Thermal Oil Heaters

What is a Thermal Oil Heater?

A thermal oil heater (hot oil heater) is an industrial heating system that carries heat with a special heat transfer oil instead of water or steam. The oil is heated in the coil of the heater and pumped in a closed circuit to tanks, heat exchangers and process equipment; after releasing its heat it returns to the heater.

Thermal oil does not boil even at 230 °C, so the system operates at low pressure at this temperature. Reaching the same temperature with steam requires a pressure in the order of 28 bar. This is why the thermal oil heater is the safest and most economical heat source for processes that need high, stable temperatures, such as bitumen, emulsion and asphalt plants.

Vimpo VTH Thermal Oil Heater

The Vimpo VTH series are three-pass horizontal coil-type thermal oil heaters built in five sizes from 500,000 to 3,000,000 kcal/h (582 – 3,489 kW). Every size is available with diesel, natural gas or heavy fuel oil firing.

The heater is built, tested and delivered ready to connect from our Ankara factory as one package together with the Vimpo VKY circulation pump, expansion tank, degasifier, control panel and chimney. The operating temperature is 230 °C and the design temperature 320 °C.

Why Choose Vimpo Thermal Oil Heaters?

• Experience in asphalt and bitumen processing solutions since 1997
• Vimpo equipment operating in more than 40 countries
• In-house design office in Ankara — engineering with SolidWorks and ANSYS
• Heater, coil and thermal oil pump manufactured in our own factory — 10,000 m² of covered production area
• Manufacturing to EN ISO 3834-2 welding quality and EN 1090-2 EXC3, CE marked; ISO 9001 · ISO 14001 · ISO 45001
• Commissioning, operator training and spare parts support from Ankara, Herford (Germany) and Pune (India)

Working Principle of Thermal Oil Heaters

In the VTH heater the burner flame burns in a combustion chamber surrounded by the coil. The flue gases change direction three times inside the heater body, pass over the coil surfaces and leave through the chimney after transferring most of their heat to the oil. The three passes keep the flue gas in the heater longer and reduce chimney losses; the heater runs at a minimum efficiency of 85% at full load.

The oil is heated as it flows through the seamless steel coil; the outlet temperature is measured with a PT100 sensor and the control panel fires the burner to this value. The Vimpo VKY circulation pump sends the hot oil to the consumers — the heating coils of bitumen tanks, jacketed pipes and valves, emulsion and PMB plants. The expansion tank takes up the volume increase of the oil as it heats, and the degasifier separates air and moisture from the circuit.

Vimpo VTH Thermal Oil Heater Features

Safe Operation

PT100 temperature measurement at inlet and outlet, Danfoss pressure sensors, overpressure protection and a high-temperature limit thermostat. Safety interlocks prevent the burner from firing when the pump is not running, when there is no oil in the expansion tank or when the temperature limit is exceeded. Because thermal oil operates at low pressure at 230 °C, there is no high-pressure risk as in steam boilers.

Certified Manufacturing

VTH heaters are CE marked and built in accordance with the Machinery Directive 2006/42/EC and the EMC Directive 2014/30/EU, with electrical equipment to EN IEC 60204-1 and EN IEC 61439. Welded fabrication follows EN ISO 3834-2 welding quality and EN 1090-2 EXC3; the coils are hydrostatically tested at 14 bar in our factory. Vimpo is certified to ISO 9001, ISO 14001 and ISO 45001.

High Efficiency

The three-pass coil design extends the residence time of the flue gas in the heater and lowers chimney losses. For every size and fuel the burner is selected to deliver full load at a minimum efficiency of 85%; two-stage or modulating operation saves fuel at part load as well. The heater body is insulated with 50 mm rock wool.

High-Quality Components

The coil is made of EN 10216-2 P235GH seamless cold-drawn steel tube, the body of P265GH / P295GH / P355GH pressure vessel plate. Danfoss is used for pressure measurement, Schneider Electric or Eaton for switchgear and Weidmüller for terminals; the panel is rated IP54 indoors and IP55 outdoors.

Minimum Downtime

The circulation pump is our own Vimpo VKY, with a mechanical seal for high-temperature service and spare parts supplied directly by Vimpo. Standard components that are easy to source worldwide, factory-tested single-package delivery and service support from Ankara, Herford (Germany) and Pune (India) keep breakdown and maintenance stops short.

230 °C Operation and Fuel Options

The heaters are designed for 230 °C operation, with a design temperature of 320 °C and a design pressure of 6.3 bar. Every size is supplied with a diesel, natural gas or heavy fuel oil burner.

One Package

The heater is delivered with the Vimpo VKY circulation pump, expansion tank, degasifier, control panel with automatic temperature and pump control, and chimney; only the connections are made on site.

Thermal Oil Heater Models

The VTH series is built in five sizes. Width × height is 2,240 × 2,400 mm on all sizes.

1. VTH-500 Thermal Oil Heater

500,000 kcal/h (582 kW). DN80 inlet / outlet, VKY 32-200 pump (7.5 kW), length 4,270 mm, weight 4,600 kg. For small tank farms and emulsion plants.

2. VTH-1000 Thermal Oil Heater

1,000,000 kcal/h (1,163 kW). DN80 inlet / outlet, VKY 65-200 pump (15 kW), length 5,270 mm, weight 6,200 kg. The most preferred size — for bitumen storage sites, asphalt plants, emulsion and PMB plants.

3. VTH-1500 Thermal Oil Heater

1,500,000 kcal/h (1,745 kW). DN100 inlet / outlet, VKY 80-200 pump (37 kW), length 6,270 mm, weight 7,800 kg.

4. VTH-2000 Thermal Oil Heater

2,000,000 kcal/h (2,326 kW). DN100 inlet / outlet, VKY 80-200 pump (37 kW), length 7,000 mm, weight 9,300 kg.

5. VTH-3000 Thermal Oil Heater

3,000,000 kcal/h (3,489 kW). DN125 inlet / outlet, 2 × VKY 80-200 pump (37 kW), length 8,700 mm, weight 12,500 kg. For large terminals and plants with many consumers.

Fuel Versions

• D — Diesel: two-stage or modulating diesel burner, carbon steel chimney.
• NG — Natural gas: natural gas burner, CE marked stainless steel double-wall insulated chimney (EN 1856-1).
• HF — Heavy fuel oil: heavy fuel oil burner with fuel preheater, carbon steel chimney.

The chimney height is 5 m on the VTH-500 and VTH-1000, and 10 m on the VTH-1500, VTH-2000 and VTH-3000.

Standard Scope

• Insulated heater: 50 mm rock wool, 1 mm galvanized sheet cladding
• Vimpo VKY circulation pump
• Expansion tank and degasifier
• Control panel with automatic temperature and pump control
• PT100 at inlet and outlet, Danfoss pressure sensors, high-temperature limit thermostat
• Burner and chimney (according to the fuel version)
• Factory tests, technical data sheet, CE declaration of conformity and operating manual

Where Are Thermal Oil Heaters Used?

Thermal oil heaters are used in every process that needs high, stable temperatures. Vimpo VTH heaters are designed especially for the bitumen and asphalt industry:

• Asphalt plants: bitumen tanks and jacketed feed lines to the burner
• Bitumen storage: tank coils and jacketed lines in bitumen tanks and bulk bitumen storage sites
• Emulsion production: thermal oil heated bitumen emulsion plants (VEP-T)
• PMB production: mixing tanks and mill line in polymer modified bitumen plants
• Bitumen melting plants:big bag and drum bitumen melting systems
• Refineries: bitumen and heavy product tanks and transfer lines
• Bitumen terminals: tanker loading and unloading lines, storage tanks
• Chemical and process industry: heating of reactors, dryers, presses and heat exchangers

Advantages of Thermal Oil Heaters

• Safety: 230 °C operation without the high-pressure risk of steam systems; protected by PT100, pressure sensors and safety interlocks.
• Certification: CE marked, manufactured to EN ISO 3834-2 and EN 1090-2 EXC3, coils tested at 14 bar.
• Efficiency: minimum 85% efficiency with three passes and a correctly selected burner; two-stage or modulating operation at part load.
• High-quality components: seamless P235GH coil, Danfoss, Schneider Electric / Eaton and Weidmüller.
• Minimum downtime: our own pump, standard components, factory testing and fast service support.
• No corrosion or scale: no water treatment, blowdown or scaling; no freezing risk during winter stops.
• One package: heater, pump, expansion tank, degasifier, panel and chimney delivered together.

Frequently Asked Questions About Thermal Oil Heaters

How Does a Thermal Oil Heater Work?

The circulation pump continuously moves the oil through the heater coil and the consumers. The burner starts when the outlet temperature falls below the set point and stops or reduces its output when the set point is reached. The flue gas leaves through the chimney after three passes. The oil, having released its heat at the consumers, returns to the heater through the degasifier; the expansion tank at the highest point of the circuit takes up the volume change.

How to Use a Thermal Oil Heater?

The circuit is filled with oil and vented; the circulation pump is started and its direction of rotation and pressure are checked. At first commissioning the temperature is raised step by step and the moisture in the oil is released through the degasifier. In operation the operator only selects the set temperature; the burner and pump are controlled by the panel. When stopping, the burner is switched off first and the pump keeps running until the heater has cooled down — stopping the oil in a hot heater degrades the oil. Vimpo carries out commissioning and operator training on site.

How to Select the Right Thermal Oil Heater?

• Heat demand: the heat losses and initial heat-up demand of all consumers (tanks, lines, plants) are added up; the required heat-up time determines the heater size.
• Fuel: NG if natural gas is available on site; otherwise diesel or heavy fuel oil.
• Flow and line size: the number of consumers and distances determine the pump and line selection.
• Growth margin: a reserve is left for tanks or plants to be added later.

Send us your requirements and we will size the right VTH model together.

How Much Fuel Does a Thermal Oil Heater Consume?

Fuel consumption at full load, calculated at 85% efficiency:

• VTH-500: 58 kg/h diesel · 71 Nm³/h natural gas · 61 kg/h heavy fuel oil
• VTH-1000: 115 kg/h diesel · 143 Nm³/h natural gas · 123 kg/h heavy fuel oil
• VTH-1500: 173 kg/h diesel · 214 Nm³/h natural gas · 184 kg/h heavy fuel oil
• VTH-2000: 231 kg/h diesel · 286 Nm³/h natural gas · 245 kg/h heavy fuel oil
• VTH-3000: 346 kg/h diesel · 428 Nm³/h natural gas · 368 kg/h heavy fuel oil

Because the heater mostly runs at part load in normal operation, actual consumption stays below these values.

What Determines Thermal Oil Heater Prices?

Thermal oil heater prices depend on the heater capacity, fuel type and burner, chimney type (carbon steel or CE marked stainless steel), the number of pumps and the expansion tank, degasifier and panel equipment in the scope. For a fair comparison, look not only at the heater price but also at efficiency, operating cost and after-sales support. Contact us for a price by model and fuel.

How is Thermal Oil Heater Maintenance Performed?

• Daily: outlet and return temperatures, pump pressure, expansion tank level and leak check at flanges, valves and pump seals.
• Periodically: burner service and combustion adjustment, filter cleaning, testing of the safety thermostat and pressure sensors.
• Annually: laboratory analysis of the thermal oil (viscosity, acidity, flash point), cleaning of the flue gas side and chimney.
• Oil change: when the analysis shows that the oil has reached the end of its life; different oil types are not mixed.

Vimpo provides spare parts and after-sales service support for the VTH series.

What Safety Measures Should Be Taken with a Thermal Oil Heater?

• Hot surfaces: lines and equipment at 230 °C must be insulated; heat-resistant gloves and workwear must be worn.
• Leaks and fire: hot oil soaking into insulation can ignite; leaks must be fixed immediately and fire extinguishers kept in the boiler room.
• Contact with water: water entering the circuit causes sudden boiling and overflow; keep water out of the circuit during filling and maintenance.
• Safety interlocks: pump, level, pressure and temperature interlocks must never be bypassed.
• Chimney and combustion: check the burner combustion setting and chimney draught regularly.

Common Problems with Thermal Oil Heaters

• Burner does not start: the pump is not running, the expansion tank level is low, differential pressure is insufficient or the temperature limit has tripped.
• Temperature does not rise: burner setting, fouled flue gas side or heat demand above the heater capacity.
• Foaming or steam in the expansion tank: water or moisture in the circuit; raise the temperature step by step and release the moisture through the degasifier.
• Fluctuating pump pressure: air in the circuit, a clogged filter or insufficient suction pressure.
• Oil thickening or darkening: overheating or oxidation; have the oil analysed.

Request a Quote for a Thermal Oil Heater

Send us your heat demand, fuel type and site conditions; we will recommend the right VTH model and send the technical data sheet and price quotation. Contact us, write to info@vimpo.com or call +90 312 354 85 09.