Question { 13364 }

why the SCAN time of DCS is more & that of PLC is less?
if the SCAN time of DCS then why we use DCS.

Answer

DCS is pc based system. The speed of the processor/CPU
decides the scan time.

Question { 68990 }

why we are using MARSHALLING PANEL? what is the role?

Answer

Marshalling means grouping of I/Os. Marshalling panel is
placed between the DCS system panel and field instruments.
In marshalling panel grouping of I/Os like Analog Input,
Analog Output, Digital Input, Digital Output and Pulse I/O
are done.From marshalling panel the I/O signals are
communicated to the system CPU/Controllers through
Isolation/Signal conditioners.

In marshalling panel we can easily identify the Input or
Output and easy diagnosis can be done in case of fault
finding.

Question { Reddy Labs, 9671 }

what is INSTRUMENTATION ? specify..

Answer

Instrumentation deals with Measurement,Control and Recording of Physical as well as chemical variables (generally called process variable)

Question { IOCL, 10414 }

without a positionar can a control valve operate? give the
difference of operating with positionar and without positionar?

Answer

Only the diaphragm actuator type control valves can be
operated without positioners provided that the spring range
of the actuator is within the range of control air pressure.

Cylinder actuator type control valves cannot be operated
proportionally without a positioner. only on/off can be
done.

With positioner we can achive the exact position of the
control valve with speed. If positioner is not there then
the actuation will be sluggish and we cannot get exact
postioning of control valve

Question { IOCL, 7405 }

what is interlock ckt? why it is necessary in industrial
machines ?

Answer

Interlock ckt or generally interlock means providing safe
conditions for startup and running of industrial
machines.For example, In some machines cooling water is
required for startup and lubrication oil pressure should be
available. In this above machine interlocking system is to
be done with cooling water flow and lubrication oil
pressure to avoid any unsafe condition for the machine.The
machine can be started only if both the conditions are
satisfied. During running of the machine if any one fails
then the machine must be tripped. Interlock is necessary in
industrial machines for safe operation of the machine as
well as the process.