Measuring Steam via a Differential Pressure Meter
Note
Steam fluid types are only supported for flow rate calculation methods using orifice meters or cone meters.
Best Practices
The QRATE Scanner 3300 calculates steam flow through outputs from a MVT connected to a differential pressure meter
in accordance with IF-97, AGA-3, and ISO-5167 industry standards. For optimum performance, ensure that the installa
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tion complies with the following industry recommendations:
Condensate Pots
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A condensate pot for a small-volume transducer like the QRATE Scanner 3300 MVT can be a simple pipe tee,
oriented so that one port extends downward (into the cold leg), the opposite port extends upward and is closed by a
pipe cap or blowdown valve, and the tee extends horizontally into the hot leg.
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The pots should be the highest point in the system.
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The pots should be mounted at the same level, and one or both should be adjustable vertically to remove zero shifts in
the differential pressure measurement.
Hot Legs
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Hot legs should be large diameter (1/2 in. recommended)
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Hot legs should be as short as possible. If these sections must be more than 1ft in length, insulate them.
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Elbows and bends should not form any traps in which liquid can accumulate.
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Hot legs should be sloped along their entire length to allow liquids to drain back into the pipe.
Cold Legs
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Cold legs should enter the multi-variable sensor through its bottom ports. Side port installation is also available.
Contact your sales representative or technical support for assistance with side port installation.
•
Cold legs should not be insulated and should be a minimum of 2 ft in length to allow proper convection cooling of
the process fluid to below 120 °F. The nominal rate of cooling is 100 °F/ft, with an ambient temperature of 70 °F.
•
If the cold leg must be installed horizontally, ensure a slope of approximately 1 in./ft to allow air bubbles to float up
into the pots.
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Elbows and bends should not form any traps for air bubbles.
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Cold legs should be filled with a suitable antifreeze. Dibutyl phthalate is recommended.
Antifreeze
Dibutyl phthalate (DBP) has the following advantages over glycol antifreeze:
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Does not mix with water, and therefore does not become dilute over time; its specific gravity does not shift.
•
It is slightly denser than water, so it will stay in the pot permanently.
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It is non-flammable.
•
It is much less toxic than glycol.
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It is available from industrial suppliers.
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Section 2
QRATE Scanner 3300 integrated control flow computer
