Lindab DRU - Measuring Bends; MBU;MBFU Assembly; MBU;MBFU Measurement; MBU;MBFU Systematic Error

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Measuring bends
MBU, MBFU
Assembly
In order to fulfil the requirements for air-tightness class D, the bends must be installed as per ‘Assembly Instruction
Lindab Safe’.
The bends allow 50 mm duct insulation without the measuring points being hidden. For 100 mm insulation, an insulation
cup, IK, is available.
Measurement
By measuring the pressure difference ∆p in Pa at the measuring points, you can achieve a flow q in l/s using the equa-
tion on the devices.
The specified flows only apply for air with a density of 1.2 kg/m
3
. For air of another density (r
other
) the flow (q
other_density
)
is achieved as per the formula:
q
other_density
= q
equation
×
ρ
other
1,2
Device
Dimension
mm
k-factor
MBU
100 6.85
125 10.3
160 17.0
200 26.3
250 41.7
MBFU
315 65.0
400 115
500 179
630 283
Systematic error
Straight stretches are required in order to achieve flows as per equations with specified accuracy. The systematic error
m
2
is 5% and 10% below the minimum requirements for straight stretches as specified.
Maintenance
The measuring bends normally don't require any maintenance.
Cleaning
The device does not limit cleaning opportunities.