|
 |
|
|
| |
|
|
 |
 |
|
| |
to Inspection
Criteria and Sling Properties Main Page |
|
| |
 |
|
|
|
| |
|
|
The 'Web
Sling and Tie-Down Association' conducted two long
time exposure test study on the degradation effects of polyester- and nylon
web sling when exposed to sunlight. The first test was done in 1981, and
the second test series was done between 1997 to 2004. The full test report
is published by WSTDA, a copy of which can be obtained by Unirope.
One of the main conclusions reached by WSTDA:
"The polyester samples tended to undergo most of their
strength loss during the first twelve months of exposure and then leveled off approximately
a 30% loss in strength. The nylon 6 and nylon 6.6 sample showed a general
trend of consistent strength loss over the entire 36 months exposure period,
with strength loss levels approaching fifty to sixty percent after 36 months
for some sample tests."
Based on the test results and conclusions reached, Unirope has decided
to discontinue the use of NYLON webbing material for Boat Lifting Slings.
However, it must be noted that, although Polyester webbing seems less affected,
even polyester slings will undergo a significant strength loss leading
to a DECREASE in strength. Consequently, the DESIGN FACTOR for such slings
will DROP from a 5:1 value to at least a value of 4:1! |
| |
| Web Sling & Tie Down Association: |
| |
 |
| |
 |
| |
 |
| |
|
|
|
| |
|
|
 |
|
The following is a WARNING
as published by the ‘Web Sling and Tie Down Association’ in
their ‘Recommended Standard Specification for Synthetic Web Slings,
WSTDA-WS-1, version 2004’: |
|
| |
|
|
5.3.5 Environments in which synthetic web slings are continuously
exposed to ultraviolet light can affect the strength of synthetic web slings
in varying degrees ranging from slight to total degradation.
CAUTION: Degradation can take place without
visible indications!
|
|
|
| a. Factors, which
affect the degree of strength loss are: |
|
| 1. |
|
Length of time of continuous exposure |
|
| 2. |
|
Web sling construction and design |
|
| 3. |
|
Other environmental factors such as
weather conditions and geographic location. |
|
| b. Suggested procedures
to minimize the affects of sunlight or ultra-violet light. |
|
| 1. |
|
Store web slings in a cool, dry and
dark place when not being used for prolonged periods of time. |
|
| c. Some visual
indications of sunlight or ultra-violet degradation are: |
|
| 1. |
|
Bleaching out of web sling colour |
|
| 2. |
|
Increased stiffness of web sling material |
|
| 3. |
|
Surface abrasion in areas not normally
in contact with the load. |
|
| d. PROOF TESTING
WARNING |
|
| 1. |
|
Slings used in environments where they
are subject to continuous exposure to sunlight or ultra violet light shall
be proof tested to twice the rated capacity semi- annually, or more frequently
depending on severity of exposure. |
|
| |
|
|
| |
|
Back
to Top |
| |
|
|
|
