Schedule 40 pipe

[Aton]

It has been quite a while since I last posted to this site. I am now working in the Arctic and have been asked by one of the small communities to design several small bridges to span steep gullies and seasonal streams. These bridges are for All-Terrain Vehicles or snow machines (pulling heavy kamutiks loaded supplies, caribou, seal, etc). One of the many huge problems in this isolated part of the planet is that material shipment is incredibly expensive: once each year a barge can get in, otherwise everything must be flown in. We have just recently torn up miles of fuel pipelines in the community. This Schedule 40 pipe is in excellent condition, and I want to use it to make these bridges. There is a certified welder who lives there, and they have competent human resources to make anything I design. So far I am starting out with these parameters: ASTM A53. Composition very similar to AISI 1018 steel. Yield strength = 30 ksi. Tensile strength = 48 ksi. Young's Modulus = 29x10^6 psi. I am specifying standard welding electrodes. Since I cannot find any specific information about the material properties of Schedule 40 pipe, I am hoping that I am in the ball-park. Any advice would be helpful.

Sustainable, Solar, Environmental, and Structural Engineering: Appropriate technologies for a planet in stress.

 

[dik]

Looks like you have some fun work ahead... your A53 steel is likely weldable... you can weld a stub to it and break it off by hammering to do a simple test. What sizes? You can flatten the ends of members and burn on an angle for a cropped web type of construction. You should be able to fabricate various joists. The members are of very low strength and local buckling should not be much of an issue.

Dik

 

[metengr]

Yes, you're in the ballpark in terms of mechanical properties. However, I would have a more serious concern about impact or notch toughness.

 

[arunmrao]

metengr a challenging poser for you. How do you ensure adequate toughness at sub zero temperatures. The weld joints and HAZ will be critical areas and need a closer look from an expert like you.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[metengr]

I would qualify the material and weld filler metal using Charpy (V-notch)impact testing. You can run some weld process qualification coupons with impact testing of the weld, base metal HAZ and the base metal itself.

Now the real concerns with design are minimum metal temperature in service and the minimum acceptable CVN value for impact testing.

 

[Aton]

Thanks (again), metengr, and dik, and arunmrao. I will be following up on this.

 

[consultmet]

What is the lowest expected temperature?

Is the A53 pipe welded or seamless? Chemically A53 is only a carbon steel with 0.25-0.3 C, with manganese- 0.95-1.20

A53 wouldn’t be similar to AISI 1018? Would it? AISI 1018 has 0.15-0.20 carbon and 0.60/0.90 Mn.

I would be concerned about consistently achieving 20 ft-lbs at room temperature with this grade. I believe Charpy values at sub-zero temperatures would be below 10 ft-lbs. If you’re expected lowest temperature is -50F I would expect CVN values below 5 ft-lbs.

Sorry I don’t believe any welding procedure will help, the main problem is the base metal is not suitable for low temperature conditions in a structural service.