11000- please take note of the following, presuming you really have to use a flexible joint:
1)it is important that you provide the joint manufacturer with correct data concerning the connected pipe dia., fluid content, design temperature, design pressure, desired overall length of the joint assembly, and the required stiffness of the joint in axial, lateral and/or angular directions, & the thermal expansion induced net displacements with respect to one end of the joint assembly. He/She should help you decide whether you need a Rubber or Steel(SS) exp. jt. Corrosiveness of the service fluid is an important factor in deciding the required material.
2)you have got to do a little searching on the internet and contact a manufacturer. If possible ask them to send you a catalogue with stiffness tables. This way if you're trying to evaluate the piping loads on the nozzle in a computer model, you can start right off and select bellows from the manufacturers' tables with given properties.
3)You'll want to minimize the dislacements on the flexible joint. You're better off connecting the joint directly to the pump nozzle and anchor the pipe as close as possible to the flexible joint. This way, as far as vibrations and pipe expansion loads are concerned, you have almost completely isolated the piping from the equipment.
4)what I explained in prong #3) should take care of pressure imbalance (pressure thrust load) developed in the bellow. With the support arrangement I explainced above, the "Pressure Thrust Load" will be transmitted to the Anchored pipe support & the Pump foundation. Depending on the design pressure in your line, significant pressure thrust loads can develop and bust your flexible joint open or make it so axially rigid that it won't function as a flexible joint any longer.
5) if you cannot place an anchor near the flexible joint, you will need "stops", "tie rods", or "limit rods" on your joint assembly. Guide spacings on the pipe are also very important within vicinity of expansion joints.
6)if your design pressure (internal pipe pressure)is higher than 5 bars, be extra careful. Make sure your manufacturers' catalogue is well documented as far as allowable displacements and stiffnesses are concerned.
7) again, if you comply by the 3rd prong, it will significantly reduce the worry and uncertainties regarding the actual displacement capacity of the expansion joint you buy. You have pretty much eliminated thermal expansion displacements from the equation. Hope your pipe layout will allow for this.
8) I hope you don't, but if you end up placing your expansion joint relatively far from the suction nozzle without an anchor after the joint; determine your governing displacements (axial or lateral) and choose the type of your flexible joint accordingly. A simple bellow might not suffice any more. You may need a lateral, hinged, or gimal expansion joint.
hope it helps + good luck,
C
