API RP 551:1993(2007) pdf download
API RP 551:1993(2007) pdf download.Process Measurement lnstrumentation.
c. A high flow rate for a given linc size is obtainable.
d. signs for scry low flow rates arc available.
c. Turbine meters arc available for a wide rangc of temperature and pressure ratings.
f. Specially designed turbine mctcrs are available for bidirecuonal flow.
Turbine meters are limited by the following characteris
a. They are susceptible to wear or damage if the process stream is dirty or nonlubricating.
b. They are susceptible to damage from overspeed and pulsing flow.
c. They require maintenance and may require return to the manufacturer for recalibration after a bearing change or other maintenance.
d. Their rangeahility is affected by high viscosity and low density.
e. Their cost is relatively high.
f. They require strainers.
g. Provers are required to maintain calibration accuracy.
2.3.4.2 Installation
2.3.4.2.1 General
Turbine meters are installed directly in the process line. The line should be relatively free from vibration. Meters with integrally mounted, direct-reading registers should he positioned so that they can be easily read and maintained.
Turbine meters are normally installed in horizontal lines but may be installed in vertical upilow lines, It is necessary to specify the position in which the meter is to be calibrated. Calibration for the installed position is required.
2.3.4.2.2 Piping
The accuracy and repeatability of measurements from turbine meters depend on the upstream and downstream piping. In addition to sufficiently long straight runs upstream and downstream, straightening vanes are required for high accuracy.
2.3.4.2.3 Bypass Piping
The need for bypass piping for turbine meters is determined by the application. It may be necessary to isolate or disassemble the meter for maintenance purposes. In continuous-service applications, where shutdown is considered undesirable. block and bypass valves must be provided to permit process operation while the meter is being serviced. Conditions that may necessitate disassembly of the meter include damage caused by foreign material, wear, or buildup of solids. If the meter is bypassed, it should he in the main run, with the line-sue block valves placcd beyond the meter’s required upstream and downstream piping runs. The bypass valves must be capable of positive shutoff to prevent mcasurcmcnt errors. Thc bypass piping installation should be free draining.
Bypasses arc not permitted for custody transfer applica
2.3.4.2.4 Strainers
All turbine meter installations should have strainers to present damage to the meter rotor. The strainer must be capable of removing particles of a site that might damage the rotor and bearings. The strainer should be located upstream of the required meter run.
2.3.4.3 Electrical Installation
The signal troni a turbine meter is a low-level pulse. which makes it especially susceptible to noise pickup. Shielding of signal wires is recommended to eliminate spurious counts. If the transmission distance is more than 10 feet (3 meters). a preamplifier is recommended. The manufacwrer’s instructions should he consulted for details.
2.3.4.4 Start—Up and Calibration
Care must he taken to prevent damage to the turbine meter at initial start-up. The meter should be placed in service only after the process line has been flushed and hydrostatically tested. If strainers are used, they should he cleaned after flushing and periodically during operation. Flow should be introduced slowly to the meter to prevent damage to the impeller blades as a result of sudden hydraulic impact or over- speed.
The calibration factor, expressed in electrical pulses generated per unit volume of throughput. is normally called a K (meter) factor. The K factor depends on fluid conditions, is determined when the flowmcer is calibrated, and is inherent for the particular meter rotor. K factors of meter rotors vary within the same meter body site. No field adjustment may be made to the primary sensor.
