The repair-rebuild-remanufacturing phenomenon has taken a strong grip on the fluid power industry in the 20th century and is here to stay through 21st century technology and beyond. The repair-rebuild concept depends upon durability and economic value. Certain types of engineering products — which are designed to be “throw-aways" — may not bring much economic value to the repair-rebuild process. Conversely, there are many products that can have a second life after the refurbishing process.

This article focuses on the repair-rebuild-remanufacturing concept in the fluid power industry — namely for hydraulic products — and will define repair, rebuild, and remanufacturing true to their sense.

Hydraulics requires precise, quality repair

The repair-rebuild industry for fluid power products has changed over the years. Centuries earlier, “repairing” broken parts of a complete unit was typical — whether the repaired unit perform the same original function or not, as long as it could be reused, repair was common. The repairing process would mean gluing, welding, and fusing two or more components. The word “refurbishing” is often used for repair work done on individual parts or components. Therefore “repairing” and “refurbishing” techniques are virtually the same, as the words imply.

Many repair processes could be termed as casual “rag-tag” operation, meaning that repaired components may not quite function as efficiently as the original one. Such repairs may be acceptable for non-engineering commodity type of products, but not for most precision hydraulic end products.

With evolving industries and technologies, repairing and rebuilding has become very common. Repaired, rebuilt components — or whole units — must function to near originality. The repair units not only should look like new, but must also perform like a new relevant one. Therefore, the aesthetic and engineering aspects are both a significantly important formula for an efficient repair-rebuild process.

Generally, the original designer or manufacturer should or must decide or spell out the extent of repair for a given product or components thereof. The original designer should put together the repair procedure and identify which components can be repaired, and which ones must not be repaired or refurbished.

In the past, among major hydraulic product manufacturers, only Vickers had come out with such an engineering-oriented procedure manual. However, such repair procedure manuals should be constantly reviewed for updated information because the extent of repair limits and changes with the advent of newer and current machining technologies. A good repair practice only enhances the image of manufacturers’ products because ultimately, no matter who repaired the product, it carries the original manufacturer’s identity and design value.

With the development of highly engineered pumps, motors, valves, and controls and related machine functions, it became necessary that repaired units and components perform with the same efficiency and adhere to form, shape, and function, like the original.

Taking ownership of hydraulic components and repairs

Often hydraulic service typically becomes the responsibility of the OEM. However, as soon as the warranty of the equipment or machinery expires, the OEMs too, may not be able to service the machinery. Therefore, it now becomes the responsibility of the end users to maintain and up keep the equipment and machinery.

The hydraulic product field population dictates the repair market potential. The end equipment and machinery are scattered far away from manufacturers, all over the globe. End users will look for an alternate, economical, and quick responsive source to upkeep their equipment and machinery, for reduced downtime. At first, the end users may look to the original manufacturer’s for timely availability of the original parts and units. This is often not possible, as delivery lead-time or high prices may eliminate the possibility of buying new. Consequently, end users are left with one good option — to look for alternate, efficient and close by repair-rebuild sources. That is why there has been an emergence of hydraulic product repair–rebuilding houses. Coupling this with an economical rebuilding process has created a booming hydraulic product “repair-rebuild-remanufacturing” industry.

Different components require different care

A repairing function is not just cleaning, flushing, regrinding, and re-machining the parts and reassembling them to a full unit. There is more to it. Hydraulic products can be divided into three categories — dynamic, intermittent-dynamic, and static.

Dynamic products are those that are called for continuous function, such as hydraulic pumps. In a system, the pumps are likely to run at all times — not necessarily in load condition, but at an idle speed. Therefore, natural wear and tear in the mating components is far more common with in a given life span than other hydraulic products. Hence, pumps often have more frequent failure within and beyond the designed life span than other hydraulic products. For example, a rated 5 gpm pump at 1200 rpm and 100 psi runs all the time at 1200 rpm, even when the machine may not be in cycle or no-load condition. The duty cycle, design, and application determines the life span of a given pump, be it a piston, vane, or gear.

Intermittent–dynamic hydraulic units are those not required to run all the time in a system, such as hydraulic motors, directional valves, and servo proportional valves. In the majority of applications, these units do not run at all during the full cycle of the machine or equipment. Case in point — hydraulic motors, which most often run in a system only for a specific time period. The rest of the time the motor is sitting idle or not running at all. Of course there are a few exceptions, such as in conveyor belt applications.

Similarly, most sliding spool directional valves and other sliding spool functions do not run all the time in a system. Therefore, the motors and directional valves in a hydraulic system will have comparatively lower wear and tear than a hydraulic pump, over a given time period or duty cycle. The natural failure rates for such type of units are less than hydraulic pumps.

Static hydraulic products are those whose internal functions in a system are virtually “open-close” type. In other words, the internal components in such products have much less natural wear and tear, thus the life expectancy for such products is much longer than the other two categories of products. Pressure, flow, sequence and check valves, and inserts come under this category.