Hanson Hydraulics Ltd. Blog

To perform a fast shaft seal replacement on a Poclain MS08/Waratah motor:

A quick reseal on a Poclain MS08-9-12A-A08-1129-DJMO motor. This unit is off of a 622B Waratah processor head. A factory seal kit is around $900.00. In this instance the customer wanted just the shaft seal replaced with absolute minimum down-time.

Ordering the high pressure double lipped shaft seal and housing orings came to $30.00. The following description of work covers only a fast shaft seal replacement. This is not a complete rebuild.

First, note direction of feed wheel. To change the direction, the wheel flips over, allowing the motor and wheel assembly to be used on the other arm. Remove the wheel.

Remove the housing bolts, remove the port end cover, be careful as the distributor may drop out of the cover, usually they stay sitting on the cylinder block, but be careful not to drop it, there are springs that load the distributor up against the cylinder block.

Remove the cam ring and the cylinder block. Remove the snap ring on the shaft, followed by the shims.  It is sometimes necessary to press on the inner bearing race to take the tension of the snap ring in order to get it off.

Support the housing, make sure there is clearance below for the output flange, and press the shaft out.

The outboard cone will remain on the shaft and is not removable without possibley destroying.  This bearing runs outboard of the shaft seal, so it does not get oil. Repack this bearing as is using a grease gun with needle attachment. There is a grease/dust seal between the outboard cone and output flange.  This will not be changed as it would necessitate removal and possible damage to the bearing.

The seal carrier is removed from the housing by driving out towards the cylinder block.  It will not pass through the inboard outer race, so this race will be driven out as well.  Find a driving tool with the largest diameter possible so the seal carrier does not become distorted. Drive or press the assembly out.  There are two seal carriers, the outboard has the double lip shaft seal, and the other has a high pressure PTFE seal.  In this instance the PTFE seal was not changed.

Pay attention to the stepped face on the high pressure seal carrier and make sure it is installed in the same direction.

Replace the double lip seal, applying a film of Ultra Blue to the outside of the seal. Make sure the housing and seal carriers OD are oil free, and apply a film of anaerobic sealant to the outside of the seal carriers.  Press back into the housing, but take as much time as you need to not distort the seal carriers! Be careful!!!. Press the inboard cup into the housing.

Put a film of grease on the lips of the seal, add a bit of grease to the cavity for the outboard bearing, and install the housing over the shaft.  Heat the inboard cone up and install it onto the shaft, followed by the shims and snap ring.

Reinstall the cylinder block, housing oring, cam ring, and install oring into the port end cover.  Clean the distributor and spring, making sure they are free of oil and grease the springs so they will stay stuck in the distributor.

Install the distributor into the port end cover.  Take a small piece of plastic round stock and insert it through one of the ports so that it will hold the distributor in place.  Tension will need to be maintained on the rod or the distributor will drop out, do not let the distributor drop out!!!

While maintaining tension, install the port end cover on top of the motor assembly, tighten the bolts up, If it appears there is any interference among the parts, investigate!!!.

Inner cup and cone A&S 31313F

Outer cup and cone A&S 33214F

Shaft seal BABSL 070090070-1  (70mmx90mmx7mm)

2-178/N1470 oring x2

 * Some units may use a 70mmx110mmx8mm shaft seal

Brand new 2078

Here is a little tool that comes in handy when working on spool valves that use snap rings to retain the springs to the spool, for example a Parker VDP12. In order to compress the spring to easily remove the snap ring, a modified KD Tools Model# 2078 “Overhead Valve Spring Compressor” can be used effectively.

Original tool pulling to the side

The 2078 can be used without modifying, but the problem is that this tool was designed to grab on to the spiral of the spring. In order to do this, the two arms are made to different lengths. We want a tool that reaches around and grabs the bottom of the spring cup, which requires arms of equal length. So the unmodified tool will work, but it is kind of awkward as it pulls over to one side.

The modification requires that you buy two of these units, or cut and weld one of the arms. To modify this tool without cutting and welding, get two of them. Take the first unit and grind off the pin head that holds the long arm on.  On the next unit, grind off the pin head that holds the short arm on. Now swap arms so that one pair gets both short arms and one pair gets both the long arms.  Use a 1/4″ bolt with a shoulder long enough to extend to the other side of the tool, loctite a nut on, and trim the bolt flush.

KD Tools – http://www.kd-tools.com/

Now it will compress the spring evenly and not pull to one side.  See the pictures below.

Holmbury’s OCUKAC2318 is a high quality  pattern changing valve with a steel body and hardened spool for pilot applications, such as switching between John Deere and Cat control patterns on excavators.

Want a good seal for your PVG32 actuator?

PVG32 Actuator PVMD

Sauer Danfoss PVG32 PVMD actuators (used on Waratah Processors), have a u-cup sealing the actuator shaft to the housing. It has been my experience that this seal is not included in the PVM seal kit. Waratah has created a seal kit, however it has also been my experience that it contains the wrong u-cup. The u-cup required is a metric size. – 11mm x 17mm x 3mm which is hard to find. The u-cup supplied in Waratah seal kits I have found is 11/16 x 7/16 x 1/8, close but not close enough. They will start leaking in short time.

 Here is a repair to replace this hard to find u-cup with an oring.

removing the nut and shaft

 Remove the nut from the housing. The oring on the outside of this nut is a 21.2mm x 26 x 2.4 oring and in this application could be 70 durometer. Remove and inspect the shaft for wear or grooving.  Have a look inside the housing, older housings had a tendency to crack. Remove the u-cup with a pick, being careful not to score up the sealing area.  Once the seal is removed, insert a blind hole bearing puller and expand into the groove, making sure that the tool will not gouge up the seal area.  Press on the tool to press the busing out the bottom of the nut.

PVMD parts

Tool assy for pressing the bushing out of the nut

Pressing the bushing out of the nut

Machine .075” off the face of the seal side of the bushing (not the shouldered side). This creates a seal groove .190” tall, perfect for a 2 series oring (205) 70 durometer. Press the bushing back in, pop in your oring, install the shaft, tighten the nut back up and you’ve got an actuator/spool cover that should be leak free for a long time.

Nut, u-cup, Bushing

The orings that seal the face of the housing against the valve body are: 5mm x 9mm x 2mm

Shimadzu gear pump failure: on a Caterpillar dozer. Here are some pictures of a recent gear pump failure. It is a Shimadzu gear pump from a D5C cat. It is the implement pump. This particular Cat has a core drill mounted to the back of it which is supplied oil from the ripper control valve. 

Before dissmantling

The main implement control valve has a pilot operated main relief as well as a direct acting work port relief for the ripper down port.  Oil from the ripper down port feeds the control valve that operates the functions of the core drill. This control valve also has a direct acting relief.

In an effort to increase available pressure at the core drill, the main relief valve  and ripper relief setting was increased. The particular shop that was working on the machine must not have been aware of the relief at the drill.  The relief at the drill was the pressure limiting factor, however the two reliefs on the implement control valve were left substantially increased.  All was well until implement fuctions were activated and dead headed that did not have work port reliefs. 

Gear teeth bent back from excessive pressure

This sudden increase in pressure bent the teeth of the gears back, producing excessive tip clearance. This resulted in a decrease in performance, as well as a decrease in maximum available pressure, as in a dead headed state, the entire volume of oil was bypassing across the gears tip clearance, overheating the oil and eventually blistering the paint on the pump.

Beyond economical repair

Situations like this can be avoided by 1) find out exactly why the pressure won’t increase past a certan level when increasing the main relief setting. The question must be asked, “where is the oil going?” and 2) always be sure to readjust the main relief pressure after making work port pressure adjustments.

The most common over pressure failures on gear pumps are split gear housings or extruded seals or extreme gear housing wear, but on this particular make of pump it seems the weak link is the amount of material at the base of the tooth.  I have heard of similar Shmadzu gear pump failures on Komatsu dozers.

Welcome to Hanson Hydraulics Ltd. Blog. This blog was formerly located at hansonhydraulics.blogspot.com . We have recently rebuilt our web page and decided to host our own blog as well as our own Forum which can be found at hansonhydraulics.com/phpBB3 .

Please feel free to sign and up and follow along, or join a discussion on the Forum page.  The next posting will be one of a gear pump failure; a Shimadzu SGP1 gear pump.