Air flow measurement grid

LAMTEC measuring grids determine the volume flow, mass flow and velocity of gaseous media. Their main use is flow measurement in ducts, above all of combustion air supplied to firing systems; with optional materials they can also measure flue gas flow. The medium must be a non-aggressive, non-explosive gas of known density. The grid geometry is adapted to each customer's conditions while keeping pressure loss low, and the LAMTEC calculation tool sizes LAMTEC transmitters or the customer's own transmitters for the given plant data.

Measurement is based on Bernoulli's equation. Parallel tubes with closed ends span the duct cross-section at right angles to the flow and form an open grid: openings in some tubes pick up the total pressure, while the others pick up the reference pressure. Each pressure is gathered in its own collecting tube and connection; the difference between them, the dynamic pressure, indicates flow velocity, and with a known duct diameter the volume flow follows from the square root of the reading. Since the whole cross-section is measured, poor flow profiles can be handled too; flow velocity has to be within 2 to 40 m/s.

The grid is fully welded from stainless steel; round versions come with or without flanges, while rectangular versions usually need none. It can be flanged, welded in or clamped onto a Jacob pipe system, and the differential pressure transmitter connects through a G1/4" threaded socket. Compared with orifice plates or venturi nozzles, pressure loss is very low and the straight inlet and outlet runs can be much shorter, so the grid is easy to retrofit in existing plants. In clean air it needs no maintenance; plants with heavy dust loads should allow access for cleaning, and the grid must not be used where sticky particles are carried in the air.