×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

# Calculation of an atmospheric vent line length

## Calculation of an atmospheric vent line length

(OP)
Dear Sirs,

we need your support to calculate the right lenght of an atmospheric vent line.
The context is a desulfuration plant on a refinery.
By using a gaschromatograph to measure H2S and H2, I discovered that the actual lenght of the vent line probably does not permit the gas sampling at atmospheric pressure. This means that the GC analyze a gas volume more great than the nominal volume that is 360 microliters.
To equalize the sample during the sampling phase of the gaschromatograph, there're two valves named ATM VLV and X1 VLV. The first valve is installed between the sampling out line from the GC and the process return line. The second valve permits the gas return to the process line (look at the attached images). The X1 VLV moves opposite respect to the ATM VLV:
-when X1 VLV is open, the ATM VLV is closed. This is fast loop mode
- contrariwise, when the X1 VLV is closed, the ATM VLV is open. This the sampling mode. In this way the GC needs atmospheric sample.
E.g.: if the calibration gas pressure from a bottle is set at 0.5barg, the measure overestimates the expected value. Trying to set the cal gas pressure below or above the above mentioned pressure value, the result is the same and also not stable or not passable.
Considering this phenomenon, I disconnected the vent pipe from the ATM VLV, that is a 6mm steel line of three meters lenght. Thus I obtained a good result. By keeping this configuration all the GC measures are close to the bottle concentrations.
If you agree with my interpretation please help me to calculate the better atmospheric vent circuit or vent line size.

Niccomasso

#### 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.

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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!