How I fixed my 30 year old standing desk
These days standing desks aren't uncommon, but in the late 90's I had never heard of such a thing. My dad picked up a few surplus Steelcase Dyna-Lift standing desks, and I've been lucky to use one ever since! My trusty desk followed me across the country to California, and held my iMac in my apartment in San Francisco for a decade before finally moving with me to Palo Alto in 2020. Unfortunately it didn't survive that final move, for as soon after I loaded it up with my usual desk accessories one side sank down towards the floor…and it was apparently leaking oil?!
While working at home during the pandemic a desk was critical and they were in short supply. Besides, having traveled with me for so many years, of course I was going to fix it. Here's how I did it:
Background & Investigation
The desk uses a hydraulic lift system that consists of a hand-cranked pump unit that contains two pistons directly coupled to hydraulic rams in the leg assemblies, which is what needed repair. At first I didn't have much to go on other than a model number sticker on the bottom of the desk. I emailed Steelcase with reference to QMSM3048R but didn't get any answer back. After some exploratory disassembly (later I discovered that I took it apart in the wrong order), I discovered a Monach Hydraulics "Dyna-Lift" sticker on the side of the pump unit. Some internet searching led me to discover that Monarch Hydraulics is now part of Bucher Hydraulics, which still produces the Dyna-Lift product line! One more email. The team was extremely kind and helpful—even locating the folks that worked on this contract-manufacturing run decades ago—but they simply didn't have the technical or repair information anymore which I needed to source the correct parts and instructions for repair.
Without much to confirm either way, I had to simply hope that the design of the system hadn't changed much and that the "custom" designed parts Steelcase were more-or-less the same as the commercially available Dyna-Lift systems still being sold today. I ordered a DH-16000 Recharge Kit and a DH-16101 Repacking Kit from Mason Dynamics, and was ready to make a mess with they hydraulic system rebuild.
I was able to remove the complete hydraulic system from the desk, take everything out to the garage, and carefully start disassembly. The kit came with very helpful instructions for repacking and recharge (and I found some more related documents online), and thought I had a pretty good idea of what needed to be done. I found this part fascinating, having never worked on a hydraulic system before. Unfortunately, the parts that came in the kit just weren't the right size for the system I had in pieces in front of me.
I had managed to pry out the seals and O-rings in the pump and cylinders. As they fell apart in my hands it was quite clear what the problem was—but sourcing these replacement hydraulic seals was a big challenge. I was able to order some suitable O-rings from MSC, but was still completely unable to find the seals I needed. I spent a week second guessing my caliper-measurements before finally identifying Maxx Hydraulics as a supplier that could custom-make the seals I needed. I emailed asking for a quote, confirmed the purchase the next day, and had them in hand by the end of the week.
The Repair
Once I had all the supplies needed, the hydraulic service was reasonably straightforward to carry out and documented perfectly well in the repacking and recharge instructions. That said, there were a few lessons learned along the way:
It wasn't completely necessary to disassemble the leg units from the desk in order to remove the hydraulic cylinders. I guess it was useful to really clean out all of the oil residue that had drained into the leg, but aside from that, the hydraulics could be removed from the desk by retracting the cylinders, lifting the desk to the maximum height, and pulling the clips out to release the cylinders. There is a little bit of a trick to it though—in order to make it possible to carry the desk around, there is a brake mechanism that prevents the leg assemblies from falling to the ground when the desk is lifted by the work-surface. It is necessary to push down on the white plastic bracket inside the leg while lifting the top in order to release the brake and fully lift the desk.
I probably should have used new fittings, or at least applied fresh thread sealant to the hydraulic connections. Subsequent to the repair I experienced a little bit of oil seepage in the following week, so I just tightened up the brass fittings a bit more, but suspect there's an appropriate sealant to use here. The only parts I could use from the recharge kit ended up being the Molykote mineral oil itself, and the handy squirt bottle to fill the pump. The included plastic tubing was the wrong diameter, and I couldn't figure out how to remove the ferrules from the tubes—perhaps it is necessary to cut them off? So, I didn't install new ferrules and unthreaded the right-angle fittings going out of the pump, which I suspect was the source of the seepage.
While the instructions were invaluable, the recharge and repacking kits weren't what I needed for this old desk. The Molykote L-0532FG Multi-Purpose Light Oil MSDS indicates it is 99% White mineral oil (CAS 8042-47-5), and given that the seals degraded so much and I rarely adjust the height of the desk—I'm not sure I'd make the same choice in the future.
I never did find the exact replacements for the plastic clips to secure the hoses to the bottom of the desk surface, but the ones I found on DigiKey were awfully close.
Conclusion
Overall, I'm happy to have one more vintage repair in the books. While nearly there, it didn't quite come out perfectly. Aside from the initial seepage (which was easily fixed), there remains some slip-stick juddering on one side when I operate the crank to raise and lower the desk. I assume this comes from me getting the dimensions or material wrong on the seals—or perhaps some residual air in the system. It took few months to get everything together and actually carry out the fix, but it's great to have the desk back and I hope it lasts another couple of decades. :)