The load on the impeller is balanced by an equal and
opposite
force applied through the pump casing to the base, or
through the pipe as reflected in a pd/4t longitudinal
stress in the
attached pipe wall. When there is an untied joint,
pd/4t will not
be transferred by the pipe wall, (or should not be --
because this
is what blows out joints), and the load is through the
casing to
the support on the pump side and into the first elbow
downstream
on the pipe side. When there is a tied joint or fixed
pipe the (p) times
(a) load thrust load is transmitted through the pipe
producing the
pd/4t longitudinal stress. The area of the joint
confuses the picture
some, and the relative stiffness of components further
can confuse
the picture, but in general the above simplification
is adequate for
visualization and design. If I'm not mistaken the
CAESAR user's
guide has some good detailed drawings of the load
transfer in
and around pumps and expansion joints. If you can't
find them there
let me know and I can fax them.
Regards,
> Feedback ?
>
> Subject: Re: Re: [PipingDesign] Expansion trust
force effect to pump
nozzle.
>
> Hi Pat
> the pump must see the thrust load or else it cannot
deliver. The sole
> purpose of a pump is to increase pressure. By doing
this it suffers the
> indignity of being pushed backwards. In order to
resist this, the pump
must
> be restrained. This is why we design pump
foundations. Sometimes they are
> large.Over to you.
>
> Cheers
>
> Steve McKenzie
> ----- Original Message -----
> From: "Pat Burg" <patburgh2001@yahoo.com>
> To: <pipingdesign@yahoogroups.com>
> Sent: Thursday, April 11, 2002 7:32 AM
> Subject: Fwd: Re: [PipingDesign] Expansion trust
force effect to pump
> nozzle.
>
>
> > --- Tony Paulin <tony@paulin.com> wrote:
> > > From: "Tony Paulin" <tony@paulin.com>
> > > To: "Pat Burg" <patburgh2001@yahoo.com>
> > > Subject: Re: [PipingDesign] Expansion trust
force
> > > effect to pump nozzle.
> > > Date: Wed, 10 Apr 2002 13:36:26 -0700
> > >
> > > Pat,
> > > The tie bars are supposed to carry the thrust
load,
> > > not the pump. Elastomeric joints are generally
> > > avoided
> > > if possible in critical piping systems.
Temperature
> > > changes,
> > > property variations, etc. can produce a system
that
> > > is
> > > susceptible to pressure pulsations, mishandling,
> > > etc.
> > > (Whereas steel systems and joints are not so
> > > susceptible.)
> > >
> > > The joint is designed to take horizontal
movement,
> > > not axial. If the loads are too high then a
> > > reconfiguration
> > > of the piping is needed, or a more accurate
model of
> > >
> > > the thermal or load case.
> > >
> > > These situations are somewhat tricky, and
someone
> > > used to modeling nuances of the program and of
the
> > > installation can usually help out. This might
be a
> > > problem to have a "consultant" look at to be
sure
> > > that the modeling and loads are accurate.
> > >
> > > Tony
> >
> >
> >
> >
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