DRAW OFF SUMP AND CATHODIC PROTECTION

Question

DRAW OFF SUMP AND CATHODIC PROTECTION

Ramil Abbaszade (Mechanical)

(OP)

10 Sep 20 13:57

Hello dear forum users,

There is a Diesel Storage Tank that will be designed in 39.9 m diameter / 18 m shell height.

My questions are:

1) How many DRAW OFF SUMPs would normally be best needed for this size of Storage Tank? and also What would be the best size of drain Nozzles coming out of these Sumps? Is there any engineering guideline or practice that you could suggest me to refer?

2) The tank will be constructed from CS, most probably A-285 Gr.C. Would any outside CATHODIC PROTECTION be required for Diesel Tank constructed of CS material? Would it be safe if yes?

Tank experts would be highly appreciated if they can reply to this thread!

Regards,
Ramil

HTURKAK (Structural) · Answer 1 · 2020-09-10 20:31:58

Quote (1) How many DRAW OFF SUMPs would normally be best needed for this size of Storage Tank? and also What would be the best size of drain Nozzles coming out of these Sumps? Is there any engineering guideline or practice that you could suggest me to refer?)

The question implies cone-up bottom. What is your position ? Are you client ?..

As far as I understand , the use of Water Drawoff Sumps is not a API 650 mandatory requirement and ,the construction of the sumps ,the number, size, and configuration is up to the tank purchaser. What is the winter ambient temperature ?

Quote (2) The tank will be constructed from CS, most probably A-285 Gr.C. Would any outside CATHODIC PROTECTION be required for Diesel Tank constructed of CS material? Would it be safe if yes?)

Will you provide some details for the bottom of the tank? CP is also not a mandatory requirement . Refer to API RP 651 for for guidelines for CP.

Ramil Abbaszade (Mechanical) · Answer 2 · 2020-09-11 11:51:41

Hi,
We are the contractor side and will be preparing Mechanical Datasheet (GA) for this tank. The Tank bottom will be Cone-Up and will probably have 1:120 slope . MDMT is -13 C deg. The Operating fluid is Diesel as I mentioned before.

Regards,
Ramil

HTURKAK (Structural) · Answer 3 · 2020-09-11 16:44:52

MDMT is -13 C deg . ( Minimum design metal temperature is -13 C deg ). I understand freezing area and you are the contractor side ..

In this case (you are not the client ) , I will suggest three shell manholes and three drawoff sumps for this diameter tank ,120° apart. Regarding size of the drawoff pit, look API 650 Figure 5-21—Drawoff Sump and Tables 5-16 .

The pipe size 3'' and drawoff valve shall be different and suitable for freezing zones.

Good Luck..

Ramil Abbaszade (Mechanical) · Answer 4 · 2020-09-15 08:46:42

Yes, for shell, I have considered 3 manholes: 2 No. 24" and 1 No. 30" size.

Thanks for suggestions anyway. I appreciate it.

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DRAW OFF SUMP AND CATHODIC PROTECTION