How do I determine the exact flashpoint of my oil?

It is important to know that light-ends are volatile and therefore, taking an open, hot sample of heat transfer oil provides a wrong result. Then, the sample shows a too high flashpoint and with this, a too positive result, although the flashpoint is possibly lower.

For the analysis it is most important to receive a representative and exact sample. This is ensured by a closed, cooled sampling technology.
In the NESS Sample Cooler (NPK40) the sample is cooled down by water to a temperature, at which light-ends cannot evaporate from the sample anymore. This ensures a representative analysis result.

Sampling takes place with a closed
and cooled sampling technology

What can I do to prevent the generation of light-ends?

There are some ways to counteract the generation of light-ends.

One of the solution approaches is the partial exchange of the heat transfer oil used. In this case, part of the oil is replaced by fresh oil, whereby a certain percentage of the generated light ends will be discharged out of the system. With this, the flashpoint will increase to a higher level for a short time. However, this solution does not replace a flashpoint management and is only a short-term solution, mostly in case of an emergency. In addition, in some circumstances, the oil change is associated with a standstill of the system and – depending on the oil used – it causes high running costs.

A widely used approach approach for driving the light-ends out of the thermal oil is the so-called boiling out of the system. Even in connection with the already mentioned problem of cavitation, the heat transfer oil systems are boiled out already before the initial commissioning to drive out possibly existing water. Later, this is also done during the running operation to drive out light-ends possibly occurred. With this, it is avoided that light-ends get into the pump housing as a gas bubble and cause damages. Mostly, this process of boiling out is simply repeated in regular intervals; however, this comes again with longer standstills.

Otherwise, in addition to the methods introduced above, light ends can also be driven out of the system by means of distillation. Correctly intergraded, this solution has the advantage that it can be carried out during the running operation of the system. In this procedure the light ends are solved out of the heat transfer oil and separated. With this, the above-mentioned active flashpoint management can be implemented.

Example for a flashpoint development without flashpoint management

An active flashpoint management as preventive action against light-ends?

Exactly! Only with an active flashpoint management you will have the possibility to minimise your risks in a way that continuous oil quality is ensured referring to the flashpoint also for a long time. Here, this durably acts against fluctuations. For users of large-size systems this is a great tool for the modern risk management.

By continuous driving out of light ends the flashpoint always remains at a high, safe level. This does not only reduce the risk of fire and cavitation itself, but with this it protects the whole system and the employees sustainably. Moreover, this reduces your operational costs caused by standstills or oil change for a long term — you will have more planning safety.

Example for a flashpoint development with flashpoint management

What is the difference between the active light-ends removal systems NALD250 and NALD250i?

Technically seen, the design of the two products is quite similar. These two solutions distinguish by the partial return flow of light-ends gases in the NALD250i. By additional returning of low-boiling gases in the distillation circuit of the system, the system becomes a pure turbo-remover. For this reason, compared to the normal NALD250, the light ends removal can run faster for up to 5x depending on the individual parameters, e.g. temperature, type of oil, and system size.

Due to this extremely efficient working principle the NALD 250i is further ideally suitable for the rotating operation of multiple separated thermal oil systems up to 400,000 litres of total volume.

Scheme of the partial return flow

What do I have to consider in the place of installation of the NALD250 / NALD250i? Which conditions must be met?

Principally, the light ends removal system should be installed in a well-ventilated area. The exhaust duct must safely lead into the open air and the deflagration flame arrester that comes with the system must be installed at the end. The area around this opening must be free from ignition sources.
The system is also suitable for outdoor installation. However, it should be roofed to protect it from weather, e.g. by a penthouse roof, to protect the components and the electronic circuits.

It should be connected to the flow line of the thermal oil system. The return flow in the thermal oil system can be led as desired.
With this, pay special attention to the following interface parameters:

Connection valve – thermal oil (inlet and outlet)Nominal diameter DN40
Cooling water valvesNominal diameter DN20
Thermal oil – flow2 – 4 bar
Thermal oil – return flow0 – 3 bar (max. 4 bar)
Recommended inlet temperature250 °C
Control air4 – 6 bar (g)
Nitrogen supply> 3 bar min. 99.0% N2
Cooling water0,5 – 1 bar
Three-phase connectionappr. 5 kW

What do I have to consider in the place of installation of the NLPA150 / NLPA250? Which conditions must be met?

Generally, the light ends removal system must be installed at least 2m above the highest point (expansion tank) to operate it using gravity. The nitrogen for the light ends removal system flows through a nitrogen anti-cavitation valve from the expansion tank.
Because the passive light-ends removal works without its own pump, the return flow and the flow of the distillation tank must be connected on the intake and outlet side of the primary circulation pump (in the return flow of the heat transfer oil heater).

It should be connected to the flow line of the thermal oil system. The flow and return flow with the primary circulation pump between them.
With this, pay special attention to the following interface parameters:

Connection valves – thermal oil (inlet)Nominal diameter DN25
Connection valves – thermal oil (outlet)Nominal diameter DN50 (NLPA150) / DN80 (NLPA250)
Cooling water valvesNominal diameter 3/4´´ (NLPW250)
Thermal oil – flowmin. 1 bar + static height of the expansion tank +
overpressure due to nitrogen blanketing
Thermal oil – return flow–
Recommended inlet temperature 250 °C
Nitrogen supplyVia expansion tank
Air-cooled (NLPA150 / NLPA250)15 – 30 °C
Cooling water (NLPW250)2 – 4 bar

How does the cooling of the condenser work for the NLPA? Are there any differences?

In case of the passive light ends removal with the NLPA150 / NLPA250, the condenser is cooled by an air-cooling system. Because it is installed on the building roof, the ambient temperature, which usually is between 15 °C and 30 °C, cools down the condenser of the light ends removal system.

Beside the air-cooled variant, the NLPA250 unit is also available as water-cooled variant (NLPW250), which makes it possible to use the system up to an oil volume of 110,000 litres. However, this solution is preferably applicable for smaller systems.

Does a passive light-ends removal system pay off as retrofitting or better not?

Generally, the integration of a light ends removal system in a thermal oil system is always an advantage. Due to the relatively simple, technical design (no additional pump, no additional control unit), pure original cost is lower. However, the fine adjustment of the system and the additional steel structure for the installation must be considered for the total cost estimate as well.

Due to its flexibility in integration and installation, an active light ends removal system is therefore optimally suitable for retrofitting. Because it has an integrated pump and its control system, its integration in existing system can be realized more efficiently.