estimate.

## What Senseible does here

Senseible reads furnace oil invoices into monthly litres and CO2 at 2.97 kg a litre, each linked to its bill, so the drop after insulation shows against the months before. The green loan check shows whether insulation qualifies as an efficiency loan.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Air preheater on a galvanizing furnace](https://senseible.earth/answers/galvanizing-furnace-air-preheater-oil-saving)
- [Zinc bath temperature control](https://senseible.earth/answers/zinc-bath-temperature-control-oil-saving)
- [Reheating furnace insulation savings](https://senseible.earth/answers/reheating-furnace-insulation-fuel-savings)
- [Galvanizing furnace: oil to wood gas](https://senseible.earth/answers/galvanizing-oil-furnace-to-biomass-gasifier)

Sources: [BEE, Detailed project report: furnace insulation improvement, Howrah galvanizing and wire drawing cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/Howrah_galvinising/DPR_on_Furnace_Insulation_Improvement.pdf)

Last reviewed 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's fuel and power prices and a current quote before you rely on the payback.