What is your take regarding transport/lifting affairs of a pressure vessel in the design phase? 1

[TrustButVerify]

I studied mechanical engineering, and my internship consisted in the thermal/mechanical design of a pressure vessel (TEMA/ASME).

Curious thing is, that when doing so, I noticed the calculation of lifting lugs/trunnions/saddles were more or less, the last topic in the design of the vessel, and there were some loopholes (maybe I'm using the wrong word) when these topics were being addressed by the standard.

What am I saying above? Because I ended up getting my first job in a lifting/transport company, and I remained pursuing a career in that field for a long time, and most of the times, I was doing the engineering to lift/transport these very same pressure vessels (from 40t to 1000t, weight).

In my career, I've seen many issues in this interface (pressure vessel design and pressure vessel handling execution), for example: saddles are not designed to have proper lashing points so the vessel can be secured to a trailer, or pressure vessel external attachments have a clash with slings/grommets/wire ropes when rigging a pressure vessel for installation, and so on......

The thing is, I worked as well for an engineering design company, and I was liaising for a short time with the pressure vessel department, so I could witness 100% that many times the handling of the pressure vessels was something taken for granted, or not attack with the level of details required.

My question for you is: what is your take about this topic? do you agree? Another approach can be: how sensible is the design of a pressure vessel to sea-transport accelerations? Do you change the thickness of your pressure vessel? Does it change internal attachments like baffles? Are lashing points for cargo securing (land transportation) being considered?

Also I would like to know: is this something sometimes overseen because of money?

 

[saplanti]

Normally, the design shall follow the design specification for the PV design. Most cases the lifting/lifting attachment are considered for the thin wall vessels. Saddles are designed for the design loads which includes full/operating weights, wind/seismic loads, pressure, temperature only. Nozzle distribution and lengths sometimes can cause difficulties.for transportation that needs to be taken into account.

In case the specification includes the transportation requirement and required attachment, they can be designed on the vessel, Sometimes, perhaps in your case, this requires a collaboration between the transport company and the vessel designer. I do not expect this unless the project manager has close relationship with design office and transporter company.

Almost in all cases the transport company takes care of the the rest. No welding on the pressure vessel is accepted. Saddle lower parts are accepted as non-integral parts of pressure vessel, and you may be able to weld attachment there by collaboration with design office.

Most of the transport company needs to manufacture the copies of original saddles under the vessel if the vessel is thin and the shell is long.most of the vessels would be wrapped around the shell and connected on to the trailer at saddle locations or at locations of circumferential stiffeners if available. But tightening loads should be checked not to cause local buckling.

The transportation requires a design acceleration value, therefore you need to have the copy of vessel which includes weight, dimensions of the vessel and saddles with locations. So you can calculate the required attachment on the trailer, and design attachment required.

I hope it helps.

 

[r6155]

The simplest is to tie down the casing (with a paint protection device) using slings
Also a nozzle as a fixed point using slings.

Regards

 

[r6155]

For thermal insulated pressure vessel, use a heavy-shaped member under the saddles, bolted with the anchor bolt holes in the saddles.

Regards

 

[TrustButVerify]

I was looking forward rather for your take or experience about dealing with this. I know there is a standard, but I think there is lack of interface between design team and transportation company.

 

[r6155]

The shaped member is provided by the PV constructor and sends the detailed drawing to the transportation company as soon as possible.

Regards

 

[TrustButVerify]

From what I've seen on site while handling PV, some PV constructors are quite cheap, and dont want to be in these kind of communications because they don't have the manpower to deal with more calculations (this is the feedback I've got from this companies), and these PV constructors are being awarded the design because they are cheap... race to the bottom.

 

[LittleInch]

Think you've nailed it there.

Same thing really with the person producing the specification and data sheet etc to give tot he PV designers and constructors.

Very often the people putting the those docs together either don't think about it or just leave it up tot he transporter and the PV company.

Only if the vessel is known to be going by ship in some rough weather, like out to a rig in the North Sea for instance or being bounced around some pretty crap roads in Africa or S America will anyone maybe think about this before placing the order.

These points though usually come up late in the day, in part because at the point of order of the PV, which could be on 50+ weeks delivery, these details are not known.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TrustButVerify]

You are right about that as well... usually performing (hands-on) seafastening is easier than doing cargo lashing for trailers (land transport) in terms of feasability..

About the lead time the purchase order is made, you are also right, but nevertheless, there should be a way to consider this kind of topics later in the downstream line of design.

Also, there you have sometimes a poor performance of the inspector who approved the dispatch of the cargo from the factory without paying attention to details, or he just might think "maybe on site they will not notice".. or "they will figure it out something on site" without letting know anybody, and increasing risks when performing transportationg/lifting/installation of that equipment

 

[r6155]

See PIP VESV1002 (my copy is May 2009)
Vessel Fabrication Specification ASME Code Section VIII, Divisions 1 and 2

Regards

 

[r6155]

I worked in a company that has a full service: manufacturing, transportation and installation, with its own transportation and cranes.
But I've never seen a specification for lifting lug testing.

Regards

 

[0707]

From my experience, presure vessels are done according a construction code. The transport of the vessel to the site is done by specialized transportation companies which have the proper logistic means todo the job.