All, Can anyone brief me about the Dike Wall Calculation..?

In non-walled situation, if the tank wall breaks then the chemical / fluid inside will spread in uncontrolled manner (so will be the hazards associated).

The Dike which is also called Bund wall is built to prevent this uncontrolled spreading. In short, Dike is retention measure. In case of single tank, it should be more than the tank's capacity. Normally it is:
Dike Capacity = 1.1 * Vessel Capacity
Please note:
1. The calculation shall be based on the inside dimensions of the Dike and not outside.
2. Any Civil constructions that are inside the Dike like foundations shall be correctly calculated and accounted for. Otherwise the calculation will result in incorrect dimensions and reduced retention capacity.

Economy and Engineering sense, mean that Tanks with similar purpose are placed together with a common Dike. In this case, the volume of the largest vessel is considered for calculation. This reduces
1. Civil work
2. Dike wall height (as the area is increased)
So it becomes more cost effective.

However, as a piper, our responsibility does not end here. Following points shall be considered as well
1. Openings for pipe entry in the Dike (Puddle flange requirement)
2. Entry / Exit for the operators with due consideration for wind direction and fire hazard.

In non-walled situation, if the tank wall breaks then the chemical / fluid inside will spread in uncontrolled manner (so will be the hazards associated).

The Dike which is also called Bund wall is built to prevent this uncontrolled spreading. In short, Dike is retention measure. In case of single tank, it should be more than the tank's capacity. Normally it is:
Dike Capacity = 1.1 * Vessel Capacity
Please note:
1. The calculation shall be based on the inside dimensions of the Dike and not outside.
2. Any Civil constructions that are inside the Dike like foundations shall be correctly calculated and accounted for. Otherwise the calculation will result in incorrect dimensions and reduced retention capacity.

Economy and Engineering sense, mean that Tanks with similar purpose are placed together with a common Dike. In this case, the volume of the largest vessel is considered for calculation. This reduces
1. Civil work
2. Dike wall height (as the area is increased)
So it becomes more cost effective.

However, as a piper, our responsibility does not end here. Following points shall be considered as well
1. Openings for pipe entry in the Dike (Puddle flange requirement)
2. Entry / Exit for the operators with due consideration for wind direction and fire hazard.

Hi Gkumar
pl. go to following link.

http://www.pstif.org/apps/dike_calculation_sheet_e.pdf

Hope this helps

Siddharth Jain

Dear All,
Do you have anything on the subject Dike wall calculation? I understand that volume of the dike should 110% of the tank volume if it is a single tank & if there are multiple tanks of the same purpose/fluid, we should consider the dike volume as 110% of the largest tank in the group.

I still have many queries to solve to become confident enough to do it myself on live projects.......
-I have already gone through number of posts on this forum but i think there is a need for an example to understand it in a better fashion?
-Are there any limitations to Length, Breadth, Height except from available space point of view?
-How we should treat the tank foundation in the dike?
-Access point of view considerations?
-Pipe connections through dike? How we make sure the spillage does not go out of the dike in any case?
-There are ready made xls sheets (with intelligent formulas) where we just put the volume of the tank & you get the results of the dike dimensions but we understand first what kind of calculations we are doing exactly ??

Thanks in advance,
Abhijit

cj.abhijit ,
"Are there any already made xls sheets (with intelligent formulas) where we just put the volume of the tank & you get the results of the dike dimensions but we understand first what kind of calculations we are doing exactly?"

Answer: I made a spread sheet just as you describe about 15 years ago. In my travels since then I have lost it. I will work on making a new one and get back to you.

Considering your other questions:
-Are there any limitations to Length, Breadth, Height except from available space point of view?
Answer: No, not formally. There is common sense which says don't put tanks storing the different product in the same dike area. Don't make the dike area so big that you cannot get access to a tank in a safe manner.

-How should we treat the tank foundation in the dike?
Answer: Calculate the displaced volume and add it to the containment volume requirement.

-Access point of view considerations?
Answer: There are two kinds of access. There is walking access for operators and there is vehicle access for maintenance. The operator access should be from a point nearest the pumps so the operator can get from the pumps to (and from) the tank (s) in the most direct line. There should also be an alternate egress (escape) route in case of fire or other hazard.
Maintenance access should be up and over the dike from a road that is preferably not on the same side as a sleeper pipe rack. On the same side is normally just too complicated

-Pipe connections through dike? How we make sure the spillage does not go out of the dike in any case?
Answer: I used and recommend a "Sleeve" type of dike penetration. I will need some time to work up a sketch to convey the details if you do not understand the following.
Basically it is:
a- a product pipe inside a larger sleeve pipe. example: 8" (DN200) inside a 14" (DN350). Adjust the sleeve size based on the required product line size by adding 6" (150mm) and round off to the closest line size.
b- the sleeve pipe is anchored in the center of the dike with a "Puddle Flange" embedded in a concrete block to form an anchor. The sleeve pipe is long enough to go through the dike at the proper elevation plus one (1) meter on each side of the dike.
c- the end of the sleeve pipe that faces the inside of the dike area is open for drainage in case of leakage.
d- the end of the sleeve pipe that faces the outside of the dike area is fitted with a "sleeve" size Slip-On (or weld Neck) flange. Slip-On is normally cheaper and there is no pressure or temperature considerations to be worried about.
e- the product pipe is fitted with "Spider Guides." These are metal spacers welded to the product pipe (3 meter spacing) that keep the product pipe centered inside the sleeve.
f- the product pipe is fitted with a sleeve size to product line size slip-on reducing flange (this flange bolts to the Sleeve flange in "d" above)
g- the product pipe continues on both sides of the dike in a normal manner consistent with your overall design.
h- Multiple dike penetrations in the same area would be done the same manner, you would just need to increase the line spacing to the sleeve size not the product line size.

I hope this helps.

I must thank you for efforts you are taking to make us understand things & the huge amount of quality knowledge you have with piping related things/activities.

Your reply is helping me a lot but a roughly drawn sketch will be a great help..!

Thank you a lot,
Abhijit

I have also one more small query in this regard...

Why it is considered that only one tank is going to get failed where as it is always possible that if one tank fails the affect of which can be the failure of other tanks near by????

Pls advice??

Abhijit

I suppose that will be a serious implication from hazard point of view. So I Googled it up:-
Following is better thread with some more links. I recommend you go through it including the links:-
http://www.cheresources.com/invision/to ... dike-wall/

From the looks of it:
The decision of grouping tanks is not binding one. The tanks can be individually 'bund' (Dike) walled. Individual bund is preferred for large capacity tanks. The grouping decision is a result after studying the hazards (HAZOP, HAZAN) and involves Safety professionals as well. I do not have any FEED or early stage work experience. But I am sure there will be people on this forum who have this type of experience. And they must have participated in those early "formative" stages of plot plan. Probably they'll illuminate us with this activity.

Pls HELP....!

The following questions were asked regarding multi-tank dike areas.

"Why it is considered that only one tank is going to fail where as it is always possible that if one tank fails the affect of which can be the failure of other tanks near by?"

"Why do we use the 110% criteria for sizing containment areas for tanks? I is it more concerned with some CODE? Is that why we take the dike volume as 110% of the largest tank even if the possibility is always there that we can have multiple tanks failed at a time!"

In the United States the Code that applies to Storage Tank location and arrangement (not the design of the tank itself) is:
NFPA 30 Tank Storage and Piping Systems
This code may or may not be used in other parts of the world. That would be a Client/Project decision. If you find that it does apply to you project then your Company or your Project needs to purchase a copy so you and others can read it.

This Code gives guidelines for which types of tanks (Fixed Roof, Floating Roof, etc) and/or which kinds of commodities (Crude Oil, Intermediate Products, Finished Products based on Flash Point, etc) can be located in the same containment area.

The issue of multiple tanks and the consideration for only one might fail: I think this is based on "Law of averages." It must be rare that two tanks in the same containment area would fail at the same time due to natural causes. There is always the possibility of an act of terrorism where multiple tanks might be hit at the same time but I don't think that is the governing factor.

The issue of 110%: The extra 10% is for a concurrent possibility of a massive rain storm and/or a lots of firewater being added to the containment at the same time before the storm drains can be opened to drain off the excess water. Remember the oil will float on top of the rain/fire water.

Sirs,

Hope you can help me with this,

Scenario: 2 Asphalt tanks of same capacity to be placed inside dike area.

Should the dike capacity still needs to be designed to accommodate the equivalent volume for one tank x 1.1 considering asphalt properties in which on the event of spillage it would just harden and mound on itself?

The reason I asked is I want to minimize plot/tank area as possible without getting a very high bund wall. I think that the dike will serve its purpose to initially contain the spillage within the area then allow remaining asphalt to cool down. Should I deviate and design the dike to hold less than that of tank capacity? What would you recommend in this case?

knives,
You did not say where your project is located. So I am going to base my recommendation on a USA location.

Two or more tanks: The Dike area capacity shall be 1.1 times the volume of the larger tank plus the displaced volume of any other tank(s) only to the height of the proposed Dike.

To assist you in Tank & Dike calculations there are tools on this web site. Look under the "Tools" button and go to "Equipment section. There are two items you should review and consider using whenever you have a Tank/Dike situation.