Hai All,
Here i want a confirmation about how to modelling Corrugated Metal Hose (with Braided Cover) since many thread in this forum said that we don't need to modelling it in CAESAER II or suggest not modelling this object. Me personally can't accept that suggestion just like that, because many project that i involved are using this corrugated metal hose at tank-piping connection and pump-piping connection, and once i was have a difficulty to do analysis because i don't kow how to modelling it in CAESAR II.
Thanks to LC Peng, i have read Peng's Book "Pipe Stres Engineering", where at page 241 section 7.5.3 analysis of Hose Assembly, it said The analysis procedure follows a few basic step. (1) The hose is divided into a series of elements along the layout shape. (2) Each element is considered a bellow having spring rates as given by the manufacturer or determined as bellow elements discussed previously. (3) Because the hose is braided, the axial spring rate is very large and shall be considered inflexible, thus, only lateral spring rates and bending spring rates are considered. (4) At the center of each element a generic flexible joint is assigned and given two lateral spring and two bending springs. This is similiar to the gimbal joint with some added lateral flexibility. (5) The element are considered rigid members, having the same unit weight as the hose and its content. The system is then analyzed in the same manner as regular piping system.

Ok, i hope COADE members can give valuable confirmation...........

Regards

Tengku Syahdilan

Hi

I would still say not to model a flex hose. Design the pipe supports and the pipe routing correctly and you do not need to worry modelling something for which you will not get correct data. To model the sytem you include all the supports etc. Add to the pipe end that axial movement from the tank nozzle if you consider the flex hose rigid. Leave the pipe end free otherwise. Analyze the system and check the end movements. Calculate the nozzle and pipe end relative movements. If too high for the flex hose then redesign the system.

Thanks Jouko,
since i know you as the one in this forum that mastering this kind of Flexible Joint element, then i need your opinion.
i am try to analyzed a system where corrugated metal hose are install as Piping to Tank connection and there is also pump connector as the piping to pump connection (Please refer to the P&ID). During maintenance of Relief Valve at Tank-04, the Metal Hose at service line(the 4"metal hose) was failed and the support near it was out of it place. I want to analyze the pressure pulsation scenario that i though may be the cause of it, but i will not get the whole picture if i can't model this metal hose.
and then after a few month there is also a fail in the relief valve and the pump connector due to operational problem. The operator said that it happened during the unloading process to truck,so once again it might be a water hammer problem. if i can't model through the metal hose and must stop before the metal hose,or i have to analyze each part separately (and i have try it) i can't get the whole picture.
Well the system is ok now, i have ask field technician to resetting the relief valve set pressure, and i have ask the operator not to open the gate valve at the filling shelter partially open, and about the metal hose at TANK-04 is have been replace and i have made a procedure of maintenance. (as asked by client), but i need to study this case for my next reference if the same problem happened again.
Ok, if any input or suggestion from you, it will be very helpful...
Thanks...



T. Syahdilan

Aghaton Mandiri

You quote Peng's page 241 but you do not mention the previous paragraph where he says: "The hose assembly is not generally analyzed for forces and stresses involved." and "... no significant resisting force is expected besides the weight of the hose and its contents."
If you know the position of points along the installed hose, you can model the hose as a group of "expansion joints" along this curve as you quote from Peng.

1
How can we modeling flex. hose as expansion joint since it only have a minimum bending radius not spring rates....the data from the vendor is Minimum bending radius in static and dynamic not spring rates like expansion joint.
so should we assumes the spring rates?