7 replies to this topic

[Abid]

I am working on one assignment of steam let down station in order to reduce the pressure and temperature of the superheated steam. In development of P& ID I need to know any standard reference or criteria for the designating the length of upstream and downstream straight pipe sections for steam pressure and temperature control valves (STEAM LETDOWN UNITS).

Secondly the placement of temperaure and pressure transmitters at the downsteam of the steam let down units. If there is any industrial standard or Process industry paractise or any paractical knowledge which cover/govern the distances or spaces for these transmitters at the downstream of steam letdown stations like we have for flow meters, we have some industrial standards references for straight pipe sections length and distances for transmitters at down stream side. Any help or information regarding this will be highly appreciated.

[joesteam]

Exact placement of sensors and actual desuperheating equipment depends on your exact conditions, flowrates, temperatures, etc... and the type of steam conditioning equipment you may use. We help out our customers on this all the time, and you should call a local representative that supplies this type of equipment.

Attached is a good starting point, a data sheet that helps calculate some of the distances you questioned.

Attached Files

•  Fisher_Desuperheater_Installation.pdf   160.13KB   152 downloads

Abid, you can try searching the spiraxsarco engineering tutorials webpage. There are lots of useful info for a start.

I have a question if anyone can help. We have steam supply coming in at 22 BarG at 227 deg C. We then reduced it to 8 BarG. The steam flowmeter placed at the 22 BarG recorded a total of 9500 metric Ton of steam per month. Should the mass of steam after the pressure reducing valve (at 8 BarG) be the same (9500 MT).

regards

[marthin_was]

It should be same, mass ballance principle.
I've checked in steam table, the steam are in superheated condition, it means 1 phase or 100% vapor, so you should not have any problems in measuring 1 phase with common differential pressure meter, such as orifice.

If it is two phase then you faced a problem. Because you should know the steam quality to measure the mass rate.

thanks,

Abid, you can try searching the spiraxsarco engineering tutorials webpage. There are lots of useful info for a start.

I have a question if anyone can help. We have steam supply coming in at 22 BarG at 227 deg C. We then reduced it to 8 BarG. The steam flowmeter placed at the 22 BarG recorded a total of 9500 metric Ton of steam per month. Should the mass of steam after the pressure reducing valve (at 8 BarG) be the same (9500 MT).

regards

[Qalander (Chem)]

It should be same, mass ballance principle.
I've checked in steam table, the steam are in superheated condition, it means 1 phase or 100% vapor, so you should not have any problems in measuring 1 phase with common differential pressure meter, such as orifice.

If it is two phase then you faced a problem. Because you should know the steam quality to measure the mass rate.

thanks,

Abid, you can try searching the spiraxsarco engineering tutorials webpage. There are lots of useful info for a start.

I have a question if anyone can help. We have steam supply coming in at 22 BarG at 227 deg C. We then reduced it to 8 BarG. The steam flowmeter placed at the 22 BarG recorded a total of 9500 metric Ton of steam per month. Should the mass of steam after the pressure reducing valve (at 8 BarG) be the same (9500 MT).

regards

Dear Abid,
Use search function since steam let -down service valve problems probably discussed elsewhere as well even if you google then some useful info can found at eng-tips site discussed the issue some two months back.

Hope you should be able to find the way forward indeed!
Best of luck.

Thank you marthin .....

It should be same, mass ballance principle.
I've checked in steam table, the steam are in superheated condition, it means 1 phase or 100% vapor, so you should not have any problems in measuring 1 phase with common differential pressure meter, such as orifice.

If it is two phase then you faced a problem. Because you should know the steam quality to measure the mass rate.

thanks,

Abid, you can try searching the spiraxsarco engineering tutorials webpage. There are lots of useful info for a start.

I have a question if anyone can help. We have steam supply coming in at 22 BarG at 227 deg C. We then reduced it to 8 BarG. The steam flowmeter placed at the 22 BarG recorded a total of 9500 metric Ton of steam per month. Should the mass of steam after the pressure reducing valve (at 8 BarG) be the same (9500 MT).

regards

[Padmakar Katre]

I am working on one assignment of steam let down station in order to reduce the pressure and temperature of the superheated steam. In development of P& ID I need to know any standard reference or criteria for the designating the length of upstream and downstream straight pipe sections for steam pressure and temperature control valves (STEAM LETDOWN UNITS).

Secondly the placement of temperaure and pressure transmitters at the downsteam of the steam let down units. If there is any industrial standard or Process industry paractise or any paractical knowledge which cover/govern the distances or spaces for these transmitters at the downstream of steam letdown stations like we have for flow meters, we have some industrial standards references for straight pipe sections length and distances for transmitters at down stream side. Any help or information regarding this will be highly appreciated.

Dear,
This is always decided by the PRDS Vendor and not inthe stage of Basic Engineering as the vendor will calculate he mixing length based on its desuperheating station specifications. So so the details are available based after the vendor's reply. There are many concerns i.e. the turn-down ratios with your desuperheater based on that the system is designed and to get the correct readings/signals of Pressure and temperature the vendor will mention the straight length requirement and all. So to get the brief idea about this you can contact the some local PRDS suppliers and understand the issue.
I searched in google with "P&T location in Pressure Reduction Desuperheating Station" and I found some useful links and documents.

[Abid]

ok. thank you very much for all of you for giving and sharing nice and useful input regarding the placement of the pressure and temperature probes at upstream and downstream of steam let down units.