How Working Load Limits (WLL) are Manipulated

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 has modeled its testing as closely as possible to the tie-down standards set forth by the Web Sling Tie-Down Association (WSTDA), the organization that governs the cargo securement industry in trucking and lifting. This is a very safe, conservative approach which yields a significantly smaller WLL than other methods in use.

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 Ratings -------------------	WLL by Weakest Component Testing* ------------------- Official Bednet® Rating	Aggregate Load Mass Allowable ----------------	Comparative WLL to Complete Assembly Test with a safety factor of 3** ---------------------------- Comparison Only: DO NOT USE	Comparative WLL to Complete Assembly Test with a safety factor of 1.5*** ---------------------------- Comparison Only: DO NOT USE	Total Failure -----------
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