KROHNE PipePatro EN - Manual (Page 9)

DEVICE DESCRIPTION
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PIPEPATROL
www.krohne.com 02/2013 - 4002275001 - MA PipePatrol R01 en
2.3 Principle of Extended Real Time Transient Model (E-RTTM)
According to API 1130, leak detection systems can be categorised into external and internal
systems. External systems include acoustic sensors and sensing cables that are placed
alongside the pipeline. Due to the extremely high installation costs the use of external systems is
usually restricted to high risk areas such as nature protection areas and near rivers. Internal
systems are systems that perform leak detection based on measured parameters such as flow,
pressure and temperature.
PipePatrol is an internal system based on E-RTTM (Extended Real Time Transient Model) and
SMB (Statistical Mass Balance).
E-RTTM E-RTTM E-RTTM E-RTTM
E-RTTM is a combination of RTTM and leak pattern recognition by means of statistical analysis.
The fundamental principle is that RTTM is a series of algorithms that allow calculation of the
flow, based solely on pressure and temperature readings at the inlet and outlet of the pipeline.
To do this RTTM uses the conservation laws for mass, momentum and energy and the
thermodynamic state equations for pressure and enthalpy.
When applying RTTM algorithms, the flow is not only measured by flowmeters but also
calculated from pressure and temperature readings at the inlet and outlet. Subtracting the
calculated flow from the measured flow gives the flow residual. Combining the two flow
residuals gives the true flow residual (inlet minus outlet). The RTTM algorithms compensate for
medium compressibility and line expansion.
Leak pattern recognition Leak pattern recognition Leak pattern recognition Leak pattern recognition
Basically the leak pattern recognition algorithm constantly monitors whether the residual
(difference between inlet and outlet flow after the transient effects have been compensated for
by RTTM) exceed a predefined threshold. If this threshold is exceeded statistical analysis will be
used to determine whether this is caused by a true leak or by a sensor drift.
SMB SMB SMB SMB
SMB is a combination of compensated mass balance and leak pattern recognition by means of
statistical analysis.
Compensated mass balance method is based on the equation of conservation of mass. The
result of this equation is permanently passed to the leak pattern recognition, which analyses it
statistical to avoid false alarms.