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[deltaChe]

I have a control loop and two flow meters(totalizer flow meter type).(Pls see attached file)

My question is follwing

N1. Refer from control loop naritive, this loop FIC-030 is to assure a correct feeding quality
of nonyl phenol into reactor, in order to reach this goal, it is
required to provided a flow controller combined with totallizers.(?? why the engineer put
two totallizer on the same process line instead of putting one totallizer on the other DEG
feed process line-although it will close when nonyl phenol feed in)

N2.Which type totallizer is better?Vortex, positive displacement, turbine, coriolis-
although we use coriolis


N3. How the engineer to determine this coriolis type mass flow meter
should be used in this process from purpose of measurement point of view?
Actually I don't understand why they use totallizer instead of using common
type flow meter. (some books totallizer always used in ratio control
and it can verify the overall correctness of total blended product and
it has memory of the amount of past error but my case seems not ratio control)


Thank you very much your kindly help.

Attached Files

•  Visio-test.pdf   47.07KB   39 downloads

[kkala]

It is assumed that mentioned reactions with ethylene oxide (EO) need special safety measures, so answers below should be considered only as an opinion from someone not having specific experience on the matter. Contact of licensors may be needed even for changing things apparently simple.

N1. Understanding / interpretation of the loop is: Two same flow meters (FE030A, FE030B) measure the flow of nonyl phenol or Diethylene glycol (DEG). A flow high selector (FHS) selects the higher flow, being used as input to FIC030 to regulate FV-030. In this way nonyl phenol or DEG is (tried to be) always in excess of EO, which is a safety issue.
Totalizers (based on two mentioned flow meters) do not seem to intervene in the control, except for giving information on total flow. Higher value of two totalized flows (>) is displayed in the control room, as well as their difference (Δ). FQDI does not look clear, since difference is already displayed. Operator follows all these values and apparently does corrective actions if the two cumulative flows deviate enough from each other.

N2. Generally coriolis flowmeters are considered more precise (their totalizers should be also so), but their maintenance may not be possible at the plant shop. See Perry, Chemical engineers’ handbook (7th edition), Process Control – Flow measurements, for several types of flowmeters, although accurancy is not reported. Type most suitable to this specific application may be advised by experienced companies.

N3. The Engineer has to complete the flow meter “data sheet”, then ask for quotations from relevant suppliers. Max and min measured flow should be specified, as well as pipe diameter, allowable ΔP, and fluid properties / conditions. We use a formula at work, common for all flow meter types, type is finally selected by Instrument Department.
Coriolis meters measure mass (not volume) flow rate.