Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Adding Uncontrolled Admission

Adding Uncontrolled Admission

Adding Uncontrolled Admission

To make things simple lets say we have a two stage turbine.

The current configuration has only one steam source through the V1 valve gear. For discussion lets say the turbine inlet steam is 1000 psi at 900 deg and the turbine area is sized to flow 1,000,000 lbs/hr of steam (even though more stages are actually designed for efficiency stay with the two stage machine).
This configuration has a specific 1st stage shell pressure curve as a function of flow which is driven by the second stage area. So at a given flow i.e. 500,000 lbs/hr, the admission pressure to the second stage is at 700 psi. If the flow is increased to the full load, this shell pressure or second stage admission pressure will rise due to the resistance the second stage area provides.

Now for the question: A customer would like to introduce an admission inbetween the first and second stage for which he has 850,000 lbs/hr 850 psi 850 deg F steam available for this turbine AND another turbine that is fed from another steam source.

At a given load for the turbine we are looking at, how do we know how much steam will be pulled in from the admission line if there is no control valve. In this example lets say we want to operate near the 500,000 lb/hr load point with the corresponding stage pressure at 700 psi. My calculations say that with a 10" pipe, that the 850 psi steam flowing into the 750 psi shell, will pull all of the 850,000 lbs/hr that is supposed to feed both turbines, and starve the second turbine of steam or, trip the boiler offline because it cant supply steam fast enough to maintain the header pressure. Do i need to size the pipe such that it acts as an orifice and restricts the volume of steam? I know a control valve can accomplish this, but i can not find a valve to handle such a large pressure drop which maintaining the wide range of operation needed. Ideally i would like to only pull in 275,000 lbs/hr at all load points, whether the steam is going from the header line of 850 to the shell pressure of 500 or 800.
Replies continue below

Recommended for you

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close