Design using AISI 1018 Steel

[smb4050]

For use in the USA, what is the appropriate design specification to use for a below the hook lifting device made of 3 7/16" solid round AISI 1018 material? It will be used to lift coils of conveyor belting material. Thanks in advanced for your time and thoughts.

 

[JStephen]

Below-the-Hook Lifting Devices ASME B30.20 - 2010
Design of Below-the-Hook Lifting Devices ASME BTH-1 - 2008

One is the standard itself, the other is the design guide.

Also, the standard references an AWS equipment welding code rather than the Structural Welding Code.

 

[smb4050]

I have B30.20, but it doesn't offer much in way of design other than FS of 3, but didn't know about BTH-1. Thanks

 

[dhengr]

Smb4050:
You are probably over-thinking/worrying this design project, in all the wrong ways. Why does AISI 1018 mat’l. figure so prominently in your question? How is it going to be used in your design; as a shear pin or as a long bent bar or hook for lifting the belting? If it’s a bent bar is that the best design? It’s just merchant quality mild steel bar stock which can be purchased from most any steel supply warehouse, isn’t it? The one thing you might do for materials on this kind of a design is get mill certs. from your suppliers, and consider those values in your design, then put these certs. in the design file as documentation. Otherwise, these things are usually fairly std. design problems for a Structural Engineer, although somewhat different than a simple beam in a building, but more interesting too. I don’t have recent copies of the ASTM BTH codes, so I can’t comment on specific paragraphs without your posting them. Any of the codes, and your client’s location and end use will dictate these, give FoS vs. Fy or Fu, etc., they give test loading instructions, in-use inspection requirements, and the like; otherwise they assume design using normal, well established, engineering and mechanical principles and methods of fabrication. They do pay some extra attention to the potential of dynamic loading, repeated loading and use, misuse and the like. So, good clean design, fabrication, welding, fatigue resistance, etc. come into play. OSHA may come into play in the plant also.

Other than the appropriate design code, you might do well to dig out a couple text books on Strength of Materials, Machine Design, Rigging/Lifting Equip. and the like. If you already have ASTM B30.20, what’s your question? You have to explain your design issues and problems in more detail, if you want more help.

 

[smb4050]

You are correct it came from a local steel supplier. It's a cold formed member, but 1018 is not listed as an approved material in AISI Standard for Cold-Formed Steel. 1018 does meet the qualifications of A2.3.1 except it's round and is more than 1" thick thus not included AISI per section A1.1.

It is a simple application. The solid shaft will be stuck in the middle of the belting coil with a sling placed around the shaft on either side of the coil.

So ya I'm probably over thinking.

 

[dhengr]

Smb4050:
Maybe over thinking was the wrong phrase on my part, just be sure you think about the right things, and understand the important aspects about this kind of design. You guys have so many more codes, standards and specs. than I can afford or have easy access to that it makes my head spin. But, AISI 1018 mat’l. has a single chemistry (composition) spec. so hot rolled or cold worked that doesn’t change much; but the cold rolling or cold drawn bar gets its added strength specs. (mechanical properties) from the cold working it has been put through. However, those mechanical properties are only in some surface depth (skin deep), due to the cold working process, not the full depth of the larger bars, and that’s probably why there is some size limit on the spec’d. Fy or tensile strengths for your application. The improved surface strength and improved surface fatigue characteristics of the cold worked rounds is particularly advantageous for real rotating shaft applications. I’d have to see those AISI stds. to comment further.

I assume you picked this piece of shafting for its Fy and dia. Can you tolerate a larger O.D., and if so, you might get the same shaft strength vs. beam length and loading out of an extra strong piece of pipe, at a lower Fy. And, this would probably be less expensive also. I think there are some mech. tubing specs. with better mechanical properties than our normal pipe specs. With what it sounds like you are going to do, you should be sure to put some sort of a retaining washer or disc on the ends of your shaft so that there is no way the slings can slip off the shaft while lifting. Are the slings vertical and off a spreader beam of some sort, or inclined up to a hook? The retaining discs don’t have to take much load, just retain the cables at a slight angle, and one could be removable for insertion through the coil. The question is, what would happen if something shifted and the shaft was inclined at 5 or 10 degrees from horiz.?

What are the length of the shaft, sling to sling lifting points and the loading condition, dimensions and loading? Compare your 3&7/16" round bar with extra strong pipe at 4" or 5" O.D. The two pipes are stiffer (greater I "^4) and have better bending strength (greater S "^3) than your round bar, and they are both quite a bit lighter in terms of someone hefting them through the coiled belting.