Keeping safe and efficient through hydraulic hose awareness
Published: 13 November, 2014
Chris Buxton, CEO of the British Fluid Power Association (BFPA), and Martin Kingsbury, the BFPA’s membership director, consider some important safety and efficiency aspects to be aware of when sourcing, fitting, using, maintaining and replacing hydraulic hoses.
As any engineering professional knows, hydraulic hoses have an invaluable part to play in the efficient running of many types of industrial and mobile plant. For example, they are often used for the supply of oil under pressure for motion control in high-powered machinery such as cranes, excavators and extruder equipment. If they are supplied to the user or OEM to the correct specifications, and installed in accordance with current guidelines, they will likely operate reliably and efficiently. It is worth mentioning, however, that because of the wide range of hydraulic hoses available for different applications – articulated, coiled, corrugated, reinforced etc. – it is important to bear in mind a number of valuable points in order for your equipment to suffer minimal downtime and be safe for the operators and maintenance engineers. Avoiding fluid injection injury When dealing with hose assembly providers, it is important to be as sure as possible that you are sourcing high-quality hose, fittings and related equipment and services. This is not just a requirement from an efficiency and reliability point of view, but also from health & safety perspective. High-pressure injection injuries as a result of a faulty hydraulic hose are comparatively rare; occurring in an average of 1 in 600 cases of hospital reported hand injuries. However, when they do occur they should be taken very seriously indeed and treated as a medical emergency. And it’s not only the injured individual whose health can be seriously affected; the question of professional responsibility, accountability and reputation of the company can also be raised. In the worst-case scenarios, where a fatality occurs, there could even be a level of managerial culpability that leads to prosecution under the Corporate Manslaughter Act. The right specification So, what can be done to substantially mitigate any risk of hose failure, or, at worst, the scenario of a burst hose that results in a fluid injection injury to users or maintenance personnel? One practice to avoid is the mixing of different suppliers’ fittings for use in the same hydraulic hose application. Not all providers supply the same sizes, thread forms or taper angles, even though two different fittings may look more or less the same. Fittings have thread sizes that are often measured using a number of different formats, such as metric, BSP and MPT. Therefore if size and thread form information etc. is not written on the fitting, it is highly advisable that you seek the guidance of someone who is capable of using a thread gauge because the thread form must be known before it is installed. It is also important to tighten a hydraulic fitting to the torsion level specified by the manufacturer or supplier. Qualified fitters know that more torque doesn’t necessarily mean more oil tightness. Moreover, too much torque can end up damaging the fitting’s thread, making it difficult to unscrew and potentially reducing its efficiency and lifespan. Also, some hydraulic fittings tighten against a locking ring, clamping ring, taper or a soft seal, so if the fitting is over-tightened the rings or seals could become distorted – and this in turn can lead to a faster rate or corrosion or wear. Appropriate material Hydraulic hose fittings are made of different materials for use in specific environments. There are two most commonly used types of material. One is carbon steel, cast, forged or fully machined and often with either a zinc- or chrome-type plating. The next most common material used in the manufacture of hydraulic fittings is stainless steel – most commonly 316 in ‘open air’ or non-corrosive environments, and alternatives such as 318 in more corrosive environments such as in marine or medical installations. With this in mind, it is important always to consider the most appropriate material for a particular application. Additionally, it is inadvisable to mix fittings with different material specifications. By using fittings made of different materials on the same hose application corrosion may occur more easily, and this could result in leaks further down the line even though the hose application might seem to work efficiently to being with. Lifespan Bear in mind also that hydraulic hoses are not permanent. A variety of factors can impact the lifespan of a hydraulic hose. Flexing the hose too much, twisting it, kinking, stretching, crushing or scratching the surface can reduce hose life. Too low or too high operating temperatures will break down hoses as will sudden sharp rises or drops in internal pressures. Using the wrong size, type or weight of hoses can also cause hoses to break down. Hoses should be replaced before they fail; especially when used with hydraulic heavy machinery, brakes or safety-critical hydraulic machinery. Hoses show swelling, cracking, blisters and bubbles when worn or may show virtually no signs at all. Replace hoses as often as recommended by the manufacturer to prevent accidents. Raising awareness The British Fluid Power Association (BFPA) has established a number of programmes aimed at raising the awareness levels of people who work with hydraulic hose at all levels; from the system designer and field engineer, to the machine operator and the person who makes the hose: The BFPA’s ‘Foundation Course in Working Safely with Hydraulic Hose and Connectors’ is an accredited and certified course aimed at personnel who are involved in manufacturing and installation of hydraulic hose assemblies and connectors. The one-day course comprises a classroom-training period, followed by a practical session on the manufacture of a range of hose assemblies and pressure testing procedures. The BFPA’s practical, workshop-based course titled ‘The BFPA Hose Assembly Skills Training Programme’ follows in logical succession to the Association’s Foundation Course. The Skills Course takes this basic level of knowledge and trains to a fully assessed level of ability in hose assembly techniques. This two-day course covers the various theoretical and practical elements involved in working with hose and connectors. During the course the candidate is trained to an assessed level of ability in working with hose and connectors. The BFPA recently introduced a new practical, workshop-based course titled ‘The BFPA Hose Integrity, Inspection and Management Training Programme’. Following in logical succession to the Association’s complementary ‘Foundation’ and ‘Skills’ courses’, this course builds upon the knowledge already gained, extending it into management-related areas such as inspection, analysis, identification, registering and recording of hydraulic hose and related equipment. Key themes covered during the one-day course include: hose life expectancy; risk analysis; competence by way of a robust competence assurance system; identify, inspect & record; hose register – recording of a hose assembly prior to it going into service; and visual hose assembly (installation) inspection check list. Reputable providers Do not trust your equipment to anyone other than a reputable hose equipment provider; whether the company in question is a member of the BFPA Hose Accreditation Scheme, a holder of the BFPDA Approved Hose Assembly Mark or runs a rigorous and reputable scheme of its own. And, in terms of hose training, make sure the provider’s courses are well-established and highly respected within the hydraulics industry; whether they run their own courses or are authorised agents for the BFPA’s own Hose Foundation, Hose Skills and Hose Integrity, Inspection and Management Training courses. When it comes to hose and fittings, don’t accept anything but equipment of a high quality. After all, when the efficiency of your plant and equipment, as well as the health & safety of your workforce is at stake, only the best product, training and service provision is acceptable. The subject of hydraulic fluid injection injury is covered in the above-mentioned BFPA training courses. The BFPA has also published a booklet titled ‘Fluid Injection Injury Emergency – The Facts’, priced at Ł3.30 for BFPA/BFPDA members and Ł6.60 for non-members. If you would like more information about the BFPA courses, booklet, authorised training bodies, the BFPA’s Hose Accreditation Scheme or BFPDA Approved Hose Assembly Mark, please contact the BFPA on 01608 647900 or email: firstname.lastname@example.org. More information is available on the Association’s website: www.bfpa.co.uk. For course-specific information, please also visit: www.bfpatrainingacademy.co.uk.