Insane Hydraulics
Bold and audacious blog about fluid power
Today I want to talk about "mystery cartridges" - i.e. - cartridge valves that carry no meaningful identification, either because the original markings were lost to corrosion or mechanical damage or because the OEM decided to label them with a proprietary part number.
People who work in sales (myself included) love it when a client inquires about a cartridge valve of a known brand with a part number in hand. What is there not to love? When a part is perfectly identified, business is as easy as ABC - get a price from the respective supplier, slap your margin on top and boom - the money's in the bag! Some say that pretty soon, such interactions won't even require a human salesperson and will be dealt with by an AI agent capable of providing the requested quote in a millionth of a second.
But what do most sales folks do when they are confronted with a quote request for a "mystery cartridge?" Like - "I need a valve just like this one right here..." In my experience - they tend to dismiss such cases and, at best, direct their client to the respective OEM.
I understand first-hand where this is coming from, I really do. When you operate at 150% capacity, taking on additional requests translates into more "loose ends" rather than increased profits. Yet I still defend the point that a technician/salesperson should always give a "mystery cartridge" a chance to teach him something new by trying to identify it through three steps: cavity -> function -> part (see the example below for details). Even if you don't manage to identify the cartridge valve, you still, more likely than not, will learn something new, and if you turn this approach into a habit - you'll be decades ahead of your "dismissing competition" in but a couple of years.
Here's a concrete example. This cartridge valve comes from a Sandvik jumbo drill, and it carries two references - HM30259200 and BG01320284 - none of which will show up in any of the standard parts lists:
So, let us fight the natural urge to "...please contact your Sandvik dealer for this proprietary part..." and see if we can learn something. The first step in identifying a mystery cartridge is identifying its cavity - and it starts with the thread:
The thread has a diameter of 7/8'' with a pitch of 14 TPI. Easy. At this point, you can already Google for something along the lines of "cartridge valve cavity 7/8-14" - and go through numerous results that pop up. If you are new to the "cartridge valve game," you will quickly realize that there are hundreds of valve manufacturers that refer to cavities with a 7/8-14 thread as SAE-10 or simply cavities number ten.
Let us refine a bit, shall we? How many ways does our valve have? Three. So, let us Google for "cartridge valve cavity 10-3." Once again - you'll get tons of results. Now, if you measure the diameters of the cartridge sections that carry seals and compare them to the dimensions of cavities from the search results, in less than five minutes, you will realize that dozens of cartridge valve manufacturers use this cavity and universally name it as "something-10-3." For example - Danfoss - SDC10-3, Parker - C10-3, Hydraforce - VC10-3, SUN hydraulics - SC-10-03, etc... The list goes on and on, but this is a good thing because it means that if there are so many manufacturers using the same cavity - we are almost guaranteed to find a replacement for our "mystery sample." So, the next step is determining the valve's function.
This one can be tricky, and you will have to "investigate" to see if it is even possible. Even if you have access to the hydraulic diagram of the equipment - you are only halfway there. Halfway - because you still need to map the function to the ports correctly. Once again - this is an educational puzzle to solve. In this case - I don't have the diagram (not yet, anyway), so my only option is back-engineering. Luckily, this cartridge valve is super easy to disassemble (no special tools required):
Now it is time for you to put your thinking hat on and see if you can figure out the fiction by carefully studying the parts. In this case, it is not too hard because the "business end" is composed of only two parts - the spool and the sleeve. The strong spring tells me that this is a direct-acting valve. The fact that the spool is so narrow tells me that the valve is not rated for high flow. Ports one and two are normally closed, pressure in port one opens the valve, and the spring chamber is always vented through an orifice to port number three - everything I know suggests that this is a sequence valve. Here's my "very scientific" napkin drawing:
There will be cases when determining the function of a "mystery cartridge" with certainty is impossible (for example - if you don't manage to disassemble it), but you should always make sure you did your best to solve the "function puzzle" before you give up.
Now that you have the function of the valve figured out - it is time to search for a cartridge that provides the same functionality, fits the same cavity, and, ideally, has a cutaway view that is equal to the parts lying in front of you.
The cartridge in my example is, indeed, a perfect "mystery cartridge" because I found many direct-acting internally piloted sequence valves for the 10-3 cavity, but none had the very peculiar design of internal parts. I am quite surprised, actually - and I wonder where Sandvik sourced this one. Still - as I looked through the numerous options - I learned about different types of sequence valves that can fit in the 10-3 cavity, and I also learned different designs from the cutaway views in the catalogs.
I am still waiting for the hydraulic diagram to confirm if my function assumption is correct. At this point, if I were to blindly replace this valve, I would suggest CP240-8 from Danfoss, SV103 from Parker, or, maybe, PS10-34 from Hydraforce. In any case - this valve got me to spend an hour of my evening time looking through a bunch of cartridge valve catalogs, instead of mindlessly scrolling through a random social feed - and I see this as an absolute win!
My point is - when you face a need to identify a "mystery cartridge valve" - you should regard it as an opportunity to learn something rather than an annoying nuisance. Even if you don't succeed - bits of knowledge from all those catalogs you just looked through will come in handy when you least expect it!