Page 43 - Fluid mechanics, heat transfer, and mass transfer

FLUID MECHANICS BASICS
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TABLE 1.4 Problems and Possible Solutions in Pressure and Level Measurements
Variable Symptom Problem Source Possible Solution
Pressure Zero shift, air leaks in signal lines Excessive vibration from positive Use independent transmitter, flexible
displacement equipment connection lines. Use liquid-filled
gauge
Variable energy consumption under Change in atmospheric pressure Use absolute pressure transmitter
temperature control
Unpredictable transmitter output Wet instrument air Mount local dryer, use regulator with
sump, slope air lines away from
transmitter
Permanent zero shift Overpressure Install pressure snubber for spikes
Level Transmitter does not agree with level Liquid gravity changes Gravity compensate measurement or
recalibrate
Zero shift, high level indicated Water in the process absorbed by Use transmitter with integral remote
glycol seal liquid seals
Zero shift, low level indicated Condensable gas above liquid Heat trace vapor leg. Mount trans
mitter above connections and
slope vapor line away from
transmitter
Noisy measurements, high level Liquid boils at ambient temperature Insulate liquid leg
indicated

. What is the optimum liquid level in a stirred tank . What are the common problems involved in pressure
reactor? and level measurements? Give suitable solutions.
& Liquid level ¼ tank diameter. It should be noted that & Table 1.4 briefly gives the problems and solutions in
tank diameters are smaller at high pressures. pressure and level measurements.