ULC S601 - Diesel Stoarge Tank in Cold Temperature Applications 2

[TRH80]

Our project, located in northern Alberta, Canada, has a requirement to specify diesel storage tanks in accordance with ULC S601, however, our project also has a minimum design temperature of -45°C. Section 4.2 of ULC S601 lists acceptable materials for the fabrication of the tank in accordance with this standard, however, many of the materials are not low temperature rated materials. ULC S601 does not address low temperature requirements.
Here is my 2 part question:
1) Is industry practice to allow use of these non-low temperature rated materials (ASTM A1011, ASTM A1019, ASTM A36) for outdoor diesel storage tanks in cold temperature climates (ie. -45°C)?
2) Is it the owner's responsibility to specify materials which meet the -45°C MDMT (ie. CSA G40.21 Cat 4) to vendors to build to ULC S601? Thanks for your input.

 

[MJCronin]

I would consider an "uprate" of your design standard to API-650.

If you have not already, review the details on selecting MOC for tanks designed under API-650.

You seem to be aware of the very real hazards of using materials not qualified for these ultra-low temperatures and the loss of the tank.

In answer to your questions:

1) NO, use your experience to develop a design methodology

2) YES, but it has been my experience that 95% of the time, the client lacks the depth of understanding and experience to be competent. Present to the client your research findings.... come to a common agreement.

IMHO, I strongly suggest that you contact a Canadian tank fabricator and informally ask about his recommendations on MOC and selection of construction standards. What materials has he used in the past ??

If you are not close to the ocean, consider pricing comparison for a stainless steel tank. Unlike CS, SS is not sensitive to low temperature brittleness, requires no coatings and might be cheaper in this appliaction

MJCronin
Sr. Process Engineer

 

[TRH80]

Thanks MJCronin. Your answer confirmed what I was thinking. I find that the ULC S601 standard can be misleading on this topic.

 

[MJCronin]

Years ago, I have dealt with fuel oil system freeze-up in eastern Pennsylvania.

The combination of low flow and a clogged strainer, stopped supply and the startup of a utility boilers.

To cope with freeze-up, some owners dilute the diesel fuel with kerosene, some people use additives, some put their systems on permanent recirc with heaters.

Just out of curiosity , how do you intend to keep the fuel flowing at extreme low temperatures ?

MJCronin
Sr. Process Engineer

 

[TRH80]

I am not sure on the details on the diesel fuel grade used by operations. However, I believe it is a low temperature diesel grade (addition of additives to keep it flowing).

 

[IFRs]

As a hopefully licensed professional engineer your first responsibility is to the public. In this case brittle fracture of the shell material and failure of the tank leading to a major product release is the concern. Using steel that retains adequate toughness at the minimum design metal temperature is one proven method to avoid such failure. You would be wrong not advising your customer of this issue and insisting on using an established guide such as API 650 to design the tank. You would not design something that is too weak, similarly you would not use materials that were not tough enough.