Reason why expansion joint (EJ)has been selected in the first place - to
protect a piece of equipment (in this case a pump) experiencing an excessive
load.
After establishing that an EJ is required, the next thing to do is to check if the selected EJ is OK or not. How was this done by T. Wanichpol? We'll he proceeded immediately with the C2 analysis then contacted the pump vendor> result - he's still having a problem with excessive nozzle load.
I would have done it differently by:
Selecting the ej from the catalog and entering the key properties into the
C2.
Run the calc to verify load/stresses. If OK, check if the cummulative
dispalcment is within the range limits (moveemnt).
If within limits, then you're OK. If outisde the range, then either you try
a diffretn type of ej, model the same ej as complex element (using the
cnode) or you contact the ej manufacturer for help.
Further comments.
According to the posting, NPS is 32 and system pressure is about 150 psi.
Axial Tension then is pi/4*d^2*P or about 120,600#. Surely the ej is not
capable of carrying this value, reason enough to provide the tie-rod. OK
thats fine.
Press. thrust load then is equal to pi/4*(effective dia)^2*P. this is what
Pat i guess is referring to as tending to blow or open the bellow apart, no?
Stated also is the effecttive dia of 820 mm. This cant be? Effective Dia is equal to pipe dia + height of convolution or its equal to square root (0.7854*thrust load/P). Effective dia then > Pipe Dia.
Basically the objective is to ensure that the system is capable of absorving this pressure thrust load - reason enough to contact the ej manufacturer (not the pump vendor)and discuss the result of your analysis. EJS (USA) and IWK (Germany) has provided us with a lot of tech support and analysis for our ej retrofit (metallic bellows) - they also have a website.
-----Original Message-----
From: Pat Burg [mailto:patburgh2001@yahoo.com]
Sent: 12 April, 2002 5:13 AM
To: <a href="/group/PipingDesign/post?postID=ucLqW7MzDgc3NzqovOx-iTyp3WdpGmzf0DyCHB73fuKhE2Fs7nMXlNkG_cmIsKSN1jkbRyUPO45qx8INc4664bVx">PipingDesign@yahoogroups.com</a>
Subject: Re: Re: [PipingDesign] Expansion trust force effect to pump
nozzle.
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
> >
> >
> >
> >
Your use of Yahoo! Groups is subject to <a href="http://docs.yahoo.com/info/terms/">http://docs.yahoo.com/info/terms/</a> Received on Sat Apr 13 04:58:00 2002
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