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General enquiries
Tel. +45 7916 6666


Semco Maritime
Esbjerg Brygge 30
DK- 6700 Esbjerg

Helideck Firefighting Systems (DiFF)


The DiFF System serves as a firefighting solution designed for helipads/helidecks. Depending on its setup, the DiFFS can function either automatically or manually.

Introduction to the DiFF system

On system activation; a valve operates – allowing water to flow through an in-line foam inductor, thereby discharging a correct admixture of foam/water solution (i.e. 1% or 3%) through an array of nozzles installed on the helipad / helideck, thus providing an effective spray distribution covering the entire deck surface.

The DiFF system is designed to meet performance criteria as per applicable standards such as:

  • NFPA-418
  • UK-CAA-CAP437
  • CAP-1264
  • HSAC-RP161
  • ICAO, NORSOK etc.

DiFF Systems are available with self-contained skids suitable for normally unmanned installations. 

Water only DiFFS are available when installed with passive fire-retardant type aluminium helidecks

DiFF Nozzles

Marsol K3GS and ULP-40 series nozzles are designed to be used on Deck Integrated Fire Fighting Systems (DIFFS). An array of these nozzles installed on the helipad / helideck provides an effective spray distribution covering the whole deck surface for a range of weather conditions.

The nozzles are manufactured with orifices drilled for horizontal and vertical flow components. The nozzles do not ‘pop-up’ on the deck and instead, discharge foam from their fixed position.

The precise number and layout of nozzles are dependent on the specific helipad/helideck type, the “D” value of the deck, the flow rate of the nozzle and its coverage.

As required by the applicable standard, a sufficient overlap of the horizontal flow components is achieved when all nozzles are discharging during system operation. Due to the non-pop-up construction, the condition of a blocked nozzle is not relevant, as required in CAP-437.

If the vertical flow is blocked by a heavy object resting on the nozzle during system operation, foam will continue to flow from the horizontal orifices of the nozzle.

Nozzle Connections

K3GS and ULP-40 Series DIFF nozzles connecting pipe are supplied with either threaded, grooved or flanged end connections based of project requirement.