Copy of Sling Failure 2
-
Upload
rajmohan-babu -
Category
Documents
-
view
216 -
download
0
Transcript of Copy of Sling Failure 2
-
7/30/2019 Copy of Sling Failure 2
1/7
SPDC - HSEGbaran Ubie Oil & Gas ProjectBayelsa StateNigeria
15/02/09
This preliminary information bulletin is to outline the contributing factors
that occurred during the lead up to the polyester webbing sling failure at
Saipem Pipeline ROW.
DESCRIPTION POLYESTER DUPLEX WEBBING SLINGSWL 8 METRIC TONDATE MANUFACTURED MAY 2007SAFETY FACTOR 6/1STANDARD No: BS 3481 BS 3481 1993EFFECTIVE WORKING LENGTH 6 MTR (8 DIA)MANUFACTURER ALLSAFE
SERIAL NUMBER 2891
Incident Summary:
Mr.Guiza Edga was preparing tie in joint of 20 concrete coated duplex steel
pipe, which was already lowered inside the trench at Zarama (Z1) ROW
access.
In this process he lifted first section of welded pipe joints around 1 feet
height inside the trench in order to reposition to align with second section
of pipe elbow joint end.
Two side booms (A&B) lift the section of pipe by positioning between 4 no:
welded joint pipes.
After visual alignment of two sections by foreman, side boom (A) lowered
the pipe inside the trench, while side boom (B) start lowering the pipe, web
-
7/30/2019 Copy of Sling Failure 2
2/7
sling attached to it snapped immediately and pipe drop back from 1 foot
height inside the trench.
No personnel has been injured.
(Twelve pipes welded together in section one.) Four pipes been lifted for
repositioning where the rest of the pipes remain stationary inside trench
surface.
1 x 20 diameter concrete coated duplex pipe is 12 meters long and weighsapproximately 4.75Ton.
Second section with elbow end laid inside the trench though not lifted
throughout the operation.
The web slings used in this operation is 8 width X 6 mts length, rated SWL
8 Ton for straight single loop lift.(As detailed above)
FINDINGS:
Webbing sling,
Under examination the sling has damage at various points along the EWL
(effective working length)
The damage was in the form of:
Deep cuts to the side of the sling
Abrasion
Broken stitching at the eyes (this indicates over loading)
Tears Total failure point
-
7/30/2019 Copy of Sling Failure 2
3/7
Broken stitching
I.D Tag With info
Deep cuts to the side of the sling could severely compromise the slings
performance and would lead to catastrophic failure before the Working Load
Limit (WLL) could be reached.
The sign of the busted stitches in the eyes of the slings is another clear
indication that the sling has been over loaded.
Abrasion to the slings is concurrent with lifting and turning pipe.
-
7/30/2019 Copy of Sling Failure 2
4/7
Sling standard,
Semec Agencies Nigeria (agent to Allsafe) sold this sling to Saipem
The standard they made the sling to is now OBSOLETE and was replaced in2000 by BS EN 1492 Part 1& Part 2.
The standard they used was introduced in 1983 and the standard has been
outdated for 9 years!
Sling inspection examination documentation:
This was investigated and it was found that the manufactures test
certificate was available on file and also that the 2009 six monthlyexamination was conducted by Nitram Land LTD on the 08-01-09,
I ask the question could this sling have been damaged at the time of
inspection and could inspector have missed the damage post 08-01-09
inspection campaign?
What are the qualifications of the inspector that inspected the sling and
what are his competence levels as a lifting equipment inspector!!!!
Daily and pre use inspection:
It is obvious that the daily and pre use before and after each time used was
not conducted as the defects would have been picked up and the sling
removed from service,
No daily inspection check sheets for slings are available for the
rigger/supervisors etc for guidance,
No daily record of inspections of slings was available,
There are control measures for signing slings and lifting equipment in and
out of the rigging store, however sling serial numbers or tag numbers are notrecorded.
-
7/30/2019 Copy of Sling Failure 2
5/7
Awareness and training:
Although Saipem had records of training for their personal we are yet to
see the curriculum of the training that is being delivered to Saipem. The
Plan now is to organise a training sessions for Saipem that cover webbing
sling and safe sling in detail.
Application of slings:
Slings were not used in line with manufactures specification- used beyond
recommended SWL.
Section being lifting weighs 18.8Ton (4 lengths) while the overall dead
weight is 57 Ton (12 lengths) at 4.75Ton per 12m lengths.
1 x 8 ton slings at zero degree x 2 slings for the overall length= 16Ton. Thus
minus 20% for choke hitch=12.8Ton for the two slings.
Besides, slings with integrity were compromised by cuts/ abrasion andbroken stiching.
Dynamic force during this operation will also contribute to the existing
excess static loading.
Force Moment Diagram
Take moment about point O (Turning)
Cog X 72=F1 X 132 + F2? X 84
O
COG
72 MTR
48 MTR
72 MTR
12 MTR127MTR
F1
R1
F2?
-
7/30/2019 Copy of Sling Failure 2
6/7
But F1=6.4Ton, Cog= 4.75 X12 (12 welded pipes)=57Ton
Substituting, 57X 72= 6.4 X 132 + F2? X 84
4104=844.8 + 84F2?
3259.2/84= F2?
38.79Ton= F2
F2?=F2= Static force.
Cog Total load of 12 length of pipe (Dead weight) 57Ton
F1 Max SWL of web sling that didnt fail (with choke) 6.4Ton
F2? Calculated load on sling prior to failure 38.79Ton
Web sling was subjected 6 times more than the Rated Load.
Graphical View of incident layout
-
7/30/2019 Copy of Sling Failure 2
7/7
In conclusion, incident occurs due to:
Over loaded web sling at approximately 6 times its Rated Load and
catastrophically failed.
Sling damaged prior to use (compromising SWL)
Lack of awareness of safe slinging & rigging practice. Non-routine lift-was not categorised accordingly.
No lift planning.
No pre use and after use inspection (No record keeping or daily
checklist for slings)
HSE GBARAN UBIE
Idada/Paul