delf
Chemical
- Feb 23, 2011
- 17
Dear Sir
As we know, steam flow measurements, being compressible, always
require both pressure and temperature compensation.
But, I am confused why a steam flow meter/indincator are installed. (Please see the desuperheater with 3 control loop drawing in the attached post)
Is this steam flow indictor just used to be constantly recored in the DCS data or receive the pressure /temperature singal to calcuate the mass flow rate?
The 2nd querry is in the the MRS steam pressure control loop
, please refer from the drawing, is necessary to set the pressure setpoint on the controller?
Thank you so much for your generous help.
Ps.The following is the 3 control loop description.
1. Loop 677-FI-008 – MRS steam flow control
The main objective of this loop is to measure the steam flow to distributor.
The Flow indicator FI-008A/B measure the steam flow relative to the pressure and temerature
by means the flow element/trasmitter FE/FIT-008A/B in the line 677-MRS-002 .
2.Loop 677-TIC-002 – MS-desuper heater temperature control
The main objective of this loop is to control the temperature of downstream steam
of DS-67710 as a function of the water flow in order to maintain the desired
temperature.
The temperature of the steam is controlled by the PID controller 677-TIC-002, in a
feedback strategy, which measures steam temperature by means of the
temperature element/transmitter 677-TE/TIT-002 in the line 677-MRS-0002, and the temperature setpoint
is based on pressure compensation to controls the water flow by means of the control
valve 677-TV-002 in the DS-67710.
3.Loop 677-PIC-015 – MRS steam pressure control
The main objective of this loop is to control the pressure of MRS steam.
The pressure of the MRS steam is controlled by the PID controller 677-PIC-015 (reverse acting
controller) which measures the pressure by means of pressure transmitter 677-PIT-015 in the
line 677-MRS-0002 and pressure setpoint is based on temperature
compensation to control by means of the control valve 677-PV-015 in the
line 677-MS-0031.
4. interlock (677-I-004) Loss of MP steam supply to close de-superheating water
To prevent the steam temperature control system from spraying into saturation, logic
shall be provided which calculates the saturation temerature(TALL-002 lo-lo) as a function of steam pressure.
When the desuperheater oulet temperature approaches the saturation temperature, an interlock will be
activated to prevents the spray valve (TIC-002 manual and TV-002 closed) from injecting any water.
As we know, steam flow measurements, being compressible, always
require both pressure and temperature compensation.
But, I am confused why a steam flow meter/indincator are installed. (Please see the desuperheater with 3 control loop drawing in the attached post)
Is this steam flow indictor just used to be constantly recored in the DCS data or receive the pressure /temperature singal to calcuate the mass flow rate?
The 2nd querry is in the the MRS steam pressure control loop
, please refer from the drawing, is necessary to set the pressure setpoint on the controller?
Thank you so much for your generous help.
Ps.The following is the 3 control loop description.
1. Loop 677-FI-008 – MRS steam flow control
The main objective of this loop is to measure the steam flow to distributor.
The Flow indicator FI-008A/B measure the steam flow relative to the pressure and temerature
by means the flow element/trasmitter FE/FIT-008A/B in the line 677-MRS-002 .
2.Loop 677-TIC-002 – MS-desuper heater temperature control
The main objective of this loop is to control the temperature of downstream steam
of DS-67710 as a function of the water flow in order to maintain the desired
temperature.
The temperature of the steam is controlled by the PID controller 677-TIC-002, in a
feedback strategy, which measures steam temperature by means of the
temperature element/transmitter 677-TE/TIT-002 in the line 677-MRS-0002, and the temperature setpoint
is based on pressure compensation to controls the water flow by means of the control
valve 677-TV-002 in the DS-67710.
3.Loop 677-PIC-015 – MRS steam pressure control
The main objective of this loop is to control the pressure of MRS steam.
The pressure of the MRS steam is controlled by the PID controller 677-PIC-015 (reverse acting
controller) which measures the pressure by means of pressure transmitter 677-PIT-015 in the
line 677-MRS-0002 and pressure setpoint is based on temperature
compensation to control by means of the control valve 677-PV-015 in the
line 677-MS-0031.
4. interlock (677-I-004) Loss of MP steam supply to close de-superheating water
To prevent the steam temperature control system from spraying into saturation, logic
shall be provided which calculates the saturation temerature(TALL-002 lo-lo) as a function of steam pressure.
When the desuperheater oulet temperature approaches the saturation temperature, an interlock will be
activated to prevents the spray valve (TIC-002 manual and TV-002 closed) from injecting any water.
