4 replies to this topic

[Padmakar Katre]

Dear All,
Please can anyone suggest me the right control scheme for the PRDS (Pressure reduction and desuperheating station) out of these two schemes.
I will be thankful for his guidance and suggestion.
Thanks in advance
Regards,
Padmakar Katre

Attached Files

•  Desuperheater__Control_Problem.doc   33.5KB   77 downloads

[muchlis nugroho]

Dear Padmakar,

Please be more clear, such as by providing operating philosophy and other things. I have no idea what this process scheme are made for. Is it for boiler system, geothermal, pulp processing or else? And why do you need to saturate a superheated steam in a pipe? Isn't that strange?

Rgds,
MNG

[Padmakar Katre]

Dear,
Thanks for your reply
This is the PRDS (Pressure reduction and desuperheating station) My confusion is that can I have a pressure Transmitter tapping prior to desuperheater and then temperature control as per the pressure and in second case the PT signal is downstream of desuperheater so what would be effect in each case for the PRDS control is concerned and which is the right scematic out of these two that was my question.
Regards,
Padmakar

[muchlis nugroho]

Dear Padmakar,

I am not familiar with this PRDS, but I guess that this is similar to steam turbine by-pass system. When the turbine trips, the steam goes to this valve and get desuperheated.

From pressure control point of view, there will not be any different if you put the PT before or after the desuperheater. It might be only a slight of difference in pressure reading and time lag, but it is still controllable.

From fluid dynamic point of view, there will be some consideration to take:
- PT location shall be located where the flow is stable, thus it cannot be located too close to any pipe restriction (such as valve).
- Liquid attomizing is best performed where the gas velocity is high (such as just downstream the valve).

Further more, there are some valve vendor that provide this kind of special valve. The water is injected inside the valve (in the vena contracta). It is said that this system will reduce nois level (and more compact piping design that can lead to less bill of material).

So, I think it is better to locate the desuperheater closser to the PCV and put the PT somewhere more downstream where the flow is stable.

Rgds,
MNG

[Padmakar Katre]

Dear Muchlis Nugroho,

Thanks for your reply.Yes what you mentioned here is 100% right actually I posted this query prior I

had my meeting with the desuperheater vendor. They geve us the detailed P&ID and the drawings

of the PRDS and given one note specifying the location of the PT i.e. distance from dsuperheater

downstream.

Once again thanks for your reply,

Regards,

Padmakar Katre,