Cable Vertical Combustion Test machine UL1581 VW-1

Cable Vertical Combustion Test machine UL1581 VW-1

I. Product Overview

The VW-1 Cable Horizontal and Vertical Flame Tester is a precision test instrument designed to evaluate the flame retardancy of wires, cables, electrical accessories, and other solid materials. Its core purpose is to simulate the burning behavior, flame spread, and self-extinguishing properties of materials exposed to a small flame under specific conditions.

"VW-1" is a flame-retardant rating designation derived from the UL standard, standing for "Vertical Wire-1." The instrument precisely controls the timing, angle, and position of the flame application to determine whether the tested sample meets the requirements of VW-1 or other similar flame retardancy ratings (such as FT1 and FT2).

This instrument is an essential testing instrument for quality control and product certification (such as UL and CSA) in the wire and cable, electronics, and building materials industries.

II. Test Principle
The basic principle of the test is to secure a sample (cable) of specific dimensions at a specified angle (usually 20° or 90° perpendicular) in a test chamber. A flame of a specified height and heat is generated using a standardized Bunsen burner (or a specialized blowtorch). The flame is applied to the lower surface of the sample for a specified time (e.g., 15 seconds). The flame is then removed, and the following behaviors of the sample are observed and recorded:

Afterflame Time: The duration the sample continues to burn after the flame is removed.

Afterglow Time: The duration for which the sample remains hot after the flame is extinguished.

Charred Length/Scorch Length: The maximum length of the sample that is burned or damaged.

Ignition of Cotton Bedding: During the test, the flame drippings ignite the dry absorbent cotton pads below, which simulate the environment.

Based on these observations and compared against the criteria specified in the standard, the flame retardancy rating of the sample is assessed.

III. Standard Compliance

This equipment is designed to strictly adhere to the following mainstream international and regional standards:

UL 2556: Test Methods for Wire and Cable

VW-1 (Vertical-Wire 1): One of the most stringent flame retardancy ratings for cables, requiring that after five flame applications, the afterflame duration of each test sample must not exceed 60 seconds, and the bedding must not ignite.

FT1 (Flame Test 1): Similar to VW-1, but with a 20° angle.

FT2 (Flame Test 2): Lower requirements than FT1, requiring a horizontal flame test.

IV. Main Features

Test Chamber:

• This test chamber is constructed of assembled steel plates and features an anti-static paint finish for an attractive appearance and rust and corrosion resistance. A smoke exhaust system is installed on the top of the chamber to discharge exhaust gases outdoors after the test. Two air inlets are located on the lower sides, along with a set of pneumatic seals.
• An observation window is located on the front of the chamber for easy observation of the test progress.
• Ventilation System: An exhaust vent is located on the top, allowing connection to an external exhaust system to promptly remove toxic and hazardous gases generated by combustion.

Sample Fixture:

• Test Stands: VW-1 and FT2 Combustion Test Stands.
• The fixture design ensures a secure hold on the sample without interfering with test results.

Burner System:

• The burner is imported from Hamburg, USA, meeting ASTM D 5025-99 requirements, with a standard power of 500W and a 20° angle.
• Gas Supply: High-purity methane or propane is used as fuel, and a U-tube pressure gauge and high-precision flow meter are provided to ensure stable and adjustable gas flow and pressure. Flame height scale: used to quickly calibrate the flame to the required standard height (such as 125mm).