April/May 2020

HYDRAULICS 26 HYDRAULICS & PNEUMATICS April/May 2020 www.hpmag.co.uk EN ISO 4413 and BS EN ISO 4414, and meet the guidelines. Both are Harmonised Standards of the Machinery Directive, which is written into legislation. Clause 5.4.6.5.1 a) – within ‘BS EN ISO 4413 Hydraulic Fluid Power - General rules and safety requirements for systems and their components’ states: “Hose assemblies shall be constructed from hoses that have NOT been previously used in operation as part of another hose assembly and that fulfil all performance and marking requirements given in appropriate standards.” It is worth noting at this stage that in CEN and ISO parlance, the word `shall` is taken as ‘must comply’ – it is non-negotiable. It is therefore quite clear that the international standard is intent to outlaw the re-ending of flexible hydraulic hoses. The scheme also adheres to BS EN ISO 4414, which mirrors this advice for pneumatic hoses. Major risks Trade associations, industry experts and health & safety bodies all agree that you simply don’t re-end hoses, the risks are too great; but the problem is that hose re- ending is still prevalent across much of the industry, with most people citing cost as the primary rationale. “It is hard to convince people to hand over £200 for a new hose assembly, when they can get it re-ended for £50,” explains Pirtek’s Martyn Smart. “With cost being such a defining factor, it’s a real battle to convince them otherwise. I have seen 2000 psi water jet hoses repaired with tape and a jubilee clip! Counter this with the fact that we have purchased and delivered over 4000 BFPA books detailing the impact of fluid injection injuries and you can see that the message just isn’t getting through – especially when bottom lines are a defining factor in the decision.” Andy Dickens, operations manager at Interpump Hydraulics (UK) Ltd, says: “Companies are put under huge commercial pressures, so much so that re- ending is seen as the commercially attractive alternative.” Backing up Martyn Smart, Dickens adds: “We have seen hoses repaired with a bundle of gaffer tape. People don’t seem to appreciate just how much pressure these systems are under. There is a massive amount of naivety, with people being blissfully unaware of the dangers of high-pressure fluid systems.” “A hose made from a ‘pick-and-mix’ of third-party components simply cannot guarantee the tolerances necessary to ensure a quality hose assembly,” says Smart “Add to this the fact that you didn’t know the operational history of the hose being re-ended and you have a potential recipe for disaster. No one will offer a guarantee or warranty on a re-end. We use matched components, all of which are tested by their manufacturers to meet tolerances, which for a swaged ferrule are +0 mm/-0.2 mm. Dickens adds: “When you’re re-ending, you’re mixing and matching components. The products may appear to be the same, but there are differences. Our ferrules fit our hoses. If you use a third-party ferrule that is at the upper end of the tolerance band, it Coupling has ‘blown off’ the hose. Coupling which has ‘blown off’ and disconnected from the hose. may not fit properly. I’m not saying that that ours are better – they just match our hoses. Anyone who has done a re-end has lost those tolerances. From where are they getting measurement information from? Whose data are they using?” “There is an extreme amount of force trying to push these components apart,” Smart explains. “In its own right it is hard to put into words, but we have showcased it by setting up an assembly with a mis-manufactured hose, which is then put under 350 Bar of pressure. In this instance, it blew within 15 seconds and decimated a 3 kg melon we had put next to it. We had to use a 2000 frames per second camera to catch the failure and resulting impact. The hose end was measured at 600 ft. per second – similar to the muzzle velocity of a rifle.” High cost of failure The consensus from Smart, Dickens and the British Fluid Power Association (BFPA) is that hydraulic hoses need to be addressed with the same level of importance and attention to detail that you would give to any precision engineered component. In addition to the simple cost of replacement, users must consider the cost of failure, from both a financial and a cost perspective. Only by using hoses from suppliers accredited by the BFPDA’s Approved Hose Assemblies Scheme, can users have the confidence that they have purchased an assembly that has undergone rigorous measurement and testing; assemblies that use matched components that are within defined tolerances and are backed by industry wide guidelines. “The more we educate people, the better and safer the industry will become,” Smart concludes. “Hoses will get damaged in their everyday use. We need users to consider how and where they are used and then develop a proactive inspection and maintenance plan. This way, early failures can be more easily predicted and even have their causes designed out. Some protective systems are highly effective and are more palatable in cost terms versus replacement.” “None of us seems to know who is doing this re-ending, but it is still going on,” says Dickens. “We will replace entire assemblies that have failed testing rather than elements of it, even though it costs us more. This is how committed we are to the safety of users, as should all of industry. We are then confident to offer warranties, which leads me onto an interesting final thought…re-ends do not come with any form of warranty or guarantee. Would you be prepared to purchase any other product without these in place?” www.hydraulichosesafety.co.uk Continued from page 24