Re: New question; blowing out gaskets on PE line; how to stop

Gents

in order to overcome my gasket problem I took the following drastic measures:
1) On every unnecessary (transportation) joint, we cut out the flange and butt welded.

2) On every necessary joint, we doubled the flange thickness by adding a split flange and longer bolts.

3) On every necessary joint, we made a gasket composed of a 3mm steel washer, 250 I.D. with 3mm of duro 60 natural rubber glued to each side. One of my fag packet designs.

Total downtime 12 hours during scheduled 20hr shut.

16 bar and not a drip - Woohooo! That was my design pressure.

Underlying problem: the PE stub ends were not grooved to capture the gasket. If you buy stub ends, make sure they have a means of mechanically clamping the gasket. Friction alone is not enough.

Cheers

Steve McKenzie

• In PipingDesign@yahoogroups.com, "Steve McKenzie" <Mechproj@x> wrote:
  > and a bloody good flange they are too.
  >
  > Cheers
  >
  > Steve McKenzie
  >
  > -----Original Message-----
  > From: Geoff Stone DD&D Australia [mailto:blenrayaust@y...]
  > Sent: Friday, May 09, 2003 12:06 PM
  > To: PipingDesign@yahoogroups.com
  > Subject: Re: [PipingDesign] New question; blowing out gaskets on PE
  > line; how to stop
  >
  >
  > Table F was in the British Stand BS 10 before that was superseded.
  The
  > Australian Standard AS 2129 still uses the nomenclature. Another
  standard AS
  > 4087 duplicates the falnges but designates them by class. They are
  peculiart
  > to
  > the antipodese.
  > --- alwyn KAYE <altecheng@p...> wrote:
  >
  > ---------------------------------
  > BAcking rings from table F ... are these AWWA.. I'm not familiar
  with that
  > table.
  >
  > I once used the appropriate cement for the material and cement
  welded on
  > stiffeners the same OD as the joint and circumferentially. Looked
  horrible
  > bit
  > it worked. Its amazing how chunks of the stuff can be molded right
  on...
  > almost
  > any shape
  > ----- Original Message -----
  > From: Steve McKenzie
  > To: PipingDesign@yahoogroups.com
  > Sent: Thursday, May 08, 2003 2:15 AM
  > Subject: [PipingDesign] New question; blowing out gaskets on PE
  line; how
  > to
  > stop
  >
  >
  > Gents
  >
  > Have put in a 250NB (355 OD) PN20 PE slurry line; expected max
  pressure
  > 16
  > bar. Flanged joints are stub flanges, gramophone finish, Table F
  steel
  > backing rings. Gaskets are 3mm reinforced insertion rubber. Have
  had a few
  > blowouts at 10 bar as we are not yet up to full output. Bolts
  were not
  > being
  > tightened properly but I think the problem is more than that.
  >
  > Need a better gasket.
  >
  > Have considered:
  >
  > No gasket; just tighten her up; the slurry solids might blind off
  any
  > minor
  > leaks.
  > CAF gasket. Not my favourite as the CAF is probably too hard for
  the PE
  > grooves to get a good bite on.
  > Spiral wound or corrugated metal.
  > Metal backing ring to rubber: my favourite but where do you buy
  them?
  > Metal ring which cuts into the plastic as the joint is tightened.
  >
  > Has anyone had this problem and if so how did they overcome it?
  No time
  > for
  > major work to the flange faces, so the solution must be with the
  gasket
  > itself.
  >
  >
  > In anticipation
  >
  > Thanks
  >
  > Steve McKenzie
  >
  >
  >
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