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P. 54
RODUCTION CONVENTIONAL METHOD
The overall efficiency of a power plant encompasses the Measuring valve bonnet temperature is the easiest
efficiency of the various components of a generating way to detect any possible steam loss through any
unit. Minimizing heat losses is the greatest factor affecting valve as it generally kept in un-insulated condition.
the loss of plant efficiency. Lower power plant efficiency Bonnet temperature of these valves is recorded with
results in more CO2 being emitted per unit of electricity an infrared thermometer (HIOKI FT3700-20) or an
generated. infrared thermography camera. Valves whose bonnet
temperatures are greater than 100oC (as a thumb rule) are
In the context of sustainability BBGS has always focused on recommended for renewal in the next outage.
efficiency enhancement, resource and cost optimization,
auxiliary reduction and digitization. This paper presents a
simple yet robust method for determining internal steam
leakages through high energy drain (HED) valves thus
helping in key decision making such as valve renewal.
PROBLEMS DUE TO INTERNALLY Figure 1:
LEAKING VALVES
Areas of concern in conventional method
Drain valves are meant to completely isolate the steam
under normal working condition. A small leaking path Temperature rise in bonnet can be due to the following
through the valve mating surfaces will result in leakage reasons:
of the high pressure steam to a low pressure sink/
atmosphere, resulting in the loss of the high energy 1. Gland/ Bonnet leak from the valve
contained in the steam. To supplement this loss more 2. Conduction heat transfer from main headers in case
water needs to be added to the cycle and more coal
needs to be burned to maintain the energy levels of the of very close installation of the valve
steam produced and delivered to the turbine to meet 3. Any live bypass line or leakage through bypass line of
the generating requirements of the plant. The additional
fuel directly impacts the efficiency and heat rate of the the valve
power plant. 4. Valve is not fully shut due to improper limit setting
5. Valve leaking internally due to any erosion in the
OBJECTIVES OF THE PRESENT STUDY
mating surfaces
1. To detect whether the valve is internally passing
or not. So the bonnet temperature being greater than 100oC
does not confirm a leakage through the valve. Surface
2. To calculate the leakage mass flow rate using a emissivity factor is not considered with the changes in
standard mathematical correlation. valve body materials. Even if the valve is passing, the
quantum of loss due to passing can’t be assessed just
3. To determine the financial loss corresponding to the from the bonnet temperature. So it is unpredictable to
leakage. select which valve is responsible for a more loss than the
4. Decision of valve renewal on the basis of the
financial loss.
54
The overall efficiency of a power plant encompasses the Measuring valve bonnet temperature is the easiest
efficiency of the various components of a generating way to detect any possible steam loss through any
unit. Minimizing heat losses is the greatest factor affecting valve as it generally kept in un-insulated condition.
the loss of plant efficiency. Lower power plant efficiency Bonnet temperature of these valves is recorded with
results in more CO2 being emitted per unit of electricity an infrared thermometer (HIOKI FT3700-20) or an
generated. infrared thermography camera. Valves whose bonnet
temperatures are greater than 100oC (as a thumb rule) are
In the context of sustainability BBGS has always focused on recommended for renewal in the next outage.
efficiency enhancement, resource and cost optimization,
auxiliary reduction and digitization. This paper presents a
simple yet robust method for determining internal steam
leakages through high energy drain (HED) valves thus
helping in key decision making such as valve renewal.
PROBLEMS DUE TO INTERNALLY Figure 1:
LEAKING VALVES
Areas of concern in conventional method
Drain valves are meant to completely isolate the steam
under normal working condition. A small leaking path Temperature rise in bonnet can be due to the following
through the valve mating surfaces will result in leakage reasons:
of the high pressure steam to a low pressure sink/
atmosphere, resulting in the loss of the high energy 1. Gland/ Bonnet leak from the valve
contained in the steam. To supplement this loss more 2. Conduction heat transfer from main headers in case
water needs to be added to the cycle and more coal
needs to be burned to maintain the energy levels of the of very close installation of the valve
steam produced and delivered to the turbine to meet 3. Any live bypass line or leakage through bypass line of
the generating requirements of the plant. The additional
fuel directly impacts the efficiency and heat rate of the the valve
power plant. 4. Valve is not fully shut due to improper limit setting
5. Valve leaking internally due to any erosion in the
OBJECTIVES OF THE PRESENT STUDY
mating surfaces
1. To detect whether the valve is internally passing
or not. So the bonnet temperature being greater than 100oC
does not confirm a leakage through the valve. Surface
2. To calculate the leakage mass flow rate using a emissivity factor is not considered with the changes in
standard mathematical correlation. valve body materials. Even if the valve is passing, the
quantum of loss due to passing can’t be assessed just
3. To determine the financial loss corresponding to the from the bonnet temperature. So it is unpredictable to
leakage. select which valve is responsible for a more loss than the
4. Decision of valve renewal on the basis of the
financial loss.
54
