Motor Pump Test Bench: Components, Assembly and Procedures

In this article, we will explore the world of the test bench in depth, detailing its components, the assembly process, and testing procedures.

What is a Motor Pump Test Bench and Why is it Indispensable?

A motor pump test bench is a system that simulates the operating conditions of a motor pump at the customer's facility. Its purpose is to test the equipment's operation, allowing the measurement of parameters such as current, pressure, and flow rate. Thus, these controlled simulations... confirm The full functionality of the motor pump after repairs, maintenance, or simply for performance validation, ensuring that it meets the design specifications.

Essential Components of a Test Bench for Motor Pumps

To build a robust and efficient test bench, several interconnected components are needed. Let's detail each one:

1. Bench for the Measuring Reservoir: A solid structure is essential to support the measuring reservoir, which can hold a mass of up to 600 kg. The material may vary, but strength is key.

2. Measuring Reservoir with Graduated Scale: Positioned on its own workbench, it allows water to return by gravity and facilitates reading the pumped volume through a graduated scale specifically designed for reading in liters and m³/h. At its outlet, a ball valve is used for maneuvers and should be kept open during flow regulation to prevent overflow and lack of water in the suction reservoir. It is recommended to fix the hose to a bar at the top, as well as to have a baffle (sheet metal structure) to even out the water flow, preventing turbulence and facilitating reading.

3. Suction Reservoir: It must have at least twice the volume of the measuring reservoir to ensure that there is no shortage of water during testing. Furthermore, to minimize turbulence generated by the return of water during flow and pressure regulation, the installation of a baffle with parallel plates is essential.

4. Suction and Support Piping: The suction line consists of a foot valve (or well bottom valve), which ensures the priming of the pump, and a threaded union. This union allows the use of... nipples and reducing bushings, facilitating the exchange of piping for different suction diameters. Additionally, an extra support is suggested to facilitate adjusting the height of the suction piping.

5. Motor pump bench: A stable structure to support the motor pump, with a minimum capacity of 50 kg, regardless of the material.

6. System with pressure gauge and gate valve: To expedite test preparation, a structure with a quick-connect fitting on the discharge side is proposed. The male component, with a female thread, allows direct coupling to the pump using nipples or reducing bushings. The female component of the quick-connect fitting is mounted on a "T" with a side outlet for the pressure gauge, whose measuring range should cover the operating pressure range of the pump. Furthermore, at the other end of the "T", the gate valve has the vital function of regulating the flow rate until the desired pressure is reached. After the valve, a fitting connects the hose to the measuring reservoir.

7. Discharge hose: Essential for directing water from the motor pump to the measuring reservoir. It is suggested that it be suspended on an appropriate support or tie rods fixed to the ceiling, thus avoiding unnecessary movement that could interfere with the test results.

8. Timer: In addition to the components that will make up the workbench, a simple stopwatch will be needed, which can be a watch or cell phone timer. He will measure The time in the methodology with a graduated reservoir.

The image below illustrates an example of how it can be assembled this bench.

Procedures for Performing Tests with a Graduated Measuring Reservoir

The execution of tests with the graduated reservoir system follows a precise script:

1. First of all, connect the pump to the suction pipe using the appropriate fittings.
2. Next, fill the pump and suction pipe with water (priming).
3. Connect the male component of the quick-connect fitting to the pump using the necessary connections.
4. Next, attach the quick-release coupling.
5. Open the pressure regulating valve (gate valve) and then the outlet of the measuring tank.
6. Make the electrical connection for the motor pump to be tested.
7. Turn on the water pump.
8. Close the gate valve until the desired pressure is reached on the pressure gauge.
9. Likewise, close the outlet valve of the measuring tank.
10. Read the initial volume on the graduated scale and then start the stopwatch.
11. Next, read the final volume on the scale and stop the stopwatch.
12. Finally, open the tank's outlet valve to allow water to return to the suction reservoir.
13. Repeat steps 8 through 12 to measure a new pressure point, thus generating the pump's performance curve.

In summary, the flow rate calculation should consider:

Alternative: The Rotameter Measurement System

Although the graduated reservoir offers precision, a system with rotameter It is an excellent alternative for those seeking speed and immediate flow and pressure readings, without the need for timing and calculations.

Rotameter: This instrument measures the flow rate of gases or fluids continuously. It works by using a piston that moves inside a graduated conical tube. indicates The flow rate allows for direct reading on the scale. Specifically, rotameters with a scale in m³/h are the most common.

• Advantages of the Rotameter: Immediate flow and pressure readings, meaning no need for a stopwatch or conversion calculations, speeds up testing. Above all, the use of rotameters allows for longer testing periods because... the pump recirculates The water immediately flows into the suction reservoir.
• Disadvantages: Generally, a rotameter has a measurement range of 1:10 (maximum flow rate 10 times the minimum). Thus, to cover a wide range (e.g., 0,2 m³/ha to 20 m³/h), it may be necessary to use two or more rotameters in parallel, with ball valves to select the appropriate instrument.

The basic structure of the test bench remains the same, with the main difference being the measurement system, where the rotameter is coupled. The test circuit will include the pressure gauge, the gate valve, and one or more rotameters. The design uses Vertical check valves at the rotameter outlets to prevent water backflow.

Procedures for Testing with a Rotameter:

1. Connect the pump to the suction pipe using the appropriate fittings.
2. Fill the pump and suction pipe with water (priming).
3. Connect the male component of the quick-connect fitting to the pump using the necessary connections.
4. Attach the quick-release coupling.
5. Open the pressure regulating valve (gate valve) and the outlet of the measuring tank.
6. Make the electrical connection for the motor pump to be tested.
7. Turn on the water pump.
8. Close the gate valve until the desired pressure is reached on the pressure gauge.
9. Select the appropriate rotameter for the desired flow range, opening its ball valve and closing the others.
10. Take the flow rate reading directly from the rotameter.
11. Open the tank's outlet valve to allow water to return to the suction reservoir (after testing, to prevent prolonged recirculation).
12. Repeat steps 8 through 11 to measure a new pressure point.

Important: After data collection and test completion, do not keep the pump running in prolonged recirculation mode. Excessive recirculation can heat the water, which impairs the rotameter's accuracy and damages the pump, especially if... the manufacturer does not design it "For working with hot fluids."

Maintenance and Safety: Pillars of an Effective Test Bench

To guarantee reliable results and the longevity of your workbench and operators, maintenance and safety are non-negotiable:

• Regular Calibration: Measuring instruments (pressure gauges, rotameters, electrical meters) must be calibrated periodically to ensure data accuracy.
• Reservoir Cleaning: Keep the suction reservoir clean and free of sediment and debris that could compromise the pump or measurements.
• Leak Detection: Regularly inspect all connections, pipes, and valves to identify and repair leaks.
• Use of PPE: Always use Personal Protective Equipment (safety glasses, gloves, ear protectors) during testing.
• Electrical Safety: Check the grounding, cables, and circuit breakers. Always have an accessible emergency shut-off point.
• Training: The bench operation should only be performed by qualified personnel trained in the specific procedures.

With a well-assembled and operated test bench, you not only verify the performance of the motor pumps, but also equip yourself with the necessary knowledge to make informed decisions, ensuring... Efficiency, economy, and maximum durability. for your equipment.

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