Don’t Be Fooled by High WLL Claims!
There are no set governmental or industry standards to rate net styled restraints.
Individual companies are tasked with rating their own products, which can lead to the temptation to run fast and loose with ratings to gain a perceived advantage in the market place. Currently, the same product could receive vastly different ratings depending upon which methodology a company chooses.
Bednet assigns its Original Cargo Restraint a WLL of 450 lbs., however, a competitor’s method would rate the same net a WLL of 3704 lbs. Seem wrong?
Common methods used in determining WLL
Weakest Component Testing assumes forces may vary dramatically depending upon changes in speed and direction. In an accident, the load will apply different forces to different parts of the net and straps at any given moment. WLL is determined by dividing the straight-pull tensile of the net’s single weakest critical component by a safety factor of 3. Thus, this method provides an applied maximum WLL for the absolute worst case scenario. This method provides a seemingly small number.
Total Assembly Testing assumes all forces engage equally on all straps, not accounting for changes in speed and direction. Accidents are not assumed. It is conducted by a basket method, where weight is added on top of the net slowly until failure is reached. WLL is determined using the max failure and dividing it by a safety factor. This safety factor used in the industry varies between 1.5 and 3. The lower the safety factor the larger the derived WLL. Thus, this method provides a theoretical maximum WLL in a controlled environment. This method also provides a big, impressive number.
Aggregate Working Load Limit measures the total weight of cargo allowable on a truck bed to be contained by a certain WLL. This number is normally twice the WLL of the direct restraint. It is a little confusing, but it is the convention used in the cargo securement industry.
|WLL by Weakest Component Testing*|
Official Bednet® Rating
|Aggregate Load Mass|
|Comparative WLL to Complete Assembly Test with a safety factor of 3**|
DO NOT USE
|Comparative WLL to Complete Assembly Test with a safety factor of 1.5***|
DO NOT USE
|Bednet® Original Cargo Restraint and Mini's||450 lbs||900 lbs||1857 lbs||3704 lbs*||5556 lbs|
|Bednet® Interior Cargo Restraint and SUV Bulkhead||350 lbs||700 lbs||1444 lbs||2888 lbs||4332 lbs|
|Bednet® Van Bulkheads||835 lbs||1670 lbs||3166 lbs||6224 lbs||9000 lbs|
|Bednet® Utility Cargo Nets||835 lbs||1670 lbs||3166 lbs||6224 lbs||9000 lbs|
*Only method used by Bednet. Secondary method used by Quarantine
** Primary method used by Quarantine
*** Primary method used by Gladiator/Gorilla
* Bednet® does not sanction the Total Assembly Test as a safe assessment of WLL. Bednet® posts these figures for comparison only. Bednet® figures for Total Failure and Total Assembly tests are extrapolated mathematically. Bednet® does not conduct testing that is inapplicable to real-world scenarios, nor testing that provides inflated results that jeopardizes the safety and reputation of fleets relying upon the derived WLL.
See more from Bednet® on testing methodologies for Working Load Limits