Monitoring ventilation on LNG ships (liquified-natural-gas ships)

Measuring air exchange in engine rooms on ships


Process data

Measuring task:
Monitoring forced ventilation on LNG ships

Measuring point:
In ventilation pipes

Measuring range:
0.5 … 20 m/s

Process pressure:

Process environment
Typically ATEX zone
salty sea air
partly SIL2 required
dislocation due to motion of sea


Your advantage

The adherence to the required gas exchange is monitored by the measurement

With these Höntzsch sensors you can measure permantently and safely all the time 

The sensors are also available for the use in ATEX zones up to 0/1

Special robust design with no moving parts


According to the International Maritime Organisation IMO the limit of sulfur in fuels was considerably limited in 2020, making the sulfur-free fuel LNG (liquified natural gas) more significant. The first big cruise ships are equipped with future technology powered with LNG. The use of LNG instead of commonly used fuel oil lowers emissions remarkably without having to use an additional, expensive pollutant emission control system (so called Scrubbers). Ships powered with LNG not only reduce the emission of sulfur oxide entirely but also of nitrogen oxide and fine dust. LNG ships also reduce carbon dioxide emissions. To ensure safe operation of the environmentally friendly LNG drive it’s required to monitor ventilation of the engine rooms. A so called forced ventilation must be a given. Controlled engine room ventilation prevents the rise of potentially dangerous atmospheres. The harsh environment at sea demands high standards from the sensor technology which limits the functionality of many measuring principles. Höntzsch vortex sensors are perfectly suited for monitoring forced ventilation and they’re already tested in use at sea.

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Shipping - environment and climate factor

Annexe VI of the MARPOL convention of the IMO (International Maritime Organization) regulates the protection from air pollution through ships‘ exhaust gases. Soon the use of polluted fuel oil will be part of the past. The cheapest fuel in shipping is fuel oil which many ships still use. When docking in European harbours according to EU regulation they have to burn a less polluted fuel like marine diesel. When burning fuel oil like marine diesel sulfur oxide, nitrogen oxide and carbon dioxide can arise. Sooty particles, fine dust and even heavy metals escape through the exhaused air into the air. These numbers show the severity of those emissions; the shipping industry causes about 3% of CO2 emissions caused by humans worldwide. On top of that it is also responsible for about 15 % of global nitrogen oxide emissions. One way out are LNG drives for ships.

Why are more LNG ships built? (LNG = Liquified Natural Gas)

Given the high emissions, the International Maritime Organization – a special agency of the United Nations – decided to gradually limit this pollution. The limit values were reduced in several stages – last time in 2020 to a maximum sulfur content in the fuel of 0.5 %. Therefore new ships are equipped with dual fuel marine diesel or LNG motors or they’re additionally equipped with complex, expensive pollutant emission control systems (scrubbers). The number of ships with LNG-drives (with Liquid Natural Gas als fuel) has been rising. In 2018 the AIDAnova was the first LNG cruise ship worldwide, built and put into service on the Meyer Werft in Papenburg. Meanwhile more and more harbours have the infrastructure for LNG ships.


Why do ships with LNG drive need special ventilation monitoring?

The engine room of Liquified-Natural-Gas ships and all other rooms connected to the gas system require forced ventilation. Staying below the lower explosion limit (LEL) must be ensured. 30 air changes per hour, so every 2 minutes is required in the LNG ship’s engine room. Air suction as well as additional air regulation is a must! The working areas of the LNG ventilation system, no matter if it’s an LNG tanker, LNG container ship or LNG cruise ship, there’s a good reason for them to be defined as ATEX zones. There are also highest demands for ventilation monitoring and air exchange in the LNG refuelling method and the tank rooms of LNG ships.


What is forced ventilation?

If gases that are hazardous to health, explosive or aggressive are possible to occur in closed rooms due to the process, multiple and complete exchange of air is necessary via the forced ventilation.
Ventilation can happen through natural air exchange or technical ventilation with fans. In both cases measurements have to be recorded. In case of failure and disturbance in the ventilation a warning comes up or the process is turned off. That’s why the flow measuring instruments are connected to the central process control. The measuring value of ventilation or exhaust flow can also be used for energy-saving control of the fans. Depending on the process and the thereby produced gas more or less ventilation is necessary. The regulated „dosage“ of supply and exhaust air optimises the energy consumption caused by ventilation measures and thus also serves to protect the climate.


Höntzsch sensors to monitor ventilation on LNG ships

The use at sea requires very robust and reliable measuring technology. All areas of application are defined as ATEX zones. Höntzsch vortex flow sensors are perfectly suited für the use on board to monitor ventilation measures. Not only in the engine room of an LNG freighter! Passengers on an LNG cruise ship are also happy about optimally ventilated cabins. The special design with no moving parts and the accreditation for ex-zone 0/1 as well as SIL2 are just some of the benefits.
The first Höntzsch flow sensors have already crossed the equator. They monitor air exchange to full satisfaction of dockyards and operators.