FORGING LAPS 3

[ayk]

DOES ANYONE KNOW WHERE TO GO FOR INFO REGARDING "FORGING LAPS"? I KNOW IT IS A PROCESS ISSUE AND MEANS FAULTS AS A RESULT OF FORGING PROCESS. I WANT TO FIND OUT HOW IMPORTANT FOR THE END USER OF A PRODUCT TO CHECK FOR SUCH FAULTS. FOR EXAMPLE, FOR SINGLE ANCHOR POINTS USED AT HEIGHTS, IS THERE AWAY FOR THE USER TO CHECK AND REPORT IF THERE ARE ANY SUCH FAULTS OR IS IT TOO COMPLICATED FOR THE END USER AND MUST RELY ON MANUFATURER'S GUARANTEES?
THANKS
AYK

 

[TVP]

A lap is a defect that forms when metal folds back over itself during forging. Nonuniformity of metal flow is often the cause, usually due to an excessively sharp radius in the die. Laps can be detected by non-destructive or destructive means. Magnetic particle inspection and liquid penetrant inspection are commonly used to detect surface flaws like laps and folds. Sectioning followed by polishing is often used to reveal laps, especially those at the root of threads which have been improperly formed. Any of these methods is well within the capability of even a modestly equipped quality lab.

 

[Rjeffery]

ayk,

The end user should NEVER have to look for defects in the product. The Manufacturer should (read, must) ensure that its product is delivered to the market free from (rejectable) defects. The end user, on the other hand, should be concerned with in service problems. (i.e. wear, work hardening, fatgue and the like.)

 

[Metalguy]

Rjeffery,

Since things like laps can easily lead to in-service fatigue cracks, the end-user frequently *has* to look for manufacturing defects. Only in the ideal world would this not be true.

 

[Carburize]

ayk, what does the purchase specification for the parts require?

 

[ayk]

Thanks to everyone for comments.

Carburize;

Maybe weird but this is actually about a standard for "static lines" used for height safety. Some static lines are made up of wire systems for workers' safety, say, at roofs. Such systems can be installed as proprierty products. As height safety is now a major, if not number one, issue to handle, it is critical to set everything right to minimise fatalities. Question is whether we must go into such details like checking against "forging laps" and similar deficiencies on the parts supplied by the manufaturers. That is why I asked for help.

 

[Carburize]

I would take a look at what the standards for similar parts require, for example how does ASTM cover the integrity of eyebolts that are used to suspend loads over people. I don't have a copy to hand but it probably says something like - the material shall be free from any injurious defects such as cracks,bursts, seams and laps .

 

[Metalguy]

Ayk,

If these parts are for emergency conditions only, and do not see applies loads normally, you can forget about fatigue cracking.

A simple proof load test should be sufficient.

 

[CoryPad]

Adding to what Carburize said, ASTM F 541 Standard Specification for Alloy Steel Eyebolts has the following information:

The eyebolts shall be of uniform quality consistent with good manufacturing and inspection practices. They shall be free of fins, cracks, seams, laps, nicks, pipe, segregation, rough surfaces, and other injurious internal or surface imperfections which, due to their nature, degree, or extent, would make the eyebolts unsuitable for the intended use.

 

[CWIC]

ASTM F 541, Section 9 is the accptance criteria for visual examination of surface imperfections. If additional requiremnts are specified, it should be done at the time of purchase (Section 3, Ordering Information).

Used similar hardware a few years ago on a space frame project and the client found detrimental discontinuities present within the hardware. The supplier beat the wrap as this was not specified at the time of purchase, repair costs were borne by the buyer on that project.

 

[CoryPad]

CWIC,

ASTM F 541, Section 9 is Workmanship, Finish, and Appearance. I disagree that this applies only to visual examination. This standard, and others that are similar, can be used to disqualify material that is found to be defective. Material free from laps is not an additional requirement, so it doesn't have to be requested at time of purchase. I am not discounting your anecdote, but the buyer on your project was correct and should not have had to bear any repair costs. I find that logic (actually the lack of logic) to be ludicrous.