Industrial wire and cable are often used in equipment installed in harsh application areas like oil and gas platforms, military vehicles, manufacturing equipment, etc. In such applications, there are possibility of fires breaking out. Fire is one of the greatest dangers that can damage and destroy industrial wire and cable. To ensure that the wires and cables are protected, manufacturers design the product with flame retardant materials. They also subject the cable through different types of flammability tests. We will elaborate about these tests in this post.
Agencies that Define Flame Tests
Agencies like UL, CSA, ISO, and NEC define tests within their respective standards to determine a cable’s flame resistance capability. All these agencies consider the following aspects for flammability tests:
- Flame Propagation
- Smoke Generation and Propagation
- Additional Support for Combustion
The NEC focuses on fire hazards in buildings, while UL and CSA focuses on application requirements.
Brief Descriptions of UL and CSA Flammability Tests
As most customers look at cable assemblies for applications, we shall be focusing on UL and CSA flammability tests. These tests are divided into small and large scale flame tests.
UL Flammability Tests: These are divided into one small, and two large scale flame tests.
- UL 1061: This is a small scale, vertical flame test. Cable that carry currents up to 500 Watts are subjected to this test. The UL 1061 is mainly used appliance wiring.
- UL Vertical Tray: This test is performed to check flame resistance of power and communication cables used in trays. The test is similar to the CSA FT4 flammability test, but not as stringent.
- UL 1666: This is also called a Riser Cable test. It is performed on cables that are used in vertical runs in a shaft. Like the UL vertical tray, the test is similar to the CSA FT4 flammability test, but not as stringent.
CSA Flammability Tests: These are divided into two small, and one large scale flame tests. FT1 and 2 are the small scale tests.
- FT1: This is a vertical flame test that should only be performed on manufactured cables. The FT1 is mainly used to test industrial equipment wire or Appliance Wire Material (AWM) with 500W.
- FT2: This is a horizontal flame test that is performed on finished cables. It is a minimum and mandatory requirement for flame testing flexible cords.
- FT4: The FT4 test is designed to test cables, which are going to be installed and used in tray and shaft applications.
Apart from the above mentioned tests, there is a test that is defined by both organizations – VW-1. This is also a vertical flame test, but is performed on flexible cords, as well as finished cables with 500 W.
These are the most important cable flammability tests that you should focus on when manufacturing industrial wire and cable. Discuss your application requirements with the cable manufacturer. Accordingly, he can suggest the appropriate test. A well tested cable can provide great performance in an application for many years.
The manufacturing of cable assemblies and wire harnesses involves a variety of processes to ensure the final product’s strength, function, and performance. One of the critical processes is cable assembly testing. The goal of this testing process is to ensure that the product will meet or even exceed the application and industrial specifications. But what are the testing procedures performed on industrial wire and cable assemblies. We answer this question with this post.
4 Cable Assembly Testing Procedures
The testing procedures described below are performed by all cable manufacturers to ensure their products are fit for application use. The tests need to be performed while referring to IPC or WHMA guidelines.
- Electrical Testing: The entire cable assembly needs to be thoroughly checked for opens, shorts, and incorrect wiring. The method to perform this test is attach the assembly’s end connectors to mating connectors, which in turn is connected to a fixture. The fixture is the device that checks the assembly for open wiring, and short circuits between shields and conductors. It can also check if the pins of the assembly’s components are in the proper place.
- Visual Testing: As the name suggests, the cable is visually inspected for any defects and deformations. Components that are tested are sockets, connectors, markings, finishes, as well as basic design and construction. Dimension inspection is also performed to ensure the cable is up to specifications.
- Environmental Testing: These tests are designed to check whether the cable can continue performing despite exposure to various environmental elements. The cable is subjected to the following types of elements:
- Thermal shocks
- High humidity levels
- Salt sprays for corrosion
- Elevated and decreased temperatures
- Mechanical Testing: This stage of testing focuses on the connectors, and the overall durability of the product. The connectors are disconnected, and then reconnected to determine how much force is required to connect or disconnect the assembly. Product durability is tested by subjecting it to a set number of flexing cycles. This helps the tester determine the approximate service life of the assembly.
It is important to come up with a testing plan, which comprises the necessary tests to ensure the performance of the product. Thorough cable assembly testing will ensure that cable will perform as required in extreme environments, and have a long service life.
As a customer searching for custom cable assemblies and wire harness, you are probably going through websites of various manufacturers and services providers. When you look at their accreditations, you may find two terms in the list – UL Listed, and UL Recognized. Generally, customers assume that these terms are interchangeable. However, this is far from true. As we realized that some customers are not able to understand the differences, we decided to write this post explaining the two terms.
UL – A Brief Description
The term UL stands for Underwriter Laboratories, an organization that provides safety consulting and certification services. UL specifically provides certifications for industrial wire and cable manufacturers worldwide. The UL label is not a certification, but an approval. It means that the product in question has been tested by UL, and has been approved for application use.
Decoding UL Listed
This label is for cables that are used in what UL terms as a Division 2 environment. Division 2 refers to any closed area where ignitable substances are used, stored, or handled. Wire and cable under UL Listed are tested to National Safety Standards, and are proven safe against fires, electrical shocks, and other unanticipated hazards. A well-known example of a UL Listed product is the VW-1 cable.
Decoding UL Recognized
The UL Recognized label is provided to wire and cable, which have been tested by UL, and are considered safe for use in commercial and industrial products and systems. Testing for UL Recognized is performed on products that are incomplete, or are restricted in terms of their capabilities. For UL Recognized products, the safety organization also communicates to manufacturers that these products need to be supported with additional protective devices, such as trays, or housing. A well-known example of a UL Recognized product is Appliance Wiring Material (AWM).
As you can see, these labels are utilized for distinct wire and cable products. For this reason, when searching for a cable manufacturer, customers always need to enquire whether the products will be UL Listed or UL Recognized, after understanding their application requirements.
When selecting an electrical cable for the project, various important factors need to be considered such as the type of application, load bearing capacity, etc. Beyond these primary considerations, the wiring expert should understand the difference between a stranded and solid cable, and their contribution to the project.
A solid cable features a single thick conductor made of solid metal, which tends to be more rigid. The conductor is usually made of copper. A stranded cable is composed of several small conductor strands (typically 7) that are twisted or grouped together to form a large wire.
Stranded vs. Solid Cable
Below are three arguments for stranded vs. solid cable.
- Flexibility: Cable flexibility is an important factor when considering cables for an assembly project. A solid cable with a single metal wire is not bendable, so is perfect for applications that don’t require bending. Stranded cables consist of a large number of small individual strand conductors grouped together. Hence, stranded cables can withstand over-bending and over-flexing.
- Applications: Solid cables are used for structured wirings as well as semi-permanent and permanent installations. Other applications of solid cables include long distance cable horizontal and backbone cable runs, wall jacks, HD applications, and power over Ethernet (PoE) applications.
Generally, stranded cables are used in patch panels for workstations. Since they are flexible, they can be used for applications, where over-flexing is common.
- Attenuation: Stranded cables are recommended for short distances because they possess higher attenuation than solid cables. Attenuation is a term for a reduction in signal strength – analog and digital. Sometimes, attenuation is a consequence of long distance transmission.
Stranded cables are usually recommended for applications 20 feet underground.
Whether you select a stranded cable or a solid cable, proper installation is key to its performance.
An overmolded cable assembly combines the connector and cable in a single design. A molten material is introduced into a mold cavity, which assumes its form on cooling. The color of the molten material can be matched to the color of equipment or cable jack being used. The types of material used for overmolding are rubber, ABS plastic, PVC, PP, PE and macro melt.
4 Important Features of an Overmolded Cable Assembly
Below are four key attributes of an overmolded cable assembly.
- Improved Protection from Abrasion and Weather Elements: During overmolding, all sensitive electrical components are encapsulated, which makes them resistant to abrasion and harsh weather elements. Thus, overmolded cables are considered cost-effective alternatives to conventional cables with black shell and EMI foil. In various industrial verticals, overmolded cables are often subjected to rough use. So a basic idea of the application environment and appropriate material to be used will help an overmolding assembly manufacturer to manufacture the right product. For example, Polyurethane is used for overmolding cable assemblies used in the military and healthcare sector. Polyurethane is abrasion resistant, has a high load capacity, and can withstand high temperature.
- Customization: An overmolded cable assembly is customizable. There permutations and combinations for materials, colors, wire types, and style options are endless. Custom colors, configurations, shapes, and imprints allow OEMs to achieve the highest aesthetic standards. A customized overmolded cable may feature a company name or logo.
- Improved Shelf Life: Overmolded cable assemblies have an improved shelf life than traditional cables because the overmolding offers complete strain relief, high pull strength, and flexible support at the cable exit.
- Compact Integration and Lighter Equipment: When compared to traditional cable assemblies, over molded electronic assemblies are smaller and allow OEM to reduce cost and the size of their equipment. Additionally, overmolding allows inclusion of circuit analysis resistors or reverse polarity protection diodes, PC board assembles, and more.
Most cable assembly manufacturers delivering custom overmolded cable assemblies follow production steps such as potting, premolding, and overmolding to determine the abrasion resistance, waterproofing, and electrical performance of the final product. Customized overmolded cables can reduce the total cost of production and improve performance. No doubt, Overmolded cable assemblies will add value to any electrical application with the above-mentioned attributes.