Quench oil cooling that heats the washers
How a heat-treatment shop quenching 25 tonnes of parts a day can cool its quench oil and heat its post-quench washers with one water-source heat pump, and what it saves against electric heaters.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Heat thrown away and bought back. Quench oil heat goes to a cooling tower, while the washers right next to the furnace are heated electrically.
- Quench oil must stay in range. Oil above its set point raises fire risk and changes hardness results, so cooling has to be reliable.
- Washers run hot all day. Post-quench washers need 65–70 °C to remove oil, and their heaters run almost continuously.
- 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 is a captive heat-treatment shop with sealed-quench furnaces and hydraulic presses. It hardens about 25 tonnes of gears and shafts a day over three shifts, washing parts after quench and dipping them in rust preventive.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Heating parts in post-quench washer | 30 → 70 °C | 25 t steel/day × 0.46 kJ/kg·K × 40 K | 128 |
| Washer tank make-up | 30 → 70 °C | 4,000 L/day, 30 → 70 °C | 186 |
| Washer surface and exhaust losses | 70 °C | 2 washers × 5 kW × 18 h | 180 |
| Rust-preventive dip tank reheat | 35 → 60 °C | 2,000 L tank, 25 K reheat each day | 58 |
| Storage and pipework standing losses | – | about 5% | 28 |
| Total useful heat | 579 | ||
Averaged over 20 running hours, the heat pumps need about 29 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-WWUHT-27 (54 kW total) (SE-WWUHT water-source, R245fa) delivering 80 °C, covering the day's 579 kWh in about 10.7 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: quench-oil cooler water at about 50 °C. Cooling the quench oil is a by-product, so the cooling tower and its fan run less.
- The electric heaters in washer and dip tanks stays connected behind a normally closed valve as standby.
- An intermediate water loop between the quench oil cooler and the heat pump evaporator carries heat at about 50 °C.
- The heat pump lifts it to 80 °C for the washer and dip tank coils.
- The cooling tower stays connected to the oil cooler and takes over automatically if the heat pump is off or the washers are satisfied.
Selected equipment
| Model | SE-WWUHT-27 × 2 |
|---|---|
| Heating capacity | 27 kW each, 54 kW total |
| COP | 2.93 estimated for a 50 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 80 °C |
| Storage | 2,000 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pump below 75 °C and stops it at 80 °C. The quench oil temperature controller has priority: if oil rises above set point, it opens the cooling tower circuit regardless of heat demand. TIC-201 and TIC-202 hold the washer and dip tank. Electric heaters remain as standby.
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 tonne of parts heat-treated | – | – |
| CO₂ per year | – | – |
06Benefits
One machine, two duties
The heat pump cools the quench oil and heats the washers at the same time.
Stable quench oil temperature
Continuous heat removal keeps oil closer to set point, which supports consistent hardness.
Cooling tower runs less
Less heat goes to the tower, saving fan power, make-up water and chemical dosing.
Lower energy cost
Each kWh of electricity delivers about 2.9 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 1/2.9 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
- Quench oil volume, set point and cooler duty
- Tonnes quenched per day and furnace schedule
- Washer and dip tank volumes and temperatures
- Installed heater kW and running hours
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Keep oil out of the heat pump. Use an intermediate water loop. Oil must never reach the heat pump evaporator, even if the oil cooler leaks.
- Fire safety. Quench oil cooling is safety-critical. The tower circuit must remain fully sized as the primary cooling path.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- 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.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
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.
Talk to us
Quench oil cooling that heats the washers
How a heat-treatment shop quenching 25 tonnes of parts a day can cool its quench oil and heat its post-quench washers with one water-source heat pump, and what it saves against electric heaters.
▶Video: Waste-heat recovery heat pumps
V10 · 2–2.5 minLifting warm water from condensers, effluent and process cooling to useful heat
Video coming soon01Problem statement
- Heat thrown away and bought back. Quench oil heat goes to a cooling tower, while the washers right next to the furnace are heated electrically.
- Quench oil must stay in range. Oil above its set point raises fire risk and changes hardness results, so cooling has to be reliable.
- Washers run hot all day. Post-quench washers need 65–70 °C to remove oil, and their heaters run almost continuously.
- 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 is a captive heat-treatment shop with sealed-quench furnaces and hydraulic presses. It hardens about 25 tonnes of gears and shafts a day over three shifts, washing parts after quench and dipping them in rust preventive.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Heating parts in post-quench washer | 30 → 70 °C | 25 t steel/day × 0.46 kJ/kg·K × 40 K | 128 |
| Washer tank make-up | 30 → 70 °C | 4,000 L/day, 30 → 70 °C | 186 |
| Washer surface and exhaust losses | 70 °C | 2 washers × 5 kW × 18 h | 180 |
| Rust-preventive dip tank reheat | 35 → 60 °C | 2,000 L tank, 25 K reheat each day | 58 |
| Storage and pipework standing losses | – | about 5% | 28 |
| Total useful heat | 579 | ||
Averaged over 20 running hours, the heat pumps need about 29 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-WWUHT-27 (54 kW total) (SE-WWUHT water-source, R245fa) delivering 80 °C, covering the day's 579 kWh in about 10.7 running hours.
- A 2,000 L insulated storage tank decouples the heat pumps from the process peaks.
- Heat source: quench-oil cooler water at about 50 °C. Cooling the quench oil is a by-product, so the cooling tower and its fan run less.
- The electric heaters in washer and dip tanks stays connected behind a normally closed valve as standby.
- An intermediate water loop between the quench oil cooler and the heat pump evaporator carries heat at about 50 °C.
- The heat pump lifts it to 80 °C for the washer and dip tank coils.
- The cooling tower stays connected to the oil cooler and takes over automatically if the heat pump is off or the washers are satisfied.
Selected equipment
| Model | SE-WWUHT-27 × 2 |
|---|---|
| Heating capacity | 27 kW each, 54 kW total |
| COP | 2.93 estimated for a 50 °C source (the data sheet is rated on a 60/55 °C source) |
| Rating | water or steam to 120 °C, R245fa |
| Supply temperature | 80 °C |
| Storage | 2,000 L insulated tank |
Capacity is sized from the heat demand above. COP is an estimate until Sunniva engineering confirms the design.
Control philosophy
TT-101 at the tank top starts the heat pump below 75 °C and stops it at 80 °C. The quench oil temperature controller has priority: if oil rises above set point, it opens the cooling tower circuit regardless of heat demand. TIC-201 and TIC-202 hold the washer and dip tank. Electric heaters remain as standby.
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 tonne of parts heat-treated | – | – |
| CO₂ per year | – | – |
06Benefits
One machine, two duties
The heat pump cools the quench oil and heats the washers at the same time.
Stable quench oil temperature
Continuous heat removal keeps oil closer to set point, which supports consistent hardness.
Cooling tower runs less
Less heat goes to the tower, saving fan power, make-up water and chemical dosing.
Lower energy cost
Each kWh of electricity delivers about 2.9 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 1/2.9 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
- Quench oil volume, set point and cooler duty
- Tonnes quenched per day and furnace schedule
- Washer and dip tank volumes and temperatures
- Installed heater kW and running hours
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
Design notes
- Keep oil out of the heat pump. Use an intermediate water loop. Oil must never reach the heat pump evaporator, even if the oil cooler leaks.
- Fire safety. Quench oil cooling is safety-critical. The tower circuit must remain fully sized as the primary cooling path.
- Source stream. The source must give up roughly two-thirds of the heat delivered. Confirm its flow and temperature over a full production day, and filter it before the evaporator.
- 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.
- Performance figure. The COP on this page is an engineering estimate, not a data sheet value. Sunniva engineering will confirm it for the actual source and supply temperatures.
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.