|For the mechanical flow meters the following measuring principles can be distinguished:|| |
|Proven in virtually any application Variable Area Flow Meters have the largest world-wide number of installations. From a highly economical solution without additional auxiliary energy to a wide range of low flow liquid, gas and steam applications with electrical signal output (HART®, PROFIBUS).|
They are indispensable where high pressure and/ or high temperature operating conditions exist.
The Variable Area Flow meter is an instrument for measuring the flow rate of liquids and gases in pipelines. It includes a vertical, upward expanding metering tube through which the fluid to be metered flows from the bottom to the top, and in which a movable float is located. This float rises as the flow rate increases in such a manner that the hydraulic forces are always balanced by the opposing force due to the float weight, which is always constant regardless of the flow rate. The height of the float is a measure of the flow rate. The flow rate value can be read from a scale.
|The sensor of this measurement instrument consists of a baffle plate with balance beam and operates according to the design deflection method. The baffle plate causes a back-pressure in the medium and the balance beam is deflected. This movement is transmitted via the beam to the indicator mechanism using a bellows bushing. A gear unit converts the deflection of the balance beam into a rotary movement of the pointer. |
The pointer movement is damped by an eddy-current brake. The bellows bushing isolates the measured medium from the display unit.
|Orifice flow meter primarily consists of an orifice plate as the sensor and a float as the display element. A differential pressure is produced across the orifice plate which is fitted in the main stream between two flanges in the piping. In a bypass this differential pressure produces a volume flow in a rotameter. The height of the float indicates the flow rate. The flow is read at the position of the floats widest diameter.|| |
|The fitting contains a measuring flap which can be rotated around an axis. At rest (i.e. no flow), the flap closes the pipeline by its own weight. As soon as there is a flow, the flap is lifted depending on the flow velocity. The respective flow quantity can be read directly in transparent liquids from the position of the flap. The bottom edge of the flap is the reference edge.|
In turbid or opaque liquids, the movement of the flap is transmitted by a magnet mounted on the flap to an external mechanical pointer, and the flow is displayed on a scale. The scale and pointer are protected against external effects and contamination by a Plexiglass or glass pane.
The scale has the standard dimension m3/h, and can be calculated for an application-specific medium and operating pressure/temperature if the density differs from 1 kg/l (62,43 lbs/cu.ft). Special scales are available at extra charge. An inductive contact is triggered by a contact lug mounted on the pointer.