Monitoring the temperature of the gas stream can provide useful information concerning
ESP performance. Temperature is measured using a thermocouple in conjunction with a
digital, analog, or strip chart recorder. Temperature is usually measured using a single point
probe or thermocouple. This method has a major limitation in that the probe may be placed at an unrepresentative (stratified) point—one that is not representative of the bulk
gas flow. Most ESPs are designed with a minimum of three fields. The gas temperature for
each field should be measured at both the inlet and outlet, if possible. Significant temperature
changes between the inlet and outlet values may indicate air inleakage problems that
should be confirmed by measurement of gas composition.
Changes in gas temperature can have profound effects on ESP performance. The temperature
variation can be very small (in some cases as little as 15oF) and yet cause a significant
change in ESP power levels and opacity. Although gas temperature variations may have
some effect on corona discharge characteristics and physical characteristics of the ESP
(corrosion, expansion/contraction), their most important effect is on particle resistivity.
For sources with the potential for high resistivity, temperature changes can cause dramatic
changes in performance, even when all other parameters seem to be the same. The gas
temperature should be checked once per shift for smaller sources and measured continuously
on larger sources and on those sources with temperature-sensitive performance.
Temperature measurement can also be a useful tool in finding excessive inleakage or
unequal gas flow through the ESP. Both of these conditions can affect localized gas velocity
patterns without noticeably affecting the average velocity within the ESP. Yet, localized
changes in gas velocities can reduce ESP performance even though the average gas
velocity seems adequate.
ESP performance. Temperature is measured using a thermocouple in conjunction with a
digital, analog, or strip chart recorder. Temperature is usually measured using a single point
probe or thermocouple. This method has a major limitation in that the probe may be placed at an unrepresentative (stratified) point—one that is not representative of the bulk
gas flow. Most ESPs are designed with a minimum of three fields. The gas temperature for
each field should be measured at both the inlet and outlet, if possible. Significant temperature
changes between the inlet and outlet values may indicate air inleakage problems that
should be confirmed by measurement of gas composition.
Changes in gas temperature can have profound effects on ESP performance. The temperature
variation can be very small (in some cases as little as 15oF) and yet cause a significant
change in ESP power levels and opacity. Although gas temperature variations may have
some effect on corona discharge characteristics and physical characteristics of the ESP
(corrosion, expansion/contraction), their most important effect is on particle resistivity.
For sources with the potential for high resistivity, temperature changes can cause dramatic
changes in performance, even when all other parameters seem to be the same. The gas
temperature should be checked once per shift for smaller sources and measured continuously
on larger sources and on those sources with temperature-sensitive performance.
Temperature measurement can also be a useful tool in finding excessive inleakage or
unequal gas flow through the ESP. Both of these conditions can affect localized gas velocity
patterns without noticeably affecting the average velocity within the ESP. Yet, localized
changes in gas velocities can reduce ESP performance even though the average gas
velocity seems adequate.
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