2 replies to this topic

[sparsha]

Hi 

I have a query regarding having nozzles on shell for a jacketed coil vessel. I am working on a batch catalyst plant design. My client requested for sight glass on all vessels. Our vessels have coils covering all the vessel length upto HLL and botttom head.

 

Can we have nozzles (LT, process nozzles & manway) on shell side for a jacketed coil vessel?

Where should I locate the sight glass?

What is the cost and stress implication of having nozzles on shell side of a jacketed coil vessel.

 

Thanks

Vijay

[latexman]

We put sight glasses on the top head near the OD but not into the knuckle radius.  Our floor level is about 1 m below the top head, so it is comfortable for the operator to use the sight glass.

[Art Montemayor]

Vijay

 

If your vessels were not fabricated with the basic allowance for nozzles - as Latexman has explained - you have, in my opinion, a serious problem.

 

The need to allow extra vessel height or space for nozzle allowance on spiral-jacketed vessels and reactors is just one reason why I always have avoided that type of jacket design and have opted for internal coils or external, circulated heat exchangers instead.

 

The only manner I can see that you may have a chance to have a level reading in your vessel is to insert a nozzle in your top vertical nozzle and your bottom outlet nozzle.  However, if you have a slurry fluid or one that tends to clog with solids, then you may not have accurate readings.

 

Yes, you can have nozzles (LT, process nozzles & manway) on the shell side for a jacketed coil vessel.  However, this is just going to further increase the fabrication problems with stress and cost implications - not to mention the time and welding techniques involved in trying to meet the critical dimensions and characteristics of the vessel.  I have had only two spiral-jacketed reactors fabricated in my career - and they were a hellish project during fabrication.  I did this in Houston, Texas in very sophisticated and experienced, modern shops but still went through the agonies of welding and heat built-up problems and vessel deformation - not to mention costs.  One fabrication attempt had to be aborted half-way through because of excessive welding heat build-up complications and damage.

 

When I consider what slight advantages a spiral jacket has - if any - and I take into consideration the restrictions, costs, fabrication problems and time consumed, I prefer to stay away from this design.  I can guarantee 100% better temperature control with simpler, more flexible, and less expensive designs than a spiral jacket.

 

My intention is not to be negative but rather, to give you some actual, personal experience in designing, specifying, and fabricating this type of process vessel.  It isn't as easy as many people imagine.  Only a welder can appreciate what the vessel involves while looking at a drawing.