Technical Paper: Hydraulic Hose Assembly Care

The benefits of using hydraulically driven systems to power oil spill response equipment include; flexible load control, high energy efficiency, intrinsic safety and the ability to power equipment remotely from the power source. However, there is a certain amount of basic maintenance associated with hydraulic systems, without which they can become unreliable and even dangerous. Even in well­maintained systems, hydraulic oil remains a potential pollutant and spills must be prevented.

Hydraulic power systems consist of three basic elements: • A hydraulic pump attached to a prime mover, which can be electrically, diesel or air driven.

• A hydraulic motor operating the equipment. • A control circuit.

Hoses, fittings and hose assemblies connect the motor to the pump and transmit high pressure hydraulic fluids. These high pressure fluids transfer energy and do useful work.

Hydraulic systems are used extensively in industry and the cost of repairing or replacing poorly maintained systems can be high. In addition, fluids under pressure can be very dangerous and it is essential that the risk of them escaping from a system is minimised. The proper care and maintenance of hydraulic hose assemblies is therefore fundamental to the safe and effective use of hydraulic power systems.

This ITAC paper is intended to give the reader an overview of the basic steps that should be taken to maximise the working life of a hydraulic hose assembly system. If correctly implemented these steps should also improve operator safety.

Hose and Fitting care

It is important to recognise when using any assembly that improper selection or improper use of hoses, tubing, fittings, and assemblies can cause failures, personal injury or property damage. Understanding the hose assembly and following the installation instructions provided by manufacturers will reduce these risks.

Some of the main areas for consideration are:

Component Inspection: Prior to assembly, a careful examination of the hose and fittings must be performed. All components must be checked to ensure that they are the correct type, size, and length. The hose must be examined for cleanliness, obstructions, blisters, kinks, cracks, cuts or any visible defects. The fitting and sealing surfaces need to be inspected for burns, nicks, corrosion or other imperfections. Do not use any substandard or defective components in an assembly.

Hose and Fitting Assembly: The manufacturer provides guidance on the selection of hose fittings, hose types and installation. These must be selected to be compatible with the pressure rating of the system and the environment within which the system is to be used.

Minimum Bend Radius: Each manufacturer sets a minimum bend radius according to the hose’s construction and proposed use. Installation of a hose at less then the minimum recommended bend radius may significantly reduce the hose life. Particular attention must be given to prevent sharp bends at the hose connection to the fitting. Any bending during installation to less than the minimum bend radius should also be avoided.

Contact: Web: www.industry­tac.org Email: info@industry­tac.org Tel: +44 (0)23 8033 1551 Fax: +44 (0)23 8033 1972 OSRL, Lower William Street, Southampton, SO14 5QE, UK

The views and advice contained in this paper represent contributions from various ITAC members. Neither ITAC nor any of its members will accept liability for any loss or damage to property, or personal injury to or death of any person caused or contributed to by the use or mis­use of the information contained herein.

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The Industry Technical Advisory Committee (ITAC) is a forum for information exchange between experts within the global oil spill response community. A key mission of ITAC is the development of Technical Papers to provide:

• Advice

• Technical Support

• Benchmarking

• Best Practice

Hose­Material Compatibility: It is important to understand that there are many variables that can affect compatibility of system fluids with hose materials, these include:

• Type of fluid • Fluid pressure • Temperature • Concentration • Duration of exposure

Environmental conditions can also cause hose and fitting degradation. Conditions to evaluate when using these systems in a response include exposure to:

• Ultraviolet light • Salt water • Air pollutants • Extreme temperatures • Ozone • Chemicals • Electricity • Abrasion damage

It is important to consult the manufacturers for more information on hose compatibility.

Proper Connection of Ports: Proper physical installation of the hose assembly requires a correctly installed port connection ensuring that no twist or torque is transferred to the hose when the fittings are being tightened.

Elbows and Adapters: When fitting hose assembly systems in some cases it is advisable to use elbows or adapters to relieve hose strain

Routing: The hose assembly should be routed in such a manner so that if a failure does occur, the escaping media will not cause personal injury of property damage.

Hydraulic Hose Assembly Care Hose and Machine Tolerances: It is also important when fitting hoses to design the layout to allow for changes in length due to machine motion and tolerances.

Motion Absorption: It is very important to provide adequate hose length to distribute movement and prevent bends smaller than the minimum bend radius.

Lengths: Unnecessarily long hoses can increase pressure drops and affect system performance. When pressurised, a hose that is too short may pull loose from its fittings, or stress the fitting connections causing premature failures.

System Check: In hydraulic or other liquid systems, eliminate all air entrapment after completing the installation. Follow manufacturers’ instructions to test the system for possible malfunctions or leaks. To avoid injury during system checks:

• Do not touch any part of the system when checking for leaks

• Stay out of potentially hazardous areas while testing hose systems

• Relieve system pressure before adjusting connections.

Hose and Fitting Maintenance and Replacement guidelines

Even with proper selection and installation, hose life may be significantly reduced if a continuous maintenance program is not in place. The frequency of inspection and replacement of assembly components should be determined by the system’s operating environment, the potential risk from a hose failure and any past experience of hose failures in the application or in similar applications.

The views and advice contained in this paper represent contributions from various ITAC members. Neither ITAC nor any of its members will accept liability for any loss or damage to property, or personal injury to or death of any person caused or contributed to by the use or mis­use of the information contained herein.

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Hydraulic Hose Assembly Care Visual Inspection: Any of the following conditions require immediate shut down and replacement of the hose assembly:

• Fitting slippage on hose. • Damaged, cracked or charred hose. • Cracked, damage or badly corroded fittings. • Leaks at fitting or in hose. • Kinked, crushed, flattened or twisted hoses. • Blistered, soft, degraded or loose covers.

The following items must be tightened, repaired, corrected or replaced as required:

• Leaking fittings. • Worn clamps, guards or shields. • System fluid level, fluid type and any air entrapment.

Function Test: Operate the system at maximum operating pressure and check for possible malfunctions and leaks. Personnel must avoid potentially hazardous areas while testing the system.

Replacement Intervals: Hose assemblies and seals used on Hose Fittings and adapters will eventually age, harden, wear and deteriorate under thermal cycling and compression set. Hose assemblies and all seals should be inspected and replaced at specific replacement intervals based on previous service life, industry recommendations, or when failures could result in unacceptable downtime, damage or injury risk.

Hose inspection and failure: From time to time hose assemblies will fail if they are not replaced at appropriate time intervals. Usually these failures are the result of some form of misapplication, abuse, wear or failure to perform proper maintenance.

When hoses fail, the high pressure fluids can escape in a stream which may or may not be visible to the user. Under no circumstances should the user attempt to locate the leak by feeling with their hands or any part of the body. High­ pressure fluids can penetrate the skin and cause severe tissue damage.

If hose failure occurs shut down the equipment immediately and leave until pressure has been completely released from the hose assembly. Simply shutting down the hydraulic pump may not eliminate the pressure in the hose assembly. It may take some time for the pressure to reduce to a safe level for inspection. The hose assembly and equipment then can be checked and faulty components replaced.

Seals used in fittings and adapters: All seals, such as Dowty and Elastomeric, will eventually age, harden, wear and deteriorate under thermal cycling and compression set. These seals should be inspected regularly and replaced when needed.

Hydraulic System Storage and Protection

Hose Sleeves: Sleeves are designed to protect hoses from abrasive wear and other hostile conditions. They simply slip over the end of a hose assembly, or they may be spilt to allow them to be installed around a hose assembly already on equipment. Hose covers are generally made of high­ strength fabric, and coated with appropriate materials to resist chemicals, heat, particles, moisture etc.

Hose storage: Temperature, humidity, ozone, sunlight, oils, solvents, corrosive liquids, insects, rodents, and radioactive materials can adversely affect hose products. Hoses should be stored in a dark, dry atmosphere away from heat sources, electrical equipment, and the above adverse elements. The ideal storage temperature for rubber hose is +50°F (10°C) to +70°F (21°C), with a maximum of 100°F (38°C).

Whilst a hydraulic assembly system may not be in use on a daily basis in the spill response industry, a number of procedures should be enforced while the hoses are stored. Routine hydraulic operational checks should be made on all hydraulic hoses based on a 6 monthly and 12 monthly maintenance schedule. Maintenance checks involve a full system check, run up to normal operating pressure, inspection of hoses for damage, cuts, ferrule slip back, coupling integrity and leakage. The date of manufacture of the hoses also needs to be checked.

Any power pack used with spill equipment will have internal hydraulic hose systems which will also have to be checked and maintained. As above; these internal hoses are checked and the system loaded to full pressure for up to one hour when carrying out maintenance checks.

Hose Storage Life: Manufacturers and safety standards generally stipulate a storage life for hydraulic hoses and these standards vary around the world. The difficulty for response organisations is that the standards are generally built around hose assemblies in continuous service, or certainly with much greater service life than those experienced in oil spill response activities. The counter to this lack of operational use, which causes the hose to only be exposed to hydraulic pressure for limited periods, is the more arduous operating environment in which they are used. Hoses can be dragged across decks and jetties, trailed into seawater and more generally abused than normal plant hoses. For this reason a system of rigorous inspection, and periodic testing should be included in the maintenance programme rather than simply using a pure replacement programme. Nonetheless, hoses do need periodic replacement and it is important to track the age of the assembly and monitor its condition.

The views and advice contained in this paper represent contributions from various ITAC members. Neither ITAC nor any of its members will accept liability for any loss or damage to property, or personal injury to or death of any person caused or contributed to by the use or mis­use of the information contained herein.

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Hydraulic Hose Assembly Care

The date of manufacture of hoses is generally marked on the hose and other information is provided, for example:

• R1 ~ 2Q/05 marked on a hose shows it is a single wire construction hose made in the 2 nd quarter of 2005

• R2 ~ 4Q/05 would denote a two wire construction hose made in the fourth quarter of 2005.

There are many different types of hoses and assemblies in production around the world and governments and manufacturers have different standards regarding safety and hose care. Oil Spill Response Organizations (OSROs) generally work over and above the stipulated standards, however government guidelines, such as the British standards, should be used as a benchmark.

Recognized industry standards ensure that the user will adhere to a maintenance schedule and understand the safety implication if not met, however it is the users duty of care to ensure these checks are not only carried out in maintenance but during any operation as well and at regular intervals. It is the responsibility of the organisation to clearly identify what is involved in all the ‘in­use’ and ‘maintenance’ checks.

In­use Safety Considerations

Pre­Use Activities: It is important for every user to thoroughly review and understand information provided in the equipment operator’s manual with particular attention being given to descriptions of safety procedures. Risk Assessments should be carried out before using the equipment.

Prior to use, always inspect hydraulic hoses and fittings for defects or leaks and to ensure that they are securely attached at connection points. Confirm that low­pressure hoses or fittings are not connected to high­pressure hydraulic systems or pumps. If a hydraulic system fails the pre­use inspection, notify your supervisor and follow all procedures to ensure it is marked ‘out of service’ until repaired.

Operating Precautions: Before starting the engine, look to see that people and obstructions are clear of the equipment. Never support any implement or equipment by its hydraulics.

Always shut the engine off and release all hydraulic pressure before disconnecting, performing maintenance or making repairs. Beware of any hydraulic pressure that may be stored in pressure vessels or accumulators. Always use supports, jacks, stands, or blocks to prevent movement of hydraulic implements or components.

When hydraulic systems are operating, hydraulic fluid temperatures range from 165° to 185°F due to the high pressure and represent a potential burn hazard. Hydraulic oil is a fire hazard and when ignited can cause severe burns or fatalities.

Remember never search for a pinhole leak by running your hand or finger along a hydraulic hose. Hot hydraulic oil at high pressure can puncture gloves and penetrate several inches into soft tissue.

Tips on Hose Assembly Care and Maintenance

Ø Try to fit male fittings on hoses and females on machines. Male fittings are easier to clean if they are dragged through sand etc.

Ø Always clean fittings before connection.

Ø Always ensure caps and plugs are fitted on hoses when not in use.

Ø Store hoses out of sunlight. Hoses left in direct sunlight will degrade and high pressures will be generated when oil expands in hose making connection difficult.

Ø Use a pressure relief tool to release pressure­locked hoses. Do not bang hoses on deck, floor etc to release locked pressure.

Ø Always wear safety goggles when handling or working with pressurised hoses.

Ø Do not use hydraulic hoses as lifting or mooring lines.

Ø Use protective tape (Densil) to protect fittings from corrosion.

The views and advice contained in this paper represent contributions from various ITAC members. Neither ITAC nor any of its members will accept liability for any loss or damage to property, or personal injury to or death of any person caused or contributed to by the use or mis­use of the information contained herein.

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