Conversion of API650 Heavy fuel oil Bulk Storage Tank to a Bitumen Bulk Storage tank 1

[Shiv1295]

Hello guys,

I am working on converting a bulk storage heavy oil tank into a bitumen bulk storage tank. This is a big vertical API650 tank O.D. 25m x 12.5m height.
Our company uses holding tanks for pumping at usable temperature for the end users with blends and additives and insulates mainly those tanks for exit mass flow rates of upto 100mm3/hr. The bulk storage tanks are fitted with floor heating coils for low product draw and suction heater for pocket heating of bitumen to transfer into service tanks. So, the bulk storage tanks aren't insulated and extract as much as 5m3/hr with pocket heating on a tubular suction heater. The product will be 60-70 bitumen
Having said that, I have confirmed the new design and operating temperature for this conversion to suit the material, foundation and limits on fill height due to the change in density and temperature of the product inline with our operating procedures for using this tank.
The tank has been API653 inspected and all modifications in the past are in line with API653 to designate it as an API650 tank for the product then.
My work requires putting a new design of suction heater, floor coils and a standby suction heater into this tank and making all the modifications on it in-line with API653 requirements. These floor coils and suction heater will be heated with thermal oil.
Before I commence my work, getting tank inspection done again is imminent, last reports have been very satisfactory in the eyes of a CPEng that I am consulting for this job.
My questions are the following and I will be grateful for getting input from your valuable experiences:
1. Bitumen once filled in the tank will coat the inner walls of the tank as we aren't doing bulk heating. This could be a good corrosion protection layer on the inside wall of the tanks. API 653 requires a tank to be inspected externally every 5 years and internally every 10 years(please correct me if I am wrong)to give it an API650 tank certificate. Is there a workaround for Bitumen Bulk storage tanks to not have this inspection done as the internal walls are already coated with bitumen or there is no possibility of avoiding an internal clean up for full tank inspection? I want to maintain it to API 653.
2. Is it a common practice to do pocket heating rather than insulation and bulk heating for bitumen bulk storage tanks? It all adds up in cost for us and hence we don't unfortunately have the luxury of insulation and cladding. Hence the holding tank on-site with those arrangements.
3. Any guides on API650 certification for Bitumen vertical tanks will be helpful
4. If foundation, fill height, material allowable and design temperature requirements are met for such a conversion, can you please recommend any other parameters to definitely check before making decisions going forward, will be getting in an API650 inspector later.
5. Before I use this tank for any modification on the inside and the outside, as this tank was used eventually for storage of diesel in the past few years, what should be the best practice to follow for clean up of the tank for working inside the tank? Tank trims will need working inside the tank.

My apologies for silly questions , if any, I am limited by resources and quite green to the API tanks.

 

[Andrew ONeill]

Hi Shiv,

I don't have experience with Bitumen tanks, but do have a lot of experience with similar sized and proportioned API 650 tanks.

1) From memory API653 lets you extend the internal inspection interval to up to 20 years, and it's all based on preventing floor leaks. In effect if you have an underfloor leak detection (think tank on concrete slab, rather than on sand, you can consider it. The only other "work around" is to go down the Risk Based Inspection route. In that case you won't strictly comply with API653, but it would still be considered acceptable (depends of local laws, regulations etc)

2) No experience
3) No experience
4) From a design check, go through the whole thing again. Don't forget wind and seismic loads. Seismic loads can often govern on tall tanks. If you are increasing the fluid density, it will be made worse.
5) No experience

Hope this helps.

Andrew O'Neill
Specialist Mechanical Engineer
Rio Tinto
Australia

 

[LittleInch]

Can you expand on what you mean by "pocket heating"?

Bitumen needs to be at about 130 to 140C to flow. That's far too high for an exposed tank surface. Also bitumen expands and contracts a lot so if you're not keeping this tank hot all the time there could be large amounts of movements and stress.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[HTURKAK]

Shiv1295 (Mechanical)

Your questions inclined me to suggest you that , your company / organisation should consult a qualified engineering firm .

I do not agree with some of your decisions..

1- The bottom of roof plates and the shell portion above the max. LL will need corrosion protection. Moreover, the selected paint/coat shall be suitable for design temperature. I would like to remind sulphur corrosion.

2- Pocket heating or ( heating the content locally around the suction ) is suggested for large tanks V=≥1000 cu-m

3/4 - Pls look API RP 2023 ,Asphalt Institute Manual The Asphalt Handbook..

5- This subject is also very important before hot works can be done and needs expert supervision ..