Author Topic: proof load testing rope  (Read 8683 times)

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proof load testing rope
« on: April 07, 2009, 05:49:15 AM »
Hello all

Anyone help me on what is the right proof load to demonstrate a rope
is good?  Or whether proof-load-testing is the right way to
demonstrate your rope is good.

I've received help in the post and thread "testing long-splices".
Which I haven't managed to do, but "preliminary" static tensile tests
have directed me to ask this question.

Taking the case of 10mm polypropylene 3-strand cut-film "builder's
merchant rope", found breaking force of 13kN (equiv. 1.3 Tonnes
suspended in gravity).  Started to hear cracking sound of fibre
breakage from about 12kN (getting to be a continuous
crackling/tinkling sound by 12.5kN).

So one might think that you don't want to be proof testing this rope,
considered to have a tensile strength of 13kN, at 12kN or above - to
avoid damaging and/or degrading the rope you wish to prove is good.
Then, you might want to put on a "safety margin" say double the
difference between the onset of audible fibre-breaking and tensile
strength - which would mean don't proof-test above 11kN.

If proof testing is good - is there any recommendation for moving from
a proof-test load to a "safe working load"?

Another aspect:

In a test where put the rope around a sharp 90deg corner - what you
get when you precision drill transversely through a steel shaft - cut
through a strand at 1.7kN (170kg in gravity).  Vastly lower than the
13kN of a "perfect" tensile test.  Obviously this is an extreme case,
but any formulation for rating a good working load in "rough"


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Re: proof load testing rope
« Reply #1 on: April 07, 2009, 04:02:25 PM »
If it helps you any, I can tell you what synthetic sling manufacturers often do.  They will apply a proof load that is double the safe working load.  The safe working load is usually one fifth (or less) of the breaking strength or ultimate strength.
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Re: proof load testing rope
« Reply #2 on: April 08, 2009, 06:01:16 PM »
I do wonder if there are some practical ways to make an assessment of
cordage as you seem to ask.  I.p., re rockclimbing ropes, if there could
be some reasonably practical (do-it-yourself-or-at-convenient-climbing-gym)
drop tests that would give an indication of diminished force-absorption
capacity (by comparing the elongation on the drop of the used with
the same measure taken with new rope).

But with used ropes, one has also the question in mind as to whether
the rope has seen uniform usage and wear or might have some
worse spots here & there (which might be missed by even sampling
the rope by testing an end (though in RC ropes, it is usually the ends
that show most deterioration--and are sometimes chopped)).


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Re: proof load testing rope
« Reply #3 on: April 10, 2009, 05:07:43 PM »
Dan, everyone

My hopefully insightful thought is - what is it we are trying to
achieve?  Are we trying to prove that whatever the overall
circumstance, because the proof load was 4Xkg the rope can be
certified to carry Xkg?  Or are you testing whether the rope is still
good - in that if it will carry Ykg when new, you load the rope to
0.8Ykg and if it takes it report it to be in an undegraded state fit
for general use in the line with accumulated experience?

I'd have thought that for climbing or construction use, you'd want to
test the whole rope.  I had thought on this matter as looney-brigade
edicts started to emerge through 2008.  With a site tower crane you
could easily pick up a proof load with the entire length of any rope
you have - and the ease and readiness of this test means that it can
be done frequently.  It becomes "what are you comfortable with?".
Every week?  Lead contractor wants that to be so - no problem.  Every
Monday morning lift a large object in the right weight range and
certify your rope for use to some fraction of that proof load.  And
mandate testing at any intervening occasion if some occurrence makes
you want to know whether the rope is degraded.  I think that fits in
with UK Legislation.  It wouldn't be good to try to interpret it for
you.  It's here
Statutory Instrument 1998 No. 2307
"The Lifting Operations and Lifting Equipment Regulations 1998"

"Simple guide to the Lifting Operations and Lifting Equipment"

"Thorough examination of lifting equipment - A simple guide for employers"

Correct me if I'm at all wrong in the following.

The legislation is absolutely and narrowly prescriptive on these 2
points: that lifting equipment will be marked including Safe Working
Load and there must exist for the equipment a report of thorough
examination on this equipment available with specified content at
specified physical location based on who is responsible for the
equipment.  LOLER specifies

"INFORMATION TO BE CONTAINED IN A REPORT OF A THOROUGH EXAMINATION                                                               
 1. The name and address of the employer for whom the thorough examination was made.                                                                                                 
 2. The address of the premises at which the thorough examination was made.                                                                                                           
 3. Particulars sufficient to identify the lifting equipment including where known its date of manufacture.                                                                           
 4. The date of the last thorough examination.                                                                                                                                       
 5. The safe working load of the lifting equipment or ...
 6. etc"

How you go about your actual duties to do with the equipment under the
legislation is definitely more generally.  Advisory indg422.pdf make
it clear that the "thorough examination" might feature a test if that
is judged appropriate by the "competent person".  The LOLER
Legislation itself says on this subject

 2.  - ..."


 "thorough examination" in relation to a thorough examination under
 paragraph (1), (2) or (3) of regulation 9 -
 (a) means a thorough examination by a competent person;
 (b) where it is appropriate to carry out testing for the purpose
     described in the paragraph, includes such testing by a competent
     person as is appropriate for the purpose,

What constitutes a "competent person" is also interpreted in
indg422.pdf.  There are other clauses about who they should and
shouldn't be, but on the abilities side

"should have enough appropriate practical and theoretical knowledge
 and experience of the lifting equipment so that they can detect
 defects or weaknesses, and assess how important they are in relation
 to the safety and continued use of the equipment;"

Advisory indg422.pdf specifically mentions that the lifting gear in
question can be a rope.  And that it is an "Accessory for lifting" and
as such the default time between inspections is 6 months.  However,
the period between inspections must be considered by the "competent
person" and, well - you better say it how it is (you can even give
longer between-inspections intervals if you can show justification
including past performance).  For a rope in rough service (is there
any other?!), much much shorter periods between inspections / tests
would be appropriate.

BTW - I found in the process that an "EU Declaration of Conformity" is
only an exemption from testing something as-received before you use it
- given many provisos about time since conformity test, etc, etc, etc.
So if a sling has a "Declaration of Conformity" which is in-date you
can take it out of the bag and use it immediately.  But that's all it
says.  When in use - you are in the same regime as any other piece of
lifting equipment.  One solution is to time-expire and discard
"lifting accessories" like slings after 6 months - the LOLER default
interval between inspections for "lifting accessories".  But whether
that is an appropriate scheme must be evaluated by a "competent
person".  A LOLER obligation.  And you can never get away from the
obligation to inspect for satisfactory condition whenever that
equipment is in use.  This in relation to a familiar issue of the 2008
construction season.  Some seem to think that if you had a
"Declaration of Conformity" and locked it away in a filing cabinet, it
bestows on them permanent immunity from any further consequences and
permanent exemption from any further obligations!

So anyway, the long-and-short of it is:

It looks like every Monday morning first thing visually inspect your
rope from end to end, flexing it back and forth as a tactile
inspection at the same time, then proof-load test the entire rope
length with the site crane - then fill in a certificate with all the
LOLER-required information, deposit it at the required office - and
you are fully on the correct side of the law in the UK.

Anyone able to say whether I've got this right?

Sorry able to contribute about climbing rope.