2 replies to this topic

[gadmen]

Can someone please help me by supplying a procedure for the safe full decommissioning of a 10,000 m3 old Ammonia tank?

Thank you,

Gad Mendelsohn

gadmen@gmail.com

[Dazzler]

One would need to know/consider what utilities and nearby plant systems you have in place to assist...

 

Perhaps you could post your draft procedure of comment/markup by our experienced members?

 

Dazzler

[Saml]

Also, it depends on several other factors like

- What it is decommissioned for (inspection, mothballing, abandoning or salvaging)

- What you will do with the plant while the tank is being decommissioned.

- What you expect to find inside. You may have a clean tank. Or you may have a foot of a mix of oil and catalyst at the bottom.

- Siting of the plant. In some cases, you may vent NH3 to atmosphere as long as you don't exceed the worplace limits (50 ppm OSHA PEL, 25/35 ppm NIOSH TWA/ST). But if you are close to a community or have schools, kindergarten, etc one mile around your site, you may need to ensure a non detectable (by smell) level in those places.

 

In general:

- Empty your tank as much as you can until the pump loses priming. 

- Remove as much as you can thru a low point drain

- Evaporate what remains. You can do it with hot ammonia if your tank don't tolerate temperatures below -35 °C or you may use N2. In this case, temperature may go down to -45°C or even -50°C

- Heat up slowly

- Dilute the ammonia with an inert gas (N2). How much you dilute will depend on the ammount you can vent. The minimum is the point where you can introduce air and be below the ammonia LEL.

- Ventilate

These last two may be avoided if you use a robotic inspection device that do not require a person inside

 

Now, a few things:

 

Someone in your organization may have been at the Aiche Ammonia Safety Conference. If so, he will have the proceedings. There are several cases with a good deal of details. As example:

- "Successful inspection of two large Ammonia Storage Tanks" during the 2007 conference

- "Successful and safe de- and recommissioningof a cold ammonia storage tank" in 2005

- "In-service Inspection of Welds in Atmospheric Ammonia Storage Tanks" in 2014

 

And, if you are going to go ahead, I'd suggest that you contact a company that have done it, and is willing to accept a visit that is able to talk to engineers and operators that have done the work in the field. With three days of travel and an air ticket, you will save a lot of headaches.

 

Regards.

Edited by Saml, 01 April 2017 - 06:54 PM.