Lugs designed for -45 ¦C MDMT vs meet impact req 20ft-lbs at -45¦C 2

[billbusy]

Lifting lugs designed for -45 °C MDMT vs meet impact req 20ft-lbs at

As a new guy in this industry, I just want to know what's the difference of these two statements. Which is right? Our QC staff ask me to change the 1st one to 2nd statement in the datasheet... But I always use the 1st one before...

Thanks.

3 years industry experience;
Oil & Gas industry in Canada.

 

[Duwe6]

"Design for -45 MDMT" gives no fixed limits. I could get stupid and pick a material with a 2 ft-lb charpy. With a 20# low-limit, your expectations are defined.

 

[doct9960]

Lifting lugs designed for -45 °C MDMT

Out of curiosity, what's the reason for the -45C MDMT?

I have seen this -45C requirement on some Owner specs. I usually ask why, but I can't get a reasonable answer. The usual answer is "it's in the specs for years" or "lifts will be done during winter". For sure there's a good reason. But until I hear one, I think the -45C requirement on lifting lugs is just a waste of money.

Let's say the ambient temperature is -45C. With winds at 15 kph, the wind chill factor could be -60C. Would rigging folks be willing to perform lifts on a brutally cold day? And surely the cold weather will affect the performance of the lifting equipment or crane (re: shock loading, hydraulics). Doing lifts on a -45°C day is just insane.

 

[billbusy]

doct9960:
In Canada, I think -45C is routine requirement for outdoor equipment.

Duwe6:
What I think is that 20ft-lbs at -45°C is a fixed requirement. But the ft-lbs at -45C should be changed per material. Some are 15 ft-lbs. Thus, I think just mention -45 °C MDMT is a reasonable clause and the vendor need to verify the detail. Not sure if this is correct.



3 years industry experience;
Oil & Gas industry in Canada.

 

[doct9960]

billbusy,

In Canada, I think -45C is routine requirement for outdoor equipment.

Where in Canada?

In Alberta, we don't routinely design vessels for -45°C MDMT. Most of them are designed for -29°C MDMT. But we do require that supports such as skirts be designed for -45°C.

 

[TomEun]

Most companies apply the following guideline for the impact test temperature (requirements and exemption) of pressure or loaded parts in Northern Canada.

- Insulated or indoor components : -29°C (please confirm it to your client)
- Uninsulated components : -45°C

Most lifting lugs, skirt, saddles, supports, and steel structures are operating under uninsulated condition.
Even though ASME BPV codes do not cover the non-pressure boundary components, most end-users are using the requirements (including mitigation and exemption) of impact test for pressure parts in ASME BPV for them.

In your case, the impact test evaluation (requirements, mitigation and exemption) per the ASME code for the vessel should be considered for the welds [-29°C (when confirmed) for insulated and -45°C for uninsulated] as well as the base metal.

Thomas Eun

 

[billbusy]

Thanks Tom,

You are correct.

I also checked with some senior engineers in house.

They told me the general rule in Alberta is
- Insulated or indoor components : -29°C
- Uninsulated components : -45°C

Both of them may be changed per process condition. Normally the client will specify their requirement.

The 20ft-lbs impact test requirement for lifting lug is a general rule we used before, even it is not in any standards or codes as you mentioned it is not within the scope of ASME SEC VIII.

3 years industry experience;
Oil & Gas industry in Canada.

 

[SnTMan]

billbusy, Duwe6 touched on the difference which could be interpreted as:

"designed for -45 °C MDMT" = meets required MDMT but possibly exempted from impact test by some means

"meet impact req 20ft-lbs at" = base metal and perhaps weld procedures etc actually tested at the temp of interest

Depending on what's actually wanted, could be a world of difference

Regards

Mike

 

[billbusy]

SnTMan,

Yes, thanks. It makes sense.

The interesting thing is that, I cannot find any clauses, neither in codes nor our client's standards, to request the 20ft-lb test.

If that is a extra requirement, it should be in a standard or specification whatever from our client or ourselves..., Right?


I also asked someone else in our company, but did not get any clue yet.


3 years industry experience;
Oil & Gas industry in Canada.

 

[SnTMan]

billbusy, SA-20 requires 20 ft-lb for some steels, as does UG-84. Other than that, I couldn't guess where the requrement might come from.

If it is indeed a requirement, it must be written down somewhere, right? Make whoever is requesting produce it

Regards

Mike

 

[rhg]

Impact req. 20 ft-lbs at -45ºC is very clear. I prefer this sentence in the data sheet plus "fine grain size 5 or higher". See SA-6 too.

Regards

rhg

 

[rhg]

Be careful with rigging hardware ASME B30.26, and Design of below- the-hook lifting devices ASME BTH-1

regards

rhg

 

[Guest102023]

I prefer not to specify grain size when toughness and the material heat treat condition have already been specified. Killing the problem in one direct, unambiguous way is sufficient (as opposed to 9 ways to Sunday).

Besides, test labs are notoriously inaccurate with grain size assessment.