Reconditioning or new?

30-year-old hydraulic cylinder whipped back into shape.

After about 30 years in use, the cylinder has a crack in the cylinder tube

New components, a general overhaul or both – for a hydraulic cylinder, several different variants can be expedient. This proved to be the case recently for a 2,000 tonne press used for steel manufacturing. The overhaul cost 60 percent of a new replacement.

Hydraulic cylinders are amongst the most heavily loaded hydraulic working components and are consequently often subject to high wear. As a result, they show evidence of wear after a certain time of operation that can endanger the entire work process. However, a defective hydraulic cylinder does not necessarily always have to be replaced by a new one. Often, an overhaul is the more economical solution. In some cases it can make sense to obtain quotes for a new part and a repair in parallel and then to choose the best solution of the two.


Advantages of an overhaul

Compared to purchasing a new part, a repair is typically less costly because all of the components of the hydraulic cylinder can be refurbished as needed so that they are, by and large, equivalent to a new cylinder in terms of function and quality. Additional advantages are:

  • Relatively short machine downtimes and production outages during a rapid overhaul.
  • Fitting accuracy is a given and the elaborate measuring procedures on site can be omitted.
  • The functionality, including with the overall system, is ensured because the hydraulic components were already operated successfully in the overall system environment.
  • Price advantages and greater speed because, as compared to the fabrication of a new part, fewer parts, if any, need to be made and many parts are in stock.


Arguments against an overhaul

Even with the many arguments that speak for a repair of a cylinder, there are also arguments against this:

  • Some cylinders are in such a poor condition that even dismantling them already involves a great deal of effort, the main components would have to be fabricated new and consequently, a repair is no longer worthwhile.
  • With cylinders which can very easily be replicated due to their small size or their design, fabrication of a new part often makes more sense.
  • If it is important for machines or systems to only be down for a few hours, then only a cylinder replacement is possible, meaning that the new cylinder must already be present on site so that the old one can be swapped against the new. Many times, the old cylinders are then given a general overhaul and subsequently serve as a fully-fledged replacement.



Cylinder for 2,000 tonne press

The last point is illustrated well by the following example: At a large German steel producer, there was an increase in leakage over the last few years on the main cylinder of one of their large presses with a compressive force of more than 2,000 tonnes. Because it was determined that after about 30 years of service a crack that had formed on the cylinder tube could not be permanently repaired, the only option was a replacement.

Because the press is vital for production and maintenance and the replacement of parts is only possible in the context of the annual revision of the system, it quickly became clear that the first measure was to have a new cylinder fabricated to be able to meet these requirements. It also became clear through this incident, however, that a redundancy needed to be established for this important system component to enable a fast replacement reaction time in the event of a serious problem with the main cylinder.

The Hydroservice Zylinderbau company, which produces hydraulic cylinders of all types both individually and in series, was engaged to fabricate a new cylinder. The cylinder was installed on time during the shutdown at the turn of the year. After the successful installation of a new part, the steel producer then had the hydraulic company overhaul the old cylinder. Although the cylinder tube had to be replaced due to the crack, the costs for this general overhaul only amounted to about 60 percent of the cost of a new cylinder therefore making it a worthwhile investment for the owner.



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