Bowed Horizontal Vessel Saddle Baseplate
Bowed Horizontal Vessel Saddle Baseplate
(OP)
I have been asked to design a fix for saddles on a large horizontal vessel. The vessel capacity is 400m3 and it operates at approx 130C.
The saddles have plastic deformation and have bowed upwards in the middle such the saddle base plate at the centreline is at least 20mm clear of the foundation.
This obviously means the load from the vessel is now concentrated at the extreme ends of the saddle and the concrete foundation is being damaged at these locations.
There is also a loss of thermal compensation in the system as the bolts on the 'sliding' ends are also being damaged.
Anyone have any thoughts on how the saddle base plate can be returned to specification?
The saddles have plastic deformation and have bowed upwards in the middle such the saddle base plate at the centreline is at least 20mm clear of the foundation.
This obviously means the load from the vessel is now concentrated at the extreme ends of the saddle and the concrete foundation is being damaged at these locations.
There is also a loss of thermal compensation in the system as the bolts on the 'sliding' ends are also being damaged.
Anyone have any thoughts on how the saddle base plate can be returned to specification?






RE: Bowed Horizontal Vessel Saddle Baseplate
I think the more likely scenario is:
The upper part of the saddle becomes too hot (or simply takes unconsidered thermal load), tries to make longer the outfit but restrained by the extreme bolts, a rotation is induced. It the temperature remains constant this plastic or elastic deformation may appear to be stable.
Be it stable or inestable, you will have to bracket the extreme thermal conditions to ensure you have reinforced foundations, anchors and steel structure to move between wanted parameters not passing more loads anywhere than wanted.
RE: Bowed Horizontal Vessel Saddle Baseplate
Hope it helps.
Ibrahim Demir
RE: Bowed Horizontal Vessel Saddle Baseplate
It would be informative to note if that 20mm clearance was at its maximum when the vessel was empty or full.
RE: Bowed Horizontal Vessel Saddle Baseplate
RE: Bowed Horizontal Vessel Saddle Baseplate
I believe the vessel was full and operational when this happened, I strongly suspect the vessel design temperature has been exceeded during operation.
I have attempted to upload a sketch, hope it works as I am just getting used to this site.
RE: Bowed Horizontal Vessel Saddle Baseplate
corus
RE: Bowed Horizontal Vessel Saddle Baseplate
-- MechEng2005
RE: Bowed Horizontal Vessel Saddle Baseplate
BA
RE: Bowed Horizontal Vessel Saddle Baseplate
What do you think about the saddles with excessive heights? In this case the thermal expansion has to be the major problem area and every high pressure high temperature heat exchanger should fail, but I could not find any problem with excessive height of the saddles under the gravitational loads, internal pressure and thermal loads (in circumferantial direction only). I do not say there is no thermal effect, however it is negligable against the effect of the internal pressure.
Therefore, I would suggest to check the saddle calculation against tension force created in that area.
Regards,
Ibrahim Demir
RE: Bowed Horizontal Vessel Saddle Baseplate
I must correct my previous post not to mislead you. Please read the following instead og the previous post:
I still believe that the bowing action comes with the total saddle vertical load rather than the differantial thermal expansion. There are many sample applications, including water heated boiler drums with saddle which the differantial thermal expansion is a lot higher than this, does not have this kind of problem. I can see from your sketch that there is not a welded wear plate either. This is another lack of material in that area to take the tension forces. Depending on the shell thickness and total saddle vertical load saddle must have certain amount of metal within very limited distance to the shell, otherwise this will happen.
What do you think about the saddles with excessive heights? In this case the thermal expansion has to be the major problem area and every high pressure high temperature heat exchanger should fail, but I could not find any problem with excessive height of the saddles under the gravitational loads, internal pressure and thermal loads (in circumferantial direction only). I do not say there is no thermal effect, however it is negligable against the effect of the total saddle vertical load.
Therefore, I would suggest to check the saddle calculation and the required metal area against tension splitting force created in that area.
Regards,
Ibrahim Demir
RE: Bowed Horizontal Vessel Saddle Baseplate