Test & measurement
Aircraft de-icing and pressure measurement Y
ou know the moment when you have to brush the snow off your car and scrape the
ice from the windows? The same process is also necessary in aircraft when it begins to snow or when ice forms. Aircraft de-icing is used in these cases to free the aircraft from ice and snow. De-icing takes place at a specially
designated de-icing area and is scheduled directly before the plane is set to take off to protect it from re-icing for as long as possible. First and foremost, de-icing is mandatory for safety reasons because ice and snow not only increase the plane’s weight, but also impair its aerodynamics.
A focus on liquids logistics De-icing is performed with a liquid formed from at least 50 per cent glycol plus water. In total, there are four different types of fluid that can be used for this. At Schiphol airport in Amsterdam,
the mixtures used for de-icing are stored in large tanks and pumped into so-called “Safeaeros” before being used on planes. This is a type
of spray vehicle which was specifically developed for this purpose. At Schiphol airport, four of these Safeaeros are used per aircraft – two on the front side of the wing and two on the rear side of the tailpiece. In order to integrate the de-icing
process as smoothly as possible into the airport’s operations, Rob Luttge from the company RMM is responsible for the implementation of the overall process at Schiphol airport. Along with logistics and quality control this also includes coordinating the filling of the Safeaeros on behalf of KLM.
MeAsuring under overpressure In order to guarantee that there is enough de-icing fluid at all times, a solution was sought in collaboration with KELLER Holland in order to automate the measuring of the tank fluid levels. This is easier said than done, because an overpressure of 2.5 bars is required to pump the fluid from the tanks to the Safeaeros. In order to measure the filling level of the tanks, each tank was fitted with a PD-33X pressure transmitter which carries out a differential pressure measurement. The liquid column in the tank is
The PD-33X pressure transmitter
The ADT1
defined by the difference between the dominant pressure above the fluid (= overpressure of 2.5 bars) and the pressure measured at the bottom of the tank. Thanks to another inserted ADT1, this information can be sent to any desired end device via a LoRa signal, which means that on-site monitoring is no longer necessary.
KELLER
keller-druck.com
50 February 2021 Instrumentation Monthly
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