Hose assemblies in manufacturing or processing plants can sometimes be a source of equipment malfunction, dangerous product spills, or even serious personal injury. Moreover, with today's rising need for faster and quicker fluid transfers, the demands being placed on hose assemblies are greater than ever -- as are the increased working temperatures and pressures that can easily diminish their holding power.

Hose assemblies can be made to fit practically any fluid transfer application, but care must be taken to select the correct hose, fitting, and attachment method. Too often, hose assemblies are put into service incorrectly or placed in an improper application. Plus, the very properties that make hose assemblies so convenient -- their light weight and flexibility -- can also make them more challenging to maintain.

In dealing with these concerns, plant maintenance engineers, safety directors, and facility managers may find an ally in hose distributors and manufacturers. Some of these companies offer in-plant hose assembly safety surveys designed to help identify conditions that could pose a risk to plant production or safety. Several programs are offered free of charge, as a service to the industry. One such program, in existence for the past 15 years, is available from the Dixon Valve & Coupling Company, a leading manufacturer and supplier worldwide of hose and coupling products.

A Step-by-Step Process

What are the steps involved in setting up a hose assembly safety survey? After the initial call to a distributor or factory representative, the process typically begins with a visit from a safety technician. This individual will view the facility, determine the resources required to conduct the survey, and meet with plant maintenance and safety personnel to introduce the concept and answer questions about the survey process.

Next, a safety team is formed that includes hose and fittings experts -- usually from the rubber/hose distributor and the coupling manufacturer -- as well as plant personnel. The on-site experience of plant personnel, bringing an intimate knowledge of the facility and its maintenance history, is a valuable resource to the team.

During the survey process, the safety team walks through the plant, viewing and noting the various hose applications and assemblies. The survey methodology focuses on the industry-standard acronym of STAMPED (size, temperature, application, media, pressure, ends, and delivery) as the basis for the assessment of the hose assemblies. Also during the survey, areas of potential concern are pinpointed and, if desired, photographed to help document the findings.

Once the survey is completed and the results are compiled, recommended corrective actions concerning the selection, installation, and maintenance of the plant's assemblies are submitted in a formal written document. In addition, suggestions concerning the storage, inspection, and testing of hose assemblies are provided. Many of these recommendations are based on guidelines issued by the Rubber Manufacturers Association and the Association for Hose & Accessories Distribution.

Covering All the Bases

Considering the size and complexity of many manufacturing and processing plants, the areas to be surveyed may appear endless! In reality, a safety survey can be conducted in a very concise, time-efficient manner. A recent survey conducted by Dixon for a large midwestern processing facility that manufactures biochemicals and organic chemicals provides a good example of the process and the actionable results.

This particular plant works with a variety of media, including nitrogen, glycol, and various solvents as well as water, air, and steam. Working pressures range from 26 to 100 psi.

During the walk-through, team members observed and noted many proper applications that reflected effective original equipment manufacture practices pertaining to hose assemblies; these were duly noted. Among them were the practice of tagging and dating hose, the tagging of hose to be taken out of service, proper hanging of hose while not in use, as well as the selective use of locking cam and groove mechanisms. In addition, the team noted the prominent and proper labeling of the different media lines throughout the entire plant.

At the same time, safety members observed a number of hose assemblies that could conceivably lead to operational failure and/or other negative side effects such as production line downtime, standard practice safety violations, or environmental compliance issues. The good news was that in each case, the action needed to remedy the potential problem was relatively minor . . . a classic case of "an ounce of prevention being worth a pound of cure!"

The Bottom Line

Among the conditions noted in this safety survey, and the remedies recommended, were the following:

1. Two-inch metal hose with cam and groove type fittings used for steam service. Steam demands respect! Cam and groove quick acting couplings should never be used for steam service. In this application, when the cam arms are opened, the couplings will separate from the adapter instantaneously. The resulting sudden burst of steam is extremely dangerous. A steam fitting must have a thread adapter and wing nut in order to be safe. When the operator unscrews a threaded union under pressure, the coupling will leak noticeably without being completely opened. This serves as a warning that the line is live and under pressure, and provides the operator with time to safely retighten and seal the coupling.

2. Bolt-style clamps required attention. The proper selection, installation, and maintenance of bolt-style clamps are key factors in the safe performance of the hose assembly. The inside and outside diameter of the hose are very important when it comes to selecting the proper clamp. The hose diameter must fall within the size range for which the clamp was designed. When installing a bolt-style clamp, it is important to know that the individual body sections of the clamp should never be allowed to come in contact with each other. There must always be an even showing of hose between the clamp sections to ensure that it is properly installed and fully functional. Bolt-style clamps can only perform to their design capabilities if the bolts are tightened to their recommended torque. These bolts are intended to bend during the tightening procedure, and although they can be torqued again while in service, it is not recommended that they be reused. They are intended for a single bend only. Also, do not replace old bolts with bolts of any other strength. Clamp bolts are a specially engineered part of the overall assembly and contribute to the usability and functionality of the clamp. Finally, the clamp halves are also designed for a single bend only. When clamp halves are removed from a hose, they should be immediately discarded.

3. Band-style clamps improperly installed. The use of band-style clamps has proven to be an effective means of retaining hose couplings in industrial hose. However, to achieve proper retention and sealing, it is imperative that these clamps be installed correctly. When multiple clamps are used, the buckles must be offset around the hose, to eliminate the possibility of a "straight line leak" under the buckle areas. Additionally, the practice of leaving excess banding material turned back over the buckle does not improve the performance of the clamp. In fact, this procedure creates a safety hazard by leaving sharp-edged material exposed to the operator.

4. Worm gear clamps observed with tangs protruding. When properly used for low-pressure air or water service, worm gear clamps provide an excellent means of holding fittings in hose. However, they can prove to be hazardous in situations where the excess material protrudes from the clamp housing and poses a safety hazard to the equipment operator. Brass ferrules are an excellent, yet economical, alternative to worm gear clamps. When properly installed, they offer excellent holding power with no sharp edges.

5. Tape used to repair a hose assembly or protect hands. The practice of taping fittings or hose, for any reason, should be discouraged. If a hose is broken, it should be properly repaired. Taping, while offering some hand protection, hides from visual inspection the area of a hose assembly most susceptible to damage: the area directly behind the coupling. This area should always be available for visual inspection.

6. Tape and other field-expedient measures used to secure cam arms. Securing cam arms on couplers in the "down" or "closed" position by means of tape, wire, string, etc., is a step in the right direction. However, lockable cam arms that are specifically designed, engineered, and manufactured for this purpose are available. Partially open or fully open cam arms on hose assemblies are dangerous. This hazardous condition can be caused by a number of different factors. Three of the most common are: the operator failing to fully close the cam arms when hooking-up the assembly; high vibration within the pumping system combined with worn or missing gaskets, allowing the arms to "work" open, and high "impulse shock" within the pumping system causing severe wear on various parts of the coupler, allowing it to fail in place. Whatever the cause, this unsafe condition must be corrected. Education of the operator is essential, and periodic inspection of the condition of the coupling parts is paramount.

7. Universal air couplings missing safety pins. Some universal-style couplings do not incorporate the built-in "safety step" feature that better-quality couplings do. This safety step, located under the ears of the coupling, is designed with a 90-degree edge that when mated with the same edge on the opposing part reduces the possibility of accidental uncoupling. In any case, all universal-style air couplings must be used with a safety pin in place. This simple step will ensure positive locking and eliminate the possibility of the assembly coming apart during service. Couplings without a properly placed safety pin may be "rolled apart" by the natural force put on the hose assembly. This causes a potentially dangerous situation. Although it can be minimized by the proper installation of a whip check device, preventing the problem before it occurs is as easy as putting a piece of wire, a nail, clip, or pin in the place designed for it.

8. Band clamps, steam hose, and "cold flow." Steam hose should never be coupled with a permanent clamping device such as a band clamp or ferrule. There is no way of servicing them following installation. An interlocking bolt-style clamp that can be retightened, as necessary, is appropriate because of the "cold flow" of the rubber in the hose. "Cold flow" is a phenomenon that describes the continued deformation of rubber under stress. In the case of a coupling clamped to a hose, the tube and cover will continually flow away from the area of stress, leaving an assembly that is inadequately torqued. It's not uncommon to find the bolts of a clamp inadequately torqued when a coupled length of hose is taken off the warehouse shelf. This happens even when a competent mechanic had previously torqued the bolts to the proper specifications. This is "cold flow" at work, and as a result, many rubber manufacturers feel compelled to install a label on their steam hose that states: "tighten clamp before using."

The Return for Time Invested

For this chemical facility -- as indeed for many manufacturing and processing plants like it -- the bulk of the safety survey recommendations turned out to be of a preventive maintenance nature, which makes them quite cost-efficient to put into practice. In the end, plant personnel concluded that the survey was a very worthwhile experience.

For Dixon and other similar suppliers, support to plant facilities does not end with the survey recommendations. If desired, Dixon can set up training sessions, present survey findings, and outline "best practices" for the future selection, installation, and maintenance of hose assemblies.

At the end of the day, an ounce of prevention produces better operational efficiencies, reduces the risk of hose assembly failures, and enhances worker safety. How can anyone go wrong on an investment that pays off like that?

Over the years, hose assembly surveys conducted at processing plants have uncovered a variety of potential concerns and risks. Among the more commonly found conditions are:

• Broken or missing cam arms on cam and groove couplings.


• Damage to protective hose coverings caused by vibration.


• Kinks in hoses, resulting in diminished pressure ratings.


• Couplings or gaskets made of the wrong material for the product being conveyed.


• The selection of couplings that are not designed (or suited) for a particular service.

While many of these conditions can be easily corrected, the potential risk to the plant could be serious, as each clearly represents "an accident waiting to happen." The wrong hose in the wrong application could result in serious damage to equipment -- or injury to the operator -- should the hose assembly fail.