Replacing Hydraulic Pumps and Motors

motor pump hydraulic

Replacing a hydraulic pump or motor in a system involves careful planning and execution.

For starters, the exact life expectancy depends on the specific pump and how frequently it’s used, but pumps often last for quite a few years. The same is true for motors.

The manufacturer of your pump should specify how many hours or cycles a pump can be expected to provide before replacement is recommended.

With preventative and daily maintenance tasks, this should only be done annually.

But when the time comes, here’s a general 5-step guide to help you through the process:

1. Preparation

Wear appropriate personal protective equipment (PPE) and steel-toed boots
Depressurize the system fully
Drain hydraulic fluid: Drain the hydraulic fluid from the system to prevent spills and contamination

2. Remove the Old Pump/Motor

Disconnect all power sources to the hydraulic system
Label connections
Remove mounting bolts
Disconnect hoses and wires from the pump or motor

3. Install the New Pump/Motor

Place the new pump or motor in the correct position within the system
Reconnect the hydraulic hoses and electrical wires, ensuring they are connected to the correct ports and terminals as per your labels
Install the mounting bolts and secure the pump or motor in place

4. Refill the Hydraulic Fluid

5. Test and Make Final Checks

Bleed the system to remove any trapped air
Inspect all connections and fittings for leaks and tighten as necessary
Reconnect power sources to the hydraulic system
Slowly start the system and test the operation of the new pump or motor
Monitor for any unusual noises, vibrations, or leaks

Finally, make sure to document the process, including the date, part numbers, and any issues encountered for future reference.

Further Consultation

We recommend consulting a manual for exact measurements. For example, the Surplus Center’s Fluid Power Data Book is a condensed collection of useful fluid power data and references available for sale at surpluscenter.com.

We consulted the guide for advice on the calculation of the theoretical GPM of a pump by measuring its internal parts.

Some of the takeaways:

When replacing a pump, catalog ratings will usually be shown in GPM at a specified shaft speed
On a motor, catalog ratings will usually be in cubic inches deplanement per shaft revolution (C.I.R.)
Use the appropriate formula and make all measurements in inches as accurately as possible
Convert fractional dimensions into decimal equivalents for use in the formulas
Make sure the catalog pressure rating is adequate for your application, and in the case of a pump, make sure the direction of shaft rotation is correct
If a pump of higher GPM must be used, it will need more HP at the same pressure and will move faster; If one with lower GPM must be used, the system will have enough power but will move more slowly

To select a replacement for a broken or worn-out hydraulic pump or motor consult the manual for formulas specific to motors and gear pumps, vane pumps, or piston pumps (page 8).

Routine Maintenance Plans

Creating a maintenance plan that prioritizes filter changes, repairs, and monitoring may seem like a lot of time spent on process and upkeep, but it is a necessary job for the health of hydraulic systems.

Whether it’s developing a preventative schedule of maintenance, or sticking to a strict monitoring routine, preparing a process for maintenance is a worthy cause that will improve the overall life and efficiency of motors and pumps between replacements.

Having a plan can keep these processes in check so filtration issues don’t go unnoticed, and hydraulics systems stay running like the well-oiled machines they should be.

Hydraulic Parts Source is a leading fluid power remanufacturer, and we’re ready to serve you. Contact us today to discuss forming an alliance by calling (866) 514-8451 or get a quote by emailing sales@hydparts.com.