Hi all,

We know that a straight pipeline anchored at both sides (which have a tank at one side and a pump at another side) with a untied bellow, the thrust force goes to pump foundation due pipeline is "disconnected" and the pump is in charge of absorb the reaction force.

In a Victaulic Coupling the problem is the same? I think that inside pipe the pressure is contained by pipewall and victaulic wall too. So, the P*A exists, but no reaction force goes to the pump once the pressure thrust is enclosured at system. I read COADE's News Jun98 and learn how to model Victaulic in CAESAR II. A paragraph shows how to input the pressure thrust in the model. But, this force may be a reaction force on pump nozzle or can be neglected?

Is this right? Or Victaulic works like a expansion joint/untied bellow?

Thanks in advance,

Miyamoto

Victaulic joints do resist axial pressure thrust.

MoverZ,

But the pressure thrust goes to pump foundation? We need consider loads on nozzle as specified in EJMA (difference in victaulic mean diameter and inner pipe diameter? Or can we consider as a straight pipeline and no loads on pump foundation?

Regards,

Miyamoto

Look carefully at a section drawing of a victaulic joint. There is a captive neoprene seal which fits in a groove in both pipe ends. Provided that the design pressure is not exceeded, the joint needs no axial restraint such as tie-bars. You should not consider it as an expansion joint even though it does allow a very small amoumt of flexibility. EJMA methods do not apply.

Fine, but what's the reaction of the pump? I believe the P*A inside pipe don't will cause many problems once system is closed and no thrust reaction goes to pump. Is this right? Can I consider a flexibility axially in pipe (due gap for thermal displacements) but no reaction forces on pump foundation (as a straight pipeline)?

You cannot have it both ways. Either you consider the Victaulic joint to be rigid axially (no PxA) or consider it to have some flexibility axially, then (PxA) will act on your pump foundation. I would say it's rigid axially, thus there will be no (PxA) reaction externally.

But, if victaulic works between 2 anchors, when pipe have thermal displacements, victaulic will have gaps. So, considering what you said, the system have some flexibility axially (gap), then PxA will act on pump foundation.

Thanks.

I give up. Victaulics do not create end thrust.

Get onto the manufacturers.

MoverZ,

Sorry. I forgot to mention. I'm talking about Victaulic Flex Coupling. Probably you are refering to Rigid Couplings, am I right?

I agree with your explanations if you were refering to rigid couplings. But, In this case, with a rigid system, loads from thermal displacement will act on anchors.

Regards,

Miyamoto

MoverZ,

Sorry. I forgot to mention. I'm talking about Victaulic Flex Coupling. Probably you are refering to Rigid Couplings, am I right?

I agree with your explanations if you were refering to rigid couplings. But, In this case, with a rigid system, loads from thermal displacement will act on anchors.

Regards,

Miyamoto

The system pressure p gives axial loads on both end (bends) F*A !
This load will be absorbed from the axial stress in the pipe.
In the case with a untied bellow the pipe dont absoberd this load an the load go in the bends or axial restraints.

Is a untied bellow left from a axial restraint then the load
F1 = p * A1 got direct in the axial restraint.
A1 = (Da2-Di2)*pi/4.
Da = inside diameter bellow
Di = Inside diameter pipe

And a load Fi = p* Di*Di*pi/4 go direct in the ellbows.