UL 1581 Cold Bend Test

COLD BEND
580 Test

580.1 The specifications for this test are located in Cold Bend, in the Standard for Wire and Cable Test Methods, UL 2556. Note – When a mandrel specified in the product standard is not available, it shall be permitted to use a mandrel with a smaller diameter. However, in the event of non-compliant results, the wire or cable shall be re-tested using the mandrel size specified in the product standard.

7.5 Cold bend

7.5.1 Scope

This test establishes the method for determining the resistance to cracking of wire or cable components
during bending at low temperature.

7.5.2 Apparatus

The apparatus shall consist of
a) a low-temperature chamber capable of maintaining the specified temperature within ±1 °C;
b) a temperature-measuring device with an accuracy of ±1 °C;
c) a micrometer or micrometer caliper with a resolution and accuracy of 0.01 mm (0.001 in);
d) cylindrical mandrels of diameters specified in the product standard; and
e) thermally insulated gloves.

7.5.3 Preparation of specimens

The specimen shall be cut to a length sufficient to perform the test and shall be straightened.

7.5.4 Procedure

7.5.4.1 The specimen and the mandrel shall be placed in the cold chamber at the temperature and for
the duration specified in the product standard. While still in the chamber, the specimen shall be bent
around the mandrel. Bending shall commence as quickly as possible and at a rate such that the time
taken to complete the specified number of turns shall be within 30 s. Flat cable shall be wound on its flat
side.

7.5.4.2 Where there is insufficient space in the cold chamber for the mandrel, or for bending the
specimen, bending of the specimen shall be allowed to take place outside of the cold chamber. Bending
of the specimen shall commence as quickly as possible. In the instance where the mandrel is too large to
be placed in the chamber, it shall be maintained at ROOM TEMPERATURE. In any case, bending shall
be completed within 30 s from the time the chamber is opened.

7.5.4.3 If the tension on the specimen is not specified, it shall be just sufficient to cause the specimen to
conform to the periphery of the mandrel. Unless rotation of the mandrel is performed remotely, the
specimen and mandrel shall be handled using thermally insulated gloves.

7.5.4.4 The specimen, whether on or off of the mandrel, shall be allowed to return to ROOM
TEMPERATURE and then straightened. The inside and outside surfaces of the components shall be
examined for cracking.

7.5.5 Results and calculations
The presence of cracks, if any, shall be noted.

7.5.6 Report

The report shall include, as a minimum, the following:
a) test temperature; and
b) indication of cracking, if any.

1. Overview
The **Cold Bend Test** described in **UL 1581 (Section 580)** evaluates the flexibility and mechanical integrity of wires and cables when subjected to low temperatures. This test ensures that the insulation and jacket materials remain intact and do not crack or degrade when bent under specified conditions.

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2. Test Procedure
The test is performed in accordance with **Cold Bend** specifications outlined in **UL 2556**, the Standard for Wire and Cable Test Methods.

• a. Sample Preparation:
  - Wire or cable samples are conditioned in a cold chamber at a specified temperature for a designated period (commonly **-40°C** for many cables).
• b. Mandrel Selection:
  - The cable is wrapped or bent around a mandrel with a diameter specified in the product standard.
  - Note: If the specified mandrel is unavailable, a smaller diameter mandrel may be used. However, if the sample fails, the test must be repeated with the correct mandrel.
• c. Bending Test:
  - After conditioning, the cable is bent around the mandrel while still in the cold environment.
  - The bending motion may involve one or more cycles depending on the product requirements.
• d. Visual Inspection:
  - After bending, the cable is removed and inspected for any cracks, splits, or visible damage to the insulation or jacket.

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3. Acceptance Criteria
The cable passes the Cold Bend Test if:

• There are no visible cracks, splits, or damage to the insulation or jacket material.
• The cable retains its flexibility without significant deformation.

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4. Purpose and Importance
The **Cold Bend Test** is critical for ensuring the durability and reliability of cables in low-temperature environments:

• a. Reliability in Cold Conditions: Verifies that cables can withstand bending stress at low temperatures without compromising insulation or jacket integrity.
• b. Material Quality: Assesses the flexibility and resilience of insulation and jacket materials under harsh conditions.
• c. Industry Applications: Essential for cables used in outdoor, arctic, or refrigeration environments.

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5. Notes and Considerations
- When a mandrel with a smaller diameter is used due to unavailability of the standard mandrel, test results are considered valid unless the sample fails. In such cases, the test must be repeated with the correct mandrel.
- Compliance with this test demonstrates a cable's suitability for environments where low-temperature performance is critical.

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6. Related Standards
- **UL 2556:** Standard for Wire and Cable Test Methods (Cold Bend specifications).
- **UL 1581:** Reference standard for electrical wires, cables, and flexible cords.

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7. Conclusion
The **UL 1581 Cold Bend Test** ensures that wires and cables can maintain their structural integrity and performance under low-temperature bending conditions. It is a crucial test for evaluating cables intended for use in environments with extreme cold.

Key Points:

• Performed in accordance with **UL 2556 Cold Bend specifications**.
• Mandrel size must meet product standard requirements; deviations must be retested if non-compliance occurs.
• A pass is achieved if no cracks, splits, or damage are observed.