Don't Get Hosed: Reduce downtime with hose maintenance and safety procedures
Written by Ron Trujillo
Never underestimate the consequences of a failed oilfield hose: downtime, cost overruns, lost production, missed schedules, personal injury, property damage and the failure of associated equipment. Just installing the best-coupled hoses is not enough to ensure optimal operation on an oil rig. Proper handling, storage, use and maintenance of rotary drilling and vibrator hose assemblies are essential for long-lasting performance and safety.
Maintenance and Safety The selection and maintenance of hydraulic hose components for oil drilling equipment can spell the difference between productivity and costly downtime, especially when the work site is miles away from the nearest parts distributor or repair shop.
• Identify Hydraulic Leakages: The first step in any preventive maintenance program involves training equipment operators and maintenance personnel about how to identify and remedy leaky hydraulic hose assemblies. Machine operators need to be aware that although the appearance of dirt on hoses and fittings is an obvious indication of hydraulic leakage, leaks often send fluids into other equipment surfaces and must be traced to their source.
Tracing the leak to its source may require machine operators to do some detective work. If hoses appear excessively wet around their fittings, check for loose couplings. If the coupling is tight, this is an indication the coupling/hose interface has reached its service life and should be replaced.
• Look for Abrasions: A frequent cause of leakage in hydraulic hoses for oil drilling equipment is abrasions resulting from cuts, friction caused by other moving parts, or from mechanical impacts. For example, hose-to-hose abrasions are likely to show up where lengths of hose travel through a boom. Hose-to-metal abrasion can occur where hoses travel through a bulkhead. In many cases, abrasion problems will be apparent during an inspection, and replacement can be initiated before failure occurs. Hose covers that are cut, torn or worn through will allow reinforcement wire or textile braids to deteriorate and/or rust. These hose assemblies must be replaced immediately. Hose manufacturers now offer a variety of hose products with abrasion-resistant covers.
• Follow Proper Assembly Procedures: Another cause of leaks can be the improper assembly of replacement hoses, which can occur when mating surfaces on couplings are incompatible, when couplings are improperly attached to the hose or when the hose assembly is installed incorrectly.
Assembly problems can be avoided by following the crimp and assembly recommendations of the manufacturer of the products being used. One common cause of failure is incorrect crimping that occurs when a hose is cut incorrectly or when the stem of a coupling is not inserted all the way into the hose. Be aware of worn die fingers when using older model crimpers. Die wear is a real concern, especially on dead step crimpers. When die fingers get worn, the crimp can become loose, and eventually, a hose assembly blowout is inevitable.
Gates engineers say 80 percent of all hydraulic failures are due to fluid contamination that often results when metal shavings and rubber dust are not thoroughly removed during fabrication of the hose assembly. Preventive measures include blowing air through the hose, flushing the hose with a solvent, or using a cleaning kit with a sponge projectile after the couplings are attached.
• Allow a Margin of Safety: When choosing a replacement hose, check the manufacturer’s specifications for pressure and temperature ratings. Hose dimensions can be critical, as well. It is important to determine the correct inside and outside hose diameters using a precision-engineered caliper. The outer diameter is especially important when hose routing clamps are used, or when hoses are routed through bulkheads. Check individual hose specification tables for outer diameters in suppliers’ catalogs.
The inside hose diameter must be capable of handling the required fluid flow without generating back pressure. It is not uncommon for pumps to deliver more than 200 gallons of fluid per minute to hydraulic cylinders and motors in various types of heavy-duty equipment, which is why it is important to know the type of hose and the working pressure in a system when making replacements. When in doubt about the system pressure, cut the failed hose and determine whether the type of reinforcement is one or two wire braids, or four or six spiral wires.
In situations where equipment has been modified to perform special operations, it is not uncommon to see spikes in hydraulic pressure that the hose and coupling manufacturer did not anticipate. As a general rule, when choosing hose to transmit fluid under pressure, it’s best to allow a generous margin of safety.
• Establish Correct Hose Length: When making a new hose assembly, always make sure it is the same length as the one being removed. Too long an assembly can lead to the hose being severed or pinched in the moving components of the equipment. If the replacement hose assembly is too short, pressure may cause the hose to contract and place excessive stress (tug) at the coupling.
Changes in hose length when pressurized range from plus-two to minus-four percent while hydraulic mechanisms are in operation. So, allow for possible shortening of the hose during operation by making the hose lengths slightly longer than the actual distance between the two connections.
• Consider Temperature Requirements: All hoses are rated with a maximum working temperature ranging from 200°F (93°C) to 350°F (177°C) based on the fluid temperature. Exposure to continuous high temperatures can lead to hoses losing their flexibility. Failure to use hydraulic oil with the proper viscosity to hold up under high temperatures can accelerate this problem.
External temperatures become a factor when hoses are exposed to heat from a turbo manifold or some other source. When hoses are exposed to high external and internal temperatures concurrently, there will be a considerable reduction in hose service life.
• Choose the Right Connections: Permanent and field-attachable couplings are common on oil-field equipment. The choice of permanent or field-attachable couplings is often influenced by cost, convenience, the type of application, manufacturer’s recommendations, the environment in which the assembly will be used and possible regulatory requirements.
Permanent fittings provide greater performance capability and durability, plus the availability of inexpensive crimpers increases their ease of use.
The JIC (Joint Industry Conference) hydraulic seal is popular among equipment designers because of its performance versatility, availability and low cost. However, metal-to-metal seals found in the traditional JIC 37° couplings can leak when the metal surfaces grind into each other and leave distortions.
• Don’t Mix and Match: Gates engineers recommend against using couplings from one manufacturer and hoses from a different manufacturer interchangeably. Although most American-made hydraulic hoses, and many imported hoses, are built to conform to SAE (Society of Automotive Engineers) specifications, SAE allows a whole range of materials to be used. Different manufacturers use different materials, which can result in a variety of hose styles.
The proliferation of thread ends from around the world in recent years has dramatically increased the possibility of mismatching threads and seats on various couplings. For example, the only differences between a conventional SAE coupling and a foreign coupling are the thread configuration and the seat angle. The ability to correctly identify all of the different types of coupling can help prevent costly mistakes when assembling replacement hoses.
Also keep in mind that rubber O-rings are not interchangeable with all couplings.
• Follow Proper Installation Procedures: Improper installation of replacement assemblies is another prime cause of leaks in hydraulic hose assemblies. One common installation error results from twisting hoses as they are being tightened. Pressure applied to a twisted hose can result in hose failure or loosening of connections, sometimes referred to as de-torquing. Always take into account the manufacturer’s recommended minimum bend radius and avoid routes that twist the hose or cause it to bend immediately behind the coupling. The use of two wrenches (one on the hex nut and one on the stem nut) while tightening the swivel fittings will help prevent twisting.
When a coupling is leaking, there is a natural tendency to tighten the fitting. However, over torquing couplings can also lead to leakage problems. Proper torquing is especially critical when flared fittings are used. Too much tightening can result in thread stripping, or deflection or scratching of the cone seat and will prevent proper sealing.
• Be Prepared: In the oil drilling industry, remote job sites are typical. Being miles from the nearest distributor may require keeping and inventory of hydraulic hoses and fittings on hand, along with a crimper, to minimize downtime. Hydraulic parts distributors can provide a selection of hoses, fittings, crimper and training necessary to meet emergency situations.
