technical NOTES

Typical Cost Benefit Analysis

Application

of Transmitter

Qty

Analog

Transmitter

(Fixed range)

Smart Transmitter

(4-20mA, HART)

Smart Profibus

Transmitter

Pressure/DP

Switches (@

Unit rate of Rs.

5000/-)

Nos. U/R Total U/R Total U/R Total Qty. Total

Coal Mill Bag

Filter Pressure

Transmitter

1

8000 8000 23000 23000 30000 30000 0 0

Cement Mill

Bag House

Transmitter-

DP Type

17

10000 170000 28000 476000 35000 595000 17 85000

Cement Mill Bag

House Pressure

Transmitter

1

8000 8000 23000 23000 30000 30000 0 0

TOTAL (^94 882000 2487000 314500091455000)
Cost differ-
ence between
various options
of transmitters
as above.
Rs
Lacs
16.05 0 (6.58) (20.32)

• Note: Operating cost shall be validated with present condition.
  7.4 Conclusion:
  a. Since the mechanical switches are not reliable for its accuracy and repeatability
  in addition to more maintenance during normal operation. Mechanical switch is
  recommended only for end limit applications like:
  i. Trip alarms
  ii. Cut off gates,
  iii. Diverters,
  iv. Dampers,
  v. Actuator, etc.
  The switches are never used where signal is used for process loop control in
  order to achieve energy conservation.

b. The analogue (fixed type range) transmitters are pre-calibrated for a definite
range. They are available have good accuracy and reliability in measurement.
The major bottleneck for this transmitter is that they cannot be re-calibrated
and its measurement span is of fixed nature. Therefore, one should carefuly
select the range of this transmitter while purchasing because wrong selection
of transmitter range leads to error in measurement. Therefore, it is recommended
to use analogue transmitters for measurement of compressed air in bag filters
due to following reasons: