Priming, bleeding and testing hydraulic pumps are crucial maintenance steps and these steps are able to maintain their high performance and improve working efficiency. Most importantly, they also can avoid costly repairs or replacements and extend hydraulic pumps’ service life.
However, you may not be very familiar with their specific implementation process or preparations. And this article will help you learn priming methods, bleeding steps and how to test hydraulic pumps and you can better maintain your hydraulic pumps with high efficiency for your project requirements.
What‘s the Purpose of Priming, Bleeding and Testing Hydraulic Pump?
Purpose of Priming
Priming is a necessary step for hydraulic pumps because proper amounts of hydraulic fluid can generate enough pressure and lubrication, which can greatly improve hydraulic pumps’ operational efficiency. In addition, it can help prevent hydraulic pumps from running dry and this will cause local overheating. Without proper priming, a large amount of air will enter your hydraulic pumps and lead to cavitation.
Purpose of Bleeding
Bleeding hydraulic pumps are used to remove air from hydraulic pumps. For one thing, air in hydraulic pumps will produce bubbles and cause unusual operating noises. For another, internal components will also be worn by shock waves of compressible air. Even trapped air will cause unstable operating pressure, which can lead to operation interruption. In order to
ensure instant response and efficient performance of hydraulic pumps, bleeding hydraulic pumps is an indispensable step.
Purpose of Testing
The purpose of testing hydraulic pumps is to check operating performance of your hydraulic pumps and repair fault components in time. Generally speaking, you can add a flow meter at the relief valve and you can easily monitor fluid volume at different operating pressures. Besides this, pump casing temperature, fluid color, components wear and other potential issues should be considered as parts of testing.
Priming Methods of Hydraulic Pumps
Most hydraulic pumps required to be primed manually before their first use such as hydraulic vane pumps and hydraulic gear pumps. But vacuum-primed self-priming pumps don’t need priming because they automatically remove trapped air through air pressure. So you first need to confirm whether your hydraulic pumps need priming and choose suitable priming methods according to your
1. Manual Priming
Manual priming is the simplest method, you just first need to cut off hydraulic pumps’ power. Then you inject the hydraulic fluid directly into your pump housing and suction line. Finally, you restart hydraulic pumps and check whether fluid pressure and flow is proper or not. If hydraulic pumps operate smoothly, your manual priming is finished successfully.
2. Vacuum Priming
Vacuum pump priming can help you avoid the complicated process of manual priming.
You need to connect an external vacuum pump to the main pump, which can help remove trapped air from suction lines and form a vacuum environment. And then the atmospheric pressure can push the fluid directly into hydraulic pumps. This priming method ensures your hydraulic pumps are always primed and helps reduce air-bound issues.
3. Jet Priming
Jet pump priming is a design that comes with the self-priming pump like internal gear pumps or external gear pumps and uses a built-in mechanism to remove internal air and start priming. This priming method is very suitable for pumps that are frequently started and stopped such as wastewater treatment systems, low flow irrigation equipment and well systems. After finishing jet pump priming, the entire pump housing and suction pipes will be primed completely and pull out trapped air.
4. Separator Priming
Separator priming is achieved by separation chamber and inclined fluid suction pipe.
Separator priming can not only form a vacuum environment in the separation chamber, but also create a sealed working room. Inclined suction pipes can guide trapped air inside hydraulic pumps to separation chambers’ top vent and discharge the air. Finally, hydraulic fluid can be sucked into the hydraulic pump by relying on atmospheric pressure.
5. Ejector Priming
Ejector priming relies on compressed air flowing through the ejector inlet, which can help create a vacuum environment. The vacuum environment helps remove air from inside hydraulic pumps and suction lines. After the internal air is exhausted, hydraulic fluid will be sucked into hydraulic pumps and suction lines due to pressure drop.
6. Foot Valve Priming
The implementation of foot valve priming is relatively simple than other priming methods and it can be achieved by a foot valve(non-return valve). Non-return values allow hydraulic fluid to flow in one direction only, such as into a pump or into a pipe, but not out. This excellent performance is able to help keep your hydraulic pumps primed without backflow.
This method ensures that your hydraulic pump‘s suction line is full of fluid when your hydraulic pump starts, which can enhance priming efficiency.
Hydraulic Pump Bleeding Steps
Step 1 : Initial Inspection
Before starting bleeding, you should first cut off the power supply to your hydraulic equipment and ensure components are stopped. And then you should check whether joints of fluid suction lines from the hydraulic tank to the pump are tight, which can prevent air into your hydraulic system. In addition, you should check fluid levels and ensure fluid is near the maximum level of hydraulic tanks.
Step 2 : Locate and Loosen Bleed Valve
This step requires you to locate a bleed valve and turn it counterclockwise to loosen bleed value. For example, the highest point of the hydraulic piston pump will be designed with a specialized bleed value or exhaust port and you just slightly loosen it.
Step 3 : Operate Hydraulic Controls
Then you need to run the hydraulic system’s hydraulic motor and operate hydraulic controls at low speed without operating any working devices. You need to note that these operations require multiple full stroke reciprocating motions. This step helps to dislodge the trapped air and push it towards the bleed valve.
Step 4 : Check for Steady Flow
When hydraulic controls are operating, you can check if there is a continuous, steady and bubble-free flow of fluid from the loose bleed value. This phenomenon indicates that the air has been completely exhausted and you can continue to the next step.
Step 5 : Close Bleed Valve
During bleeding, hydraulic fluid level in your hydraulic tanks will drop. You need to check timely and add fluid to the specified range and avoid hydraulic system failures. Everything is finished, you finally close the bleed valve and turn it clockwise.
Pre-Test Preparations for Hydraulic Pumps
System Pressure Relief
System pressure relief before hydraulic testing is a crucial safety practice, you may not perform any component functional tests or loosen pipes while the system is under pressure.
Before hydraulic pump testing, you need to operate all control valves to release the residual pressure in your hydraulic systems.
Component Inspection
Component inspection includes confirming your hydraulic pumps’ pressure gauges, flow meters, temperature sensors and other measuring instruments are calibrated and within the validity period.
Check for Fluid Level
In order to accurately check the correct fluid level, you need to shut down your hydraulic system and you should check after the fluid has cooled. And then you can add or remove appropriate amounts of hydraulic fluid according to your specific needs.
How to Test Hydraulic Pumps?
Fluid Check
When you start hydraulic fluid check, you can firstly judge whether hydraulic fluid is contaminated by its color. For example, if you find the hydraulic fluid is milky white instead of transparent, it may be contaminated by water and you need to replace old fluid in time to avoid reducing the efficiency of your hydraulic pump.
Check for Leaks
Visual inspection is easy to find leaks of hydraulic pumps. You can check whether there is any hydraulic fluid leakage at pump interfaces and housing connection surfaces.
Moreover, internal leaks can’t be found directly and disassembly of hydraulic pumps will result in long downtime. You can use ultrasonic leak detectors to check specific location and components of internal leaks.
Pressure and Flow Testing
Flow testing needs to add a flow meter at hydraulic pumps’ relief valves and pressure testing requires pressure gauges on pump outlets. You must first measure its free flow when opening load values and without pressure. Then you can slowly close load values and your hydraulic system’s pressure will gradually increase toward max system pressure.
In addition, you need to check your hydraulic pumps’ performance based on this data. If your hydraulic pump can flow up to 70% of its maximum free flow rate under strongest system pressure, your pump is functioning properly. But when your hydraulic pump cannot reach the required flow rate without pressure, you may need to add hydraulic fluid or check for leaks.
Temperature Monitoring
Temperature monitoring can reflect the degree of wear inside your hydraulic pumps. Pump case temperature, case drain temperature and fluid temperature all should be considered.
You can install temperature sensors at pump outlets, reservoirs, tank drain lines or other strategic locations to monitor your temperature data timely. You should note if your hydraulic fluid temperature exceeds 80 ℃, your hydraulic pump is more worn.
Conclusion
After reading this article, I believe you must have a deep understanding about priming, bleeding and testing hydraulic pumps. And you may be able to better maintain your hydraulic pumps and improve its operating efficiency. If you need further assistance with hydraulic pumps, Target can give you an effective solution.
FAQ
How to avoid hydraulic pumps operating without priming?
Preventing your hydraulic pumps from running without fluid is the key to ensuring its lifespan.
For one thing, you need to regularly monitor whether there is sufficient hydraulic fluid in hydraulic tanks. You can install a level sensor to detect fluid level timely. For another, you also need to ensure suction lines are sealed and suction filters are replaced regularly to prevent air ingestion and cavitation. If not, your hydraulic pumps will cause higher energy consumption or even lead to hydraulic system failure.
