Flow rate measurement device for a fire extinguishing apparatus

A fire extinguishing apparatus comprising a flow rate measurement device and an additive metering valve, wherein the flow rate measurement device is configured to control the additive metering valve in the fire extinguishing apparatus and for detecting a flow rate of an extinguishing agent,

• the flow rate measurement device comprising a control element arranged on a control rod, which control element has a substantially conical section, and a housing surrounding the control element, which housing comprises a hollow cylindrical control element seat at least in a contact section with the control element, the control element being received in the housing so as to be displaceable in an axial direction of the control rod, the position of the control element essentially depending on how much extinguishing agent is flowing through the flow rate measurement device, wherein the positioning of the control element relative to the housing is therefore directly correlated with an extinguishing agent flow rate,
• wherein the control element further comprises a cylindrical subsection which is positioned downstream of the conical section as viewed in a flow direction of the fluid to be measured, and which cylindrical subsection is adapted in terms of its cross-sectional contour to the hollow cylindrical control element seat so that the cylindrical subsection of the control element can be pushed into the hollow cylindrical control element seat without a gap, and in which cylindrical subsection of the control element at least one recess is also provided, which interrupts shell surfaces of the conical section and the cylindrical subsection of the control element,
• wherein the flow rate measurement device is configured such that in the event of an increased flow rate, the cylindrical section of the control element is lifted completely out of the control element seat,
• wherein the flow rate measurement device and the additive metering valve are configured such that in the additive metering valve, a quantity of an additive to be mixed to the extinguishing agent being conveyed in the flow rate measurement device is metered on a basis of an actual position of the control element and a desired proportion as a percentage of the additive to be mixed with the extinguishing agent being conveyed in the flow rate measurement device,
• wherein due to the at least one recess in the control element, when the cylindrical section of the control element is not lifted completely out of the control element seat, a change in the extinguishing agent flow rate results in a movement of the control element over a first distance, and when the control element is lifted completely out of the control element seat, the same change in the extinguishing agent flow rate results in a movement of the control element over a second distance, wherein the second distance is smaller than the first distance.