Selecting cable and hose carriers
Cable and hose carriers are a practical way to protect multiple electrical, hydraulic, pneumatic, and other cables and hoses on moving machinery from premature wear and fatigue due to flexing and abrasion. At the same time, they can improve the appearance of equipment by keeping cables and hoses neat and orderly.
Carriers prevent cables and hoses from over-flexing and maintain their proper bend radius. As carriers move, they impart a gentle rolling action that feeds lines in or out. Although these devices are simple in appearance, getting the right one for the job isn’t as simple as it might seem. The wide variety of designs, materials, and sizes makes it important to work closely with the manufacturer to ensure the optimum combination of performance and longevity.
Fig. 1. Carriers use standard components in many combinations to satisfy most applications.
Although they are usually assembled from standard components, because of the many combinations, simply picking one out of a catalog is not likely to provide the best possible solution. The service conditions and physical configuration of each application require specialized engineering analysis.
Most cable and hose carriers are made up of parallel side links joined by crossbars that support the hoses. Pivot pins and stops allow the links to travel through a predetermined arc. A carrier may be made with either metal or nonmetallic links (Fig. 1).
Some link-type designs are completely enclosed, to provide greater protection for cables and hoses, as well as for use in corrosive environments. Other designs are open between the links. Another variety, usually made of metal, is a conduit-type design, which is completely enclosed but made with convolutions instead of links.
Open nonmetallic link-type carriers should be the first choice for applications where high speed and long travel are factors. Made of heavy-duty fiber-reinforced nylon, they are nonconductive and corrosion-resistant.
Typical uses include machine tools and industrial robots. Some lighter designs are well suited for light automation machinery and for applications where quiet operation is imperative.
To accommodate these applications, nonmetallic carriers are available in a wide range of sizes, starting from less than 1-in. wide for use with ribbon cables to some that can handle cables and hoses larger than 4 in. in diameter. Some carriers can accommodate travels as long as 300. ft.
Various accessories and design variations are available to help meet specific application needs. One example is a choice of bars that are used to connect the two linked side members and support the hoses and cables. The bars on many designs are easy to remove, but some offer hinges or snap-outs (Fig. 2) that allow easy access and make it possible to install cables and hoses with fittings that cannot be fed through the carrier.
Fig. 2. Hinges and snap-outs provide easy access to cables and hoses.
Some types of nonmetallic carriers are equipped with replaceable bearings, for applications with a lot of movement or where elements in the environment may cause excessive wear.
Completely enclosed nonmetallic carriers are also of link-type design, but they are enclosed on the top and bottom to provide cost-effective protection for hoses and cables in environments where abrasive materials could cause damage.
They work well for long travel lengths and high speeds. With proper guiding, some designs can be used for travels as long as 300 ft. There are many different enclosure methods, including designs that allow easy access to cables and hoses, either with a removable slide strip or easy-to-remove plates.
Metallic link-type carriers are ideal for applications that include machine tools, cranes, industrial robots, and steel mill machinery. They usually consist of metal links joined by hardened steel pins that provide both a bearing and lock point.
One design features a half-shear lockout system that eliminates parts, adds strength, and reduces cost. Some types achieve the strength and ruggedness of steel carriers yet maintain the lighter weight of non-metallic carriers with a combination of metal links and nylon or aluminum bars, which are also easy to remove for access.
Conduit-type carriers are formed with small convolutions and are designed to keep chips, weld spatter, coolant, cutting oil, and similar contaminants away from control cables, power cables, and hydraulic and air hoses on machinery with horizontal or vertical motion. The totally enclosed design of these carriers also improves machine appearance and provides noise-free movement.
Because the motion of individual links does not restrict these carriers, they can operate at higher speeds. Their low weight and vibration-free movement makes them suitable for applications where fast acceleration is needed.
Conduit-type carriers are constructed from heavy-duty galvanized steel, supported by a stainless steel band attached to the inner radius of the carrier. Standard conduit-type carriers can be used at travel speeds up to about 200 fpm and are suitable for use in ambient temperatures ranging from -20 to 180 F.
Choosing the right carrier
The cross-section of the carrier should allow 10% clearance around cables and 20% clearance around hoses to prevent binding. Similar diameters and services should be grouped, and separators should be used to keep unlike services and diameters apart.
Minimum bend radius of the carrier should be equal to or greater than the recommended bend radius of the stiffest cable or hose it will carry. Accurate minimum bending radius specifications can be obtained from the cable or hose manufacturer. Generally, when this information is not known, the recommended minimum carrier radius should be eight times the diameter of the largest cable or hose.
Length of the carrier may vary, depending on mounting and machine configurations, but typically, the length is approximately half the total travel plus the curve length. The total weight per foot of the cables and hoses within the carrier should also be provided, including the weight of any liquids contained in the hoses.
Fig. 3. Carriers must support cables and hoses as well as any liquid in the hoses.
Several accessories are available to make installation easier. Mounting brackets are available in a variety of configurations. These are usually furnished as an integral part of the carrier and must be specified when ordering.
Support trough systems are sometimes needed for nonmetallic carriers when the total travel length exceeds the carrier’s maximum free load-carrying potential. In certain applications, some degree of sag is acceptable. If long travel and high speeds are involved, a support trough is usually required.
Carriage support systems are available for metallic link carrier applications that require higher cable/hose loads and high travel speeds. They incorporate major rollers and intermediate carrier supports, which together support the carrier for the complete length of travel. The entire system rolls on channels mounted to the floor or crane bridge and allows speeds up to 450 fpm, which is ideal for overhead crane applications.
Operation and maintenance
Carriers require very little maintenance once installed. However, there are several ways to ensure a long life and trouble-free operation.
Recheck the carrier’s operation after a month or so of use, to ensure the cables or hoses have not become loose.
Check the cables for wear and to ensure they aren’t rubbing, pushing, or pulling on the outside or inside radius bars.
Adjust the cable length inside the carrier by repositioning the end clamps so the cable is in the center of the carrier’s bend radius. This reduces wear on both the carrier and the cable or hose.
Check carriers and cables every six months for adjustment and wear. Misalignment of the carrier can cause crossbars or pins to wear. Cables and hoses can expand, shrink, or slip allowing them to rub against the carrier instead of being properly supported by it.
To monitor wear over a period of time, one useful indicator is the development of excessive sag in the unsupported span. In the same way an industrial chain elongates as it wears, parts of the carrier may eventually wear over time and cause the carrier to lengthen and sag. A nonmetallic carrier may sag until it rides on itself without causing undue wear.
If sag is a problem, and the carrier has removable links, its life span can sometimes be extended by removing a link, as long as it continues to operate smoothly. If wear causes the carrier to bind or chafe, the carrier should be replaced.
Many carriers are designed so wear points can be replaced, including such parts as easy-locking removable hubs and replaceable wear shoes on nylon carriers. This is especially useful on applications that involve long travels or high cycling, since it is less expensive and easier to replace worn parts than the entire carrier.
Polyurethane rollers, available on both nylon and steel carriers, are designed to wear instead of the cable or hoses they protect, thus extending their useful life. Many carriers are designed with modular construction, using pins and snap rings that make them easy to disassemble and replace components.
Since most nonmetallic carriers are manufactured from nylon, they do not require lubrication. In some unique applications, a carrier might benefit from lubrication, but in most cases it is not necessary. Generally, spray lubricants are preferred and they should be compatible with the cables and hoses.
Mr. Bohne is available to answer questions on carrier selection and application and can be reached at 800-394-1547. Article edited by Joseph L. Foszcz, Senior Editor, 630-288-8776, firstname.lastname@example.org
Guidelines for selecting metal and nylon carriers
Use metal if loads exceed 15 lb/ft.
Use nylon with speeds over 100 fpm.
Metal carriers are most practical for travels up to 50 ft. beyond that, nylon is more economical and functional.
Temperature may be a factor. Most nylon carriers perform best between 0 and 250 F.
Conduit-type metal carriers are designed for temperatures from -20 to 180 F, while other metal carriers can handle wider temperature ranges.
Appearance should be considered when choosing carrier material, as well as open or closed construction.
Information the manufacturer needs
Carrier cross-sectional size
Length of travel
Height and width clearance limitations
Number and types of cables or hoses
General installation guidelines
Cables should be positioned freely, side by side, to prevent binding and should not be twisted or kinked. Cable or hose tension can be adjusted by loosening the clamps that hold the cable within the carrier and adjusting the length of the cable.
Cables and hoses can be installed either before or after the carrier is installed on the machine. The choice depends on the type and size of the carrier, the type of hose or cable end fittings, and the accessibility of the carrier once it is installed.
Use separators to group cables and hoses by type of service, such as electrical power cables, control lines, and standard or high-pressure hydraulic hoses. Surging high-pressure hydraulic hoses should be kept separate to avoid pinching. Cables might cause electrical interference if in too close proximity to each other.
Once the carrier, cables, and hoses are installed, operate the machine slowly through its entire travel to ensure the carrier is running true and travel limits are not exceeded.