hi, i have a problem with my main steam flow measurement where it will go to error & cause the drum level control jump to single element. The measurement used are dp and the setting is 4-20mA is 0 to 750mB. The DCS will give error if the dp when more than 22.5mA. can i increase the dp range at the transmitter and DCS i/p card without disturbing the drum level control or other process?or do i need to resize the oriface ?

 

Hi SI,

You may be able to change the transmitter. Recalculate the DP for a higher flow rate then change the transmitter range to match.

If the transmitter upper range limit is too low you will need to purchase a new orifice plate, or transmitter with higher DP range. Don't forget to change the input range of your control system to match the new upper range value. A machine shop could increase the orifice size for you, if you go this route make sure you talk with the machinist and stress how criticle the shape and size is otherwize it will come back with a nice smooth round edge, stamp the new size on the plate otherwise down the road some-one will re-calculate the range using incorrect data. You may need to check all the process data as it has may have changed since the plant was first comissioned.

Roy