Currently, there are two main types of devices for continuous measurement of airflow in HVAC systems (ASHRAE 2013a): pitotmetric measuring stations and orifice meters
The location, size and construction of the orifice meter
pipe taps can affect the meter's accuracy.
A rotameter, specially designed for diesel engine exhaust gas was used to measure the flow rate of the exhaust and the same is verified using an orifice meter
. A settling tank was used to minimize vibrations of the gas and a filter with wire mesh filled with glass wool arrests soot partials entering in to the engine.
However, although wet gas flow DP has a significantly higher standard deviation than the dry gas flow DPs, massed orifice meter
wet gas data sets have shown that the average DP is still repeatable and reproducible.
Similar to orifice meters
, Venturi and other pressure-differential type flow meters are susceptible to the same buildup of hydrates within the meter bodies and impulse tubing.
Elbows, branch lines, and constricting valves can distort the velocity and turbulence of the flow entering an orifice meter
. The typical solution, as per existing gas-industry standards, is to install a bundle of pipes called a flow conditioner seven pipe diameters upstream from the orifice plate.
Table 1 is color coded to illustrate that most operational errors in orifice meter
measurement are biases that can be either positive or negative, depending on the specific operating condition that creates the error.
It should allow field technicians to electronically report orifice meter
tests and calibrations, orifice plate inspections, gas use/loss, meter status changes, equipment inventory, manual meter reading and more.
Weymouth introduced the orifice meter
a century ago.
During the test, the fuel was measured with an orifice meter
. The equation for converting the orifice meter
fuel readings (static pressure, temperature and differential pressure) used was the standard ASME MFC-3M 1989 equation for flow through an orifice meter