Written for Hanson Hydraulics Ltd. Blog: Here is a not so easy “quick reseal only” hydraulic cylinder repair.  First step was using an industrial sized face spanner with 12′ of pipe, didn’t budge. Heated the barrel up around the gland, didn’t budge.

Next step, build a socket to fit the hydraulic wrench. Started with two sector rings. Used the holes in the sector rings as a jig to drill and tap the face of the gland.

The hydraulic wrench drives the socket below, which is welded to the two sector rings

This one took about 5000 foot pounds of torque to break loose.

Getting it back together again is also a little tricky. The large piston seals have to get past the threads at the front of the barrell. This requires shim stock.

Cut a piece of shim stock to a length to match the appropriate circumference.  Then cut fingers into it, leave the portion that will cover the threads uncut.

Place the shimstock in the barrell, covering the threads, but be sure that it does not stick in the bore past the threads, or the piston will drag it in.  Use duct tape to secure the shimstock to the outside of the barrel.

Grease up the pistons seals, and work the piston into the shim stock and into the bore.

They can’t all be easy.

Hanson Hydraulics Ltd. Blog article:

Start inspection with the rod.  Measure the cylinder rod diameter with a micrometer, checking over the entire length and at various spots around  the diameter. You’re looking for low spots. A low spot that you can’t see may exist from previous rod repairs.  Check the rod for pits, dents, dings, or scratches, if they are present, the rod will need repairing or re-chroming. Excavator cylinder rods are often nickel plated, then chrome plated over nickel. If the rod requires re-chroming it is stripped in a strip tank, however the nickel will not strip of electrically, so it must be mechanically removed.  You don’t need to worry about this as the rod will have to go out to a chrome shop. I’ll save the chroming info for another posting.

 Roll the rod on rollers or V blocks, and with a dial indicator check for run-out indicating a bent rod.  If it is bent, it will need straightening. If the rod needs re-chroming, get the rod straightened at the same time. Chrome work is usually charged by the square inch and can be anywhere from $.50 to $1.00 per square inch.  Measure the diameter in inches, multiply by PI (3.1416) then multiply by the chrome length, then by the price per square inches. In this case it was 80mm / 25.4 = 3.1496 inches, multiply by 3.1416 = 9.895 inches, multiply by length of 40″ = 395.79, multiplied by $.70 equals $277.05. Please note some shops have minimum charges, and if your rod requires extensive repairs, the job will cost more.

 Before sending your rod out, remove the pin wipers from the rod eye, grease fitting and remove grease from the rod eye and check the rod bushing condition and determine if this is to be replaced. If there are plastic rings on the rods stub, under the snubber rings on either side of the piston, save these rings, they will be re-used unless broken. They do not come in a seal kit, and usually have to be ordered through the OEM. Measure the pin eye wipers, they are ordered by ID, OD, and height. These ones were 71×86x5  W071086050WS

 Now inspect the barrel condition. Look for internal scores or bulging. The barrel will hopefully have its original burnished finish. This finish is achieved with a head consisting of burnishing rollers; it should have a black mirror look to it.  If there is no damage in the barrel, do not hone it, the burnished finish is much better than any finish you can get with a hone. Measure the barrel internal diameter where the gland seals in the barrel, referred to as the gland seat. Clearance here should not exceed .009″ Remove the pin eye wipers, they are ordered by id, OD, height.  Replace the eye bushing if required. These wipers were 65×80x5 W065080050WS

Measure the diameter of the piston wear band groove that has the phenolic wear bands (the two closest to the piston seal). Add twice the cross section of the wearband (2.5mm) to the wear band diameter. This size should be around .006″ smaller than the bore and not to exceed .011″. Phenolic wear bands are ordered by OD, cross section, and height, or ID, OD, Height. These ones were 110×115x8 or G115110080GC.

The Teflon wear bands, even though referred to as wear bands are in fact wipers. The wipers take advantage of Teflon’s tendency to absorb contamination and draw it away from the walls of the barrel.  Teflon has very little compressive strength and would not have much benefit as a true wearband. Measure the cross section of the wear band, usually 4mm, the bore size you know, measure the groove height. These wear bands are often ordered in strips, so convert the diameter to a circumference and order 2 lengths plus a little bit extra.  These ones were 4mm cross section, 6mm tall. The wear strip in this case is WS0060040/CG and two 14 ¼” strips were required.

Piston seals come in lots of different cross sections and heights.  Make note of the seal style, in this case it is a two piece with a loader and a Teflon cap. Measure the seal groove diameter, the bore size you know, measure the groove height. This particular seal was a P115094081P2B

Now for the gland. As mentioned previously, do not remove the DU bushing until you have a replacement. What you need to know to order the new one is the rod diameter and the height of the DU bushing, in this case it was 80mmx30mm. GMB8030DU

Check the buffer seal and rod seal groove for rust, if rusty, polish up with a fine grit flapper wheel. If the rust is severe, have a machine shop take a very light cut out of the seal groove. Take a maximum of .010″ above the original diameter. If you want a super duty cylinder, order a custom made rod seal backup machined out of hard nylon. Order the id .003″ larger than the rod diameter, order the OD .002″ smaller than the seal groove diameter. Make the height the same as the old back up, order this with NO split. Be sure to install the backup when the time comes, before the rod seal. You may need to soak it in hot water first. BU080095100RA. Specify NOK rod seals, do not use SJ seals. They are also ordered by ID, OD, and height. R080095090RA.

Measure the diameter of the buffer seal groove. A set of bent inside calipers are usually required for this, and it takes a sensitive feel. You need to use the calipers like you would with an inside micrometer, adjusting until a very light drag is felt. It takes a bit of practice to get consistent sizes.  In this case the diameter was 3.759” or 95.5mm. It was a solid Teflon cap with a square loader, it will be replaced with a lip type buffer R80095060RH-1

Between the rod seal and rod wiper may be another Teflon wear band, although like the Teflon wear bands on the piston, this is also actually more of a wiper than a wear band. It is supposed to catch any contamination that made its way past the rod wiper. Flap this groove up as well if rusty; don’t worry about getting all of the pitting out if present, just the loose rust, the important thing is that it clean.  This wear band is ordered as a strip. 10 ½” of WS0097025/BR60 was required. The rod wiper- Give this groove a light polishing as we will use a small amount of bearing retainer to form a seal on the outside of the wiper, this prevents water from getting around the wiper, especially problematic on boom lift cylinders. ** Only use retaining compound on wipers with metal cases, do not get any on the rubber portion of the wiper as they will deteriorate. The wiper is ordered by ID, OD, and height. W080094080WR

Measure the cross section of the oring and backup on the outside of the gland, they are not the same cross section. The cross section of the oring is always heavier than the back up ring. There should be no crush on the backup ring, just the oring. JIS, or Japanese Industrial Standard orings are always an odd cross section. Instead of 3mm, it will be 3.1mm. The groove diameter is the same as for a 3mm, but there is extra crush provided on the 3.1.  Do not use a 3mm.  If you want to build a super duty cylinder, have a custom backup machined out of hard nylon.  Make the id of the backup .003″ bigger than the groove diameter, make the OD .003 bigger than the gland seat diameter of the barrel. Then scarf cut the backup ring so that the joint overlaps at an angle.  Use a razor, the .003″ extra on the OD and ID should allow for the kerf in cutting.  Put the back up in the groove and trim if necessary with a bench grinder. If the backup is small in cross section relative to the bore size, like the 2.5mm cross section in this example with a 115mm bore, you can sometimes install the back-up ring without splitting it. The oring and backup in this example are: MOR1094031/NBR90 &  BU110115012SD/T

 Order any orings required for fittings or flow tubes and extra pin eye wipers for the link arms if required. The next step is prepping the parts for assembly.

 Rod Wiper – W080094080WR

Gland wear strip – ½” of WS0097025/BR60

Rod seal BU – BU080095100RA

Rod seal – R080095090RA

Rod Buffer – R80095060RH-1

DU Bushing – GMB8030DU

Gland oring – MOR1094031/NBR90

Gland BU – BU110115012SD/T

Piston wear strip – two 14 ¼” strips WS0060040/CG

Phenolic wear bands – two G115110080GC

Piston seal – P115094081P2B

Rod Pin Wipers – W071086050WS

Barrel Pin Wipers – W065080050WS

Find all of your seal needs here: http://sealsonline.com/website/light_page.asp?code=homepage

Next post will be prep and assembly.

Written for Hanson Hydraulics Ltd. Blog

Dissmantling and repairing  a Hitachi EX150 Bucket cylinder.

Hanson Hydraulics Ltd. Blog article:

Remove the flow tubes, grease fittings and pin wipers from the eyes

Strap the barrel down and put a bar through the barrel eye to prevent the barrel from turning. Match mark the gland to the barrel as the port in the gland must return to its position when reassembled in order for the flow tubes to line up again. 

Remove the eight socket head cap screws that hold the gland to the barrel. If you forgot to mark the gland have a look at the face of the barrel, there may be a blind hole that is not used, and this hole should have left a mark on the face of the gland.  Mark accordingly as after the parts are cleaned up for reassembly, you may not be able to see the mark any more.

 Have something ready to catch the oil when the gland comes out. Use a sling and a lifting device to support the weight of the rod, and slowly pull the rod assembly out.  Be careful when the piston gets to the end of the barrel. When the piston comes all the way out, if the rod is not properly supported, the rod will drop down and the nut the holds the piston on will mark the barrel right where the gland seals. Use the piston to meter the oil out of the barrel and avoid making a mess.

Let the oil drain out of the barrel, lifting the barrel eye end up if needed. Remove the barrel from the bench and secure the rod assembly for disassembly.  The piston nut is extremely tight and will require a hydraulic wrench (it is possible to crack the nut loose using another excavator, but it may result in a bent rod.

Remove the set screw that keeps the nut from backing off.  Depending on which series the cylinder is, there may be a ball under the set screw (there should have been one under this set screw, but it wasn’t there).

Do not forget this step or the rod threads and piston nut will be destroyed!!.

Torque the nut loose with the appropriate hydraulic wrench. Once the nut is cracked loose, it should spin right off, unless it is a nylock found on some machines.

Remove the nut, shim if used, piston, snubber sleeve and gland. If you do not have a new DU bushing to install in the gland, be careful the threads of the rod do not scuff the bushing up. Keeping the snubber sleeve in the gland will help.

Pick out the wear ring, rod seal, back up ring, buffer seal, buffer seal loader, oring and back up on the outside of the gland.  Remove the rod wiper by using a small prybar. Tap it in under the wiper, be careful not to gouge up the gland.  Using a wrench on the prybar, twist the wiper out.

If you have a new DU bushing, first check to see that the diameter and length are correct. Once your sure you have the right bushing, you can remove the old one, start by removing the snap ring that retains the bushing.

Using a bull nose chisel, work your way around the edge of the bushing to drive it out. Start on both sides of the split. Be absolutely certain that the chisel is not in the buffer seal groove!!!.  Be sure to have enough angle on the chisel that it bites into the bushing, but be careful that the chisel does not slip and gouge into the gland, or that the chisel does not pierce through the bushing and gouge into the gland.

Larger bushings may require ‘relieving’. Take a carbide burr and die grinder, and cut a groove down the length of the DU bushing on the side opposite the split. You need to cut as deep as possible, without damaging the gland. If you are careful while doing this, you can see a color change in the groove when you cut through the OD of the bushing. It takes patience, but once you get used to it, it’s pretty easy. You don’t want to cut all the way through for the entire length, as this old DU can be used on assembly for installing the new DU if you don’t have a tool and can’t machine one up. Try to drive the bushing out fairly straight if you need the old DU as a tool.

Pull the seals off the piston. The cap seal in the middle will be a little tricky. Watch the fingers, usually if you pierce the Teflon cap with a pick, you will be able to break the seal off when prying it off. Pick the seals loader out. Be careful not to gouge the seal groove up.

Click this link to take you to Part II of this series, Excavator Hydraulic Cylinder Seals and Inspection

Written for Hanson Hydraulics Ltd. Blog.