The Anatomy of a Jack Replacement

Now that we’ve introduced elevator pits and mentioned hydraulic jacks, we thought we’d share the story behind replacing one.  Normally jacks, which are large pistons, given that they’re just a couple pieces of steel, last indefinitely.  The seals need to be replaced periodically, but the metal parts live on and on for decades.

The main reason you’d need to replace one is that it’s buried in the ground and the exterior cylinder rusts out, allowing the oil to leak.  If this happens, the elevator could drop suddenly and you also could create an environmental mess.  Think Exxon Valdez, albeit on a much smaller scale.  The Valdez had a single hull, and after its crash, double-hulled tankers became the norm, as a protection against another catastrophe.

Similarly, elevator jacks used to be manufactured with a single wall casing.  In 1978 or so, they went to double walls, and later it became standard to encase the whole thing in PVC.  So if you sink a jack into the ground now, it will never rust out.  But if you’ve got one of the old ones, it just might.

We recently did a modernization on a 50-year-old elevator in a local bank.  The state required that when we do the modernization we also replace the in-ground jack, even though there was no indication that it was yet leaking.

The old elevator jack had to come out first. A little bit of jack hammering and it was ready.
The easiest part is tear down. But the jack had be cut into pieces to get it out.

So our bull gang came in, jackhammered the pit concrete around the cylinder, and pulled out the piston. It was about 24 feet long, so we had to chop it into 3 pieces so it would fit out the door.  Then we hoisted up the cylinder, chopped it into 3 sections, and sent it out the door as well.

A steel casing was driven into the hole in five foot sections and then the sand was drilled out.
The hole needed to be cased to keep it from collapsing around the jack.

Then we examined the hole.  The jack had been set directly into the sandy hole, so when we removed it, the walls of the hole collapsed.  Nowadays, new jack holes have a casing to prevent collapse, so we brought in specialty drillers to give us a clean, modern, cased hole.  They pounded 5 foot sections of steel casing into the hole, welding sections together, until the entire hole was solid.

They then drilled the sand and muck out of the hole. Work then moved back to us, to install the new jack.  First a PVC liner was sunk in the hole for permanent water protection, again in 2 pieces so it fit through the doors.  We let it set overnight to make sure there were no leaks in the glue.

A PVC pipe was placed inside the casing to keep the elevator jack dry.
The PVC pipe was placed inside the casing to prevent water damage to the jack.

Then we installed the cylinder. The most critical step is plumbing the jack so that it lifts the elevator up without wearing on one side of the piston.  This is done with a simple tool called a spider: a flashlight on the end of a string, dropped down to the bottom of a cylinder, where you can tell by the light it casts when the cylinder is perfectly plumb.

Once hte jack was put into place and the pit cleaned, the elevator was ready for many more years of service.
The jack was put into place, the pit cleaned and it was ready for operation.

Once the plumbed-up cylinder was bolted down, we dropped in the piston, again in 2 pieces that screwed together.  We poured concrete back in around the new jack assembly, to cement it into place, never to move again for 100 years.

So that’s how you replace an in-ground jack.  Lots of elbow grease and regular grease and grime to make it happen.

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