Turbomachinery for Nitric Acid Plants - MAN Diesel & Turbo

Control and safety equipment
A complex machine train of the kind
used in a nitric acid plant makes very
great demands on the control and protection
systems in terms of quality and
flexibility. Such systems must consider
the requirements of the process and
provide all functions from start-up to
emergency shutdown of the machine
train and process. MAN Turbo has developed
electronic control and protection
systems which interface with
the mechanically/hydraulically actuated
final control elements.
Anti-surge control, surge detector
In the performance graph of a turbo
compressor the surge line is the dividing
line between ranges of stable and
un-stable operation. Reduction of the
volume flow rate beyond this line causes
separation of the flow from the
blading, the gas flows periodically from
the discharge end to the suction end –
a phenomenon referred to as compressor
surging. The resultant extreme
load reversals and temperature fluctuations
in the gas-handling components of
the machine must be avoided. This is a
task of the anti-surge control, a system
which, by controlled opening of the
blow-off or by-pass valves, always
keeps the compressor flow rate in the
stable range of the performance graph.
A special development of MAN Turbo
for this purpose is the electronic control
and protection system called “Turbolog
S7-400”.
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Speed control
To allow speed and therefore process
pressures and flow rates – to be controlled
as well as the machine train to be
protected against overspeed, MAN
Turbo has developed the turbine control
and protection system “Turbolog S7-
400”. This system by far surpasses the
requirements of NEMA specification SM
23, class D. Depending upon specific
requirements, it is designed for any of
the following functions: (Refer also to
the special brochure “Turbolog S7-
400”.)
redundant turbine speed control
redundant overspeed protection
complete functional testing of all trip
circuits during normal operation
speed-controlled starting of the
turbine from standstill
combined control of speed and
extraction pressures
back-pressure control
control of turbines with sidestream
admission
inlet pressure control
power output control
frequency control