Insane Hydraulics

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Aftermarket Spares - Thoughts and Examples

In this article I would like to throw in my modest opinion about non-original spare parts - a frequent discussion topic among folks involved in the business of hydraulic pump and motor overhauling.

Although workshops can't repair pumps without spare parts, they can choose where to buy the spares, and this choice is the key factor that defines how much money they make and how much "overhauling quality" they deliver. With so many suppliers and resellers of non-genuine replacement parts for hydraulic pumps and motors popping up every day, choosing the right "economic" supplier has become all but an easy task involving trial and error overhauls, pissed-off mechanics, pissed-off customers and even forever lost contracts and clients.

Naturally, an opinion about something depends a great deal on what exactly you do with it. Allow me to elaborate:

A mechanic, for example, being the person who shoves the parts into them pumps and motors, will always prefer genuine replacement parts over any aftermarket ones for one simple reason - they are easy to work with, they always fit and require no "finishing touches" - ergo his work is faster and simpler. Genuine parts last long and are hardly ever faulty, which makes the testing and adjustment procedures safer and reduces the risk of having to re-open overhauled units to a minimum. A mechanic doesn't care about how much they cost because he's not the one paying for them.

A "pure-blood" businessman, on the other hand, being the person who directly profits from sales, will always give preference to cheap aftermarket parts for another simple reason - they can be sold at the price of genuine but cost ten times less, read - more money in his pocket. He doesn't care about their quality, or if they're easy to work with because he's not the one who is "touching" them.

The truth lies, as always, in the golden middle, and I, personally, came to the conclusion that although most of the times you do get what you pay for, this doesn't mean that you can't get a bargain for a penny every once in a while, so a sound overhauler keeps his eyes and mind open and uses both genuine and aftermarket parts in a combination defined by his trial an error experience and the pump/motor application demands. This approach is sound because even in pre-recession years there were hydraulic equipment owners who actually preferred aftermarket to genuine in the pursuit of cutting down overhaul expenses. So, some clients will want the genuine quality, and some will want the lower price - and in order to satisfy both you, naturally, have to be able to serve both, but - if your goal is to deliver quality repairs, aftermarket part suppliers should be chosen with a cool head and on the basis of quality, not price!

OK, you say, so I am a hydraulic equipment owner, and I've got this excavator pump to repair, how do I know if I am going to be scammed with them Chinese spares? Well, there is no simple answer to this question...There is an opinion that if an overhaul is backed up by warranty than you're on the safe side, no matter what parts were used - this, unfortunately, is not entirely true, because if you're the unlucky hydraulic pump owner caught in the "error" stage of the new supplier trial and error validation process, you can get two different answers and two very different bills depending on how honest the company you are dealing with is. An honest workshop will admit their fault and try to correct the mistake as fast as they can, and if you are not the first-time customer you might even get the - "sorry about that, dude, the parts're all **cked up..." confession, while a less candid workshop will give you the standard "commission errors committed by non-qualified personnel plus hard particle contamination in conjunction with the inappropriate oil temperature and deficient system design" excuse, and make you pay for their poor part supplier choice. So I'd say that warranty alone isn't a guarantee, and would cast my vote for warranty combined with transparency - if a workshop has good experience with their non-genuine spare parts supplier - they won't be ashamed to admit that the parts are not original.

Now, a separate word must be said about Chinese suppliers of spare parts for hydraulic pumps and motors. There are hundreds of companies in China that will sell you spare parts for almost any existing brand, with the quality ranging from superb to unacceptable and even ridiculously unacceptable. However with most suppliers (and especially resellers) the fact that you have received a batch of supreme quality spares doesn't guarantee that you will get the same quality in the next batch. So if you ever decide to "go oriental" - be prepared for nasty surprises! (At least that was the situation at the moment of writing - December 2011).

My calling is more technical than commercial, therefore I am mainly interested in the quality of the spares rather than their price or where they come from - so please, don't bother asking me for a list of "unofficially approved" Chinese suppliers of cheap yet extremely high quality spare parts for hydraulic pumps and motors - I won't provide it because I frankly don't have it! We do use some aftermarket spares from China, we did have our share of mishaps and disappointments with Chinese made parts, and our initial "Hurrays" got eventually replaced by "Boos" for most of them. Since our policy has always been to never let a client pay for a breakdown caused by a low quality part, a couple of lessons "learned the hard way" taught us that in most cases (not all, though) using Chinese spares in hydraulic pumps and motors is like using bathroom soap for filling cakes - looks and smells nice, yet still tastes like crap...

I would like to conclude this post with a list of illustrated examples of low quality parts and "what they can do" - not to discourage the use of non-genuine replacement parts, but to objectively expose the information I gathered through my "practice". If you have any examples of your own, do send them to me - I will be glad to add them to the list below:


Barrels - Deficient Bimetallization
Piston Rings
A4VG Swashplate
More Swashplates
A6VM Valve Plate
Parts for Komatsu Pumps
Low Quality Casting
Valve Plate for Sauer Danfoss Series 90
A10VO Craddle Bearings
A8VO Shaft
Swashplate Comparison
A10VO Swashplate
A10VO Ball Guide Pins
Sauer Danfoss Series 20 Ball Guide
Sauer Danfoss Series 20 Cylinder Block
A6VM Pistons
Seal-Kits for Pumps and Motors
NG10 Directional Valve