Hydraulic gear pumps are the core components of hydraulic systems. Whether you are repairing and replacing worn parts or assembling a new pump from scratch, mastering the correct assembly method of hydraulic gear pumps is the key to ensuring efficient operation, safety, stability and long service life of the equipment.
In this article, Poocca Hydraulic, an experienced global hydraulic product supplier, will bring you a detailed set of hydraulic gear pump assembly process guidance. From preliminary preparation, parts inspection, installation and commissioning, to final performance testing, this guide is designed to provide practical technical references for front-line assemblers, maintenance engineers and hydraulic equipment procurement managers, helping the system to run more reliably and longer.
1. Introduction to Hydraulic Gear Pump Assembly
A hydraulic gear pump is a positive displacement pump that transfers liquid from one side to the other through a pair of meshing gears. It has a simple structure, stable operation and easy maintenance. However, to complete its assembly work correctly, it is necessary not only to have a certain mechanical foundation, but also to ensure the accuracy and cleanliness during the assembly process.
Whether assembling a single gear pump or a multi-gear pump (such as a double or triple structure), the basic assembly logic is roughly the same. The entire assembly process is usually divided into the following key steps: preliminary preparation, parts inspection, component installation, pump body positioning and alignment, seal installation, bolt tightening and final performance testing.
Tool and work area preparation
Before you start, make sure your workbench is clean, well-lit, and equipped with the following tools:
Torque wrench
Assembly fixture (optional)
Hexagon wrench and hexagon wrench
Oil-resistant gloves
Lint-free cloth
Sealing glue or O-ring (depending on the design)
Caliper or micrometer
Clean hydraulic oil
Poocca expert tip: Avoid assembling the pump in a dusty or humid environment. Even tiny contaminants can impair the performance of the pump.
Hydraulic Gear Pump Parts List
Typical parts of a hydraulic gear pump include:
Front and rear covers (or flanges)
Gear train (driving and driven gears)
Drive shaft with bearings
Bushing or needle bearings
Pump body (pump housing)
Shaft seal and O-rings
Dowel pins (optional, for alignment)
Fasteners (bolts/screws)
Poocca Hydraulic offers complete gear pump kits with all precision-matched components for original equipment compatibility and aftermarket repair.
Hydraulic Gear Pump Assembly Steps
Step 1: Clean all parts
Clean all parts with a lint-free cloth. Even new parts may have dust or protective grease on them, which should be removed before assembly.
Step 2: Install bushings or bearings
Press bushings or bearings into the front and rear covers. Make sure they are fully seated and aligned. Use a bearing press or hydraulic press if necessary.
Step 3: Insert the gear train
Place the gear train into the housing:
The drive gear is connected to the input shaft.
The driven gear rotates with the drive gear.
Make sure both gears mesh smoothly and rotate freely in the housing.
Note: If your pump is a center section design, the gears are mounted between the side plates.
Step 4: Insert the shaft and seals
Insert the drive shaft into the corresponding gear. Install the shaft seal into the front cover or bearing housing. Make sure the seal lip faces inward to retain oil.
Apply a small amount of clean hydraulic oil to the shaft to make insertion easier.
Hydraulic pump body assembly
Align the front and rear covers with the housing:
Use locating pins if available.
Make sure the ports (inlet and outlet) are oriented correctly.
Avoid excessive force when aligning the components.
Then, tighten the pump body bolts in a crisscross pattern to evenly distribute pressure.
Torque specifications: Follow the manufacturer's torque chart. Poocca recommends tightening in 2-3 stages.
Leak-proof sealing and final inspection
Install O-rings or washers at all sealing interfaces. Use high-pressure rated seals suitable for hydraulic applications.
Common sealing problems to avoid:
Twisted or squeezed O-rings
Reusing old washers
Over-tightening of bolts
After sealing, manually rotate the shaft to check for smooth operation. There should be no binding or noise.
Test the assembled gear pump
Before installing the pump on the machine, test it on a hydraulic test bench.
Basic test bench setup:
Oil tank
Pressure gauge
Flow meter
Pressure relief valve
Drive motor
Start by running the pump at a low speed and then gradually increase the speed. Monitor flow and pressure. Make sure there are no external leaks.
Target performance:
Smooth operation
Rated flow output (at rated speed)
No vibration or overheating
Poocca Hydraulic offers pre-tested gear pumps for customers who need a ready-to-install solution.
Common Mistakes During Assembly (and How to Avoid Them)
Effects of Mistakes Solutions
Misaligned gears Noisy operation Use calibration tools
Dirty environment Early failure Clean area before assembly
Overtightening Damaged seal or cracked housing Use a calibrated torque wrench
Missing seal Internal leakage Double check seal position
When to Replace Rather Than Repair
Sometimes it is better to replace a worn gear pump than rebuild, especially if:
Casing or gears scored/damaged
Bent shaft
Excessive internal leakage
Obsolete or discontinued models
Poocca Hydraulic Manufacturers offers new and replacement gear pumps for brands such as Parker, Marzocchi, Shimadzu, Rexroth, and more. Custom OEM/ODM orders are accepted and products are backed by a 12-month warranty.
Expert Tips from Poocca Hydraulic Manufacturers
Always consult the technical manual for your gear pump model.
Use OEM standard parts for best reliability.
Avoid using thread sealants on internal hydraulic passages.
If assembling a multi-section pump, clearly mark each section to avoid flow path errors.
After 20-30 hours of operation, recheck bolt torque to ensure stability.
Assembling a hydraulic gear pump requires precise assembly, extensive expertise, and the right parts. When done correctly, your pump will provide years of reliable service. Whether you are a maintenance technician or a purchasing engineer, understanding the complete assembly process can help improve equipment performance and reduce downtime.
If you are purchasing a hydraulic gear pump for your operation, or looking for a reliable aftermarket replacement, trust Poocca Hydraulic Manufacturing. We offer:
✅ Fast global delivery
✅ Competitive B2B pricing
✅ Custom design and brand selection
✅ Technical support from experienced engineers
Ready to purchase or assemble your next hydraulic gear pump?
