Micro Diaphragm Pump Selection Guide

Micro diaphragm pump has the characteristics of small size, completely oil-free and long life. It can be used for gas sampling, vacuuming, positive pressure, etc. This kind of pump is widely used in various industries such as medical treatment, environmental monitoring and analytical instruments. There are many brands and models of miniature diaphragm pumps, so how do we choose the most suitable diaphragm pump according to our application needs? This article sorts out vital 14 key points for choosing a diaphragm pump.

Table of Contents

1. Pressure and vacuum load
2. Installation space
3. Power consumption
4. Starting current
5. Chemical compatibility
6. Medium temperature
7. Ambient temperature
8. Working point pressure load and flow
9. Flow adjustment function
10. The gas tightness of the pump
11. Start with pressure
12. Actual operating life
13. Operating noise performance
14. Pipeline connection method

1. Pressure and vacuum load

First, select the product category according to whether the exhaust port is loaded or not. If the suction port is loaded and the exhaust port goes straight to the atmosphere, this kind of pump is usually called a vacuum pump. If the suction port is open to the atmosphere and the exhaust port is loaded, this kind of pump is called a gas compressor. If there is no load on the suction and exhaust ports or the pressures at the suction and exhaust ports are basically the same, either a vacuum pump or a compressor can be selected. Taking hilintec products as an example, if the exhaust port is unobstructed, the C series micro vacuum pump and the D series pumping dual-purpose air pump can be selected; if it is an application with a load on the exhaust port, the D series micro pumping air pump must be selected.

2. Installation space

According to the actual installation space of the equipment, determine the micro diaphragm pump size recommendations and installation methods. Generally, the operation of the diaphragm pump is not restricted by the installation direction, and it can work normally when installed in any posture. In order to facilitate the understanding of the installation space, the manufacturer of the diaphragm pump can provide 2D size drawings or 3D size models according to customer needs to facilitate the design of the installation of the pump.

3. Power consumption

Consider the supply voltage, load current and rated power of the micro pump according to the power supply of the equipment. Especially for battery-powered equipment, the voltage drop of the battery needs to be considered, and a wide-voltage-powered air pump can be selected. Some special micro diaphragm pump models are especially suitable for battery scenarios by integrating a built-in voltage regulator module. This kind of diaphragm pump can work in a wide voltage range, and when the voltage changes, it does not affect the output fluid parameters.

4. Starting current

At the moment the micro pump starts, the motor changes from stationary to rotating. At this time, the motor needs a larger starting torque to start quickly. Therefore, the starting current of the motor is very large, and the current value is generally 5-10 times the rated current. Of course, the starting time of the micro pump is relatively short, basically in tens of milliseconds. By asking the manufacturer for the “starting current curve” parameters, it can be used to evaluate the requirements of the starting current on the power supply. The instantaneous output power of the power supply determines whether it can meet the starting current requirements of the micropump. If the output power of the power supply is insufficient, it may cause difficulty in starting.

5. Chemical compatibility with the transmitted medium

Regardless of gas or liquid media, if their chemical composition reacts with the pump body, it will cause corrosion. When selecting the type, you need to know the composition of the medium passing through the micro diaphragm pump, and check the chemical performance table to determine whether the composition of the medium reacts with the contact materials of the pump (including the pump body, diaphragm, and one-way valve). If the pumped medium reacts with the contact material of the pump, consider customizing a material that does not react with the pumped medium.

6. Medium temperature

The temperature of the medium needs to be evaluated during the selection. Micro diaphragm pump products are generally allowed to extract gaseous medium at 0℃～50℃. If the micro diaphragm pump needs to be used to transport high-temperature gas, high-temperature medium type products can be selected, and the temperature range of the gas medium allowed to be transported is 0℃～100℃. For the transmission of higher temperature media, special high temperature resistant pump head and elastomer materials, such as stainless steel pump body and high temperature resistant elastomer, need to be selected.

7. Ambient temperature

The working environment temperature of the micro diaphragm pump will also affect the operation of the pump. Conventional diaphragm pumps are recommended to work at an ambient temperature of about 0°C to 50°C. At the same time, if the installation space of the pump is not conducive to heat dissipation, it is recommended to add heat dissipation holes, fans and other heat dissipation measures. For special applications, the pump may be required to work at a higher or lower ambient temperature. At this time, higher requirements will be put forward for the environmental reliability of pump materials, motors, and electronic devices. These requirements can be met by customizing special high temperature or low temperature resistant models.

8. Working point pressure load and flow

The nominal flow of the micro diaphragm air pump manual is usually the no-load flow. No-load flow refers to the flow of the pump at normal temperature and pressure when the micro diaphragm pump is at sea level. In fact, under different pressure loads, the pump output flow will change with the pressure. Therefore, the actual flow rate needs to be further determined according to the actual working conditions. In order to help customers determine the actual operating point flow, the micro pump manufacturer will provide a “pressure-flow curve”, which can be used as a technical reference curve for customers to confirm the operating point.

The following figure shows the pressure-flow curve of the micro diaphragm pump as an example:

The nominal relative vacuum of C61L micro pump is -65kpa, and the nominal average flow is 26.5L/min. When the pressure at the suction port of the vacuum pump is zero, the average flow rate of the pump is the nominal average flow rate of the pump 26.5L/min. When the maximum relative vacuum of the micro pump is close to -65kpa, the flow rate of the micro diaphragm pump is close to zero. If we use a C61 mini vacuum pump to sample gas, but there is a pressure difference or resistance of -40kpa at the pumping end of the pump, according to the “vacuum-flow curve” of C61 to find the relative vacuum of the micro pump at -40kpa, we can determine this The reference average flow rate at the working point is about 9L/min.

9. Flow adjustment function

Most of the modern miniature diaphragm pumps can adjust the flow rate of the pump through the control signal. Customers can decide whether they need to adjust the gas flow of the pump through electronic control according to application requirements. In order to facilitate the integration of various types of systems, some diaphragm pumps have a wealth of control methods. For example, the flow can be adjusted by adjusting the motor speed through manual knobs, touch LCD screens, input PWM signals, input frequency signals, input voltage signals, etc., of course, special signal interfaces can also be customized according to customer conditions.

10. The gas tightness of the pump

The gas tightness of the pump reflects the situation that the gas inside the pump leaks to the outside when the micropump is used for gas transmission. For application scenarios that require gas tightness, such as gas composition analysis, it is necessary to select an airtight pump with better gas tightness to prevent the leakage of the pump body from causing air to enter the analysis pipeline and affect the analysis data. The factors that affect the air tightness are the design of the pump body structure. Whether the sealing structure is specially designed for high air tightness requirements. Secondly, in the production management process of the micro pump manufacturer, whether the product air tightness is tested is also an important factor. For example, in the field test report, whether the air tightness of the product can be tested.

11. Start with pressure

The start-up capability with pressure refers to the maximum allowable start-up performance index of the pump. Products with good start performance under pressure are allowed to start under pressure at the nominal maximum working pressure (relative vacuum or relative positive pressure, the vacuum pump cannot work in the positive pressure range). For models that do not have good starting capacity under pressure, the maximum starting pressure is less than the maximum working pressure. For high-vacuum and high-pressure pumps, being able to start at the maximum pressure is a greater challenge to the micro diaphragm pump design.

12. Actual operating life

When the micro pump runs under different loads, the operating life of the micro diaphragm pump is also different. Currently, different brands do not have a unified standard for product life. For life, the indicators that need to be paid attention to include the life of the whole machine under maximum load, the life of the whole machine under low load, and the life of the motor. In addition to providing the life of pump parts, professional and rigorous manufacturers can also provide test life test data under multiple working conditions for customers’ reference. For details, please refer to the life test data in the product manual.

13. Operating noise performance

Certain application scenarios have harsh requirements for micro diaphragm pump operating noise. For example, medical industry applications require near-quiet pumps. The reciprocating movement of the diaphragm pump and the operation of the motor will bring mechanical noise, and the flow of gas will also bring noise. Through the inertial force dynamic balance technology, the magnetic elimination of the motor’s axial movement technology, the connection of the air path silencer, and the flexible mounting bracket and other technical solutions, the vibration and noise of the pump can be greatly reduced. There are some special designed low noise micro diaphragm pump models on the market.

14. Pipeline connection method

Different application scenarios have different requirements for the details of the connecting pipeline. For example: in the scene of pumping corrosive gas, ordinary silicone hose will be corroded, and Teflon hard gas pipe must be used. Common micro diaphragm pumps with hose connectors cannot be connected to hard air pipes or require adapters. If a pump has multiple connector options, different joints can be customized according to different materials or different sizes of pipes, which can greatly facilitate the connection of pipelines. Common connectors include hose connectors, PC8 push-in quick connectors, PC6 push-in quick connectors, internal threaded connectors, and so on.