×
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

Seat leakage classes
2

Seat leakage classes

Seat leakage classes

(OP)
Can the ANSI/FCI 70.2 (IEC 60534-4) control valve seat leakage classes be applied to ball valves?  Well, OK, yes I know they can, but would a supplier/manufacturer supply/manufacture to such standards?  Is there a standard specific for ball valves?

RE: Seat leakage classes

When it comes to ball valves, yes manufactures can and will specific their leakage class as III, IV, V, etc.  Some manufacturers will state they are bubble tight.  You need to read there test proceedure on how they determine bubble tight thou.

Hope this helps.

RE: Seat leakage classes

(OP)
Thanks gsxra.  I suspected that they might use these standards.  I have seen 'bubble tight' countless times, but in my (limited) experience, 3rd party inspectors aren't impressed by such phrases.

RE: Seat leakage classes

"Bubble Tight" does not come with a procedure to quantify it.  

FCI 70.2 at least specified that you test on air or water at around 50 psi, and it strongly hints at how much leakage is allowed.  It has no correlation to how much leakage you are going to get at operating pressure, though in any class except for class V.  I think the Sierra club should pursue FCI for all the trees that have been killed in the printing of Class 1, which is absolutely and completely meaningless, exceeded in meaninglessness only by its uselessness.  

MSS-SP61 is probably more appropriate for shutoff valves as is API 6D.  

RE: Seat leakage classes

mikeg8,
        may be you'll find useful to consult the other posts about the issue in object within this forum:
                -        thread408-23297 ;
                -        thread408-76110 ;
                -        thread408-122060 ;
                -        thread408-135434 .

Hope this helps,                'NGL

RE: Seat leakage classes

Check standards such as API STANDARD 598 Valve Inspection and Testing and find the requirement for zero bubbles per minimum specified test duration.  Bubble tight is a phrase applied to isolation valves - and not to control valves.

John

RE: Seat leakage classes

As above post people get confused about class of leakage.
Control valves because there primary function is to control are often not leak tight - the class rating is so that clients can specify a control valve which has also got a tight shut off capability.
This is not the same as Isolation valves - API598 does allow metal seated isolation valves to have a small amount of leakage across the seats but, soft seated valves are to have Zero leakage when tested.

Class VI is for soft seated control valves and does not specify zero leakage

RE: Seat leakage classes

Wasn't the original leakage class standard developed for globe control valves which are unbalanced? Trying to hold a plug down on a seat ring to provide tightness as the differential get higher is tough. Do the math... This is why class five allows more leakage per more inches of diameter per psiD.

A ball valve gets tighter with more differential across it.

Doesn't the standard also only go to 8"???

I can't count the number of times I've seen a 12" butterfly valve to class six tightness...

RE: Seat leakage classes

For high performance butterfly valves with offset design refer to MSS SP-68.  Seat leakage is covered in 5.2.2 Each valve furnished for  shutoff or isolation service shall be subjected to a seat test using fluid as described in 5.1. at 1.1 times the shutoff differential pressure rating of the valve at ambient
temperature. No visible leakage through the body or the disc or past the seat shall be allowed. Test duration shall not be less than shown in Table 4. I TABLE 4. SEAT TEST DURATION - see the standard.

John

RE: Seat leakage classes

The predominant standard for ball valve leakage is API 598. My company tests thousands of ball valves each year and other standards are rarely referenced. About once every 2-3 years someone (probably a control valve engineer) will request testing per ANSI/FCI 70.2 on ball valves.

I was a member of the API workgroup that made the latest revision to API 598. There are some important changes in the standard, so if you are working with any version prior to the current 8th edition (2004) you need to get the updated volume.

Greg Johnson
United Valve

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