Baker Hughes PanaFlow Z1G, Руководство пользователя

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Chapter 1. General information
1.1 Theory of operation
The PanaFlow Z1G/Z2G Process Gas Flowmeter system uses
ultrasonic transit-time technology. A brief description of
transit-time theory follows. For more information about the
theory, and the use of Panametrics ultrasonic flow meters for
measuring flow, please refer to Ultrasonic Measurements for
Process Control by L.C. Lynnworth (Academic Press, 1989).
1.1.1 Transit-time method
The transit time technique uses a pair of transducers, with
each transducer alternately sending and receiving coded
ultrasonic signals through the fluid. When the fluid is flowing,
signal transit time in the downstream direction is shorter
than in the upstream direction. The difference between
these transit times is proportional to the flow velocity. The
PanaFlow Z1G/Z2G Process Gas Flowmeter measures this
very small time difference and, using various digital signal
processing techniques combined with programmed pipe
parameters, determines the flow rate and direction.
1.1.2 Transducers
When in a transmit cycle, transducers convert electrical
energy into ultrasonic pulses and then convert the ultrasonic
pulses back to electrical energy when in a receive cycle. In
other words, they act like loudspeakers when transmitting
the signal and like microphones when receiving it. They
perform the actual data transmission and collection, thus
interrogating the flow.
1.2 Multi-path design
Multi-path ultrasonic flow meters are designed to
accommodate more than one pair of transducers to
interrogate the flow field in different locations and more
accurately determine the actual flow rate. The PanaFlow
Z1G/Z2G Process Gas Flowmeter system is available in
either a 1-Path or 2-Path configuration. For the 2-Path
configuration, the measurement paths are located either at
Diametrical path or at Midradius configurations. In addition
to the flow transducers, the PanaFlow Z1G/Z2G Process Gas
Flowmeter can befitted with optional temperature and
pressure transducers to permit mass flow measurements.
1.3 Flow profile
One of the main factors affecting an ultrasonic flow
measurement is the flow profile. If the flow profile is known,
mathematical modeling of the flow and the relationships
between the raw data of the two paths can be made.
Maintaining a constant flow-profile shape across all flow
velocities, pipe sizes and upstream flow disturbances can
be difficult. For this reason, Panametrics has tested the
PanaFlow Z1G/Z2G Process Gas Flowmeter under various
conditions in an effort to determine its operational limits.
1.4 Unpacking
The PanaFlow Z1G/Z2G Process Gas Flowmeter is typically
packaged in a wooden crate, the size of which will depend
on the size of product ordered. The flowcell is secured by
several 2x4 wood blocks to prevent shifting during transit.
Simply remove these 2x4 braces to unpack the system. For
local-mount systems the transmitter electronics enclosure
is installed directly on top of the flowcell via an adapter.
For remote-mount systems the transmitter electronics
enclosure and the remote cable may ship in a separate
package.
1.5 Inspection
Prior to installation, inspect all materials to be used in the
installation:
• Gaskets - check for cracks, tears and over compression
• Nuts and Bolts - check for damaged threads and for
debris
• RF Flange Faces - check for damage to serrations that
may cause gaskets to not seal properly.
In general, check for anything that may prevent safe
operation of the equipment.
IMPORTANT:
If pipes are shipped pre-assembled as a single section,
care should be taken to inspect and check the bolts and
gaskets.
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