trunnion lifting capacities

[BurnettBmr]

hello
I am looking for an insight for trunnion capacities during lifting operations in the static state during the 0-90 degree change in wire rope sling angle.

Have been looking for calculations to start getting my head round this but so far have come up short

Any help apprecieted

 

[SnTMan]

BurnettBmr, a nozzle load calculation such as WRC-107 etc is often used for this.

Regards,

Mike

 

[BurnettBmr]

Thanks for the input. Does this apply when the trunnions are side-mounted ?

 

[SnTMan]

yes, assuming they are of a design that WRC-xxx would apply, typically a pipe section welded to shell with / without pad etc.

WRC-xxx typically uses a vessel coordinate system, Longitudinal, Circumferential, Radial. You will have to apply the load appropriately. Normally only one shear load (causing one moment) involved. If lifting from horizontal to vertical you should check two or more directions of load application and design for the worst. Note no pressure involved, but good practice to apply any CA to the shell.

Regards,

Mike

 

[BurnettBmr]

Thanks Mike

Been reading some interesting material in the Pressure Vessel Design by Moss.
But the calculations seem pretty minimal especially for calculating the load at any angle.

 

[SnTMan]

BurnettBmr, Moss should work for you. Don't know what your level of experience is, but I kind of glossed over (my apologies) the fact that the WRC-xxx calculations only provide stresses in the shell due to external loads. This may also be checked by the methods in Moss, Ch 5. The balance of the trunnnion design will need to be checked by other methods, such as Moss, Ch 7.

Regards,

Mike

 

[BurnettBmr]

What I am after Mike is the force applied on each trunnion from the 18t pipe throughout the lift. Moss seems to cover this from what I can take from it.

 

[chicopee]

Draw a sketch of the object with tunnions and various angles of the wire rope sling so that we are all on the same page..

 

[BurnettBmr]

the pipe section is starting horizontal at grade and being tailed into vertical position as shown in drg. therefore wire sling angles move from 0-90 degrees throughout lift. wire slings will be cradled round trunnion therefore as good as parallel after accounting length to the spreader beam.

cheers Mike

 

[SnTMan]

BurnettBmr, one (conservative) way to do it is to apply the full load experienced by the trunnion simultaneously in both the circ and long directions. It won't exceed that. Otherwise, you find the worst case over the 90 degree range and solve it. For example at 45 degrees you've got 0.7 of the load in the both the circ and long directions.

Regards,

Mike

 

[BurnettBmr]

cheers Mike
goin by whats in PVD seems to be the way forward thought that there would be more in it than that !!

 

[SnTMan]

BurnettBmr, 20 years in the business has taught me it ain't rocket surgery

 

[chicopee]

You should use two cranes and each fitted with two leg slings. Assuming the center of gravity (CG) being between the two trunnions, both crane operators will start lifting at the same time to a height to clear the tail end of the pipe in order to rotate it to the vertical position. Then crane operator closest to the top end of the pipe will raise his end higher up while the second crane lift will stay where it originally stoped; ultimately the pipe will be nearly vertical but not quiet vetical because at that point the crane hook will be lined up with the CG of the pipe; also you don't want the two sets of sling interfere with each other. At that point I imagine that the upper trunnion is nearly resting on its bracket and the lower trunnion is still off the lower bracket,so a ratchet will be needed to bring in the lower tunion closer to its resting place and the lower spreder disconnect from the crane. Each two leg spreader should have a lifting capacity excceding the weight of the pipe since the pipe will eventually be lifted by one crane. The reason for the two sets of two leg slings being equal in lifting capacity is so that there is no mismatch of the position on the pipe.

 

[BurnettBmr]

Chicopee took me back there !! Yeah the lifts the easy part !

 

[chicopee]

Yes the lift is the easy part and you should let qualified crane operators and iron workers do the work. Qualification of worker may require you to use union members as they are trained to do work of that nature. Pre-pPlanning of the work procedures is very important.

 

[BurnettBmr]

If my apprentices couldn't lift that in they would be getting sent up the road chicopee !