Upending Monoplie 2

[sinu21]

Hi Friends
I need to know your openion on the concept we are devoloping for upending a monopile .

I have attached a schematic dig of the upending procees.
We are planning to use a bearing pad of elastomers or sand bags for bearing of the pile.
The length of pile = 75m
Dead Load = 350T
Dia = 4.5m

If anybody expert in upending like to comment, i can give more details.
I am sure someone might have gone through such an idea before.
Kindly put your comments. i am looking for your comments. thanks

Regards

 

[Ussuri]

Is this onshore or offshore?

The use of shear key to pull the pile against is a common way of doing it for offshore pile upending. I haven't seen it done with piles as large as yours but would assume the process would be similar. To upend a 75m pile using a single crane is going to require a lot of hook height, its a big crane.

Normally the end of the pile is held captive and there are bumper bars/ guides to ensure the pile does not become uncontrolled and impact something or someone. The guides ensure the pile can only move in a single plane.

A lot of the time you will see people using timber where you have an elastomer. It gets ripped to pieces pretty badly. However, at your weight timber might not be suitable.

You can hire 'shoes' and other upending frames from the likes of IHS.

Another option for subsea piles is to lift horizontal, deploy to the seabed and then upend subsea.

 

[sinu21]

Thanks Ussuri

This is an Offshore Lifting on a vessel.The Vessel i shaving only once crane and its capable of lifting such a long pile vertically. As you tolf if we need to lift the pile horizontaly we needed two cranes, so that option is gone.This long pile is a one time installation so we are not looking to pay IHC or someone to pay a huge sum of about 90K.

Why i was thinking of elastomers is that they can take huge bearing load and they are flexible to an extent to rotations.

Ussuri can you look at the image file i am senting now , its a concept i was thinking to make it little more simple.Can you plz put down your comments.I have made a slight funneling along the area of pile pivoting so that pile is guided/controlled to the vertical location.

Looking forward for your kind reply

Regards

 

[dhengr]

Sinu21:
I think I’m pretty much repeating what Ussuri is trying to tell you. The trailer under the lower end is intended to move toward the crane during the lift, whether self powered or pushed under some control. I would like to see some stanchions on the trailer bed, on either side of monopile, so it can’t move or roll laterally. They would provide this guidance through the full lifting operation, 0° to 90°. Then, I would like to see some sort of stiffening structure at the base of the monopile, to hold it to its shape and distribute the concentrated reaction loads during the lifting process. As part of this stiffening structure, and at its lower edge, near the trailer deck elevation, I would want two semi-circular rotating shoes, maybe large pins in saddles, which would allow the rotation and apply the loads to the trailer deck. I don’t know that this system has to cost 90k, maybe or maybe not rented, but it is much more controlled and you can actually analyze the loads and process. Your sand bag idea seems a little arbitrary, difficult to really analyze for the various loading conditions, and kind of difficult to control exactly. If you had a couple sand bags rip and fail, you could have a very unstable situation.

 

[BAretired]

What is upending? What is a monopile?

BA

 

[dhengr]

BA:
Take a look at his first attachment, with the OP. It’s a steel cylinder, 75m long and 4.5m dia., weighing 350tons. Upending is to lift it from one end, from a horiz. transport position, to a vertical position for installation. When you do this with a single crane, the lower end is usually on some moveable system so that the bottom end of the vessel can move toward the crane as the crane lifts the other end.

 

[BAretired]

Thanks dh, I am not sure I am still clear, but carry on.

BA

 

[Ussuri]

BA

dh is correct, the OP is talking about taking a 75m length of pipe, lying on its side, on a vessel, and tipping it up to the vertical position by attaching the crane wire to lift it.

dh, when done offshore it is the typically the top end that moves because the upending frames are usually welded to the vessel deck. For much smaller piles the cheap and cheerful approach is just weld a plate to deck, put the free end of the pile against it and then lift and pull against it using the vessel crane. In essence pivoting it about the plate.

What this does is cause the edge of the pile to gouge at the deck so it is protected by timber. I takes a lot of damage. However everytime i have done this it is using piles around 20-25m long, 30" OD. So nothing of this size. We couldn't do what the OP is doing as our vessel cranes are not big enough.

For a pile of this size I would be inclined to lift it horizontally using a two leg bridle with a third loose leg attached to the same masterlink running too the lift cap. I would then lift it to the seabed and use the ROV to disconnect the two leg bridle leaving just the single wire to the lift cap, and then upend subsea. I would have thought if your crane has the hook height, and capacity to upend it on deck, it would have the height and capacity to lift it horizontally.

If this is not an option and i'm not sure just using the key will work for a pile of this size and weight because it will be hard to control on deck. Even of you corral it with bumpers, for a 75m long pile they will be substantial (you need to consider the safety of the deck crew who you will be asking to do this, imaging getting thumped by a 350 tonne pile).

If i had to do it this way I think I would look at using a shoe. Effectively a length of pipe with and ID larger than the OD of your pile. The shoe is mounted on trunnions to allow rotation. The pile is lifted into the shoe horizontally. The shoe holds the pile end in one place, but does little to stop it swinging about at the crane wire end.

I dont like the sand bag idea. I think they would get ripped to shreds, the sand would become loose and the your pile end would be free to move.

 

[sinu21]

Thanks Ussuri and dhengr, thats useful comments from your side.
I have made some more refined mechanisum for upending. If you see my attached picture, you will have some more ideas.Kindly put your comments its really intersesting and support for me.

I have now elastmeric pads that is shown as the green hatches in the figure.
If you see the mechanisum, i feel that the pile due to the horizontal load will be always in contact with the
curved profile of the bearing pad.
We can take more load on the crane and pull the crane up during all the stages of upending so that the major vertical load goes to the crane and the pile is just restrained in the horizontal direction by this arrangement.
Can you kindly comment of this arrangement.

Regards