×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Maximum Discharge Pressure of a Flooded Screw
2

Maximum Discharge Pressure of a Flooded Screw

Maximum Discharge Pressure of a Flooded Screw

(OP)
One of the projects we have in our scope (pre-feasibility phase) considers 2-stage compression trains, from 1-3 barg suction pressure to 25-30 barg discharge pressure. We intend to look more deeper into flooded screws for this particular case.

I have looked into various literature (Hanlon, Bloch) and compressor manufacturer sites (Howden, Mycom, Kobelco), trying to find the maximum discharge pressure (or maximum pressure ratio) for flooded screws. Hanlon, Bloch, and Howden quote the maximum discharge pressure range of 20-20 barg (without mentioning the minimum suction pressure), whereas Kobelco and Mycon quote much higher figures (Mycom = 50 barg @ 5 barg minimum suction pressure, Kobelco = 100 barg @ unspecified suction pressure). I ended up this reasearch without having a final conclusion - what would be the figures applicable for our project case, considering suction and discharge pressures as given in the first paragraph of this post? Is it achieveble with a single-stage flooded screw?

Any help is much appreciated.

http://antwrp.gsfc.nasa.gov/apod/astropix.html

RE: Maximum Discharge Pressure of a Flooded Screw

2
I generally consider "feasible" as within +/-10% of peak efficiency. That range is highly dependent on the VI selected. For a 4.6 VI the peak efficiency occurs at around 4.75 compression ratios and the range is 2.8-11.0. This means that for a 31 bara discharge you should try to keep suction above 2.8 bara with a 4.61 VI. For a 2.5 VI the peak is at 3.5 ratios and the range is 2.0-6.25 so for 31 bara discharge you'd want to stay above 4.7 bara.

With the 4.6 VI case, above 4.75 ratios you are "under compressing" which means that you are making the gas compress gas instead of using steel to compress the gas. That part of the efficiency vs. compression ratio graph is reasonably flat. The peak efficiency is around 76% and 11 ratios is at 68%. By the time you get to 20 ratios (which several authors claim is a physical limit, but I'm not sure that is true) the number is still above 60% for a 4.61 VI.

I'd go for it, making sure that I got the max VI that the vendor offered and building everything to ANSI 300.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Maximum Discharge Pressure of a Flooded Screw

have used some 2 stage leroi flooded screws with success in the past

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!


Resources