Steam Flow Measurement
ByD K Singhal
Disclaimer
This presentation is supplied as a self learning
presentation, and is subjected to the condition that
the author accepts no liability from the use of the
same or from the techniques or information provided
within the same.
It is strongly recommended to consult your mechanical
engineer, process engineer and other technical
experts, before making any changes to the existing
system.
Preface
Steam consumption is one of the
significant cost factors in paper and
other process industries. In absence of
any steam flow metering control and
optimization of steam consumption is
not possible.
Available Systems
Steam flow measurement systems
available in the market are very costly,
and hence most of the mills cannot
afford them to install. But, nothing can
be controlled if it is not being
monitored.
Proposed System
This must be indicated that the proposed
system is of very low cost. In the proposed
system, reading is taken from the instrument
and with the help of calibration chart, steam
flow is estimated. Accuracy may be a little
lower, but benefits obtained by the proposed
system may even encourage the user to
purchase and install steam flow meter from a
reputed supplier.
Concept
Pressure Drop across a saturated steam
pipeline is a function of steam flow rate,
steam pressure (and hence specific
volume) and pipe diameter.
For most of the cases, steam pressure
is normally kept constant, or varies
within narrow limits. Pipe diameter, of
course, is fixed for a particular position.
Steam Flow
The proposed system works on the basis of
pressure drop in a horizontal steam pipeline,
which is proportionate to square of steam
flow rate. i.e. for any flow rate say pressure
difference is 100mmWC, a 10% reduction in
steam flow will be indicated by a reduction in
pressure drop to 79mmWC. Thus, one can
very easily achieve the optimum steam
consumption for a particular application.
Schematic Drawing
Distance for which dP is to be measured
Steam Flow
Pressure
Gauge
Gauge Glass Assly.
Closed
Tank
Steam
Trap
Baffle
Plate
T
Zero Level
About the Equipment
As indicated in figure, the tank has a
partition in the center. The lower
chamber is filled with water upto zero
level prior to installation. Any further
water coming into the tank is drained
from the excess water removal line
through valve and steam trap installed,
as indicated in the left side of figure.
Operation
Initially, the lower chamber is filled with
water. When the system is connected to
steam line, steam from upstream side fills
lower chamber and exerts a pressure inside
gauge glass. The downstream side steam
pressure fills upper chamber and tries to
counterbalance the upstream pressure. The
pressure drop is indicated in the gauge glass.
Initial Measurements
Distance between the two points at which the
unit is connected is measured. Steam pipe
diameter is also measured. The line pressure
can be measured by the pressure gauge
mounted on the unit, as indicated in
schematic.
Gauge glass initial level is marked when there
is no steam flow. Any increase in gauge glass
level, thus, can be measured.
Also, the pressure can be measured by the
pressure gauge mounted on the unit.
Flow Estimation
The steam flow will be proportional to the
square root of gauge glass level increase, and
inversely proportional to the steam pressure
as indicated by the pressure gauge.
Formulae are available to calculate pressure
drop in the pipeline, and depending on the
distance between two points in the steam
line, working pressure, pipe diameter etc., it
is possible to develop a plant specific
correlation.
Flow Optimization
To optimize the steam flow, just
measure gauge glass level increase at a
particular operating condition and
pressure.
After altering process variables, if the
gauge glass reading decreases, it will
clearly indicate that the steam flow has
reduced.
Feedback
Please send in your comments on this
presentation to-
D K Singhal
Deveshksinghal@rediffmail.com
Deveshksinghal@gmail.com
Thank You.