Urv: rh, H - r, Span (dp): r – Fujimoto Fuji Differential Pressure Transmitter FKK 4 User Manual

Page 54: Density h, Hspan (dp): r, Liquid level, h: liquid level change

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48

Pressure measurement (in case of gas)

Mount the transmitter above the process pipes to
preventing moisture from entering the inside of
transmitter.

Level measurement

(1) In case of wet leg:

For measurement, connect the highest liquid level tapping of tank with the low pres-
sure side of transmitter, and the lowest liquid level tapping of tank with the high
pressure side of transmitter.

< Level calculation formula >

LRV: rH

2

- r

0

H

1

URV: rH

2

+ r

1

h - r

0

H

1

Span (DP): r

1

h

LRV: Low limit of measurement (0% point)
URV: High limit of measurement (100% point)
r

0

,r,r

1

: Density

H

1

, H

2

: Liquid level, h: Liquid level change

(2) In case of dry leg:

For an open tank, leave the low pressure side of transmitter open to atmosphere.

< Level calculation formula >

LRV: rH

1

URV: rH

1

+ r

1

h

Span (DP): r

1

h

LRV: Low limit of measurement (0% point)
URV: High limit of measurement (100% point)
r,r

1

: Density

H

1

: Liquid level, h: Liquid level change

Stop valve

Process pipe

Pressure source

Manifold valve

Impulse pipe

Atmospheric
air inlet

H

1

H

2

Max. liquid

level

Min. liquid

level

Condensor

ρ

0

ρ

Manifold
valve

High
pressure
side

Low
pressure
side

h

ρ

1

H

1

Max. liquid

level

Min. liquid

level

Manifold
valve

High
pressure
side

Low
pressure
side

Atomospheric
air inlet

h

ρ

1

ρ

5

6

(1) Protection is required to prevent dust from entering through the atmospheric

air inlet after installation of the manifold valve.

(2) If process pressure range is narrow (below 10kPa (1000mmH

2

O)), the follow-

ing should be considered.

• Pressure variation due to wind around atmospheric air inlet
• Temperature variation near process taps
• Difference in atmospheric pressure between process tap and transmitter

location.

To overcome this, provide atmospheric pressure-side pipe with a proper orifice
and consider accommodating the transmitter and atmospheric air inlet in a box.

Important

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