Nicholas Fluhart

Another actuator post….This Morin unit is a typical double-acting rack and pinion type that I rebuild. It came in with an internal leak-through problem. Although each brand of actuator has its own unique characteristics and components, most of the basic principles are the same. In this post, I’ll outline what it took to rebuild this particular unit.

In for Rebuild

I applied air to it and determined a piston o-ring must be damaged. I begin disassembly by removing the end caps and then the pistons. The end caps are held on by four bolts and come off easily. To remove the pistons I unscrew each stop screw and rotate the pinion a full rotation which pushes the pistons out to the end of the cylinder. If needed, I carefully apply compressed air to push the pistons the rest of the way out.

End Cap Removed

Piston Removed

When I pulled the first piston I immediately saw a broken piston ring. I continued dismantling the unit further by removing the pinion. I begin by removing the pinion retainer, then the pinion can be pulled out directly. Note that I marked the orientation of the components with a white liquid paper pen. This will make it easier to time the unit upon assembly.

Removing Pinion Retainer

Disassembled

Now it is time to clean and inspect the hard parts. I look for any type of damage or excessive wear while cleaning the old grease, o-ring, and bearing material from the components and the bore.

Pinion Inspection

Inspecting the Bore

Once everything is cleaned and inspected I begin installing the soft parts, such as the new bearings, seals, and o-rings. This also includes guide bands on the piston.

Soft Parts Installed

Once the soft parts are fitted to their appropriate parts, I begin the unit assembly by first installing the pinion and then I apply  grease liberally to the gears and the bore of the cylinder.

Now it’s time to install the pistons and time the actuator. The unit must be timed properly or the pistons may not stroke equally resulting the inability of the pinion to make a complete revolution, which in this case is 90° so I’m not sure “revolution” is the correct word. It’s also imperative to install the piston gears on the correct side of the pinion to ensure the pinion rotates in the right direction, which in this case the functional direction is counter clockwise making the return direction clockwise.

Piston Installation

Once the pistons are installed I replace the end caps and begin testing the unit. First I pressurize the actuator and begin testing for leaks by spraying soapy water on the sealing components. Then I stroke the actuator at the appropriate air pressures and set the stop screws.

Leak Testing

I finish up by cleaning the exterior to the desired cosmetic status, insert any needed cap plugs in the air ports, and it’s ready to ship.

Finished Product!

Until next time…

My company OmniSales International recently expanded our diversified offerings into industrial service work. Specifically, we are now offering a rebuild service for industrial actuators.

What is an actuator? A basic definition can be seen here. The applications for which our actuators are typically used is on industrial valves. The actuators provide a way for operators and/or computers to open and close valves remotely. The two most widely used types of actuators are electric and pneumatic. The type we service is pneumatic. Of those, we service vane type, rack and pinion type, and linear type.

One of the vein types we service is the Xomox Matryx series.

Xomox MX200's just unloaded for rebuild.

Parts and Tools laid out for the project.

I begin by cleaning the external surfaces of the unit in my parts washer. I then place the actuator in my vise which has specially designed jaws which are useful for gripping odd shaped items. Once secure, I remove the case bolts and fix a puller onto the actuator and use it to evenly separate the case halves.

My Bench Vise

Placing the actuator in the vise.

Splitting the cases.

Once I split the cases and disassemble the unit, the soft parts (i.e. o-rings, seals, etc.) are removed and the components go back to the parts washer to be cleaned of any dirt or grease.

Disassembling the Components

The Inside

Once cleaned, the rebuild process can begin. Typically, the components replaced during the process are known as “soft parts” which consists of o-rings, seals, guide bands, and in some circumstances bushings and bearings. For most used actuators, if hard parts, such as veins, pistons, cases, etc. need to be replaced, the actuators are usually scrapped as the cost of the new parts exceeds the value of the used unit. For this reason, I try to keep a supply of these scrapped actuators on hand for parts. That way, I can offer the customer a used part for a fraction of the cost of a new one.

Cleaned and ready for final inspection.

When the parts are clean I can closely examine them for wear or damage. Once inspected, I use a fine, high speed, concave style wire wheel to polish the inside of the cases where the main o-ring wiper seal rides forming the air-tight seal between the cases and the vein. I then apply the grease supplied by the manufacturer to all the components and install the new o-rings and seals.

Polishing the seal surfaces.

Assembly

I apply sealant to the case joints and assemble the body, replacing any nuts or bolts that show wear. I coat the actuator in a corrosion resistant, high temp enamel coating. Once the sealant and coating have set up, it’s time to test the unit and set the adjustable stop screws. I plumb an air pressure regulator to the unit and begin leak testing.

Testing an MX200

Testing an MX60

The max air pressure for the Matryx MX series is 120 psi. I run the pressure up to 120 on the dot and spray the joints with soapy water to look for leaks. When everything checks out, I stroke the actuator starting at about 25 psi and continue to do so up through 80 psi which is the normal operating pressure. I ensure the actuator strokes easily in both directions with no internal leak through. If there is any binding or catching, it will be very evident at low pressure which is where the actuator would have the least torque. Typically, if the actuator strokes easily at 25 psi, it will perform well at any higher pressure.  When it passes my tests, I unhook my testing apparatus and install cap plugs in the air ports.

Ready to ship!

Off they go!