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API 650 clause and figure 4.1.a.

API 650 clause and figure 4.1.a.

API 650 clause and figure 4.1.a.

Dear experts,

API 650 paragraph states : For all materials to be used at a design metal temperature below 10 °C (50 °F), the qualification of the
welding procedure for vertical joints shall include impact tests of the weld metal. If vertical joints are to be made by a
machine, automatic, or semiautomatic process, impact tests of the heat-affected zone shall also be made.

API 650 Figure 4.1.a. specify the impact requirement based on material thickness and minimum design metal temperature.

There is a case we are exempted for impact test based on Figure 4.1.a but we are not exempted by clause

So we need to perform the impact test to satisfy clause

Any comments ?


RE: API 650 clause and figure 4.1.a.

Sounds correct.
Note that the Fig. 4.1 exemptions are for the actual material used for that particular tank. The clause relates to the testing done during development of the weld procedure and wouldn't need to be repeated for each tank.

RE: API 650 clause and figure 4.1.a.

JStephen has eloquently stated the answer to your question, the following is mere embellishment:

API 650 provides design guidelines for the long-term suitability of your tank and in particular the need to avoid failure by brittle fracture.

Figure 4.1 illustrates materials and their acceptable use without impact testing, determined by API group number, thickness and design metal temperature. This can help you choose material for the tank that can be used without further toughness qualification.

Section 9.2 discusses toughness of the as-welded material and the weld metal itself, again to avoid brittle fracture issues and gives guidelines and requirements to help you create and use proper weld procedures.

These two sections ( material and welding ) are independent and both must be satisfied.

RE: API 650 clause and figure 4.1.a.

Dear JStephen and IFRS,

Many thanks for you explanation.

In my case I have A516-Gr. 70(N) which is Group V per API 650.

The MDMT is -3 celcius.

Thickness of the plates are 36 mm to 10 mm.

The other tank is A283C which is Group I per API 650 with MDMT -3 C as well. Plate thickness 6 mm all shell course.

Looking to figure 4.1.a. we are exempted from impact test.

But due to clause in API 650 we have to conduct impact test on our PQR coupons.

And due to this impact test the welding position will be essential factor.

Also due to impact test requirement the thickness of the PQR coupons will be various to cover those 36 mm to 10 mm thickness range. The PQR Coupons will be A516-Gr. 70(N).

Maybe I need to prepare separate PQR coupon to cover A283C.

Your comments is highly appreciated.


RE: API 650 clause and figure 4.1.a.

I'd have to check on that. But I didn't think the requirement for impact test in the procedure triggered the supplementary-essential variables option, though.

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