Forces, Defined – KN, KGF, DAN & Breaking Load

What do Kilonewton [kN] and Dekanewton [daN] mean?

The newton (symbol: N) is the International System of Units (SI) derived unit of force. It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton’s second law of motion. It is equal to the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second per second.

On Earth’s surface, a mass of 1 kg exerts a force of approximately 9.8 N [down] (or 1.0 kilogram-force; 1 kgf = 9.80665 N by definition). The approximation of 1 kg corresponding to 10 N is sometimes used as a rule of thumb in everyday life and in engineering. It is common to see forces expressed in Kilonewtons or kN, where 1 kN = 1,000 N.

1 Kilonewton [kN] = 100 Dekanewton [daN] = 1000 newtons [N]

1 Dekanewton [daN] = 10 newtons [N]

1 Kilogram-force [kgf] = 9.80665 N

An amusing rule of thumb to help remember the Newton: On earth, a newton [N] is equivalent to ~100 g; coincidentally, this is about the mass of an apple. So, you can think of a newton [N] as getting hit on the head with an apple.

Kilonewtons are often used for stating safety holding values of fasteners, anchors and more in the building industry. They are also often used in the specifications for paragliding, paramotoring, hang gliding and rock climbing equipment (e.g. karabiners and maillons). The safe working loads in both tension and shear measurements can be stated in kN (Kilonewtons).

1 kN equals 101.97162 kilograms of load, but multiplying the kN value by 100 (i.e. using a slightly pessimistic and easier to calculate value) is a good rule of thumb.

Examples…

  • “Strength: 18KN” = 1800 daN = approx 1800 kg
  • “Breaking strain 1800 daN” = 18 kN = approx 1800 kg
  • “Breaking strain 2000 daN” = 20 kN = approx 2000 kg
  • “Breaking load 2500 kg” = approx 25 kN = 2500 daN
  • “Breaking strain > 2500 daN” = 25 kN = approx 2500 kg
  • “Guaranteed load 26 kN” = 2600 daN = approx 2600 kg
  • “Breaking load 32 kN” = 3200 daN = approx 3200 kg
  • “Breaking strength 40 kN” = 4000 daN = approx 4000 kg 

For more info, see Newton (unit) – Wikipedia, the free encyclopaedia

 

Working Load Limit (WLL) and Minimum Breaking Load (MBL)

Working Load Limit (WLL) aka Safe Working Load (SWL) or Normal Working Load (NWL) is the maximum working load designed by the manufacturer. It is the force that a piece of lifting equipment, lifting device or accessory can safely use to lift, suspend or lower a mass without fear of breaking.

The WLL represents a force that is much less than that required to make the lifting equipment fail or yield, which is usually known as the Minimum Breaking Load (MBL) or aka Minimum Breaking Strength (MBS).

The WLL is usually marked on the equipment by the manufacturer and is calculated by dividing the MBL by a Safety Factor (SF) i.e. WLL = MBL / SF.

The SF is often 5 (5:1, 5 to 1, or 1/5), although other values may be used such as 4, 6 and 10. Paragliding, hang gliding and paramotoring equipment usually uses a SF of 5, for example.

For example, a maillon that has a MBL of 2250 Kg would have a WLL of 450 Kg if a SF of 5 is used.

Put another way, a maillon that has a WLL of 450 Kg would have an MBL of 2250 Kg if a SF of 5 is used.

For more info, see Working load limit – Wikipedia, the free encyclopaedia