An Ultimate Guide of Orifice Tube

Inside the intricate industrial system, fluids travel through countless pipes to provide power or cooling for various equipment. However, how to ensure the smooth flow of fluid, and also to accurately control its flow to avoid resource waste or equipment overload? And this is actually where orifice tube plays an important role.

Orifice tube is a tubular device with a precise orifice inside that regulates the flow by limiting the area through which fluid can pass. Unlike traditional valve control, the throttle tube design is more compact, simple, and lower maintenance costs, and can achieve accurate flow control without affecting the stability of fluid pressure.

Working Principle of Orifice Tube

Orifice tube is a key component in automotive air conditioning systems and is used for throttling and pressure regulation of refrigerants.

The core of the orifice tube is the orifice inside it. The size, shape and position of this hole are carefully calculated to ensure that the fluid can pass through at a predetermined flow rate under certain operating conditions.

First and foremost, orifice tube is usually installed in the liquid pipe to orifice a liquid refrigerant under high pressure. And the pressure quickly drops to a low-pressure, cold-temperature mist.

When the fluid flows through the orifice, due to the sudden reduction of the cross-sectional area, the flow rate will increase and the pressure will decrease accordingly, and this change follows Bernoulli's law. By adjusting the size of the orifice, the pressure drop and flow rate of the fluid passing through can be precisely controlled, thus achieving the purpose of adjusting the performance of the system.

Basic Types and Structure of Orifice Tube

Orifice tube can be divided into several basic types based on their structure and function, and their structural design is relatively simple but efficient.

First type is called fixed orifice tube, which is aperture fixed, not adjustable, and suitable for systems with relatively stable refrigerant flow requirements.

The other type is called variable orifice tube, inside which the aperture can be automatically adjusted according to the system requirements, suitable for systems requiring more precise control of refrigerant flow.

The structure of orifice tube usually consists of the following parts.

Features and Advantages of Orifice Tube

Accurate Flow Control

One of the most prominent features of orifice tube is the ability to provide highly accurate flow control. Whether the device needs a stable small flow supply or a rapid adjustment of a large flow, orifice tube can achieve the requirement by adjusting throttle hole.

Compact Design

Then, another significant advantage of orifice tube is compact design. Unlike traditional flow control valves, orifice tube is particularly beneficial in applications where space is limited, such as in aerospace vehicles, compact machinery, and integrated fluid systems.

Cost-Effective

Meanwhile, because of its simple structure, relatively low manufacturing and maintenance costs, long-term use can save a lot of operating costs for enterprises.

Durable Materials

Last but not least, orifice tube is designed specifically to be used in liquids and gases under harsh temperature and high pressure. Materials such as stainless steel, brass, and specialized alloys are often used to construct orifice tubes, ensuring high adaptability and extending the lifespan of the device.

How Do I know If Orifice Tube Needs Replacing

Orifice tube is a key component in an automotive air conditioning system, which is usually located in a high-pressure line between the condenser and the evaporator. When orifice tube is aged or damaged, the cooling efficiency of the system will be significantly reduced. So how do I know if orifice tube needs replacing? And how do I replace it? Let's take a look!

Step 1: Inspect for Damage

For one part, you can determine if orifice tube needs replacing by looking for signs of aging or damage inside and outside.

As for external signs of orifice tube replacing, for example, surface cracks, deformation, or corrosion (commonly seen in metal materials). And plastic throttles may be embrittlement or fracture due to high temperature or pressure.

O-ring aging is also an indication for orifice tube replacement. The O-ring at the throttle pipe interface may harden, crack, or lose elasticity, resulting in refrigerant leakage.

Step 2: Observe System Performance

Oil or metal debris at external pipe joints may indicate internal system wear or contamination.

It is also suggested to find out the problem by observing the air conditioning system. For instance, cooling effects decrease, abnormal noise and evaporator frosting are illustrating ages and damages, like  blockage of the throttle tube may result in frosting on the evaporator surface (due to low refrigerant flow).

Step 3: Check Internal Condition

As for internal signs of orifice tube replacing, like the filter inside the throttle tube is blocked by metal debris, desiccant particles or impurities, resulting in blocked refrigerant flow. And this can be indirectly judged by the abnormal pressure of the air conditioning system (the high pressure side is too high, the low pressure side is too low).

Or orifice tube operating failure due to long-term wear, resulting in abnormal refrigerant flow (refrigeration effect fluctuation or insufficient). And if black sludge, metal powder, or desiccant particles are found inside the throttling pipe, the system is contaminated. Timely replace the throttling pipe and clean the entire system.

After judging the problem of orifice tube, it is time for replacement. And the following table may help you quickly understand the steps for replacing orifice tube.

How to replace orifice tube

How to Choose the Best Orifice Tube

When choosing the most suitable orifice tube, several factors need to be considered to ensure that the selected product meets the specific application and performance requirements. Here are some detailed tips to help you make the best choice.

Environemnt

To begin with, define your needs and requirements. For instance, where will the orifice tube be installed? Does it need to work in high temperature, high pressure or corrosive environments? These factors will directly affect the material selection of the orifice tube. Also, it is significant to determine the flow and pressure range that the tube needs to handle. This will help to select the right size and type of orifice tube.

Material

Then, it goes to material selection. If orifice tube needs to work in a corrosive environment, such as acid and alkali zones, then a corrosion-resistant material such as stainless steel or special alloys should be selected. Or for applications requiring higher pressure or stress, materials with higher strength and stiffness should be selected to ensure the stability and durability of the tube.

Flow and Pressure

Moreover, according to the flow and pressure requirements, select the appropriate diameter and length. Larger diameters can provide greater flow, while longer lengths may help increase pressure drop.

Shape and Configuration

Meanwhile, the shape and configuration of orifice tube will also affect its flow and pressure drop. Choosing the right shape and configuration can optimize its performance.

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Final Verdict

Orifice tube, with its unique structure and advantages, is becoming an integral part of industries. Through continuous exploration and innovation, it is believed that in the near future orifice tube will be more intelligent, better integrated into the automation and Internet of Things system, providing strong support for intelligent transformation of industrial production