Tests and test methods UL – Underwriters Laboratories

The tests referred to are based on the following standards:

  • UL 94
  • UL 50
  • UL 746C

with all associated amendments and extensions.

UL 94

„Tests for Flammability of Plastic Materials for Parts in Devices and Applications“

This regulation describes the test for evaluating and classifying the flammability of plastics.

UL 50

„Standard for electrical equipment intended to be installed and used in non-hazardous locations“ This regulation sets standards for electrical appliances that are not intended for use in areas subject to explosion hazards.

UL 746C

„Standard for safety for polymeric materials – use in electrical equipment evaluations“ This regulation sets standards for materials made of polymer, for use in electrical equipment.

Tests for Flammability of Plastic Materials for Parts in Devices and Application

UL 94

The test is conducted with an open flame. Depending on the classification, the flame has a power of 50 watts (20 mm high flame) or 500 watts (125 mm high flame). The ignition source acts on the test object for 30 s in the case of the horizontal burning test (HB), twice for 10 s with the vertical burn test (V) and five times for 5 s with the 5V test and is then removed again. The burning time and also the fragmentation of burning parts in the case of V-tests are assessed. A cotton ball placed under the test set must not ignite.

Classifications:
A material sample (thickness <3 mm) is placed horizontally above a 50 W flame 20 mm high.

Classification

Conditions

HB

Self-extinguishing

HB75

Burning < 75 mm/min.

HB45

Burning < 40 mm/min.

A material sample is placed vertically above a flame with 50W power and a height of 20 mm.

Classification

Conditions

V-2

Self-extinguishing up to 30 s following removal of the flame, burning drops permitted

V-1

Self-extinguishing up to 30 s following removal of the flame, no burning drops permitted

V-0

Self-extinguishing up to 10 s following removal of the flame, no burning drops permitted

A material sample is placed vertically above a 500 W flame with a height of 125 mm ± 10 mm.

Classification

Conditions

5VB

Self-extinguishing, no burning drops, burn holes are permitted

5VA

Self-extinguishing, no burning drops, burn holes are not permitted

Note:

As an alternative to materials with the material classification 5VA , the UL 50 Regulation also permits material that has the classification HB and has passed the flame test according to UL 746C, Selection 17 „Flammability 127 mm (5 inch) flame“. The material thus tested is comparable to material with the classification 5VA according to UL 50.

Test of proof against mechanical stress

UL 746C

In order to prove protection against mechanical stress, impact stress must be applied to the equipment under test. Equipment intended for outdoor use is cooled for three hours in a cold chamber at -35 ± 2°C and then mounted on a rigid frame appropriate to its planned use. In the cold state, a single blow is applied with a steel ball of 50.8 mm (2 inches) in diameter and weighing 0.535 kg (1.18 pounds) to the surface being tested.

In order to furnish proof, the equipment under test must be free of any damage that may interfere with its proper use. Furthermore, the intended protection rating must not be changed negatively.