GUNITE 2

[picasa]

I am looking at drawings for a 30 year old 4’-0” I.D. sour water stripper with internal trays. In the drawing I see that the tower has GUNITE layer on the inside. Now we are planning to replace the trays with new better performance trays. Now if the GUNITE layer has chipped at some places, I was wondering if there might be any problems with the fit up of downcomer panels with the tank walls on the inside. Please comment. Share any similar experiences if you have any.

 

[waskillywabbit]

Since you are updating the trays and obviosly taking the stripper out of service to do so, update the lining or r/r it. Better proactive in cases such as these (repairing old PVs) than being reactive. The latter usually costs you more money in the long run and money is often the bottom line.

Good luck.

 

[picasa]

Can someone also comment on the necessity of Gunite layer? Why is it typically put on the vessel surface? In what cases is it required?

Can you suggest vendors that can update Gunite lining?

 

[unclesyd]

The Gunnite was for corrosion protection due to the H2S compounds. There are people that can repair the lining. A lot of old municipal CI sewers are being relined/reclaimed with cement for the same reason.

We have over thirty 500-1000 gal hot water storage tanks/heaters that are cement lined for corrosion protection and have been in service for 50 yrs or better. About 80 percent of the underground piping is cement lined for the same reason. We have a river water distribution system that has 3" thick lining as the river water gets quite brackish during the summer. AT one time the system had two large cement lined chlorination and aeration vessels.
Gunnite was also used on skirted tanks for fire proofing. The only problem with this was that the cement had a good percentage asbestos fiber added.


Some good information on gunnite.

http://www.sangerssilo.com/Gunnite.html

http://www.shotcrete.org/index.htm

 

[roca]

Gunnite is not only used for corrosion protection but is also used for insulation purposes
I am working on some Adsorber vessels which have Silica Gel beds in them. The silica bed drys the gas. The vessels operate in a cyclic temperature fashion and are lined with gunnite. Each vessel will undergoes a heating and cooling cycle twice per day. 20°C ? 300°C ? 20°C
The gunnite is used as insulation as it would take an enormous amount of heat and time to bring the 100 mm thick wall shell up to the required operating tempeature only to have to cool it down again.

 

[valero]

Is this tower in a sulfur recovery unit in an oil refinery? This is a first for me, but I have not been around long. I am assuming the liner starts above your feed tray. If it is in good condition I would leave it as is. I would recommend a good inspection of the liner consisting of visual and hammer test. You should be able to see cracks and hear disbanded areas. Make repairs to the liner as necessary, and be sure to check the base metal visually and ultrasonically prior to Appling the new liner. If you remove the liner in it’s entirety, and decide to bring it up to modern standards you could go with an automated 316L overly, but it would probably be cheaper to just have a headed can section fabricated with a 316L clad and make some piping welds and one circumferential weld.