×
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

Triple offset butterfly valve torque

Triple offset butterfly valve torque

Triple offset butterfly valve torque

(OP)
I have a question on the triple offset butterfly valve torque and hope the experts here can help.

Question:

why the ETC torque is lower than BTO torque for triple offset butterfly valve products?

Many thanks

RE: Triple offset butterfly valve torque

Generally the valve is installed with the flow tending to keep the valve closed - one of the offsets being the the shaft is not centrally located through the vane, therefore there is a larger area against which the pressure acts to 'close' the valve than open it. Hence when one comes to open the valve this force has to be overcome. When closing the valve the line pressure assists the action.

RE: Triple offset butterfly valve torque

What PeterIgg mentions, plus also the difference between static and dynamic friction. When closing, the sealing surfaces are moving so it has lower friction. When opening, the sealing surfaces are static (not moving), and is why it is called "break" to open.

RE: Triple offset butterfly valve torque

(OP)
Many thanks to Peter and BCD.

RE: Triple offset butterfly valve torque

Triple Offset Valves or TOVs have an Elliptical Shaped Seat. When TOV Manufacturers tout "Dynamic Torque Sealing" they are highlighting the Sealing Mechanism (Torque Seated) and the reason the torque at Seating is so high, since the Elliptical Seat is being compressed into a circular shape. This is why a Torque Seated valve can be in the proper position, but still not seal unless the correct torque is achieved.

The BTO or Break to Open torque is actually lower regardless of line pressure and hydrodynamic torque. Hence if there is was no pressure on the valve, the ETC or End to Close Torque will still be higher.

Let me know if you have any questions!

RE: Triple offset butterfly valve torque

What BryceBunting commented make me wonder what kind of torque seating mechanism quad offset design utilizes.

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