Furnace oil tanks kept pumpable at lower cost
How a forging plant storing 100 kL of furnace oil can keep its tanks and day tank at 45–70 °C with heat pumps, and what it saves against electric tank and line heaters.
▶Video: Process heat for engineering and utilities
V06 · 2–2.5 minPlating, phosphating, washers, curing and boiler feedwater
Video coming soon01Problem statement
- Oil must stay warm all day and night. Furnace oil thickens sharply below about 40 °C. Tanks are kept warm round the clock even when the furnaces are idle.
- Electric heaters run constantly. Immersion and suction heaters are simple to install, but they turn costly electricity directly into low-grade heat.
- Hot spots and sludge. Electric elements run at high surface temperature, which cokes the oil around them and builds sludge at the tank bottom.
- Electric heating is expensive heat. Resistance heaters turn one kWh of electricity into one kWh of heat, at the full commercial tariff. A heat pump moves two to four kWh of heat for the same unit.
- Large connected load. Heater banks take a big share of the sanctioned load and push up maximum-demand charges.
02Use case
The reference plant runs oil-fired forging and heat-treatment furnaces over three shifts. It stores furnace oil in two 50 kL tanks held at about 50 °C and burns about 8,000 litres a day from a day tank kept at 70 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Storage tank holding losses | 50 °C held | 2 tanks × 90 m² × 3 W/m²K × 25 K × 24 h | 324 |
| Heating oil received | 30 → 50 °C | 10,000 L/day received, ρ 0.95, cp 1.9 | 100 |
| Day tank and outflow heating | 50 → 70 °C | 8,000 L/day burnt, ρ 0.95, cp 1.9, 15% line losses | 92 |
| Storage and pipework standing losses | – | about 5% | 26 |
| Total useful heat | 542 | ||
Averaged over 20 running hours, the heat pumps need about 27 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-SHT-16C (32 kW total) (SE-SHT cascade heat pump) delivering 80 °C, covering the day's 542 kWh in about 16.9 running hours.
- A 1,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The electric tank, suction and line heaters stays connected behind a normally closed valve as standby.
- Hot water coils replace or sit beside the electric immersion heaters in each storage tank, with a suction heater coil at the outlet.
- The day tank coil runs from the same 75–80 °C storage tank to hold the oil at 70 °C.
- A small hot-water tracing loop replaces electric tracing on the transfer lines.
- Final heating to atomising temperature stays with the existing electric heaters at each burner.
Selected equipment
| Model | SE-SHT-16C × 2 |
|---|---|
| Heating capacity | 16 kW each, 32 kW total |
| COP | 2.7 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 11.9 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 80 °C |
| Storage | 1,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 74 °C and stops them at 80 °C. TIC-201 holds each storage tank at 50 °C and TIC-202 holds the day tank at 70 °C through their coil valves. The electric heaters stay wired as standby and switch on only if a tank falls 5 K below set point.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per kL of oil burnt | – | – |
| CO₂ per year | – | – |
06Benefits
Lower heating bill for oil
Each kWh of electricity gives about three kWh of tank heat, so the cost of keeping oil pumpable falls sharply.
Less sludge and coking
Hot water coils run at 75–80 °C surface temperature, far below electric elements.
Safer tank heating
No exposed electric elements inside the oil tank during normal running.
Lower energy cost
Each kWh of electricity delivers about 2.7 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
Smaller electrical load
The heat pump draws roughly 1/2.7 of the power of the heaters it replaces, which frees sanctioned load and cuts demand charges.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Tank sizes, number and insulation condition
- Oil grade, holding and day-tank temperatures
- Daily oil receipt and consumption
- Installed electric heater ratings and running hours
- Tank farm layout and safe distances
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Fire safety. Keep heat pumps and electrical panels outside the tank farm dyke area and follow the site's petroleum storage rules.
- Coil leaks. Use a closed water loop with a pressure gauge and sight glass so any coil leak into the oil is seen early. Drain water from the tank bottom regularly.
- Insulation first. Insulating bare tank shells often halves the holding loss and should be done before sizing.
- Electrical. About 12 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
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Furnace oil tanks kept pumpable at lower cost
How a forging plant storing 100 kL of furnace oil can keep its tanks and day tank at 45–70 °C with heat pumps, and what it saves against electric tank and line heaters.
▶Video: Process heat for engineering and utilities
V06 · 2–2.5 minPlating, phosphating, washers, curing and boiler feedwater
Video coming soon01Problem statement
- Oil must stay warm all day and night. Furnace oil thickens sharply below about 40 °C. Tanks are kept warm round the clock even when the furnaces are idle.
- Electric heaters run constantly. Immersion and suction heaters are simple to install, but they turn costly electricity directly into low-grade heat.
- Hot spots and sludge. Electric elements run at high surface temperature, which cokes the oil around them and builds sludge at the tank bottom.
- Electric heating is expensive heat. Resistance heaters turn one kWh of electricity into one kWh of heat, at the full commercial tariff. A heat pump moves two to four kWh of heat for the same unit.
- Large connected load. Heater banks take a big share of the sanctioned load and push up maximum-demand charges.
02Use case
The reference plant runs oil-fired forging and heat-treatment furnaces over three shifts. It stores furnace oil in two 50 kL tanks held at about 50 °C and burns about 8,000 litres a day from a day tank kept at 70 °C.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Storage tank holding losses | 50 °C held | 2 tanks × 90 m² × 3 W/m²K × 25 K × 24 h | 324 |
| Heating oil received | 30 → 50 °C | 10,000 L/day received, ρ 0.95, cp 1.9 | 100 |
| Day tank and outflow heating | 50 → 70 °C | 8,000 L/day burnt, ρ 0.95, cp 1.9, 15% line losses | 92 |
| Storage and pipework standing losses | – | about 5% | 26 |
| Total useful heat | 542 | ||
Averaged over 20 running hours, the heat pumps need about 27 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-SHT-16C (32 kW total) (SE-SHT cascade heat pump) delivering 80 °C, covering the day's 542 kWh in about 16.9 running hours.
- A 1,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The electric tank, suction and line heaters stays connected behind a normally closed valve as standby.
- Hot water coils replace or sit beside the electric immersion heaters in each storage tank, with a suction heater coil at the outlet.
- The day tank coil runs from the same 75–80 °C storage tank to hold the oil at 70 °C.
- A small hot-water tracing loop replaces electric tracing on the transfer lines.
- Final heating to atomising temperature stays with the existing electric heaters at each burner.
Selected equipment
| Model | SE-SHT-16C × 2 |
|---|---|
| Heating capacity | 16 kW each, 32 kW total |
| COP | 2.7 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 11.9 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 80 °C |
| Storage | 1,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 at the top of the tank starts the heat pumps below 74 °C and stops them at 80 °C. TIC-201 holds each storage tank at 50 °C and TIC-202 holds the day tank at 70 °C through their coil valves. The electric heaters stay wired as standby and switch on only if a tank falls 5 K below set point.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per kL of oil burnt | – | – |
| CO₂ per year | – | – |
06Benefits
Lower heating bill for oil
Each kWh of electricity gives about three kWh of tank heat, so the cost of keeping oil pumpable falls sharply.
Less sludge and coking
Hot water coils run at 75–80 °C surface temperature, far below electric elements.
Safer tank heating
No exposed electric elements inside the oil tank during normal running.
Lower energy cost
Each kWh of electricity delivers about 2.7 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
Smaller electrical load
The heat pump draws roughly 1/2.7 of the power of the heaters it replaces, which frees sanctioned load and cuts demand charges.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Tank sizes, number and insulation condition
- Oil grade, holding and day-tank temperatures
- Daily oil receipt and consumption
- Installed electric heater ratings and running hours
- Tank farm layout and safe distances
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Fire safety. Keep heat pumps and electrical panels outside the tank farm dyke area and follow the site's petroleum storage rules.
- Coil leaks. Use a closed water loop with a pressure gauge and sight glass so any coil leak into the oil is seen early. Drain water from the tank bottom regularly.
- Insulation first. Insulating bare tank shells often halves the holding loss and should be done before sizing.
- Electrical. About 12 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.