4 replies to this topic

[tarafdar]

We have 3 Ammonia Storage Tanks (10,000MT each) at 3 Ammonia/Urea complexes at different sites.All of these tanks are more than 15 years old.These tanks are double-walled atmospheric(-33⁰C).The tanks are never inspected by emptying.The tanks have vapour recovery package refrigeration units.

Is it mandatory to inspect ammonia tanks after certain years of use?We don,t plan this considering the production loss.Is it necessary to construct a small tank to keep on production during the inspection?(A reputed vendor suggested it).

What is the approx. time requred for such inspection(emptying,inspection,small repair if any,air removal,cooling-down) from your experience?

Thanks

[wojtar]

You may read that:
http://www.continent...s.nl/Paper2.pdf

http://www.efma.org/...ks%20(2002).pdf

http://books.google....epage&q&f=false

The tank that I know (some fertilizers plant) is inspected every 10 years.
Anyway it is strange that such ispection was not planned.


Regards.

Edited by wojtar, 06 December 2011 - 01:10 PM.

[breizh]

I would advise you to check the regulation in your country . If I remember well , in France we were doing an inspection every 10 years . Consider a safety study on the impact of a leak or a rupture of piece of equipment on your storage tank .



Hope this helps

Breizh

Edited by breizh, 07 December 2011 - 04:21 AM.

[jrtailor09]

Tarafdar,

Find attached file provide guidlines of ammonia tank inspection for europian countires.

Regards,

Attached Files

•  Guidlines Tanks of tank inspection.pdf   836.47KB   154 downloads

[kkala]

A. Below are some notes understood from "Recommendations for inspection of refrigerated atmospheric NH3 tanks" (by EFMA), attached to the post by jrtailor09; the attachment gives useful insight, recommending a Risk Based Inspection, sort of preventive maintenance based on plant data and observed status.
1. Internal inspection is obligatory every 10-12 years in most countries of European Union, it varies from 6 to 20 years. This represents max interval. Some countries do not specify time, other countries do not have rule (Appendix 1).
2. Meanwhile the tank is under frequent evaluation / external inspection, the results of which can shorten mentioned interval.
3. Necessary decommissioning and recommissioning increases the risk of stress corrosion cracking, so internal inspection at shorter time should have reason to take place. About 10% of such tanks present stress corrosion cracking after some years of operation.
4. The evaluation / external inspection (Appendix 6) clarifies questions about tank condition and operation (leaks, flexible pipe connections, observed stress corrosion cracking, H2O & O2 content in NH3, tank double wall, bund wall, location, etc). Result through a point system recommends internal inspection every 3 to 20 years.
B. Consequently EFMA advises when the tank should be internally inspected, if the recommended procedure is followed.
Two clarifications would be welcomed:
1. Is 100% radiography applied to welds? Not clear, codes are addressed (para 3.5.1).
2. Tank roof can be repaired, while tank is operating (para 3.5.2). Is welding possible?