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Safety should be paramount when using hydraulics,†says Garnett Cross, director of Garnett Cross Hydraulic Courses.
Cross, who has been presenting hydraulic training courses since 1974, has compiled a list of some of the most important factors to take into account when using hydraulics.
His list of 15 safety hints includes reminders such as that nitrogen is the only type of gas to be used in an accumulator, and that pipe fittings should never be tightened when a system is under pressure.
“Every year people are injured, sometimes fatally, by ignoring the basic and simple rules of safety when working with hydraulics,†Cross says.
He calls for all involved in hydraulics to adopt good practice, such as having hoses pressure tested before assembly, and replacing hoses at least every five years.
Cross presents courses to all sectors of industry using hydraulically-driven machinery, including South Africa’s gold-, platinum- and coal-mines.
“I start all courses off with a lecture on safety, as hydraulic machinery mostly operates under high pressures, which could be hazardous if handled incorrectly,†Cross says.
Apart from safety, his courses also focus on the design, operation, construction, and maintenance of the different components comprising hydraulic systems, including, hydrostatic drives, hydraulic cylinders and valves.
“Hygiene is another important aspect to take into account with the use of all hydraulic systems.
“This in itself seems to be a paradox, as hydraulically-driven machinery is used in very dirty applications, such as surface mining,†Cross states.
He explains that artisans maintaining hydraulic equipment should work as cleanly as possible, as dirt entering these systems will result in parts having to be replaced.
When removing a hose, the artisan has to ensure that the work area is clean, and seal off the hose and cylinder once it has been removed.
If parts are being replaced, they have to remain sealed until the last moment before they are assembled.
Cross adds that all new oils should be regarded as contaminated prior to being filtered down to ten micrometres.
“Experience has proved that when hydraulic systems are maintained making use of these simple rules, they last and require longer maintenance intervals.
“Hydraulically-driven machinery plays an important part in underground and surface mining operations, and unforeseen downtime due to breakdowns could result in severe financial loss,†he says.
His hydraulic training courses are attended by about 200 people a year, including mine artisans, foremen and engineers.
“The biggest challenge is to create a pool of people who are well trained in hydraulics.
“Hydraulics should be approached in the same way as an electrician would approach an electrical system,†Cross states.
He explains that, where a mechanically-inclined person would focus on taking a system apart to find the fault, a person working on hydraulics should rather use an analytical approach.
“One should always bear in mind that pressure is caused by the resistance to the flow, and never by the pump.
“Relatively simple calculations can quickly determine the fault in a system, saving much time and expense.
“It is not always necessary to change expensive components – sometimes the problem can be as simple as an empty oil reservoir or a broken spring,†Cross adds.
The sizing of piping on a hydraulic system should be taken into consideration when trouble-shooting, as the correct piping keeps the system cool since there is less friction in the pipes.
When piping is under-sized, it also causes turbulence in the piping itself, and hoses become over-pressurised, which could lead to failure of the equipment in both cases.
Cross’s courses also focus on the build-up of hydraulic system circuitry, and he uses circuit drawings to teach people to use a systematic approach to do quick fault-finding.
He says that one of the latest trends is to install electronics on hydraulic systems, and there have been significant new developments in using electronics on hydraulic mining machinery, especially trackless and underwater mining applications.
By using electronics, the operation of hydraulic machinery is simplified and, in some instances, remotely controlled.
However, Cross adds that the lack of skills to maintain the electronics on hydraulic equipment is preventing some companies from buying this machinery, and some have even gone to the extent of removing the electronics because they do not have a skilled labour force to maintain them. For more information,please visit http://www.bossgoo.com
