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 FIGURE 5-4.
Orifice Meter With Flange Taps
5.1.1 Orifice Flanges. Special orifice flanges are the most commonly
recommended method for meter installation. The pressure taps are drilled into
the flanges themselves, which are welded onto the pipe. The orifice is
inserted and secured between the two flanges (Figure 5-4).
5.1.2 Carrier Rings. Carrier rings are the second q ost common method of
orifice plate installation. Pressure taps, typically corner taps, are drilled
into the rings and the orifice plate is inserted between the rings. The rings
and orifice are then inserted between existing pipe flanges (Figure 5-5).
5.1.3 Existing Flanges and Special Taps. The orifice plate can be inserted
between existing pipe flanges and pressure taps drilled into the pipe. This
method was widely used in the past, but has since been replaced with the more
standardized orifice flanges (paragraph 5.1.1).
PREFABRICATED METER ASSEMBLIES
6.
6.1 Insertion Fittings. Some manufacturers produce a dual-chambered,
hand-operated, gear-driven apparatus which allows one person to change an
orifice plate. An insertable plate can be changed without system shutdown or
removal of flanges. The mechanism is constructed so that there is no fluid
spillage or loss and no danger to the operator. For specific product
information consult manufacturers of fluid flow metering equipment.
6.2 Recommended Applications. Prefabricated meter assemblies are
Particularly suited for low flow in pipes of less than 2 inches in diameter"
A common application is for measuring natural gas flow to specific pieces of
equipment.
5-8
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