Emptying of Nitric Acid storage tank(98% HNO3) 2

[panteo]

I'm working at Fire and Safety division of Huchems fine chemical corporation in Rep' of Korea.
The company's website is

http://www.huchems.com

Huchems corp. is the Korea's largest producer of Concentrated Nitric Acid(CNA: 98%) with a capacity of 104,300 MTPA.
We have two CNA plants designed by CHEMICO(33,000MTPA) and PLINKE(71,300MTPA).
The plants were built in 1979 and 1990. We have two CNA storage tanks made of aluminum.
The capacity of the thanks are 1,360 and 1,019KL each.
As our production quantity is little short of demand, we have to buy some CNA from the other domestic companies.
We use the CNA to produce DNT(Di-nitro-toluene).

The Korean law, revised in 1999, states that the storage tanks for dangerous chemicals of over 1,000 KL capacity must be inspected internally every 10 years.
There has been no need for the internal inspection of the CNA storage tanks according to the previous law.
So, there has been no internal inspection for the CNA storage tanks.

For over 25 years, nobody performed the internal inspection of the CNA tanks in the company.
Besides the danger relating the task, it will cost too much for us to treat the acidic waste from the CNA tanks.
I heard that if we try to clean aluminium tank with water, it will form weak nitric acid inside the tank and will corrode the tank very fast, since Aluminium tank is not suitable for Nitric Acid less than 90% concentration.

In this regard, I would appreciate it if someone could provide me any idea for this matter.

Many thanks in advance,

Jae-Hyuk Im

* You can see picture of the CNA storage tanks at the following web page.

http://www.antlove.com/cna_tank.htm

* If someone has proprietary technical reference, please contact me personally. We are willing to pay for the information on the required works for the inspection. (Detailed procedure for emptying, cleaning, waste water disposal, safety)

 

[TVP]

You should post this question in the Corrosion engineering forum. You should get more responses there.

 

[monkeydog]

Does the law tell you how to inspect the tank interior, or what to inspect for? Does a person have to enter the tank or can you use a video borescope (some have very long articulated probes). After you empty the tank, can you establish a dry air purge (to prevent moist air entry) and perform borescope inspections?

 

[panteo]

Thank you very much for your consideration.
1) The welding seams of the bottom plate must be inspected using non-destructive test.(15% of all welding seams)
2) The thickness of the bottom plate must be checked.
3) Inspectors must enter the tank for vaccum box test.
4) The problem is that "emptying" and "dry purging" the tank is very very difficult task for me.