UFC 3 -430-11
14 February 2001
5-2.8.5 Elbow Meters. Elbow meters may be used for measuring relative flow rates
and where absolute readings a re not required. Elbow meters provide good repeatability
and can be installed using an elbow in the regular piping.
5-2.8.6 Pitot Tubes. Use pitot tubes for large ducts where high accuracy and
rangeability are not required and where pressure drops must kept low.
5-2.8.7 Rotameters. Rotameters are used for flow measurement in small lines such
as fuel oil and purge air. Use glass tube rotameters only for purge air. Otherwise use
armored type rotameters.
Recommended practices on rotameters are defined by ISA-RP16.1, 2, 3,
Terminology, Dimensions and Safety Practices for Indicating Variable Area Meters
(Rotameters, Glass Tube, Metal Tube, Extension Type Glass Tube), ISA-RP16.4,
Nomenclature and Terminology for Extension Type Variable Area Meters (Rotameters),
and ISA-RP16.5, Installation, Operation, Maintenance Instructions for Glass Tube
Variable Area Meters (Rotameters).
5-2.8.8 Magnetic Flowmeters. Magnetic flowmeters provide obstructionless flow,
good accuracy, and a good turndown ratio. They have the disadvantage, however, of
being costly, large, and heavy.
5-2.8.9 Positive Displacement Meters. Use positive displacement meters only for
high accuracy totalizing where measurement of flow rate is not required. These meters
would typically be used for the measurement of fuel oil, fuel gas, and feedwater flow.
Furnish a removable strainer installed upstream of the displacement meter.
5-2.8.10 Turbine Meters. Turbine meters are extremely accurate and have a high
turndown ratio. They do, however, present a high pressure loss to the system. Refer to
ISA-RP31.1, Specification, Installation, and Calibration of Turbine Flowmeters for
additional information on turbine meters
5-2.8.11 Vortex Meters. Vortex meters are extremely accurate, have a high turndown
ratio, and present a low permanent pressure loss to the system.
5-2.8.12 Annubar Meters. An annubar meter is a rigid tube device that measures
flow by producing a pressure drop signal that is proportional to the square of the flow
rate. Multiple sensing ports along the tube average the velocity profile of the fluid.
Meters of this type provide less permanent system pressure drop than orifice plates and
can be used for all applications that involve clean fluids. Measurement accuracy and
repeatability is good and turndown ratios of 4:1 to 11:1 can be achieved depending on
meter tube design.
5-2.9
Temperature Measurements. Temperature instruments include
thermocouples, resistance-temperature detectors (RTDs), filled bulb systems, and
bimetallic thermometers.
5-6
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