A restriction orifice plate is a simple-structured yet crucial component in industrial fluid control systems. It is mainly used to control fluid flow rate, reduce fluid pressure, or achieve quantitative fluid delivery.
With advantages such as low cost, compact structure, and easy maintenance, it is widely applied in numerous industrial fields including petroleum, chemical engineering, electric power, metallurgy, and water treatment.
A restriction orifice plate is a throttling device installed in a pipeline system, usually composed of a metal plate with a through-hole of specific size. Its core structure is the orifice plate itself. The shape, size of the orifice plate, and its connection method with the pipeline are designed based on specific working conditions and fluid characteristics.
For an orifice plate with a specific hole diameter, when there is a certain pressure difference across the orifice plate, the flow rate of the fluid passing through the orifice plate increases as the pressure difference increases. However, when the pressure difference exceeds a specific value (i.e., the critical pressure difference) and the flow velocity reaches the speed of sound, the flow rate through the orifice plate will no longer increase with the increase in pressure difference. It is based on this principle that the restriction orifice plate limits the fluid flow rate and reduces the pressure.
- Simple structure: The restriction orifice plate has a relatively simple structure, consisting of only a few components. Its manufacturing process is straightforward, and the cost is low.
- Easy installation and maintenance: Its installation method is simple. Whether it is flange connection or welding connection, the construction is convenient. During maintenance, if problems occur, replacement or repair is relatively easy, without the need for complex tools and technologies.
- Wide application range: It can be applied to various fluid media (liquids, gases, steam, etc.) and different working pressure and temperature ranges, and can function in various industrial scenarios.
- No moving parts: Unlike valves, the restriction orifice plate has no moving parts. Therefore, there are no failure problems caused by component wear, jamming, etc. It has high reliability and a long service life.
- Limited flow adjustment range: The hole diameter of the restriction orifice plate is fixed. Once designed and manufactured, the flow range it can control is basically determined. It cannot perform continuous flow adjustment like a control valve, so it has poor adaptability to working conditions with large flow changes.
- Large pressure loss: Due to the throttling effect generated when the fluid passes through the restriction orifice plate, a certain pressure loss will occur. In some systems sensitive to pressure loss, this may increase energy consumption.
- Sensitivity to fluid properties: When the properties of the fluid (such as viscosity, density, etc.) change, the flow restriction effect of the restriction orifice plate will be affected to a certain extent, which may cause the flow rate to deviate from the expected value.
- Easy to be blocked: For fluids containing many solid particles and impurities, the through-hole of the restriction orifice plate is easily blocked, which affects its normal operation and requires frequent cleaning and maintenance.
The main functions of a restriction orifice plate are to limit flow rate and reduce pressure, so it can be used in the following occasions:
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Process material pressure reduction occasions
When process materials flow from a high-pressure area to a low-pressure area, the restriction orifice plate can control the pressure drop. By installing the restriction orifice plate, the material pressure can be reduced step by step to meet the operating pressure requirements. The restriction orifice plate is relatively simple, reliable, and low-cost, so it has more advantages than some complex pressure reducing devices in such occasions.
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Valve protection occasions
When a large pressure drop is required between the upstream and downstream of the valve in the pipeline, the fluid will cause severe erosion to the valve. If throttling through the orifice plate does not generate gas phase, connecting the orifice plate in series at the upstream of the valve can effectively reduce the impact of the fluid on the valve.
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Small flow continuous circulation occasions
(1)
Pump flushing pipeline: In chemical equipment, some parts such as the mechanical seal of the pump require continuous flushing fluid to prevent medium leakage and seal damage. The restriction orifice plate can ensure the stable supply of flushing fluid at a small flow rate. After installing the restriction orifice plate, an appropriate amount of flushing fluid can be provided, which not only ensures the cooling and flushing effect of the seal but also does not have an adverse impact on the operation of the pump.
(2)
Bypass pipeline of hot standby pump: In a system with a standby pump, a certain bypass flow is required to keep the standby pump in a hot standby state. The restriction orifice plate can control this bypass flow to ensure that the standby pump can be put into use at any time.
(3)
Analytical sampling pipe: When analyzing the composition of process fluid, the analytical sampling pipe requires a small and continuous sample flow. The restriction orifice plate can accurately control the sample flow rate.
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Pressure reduction and noise reduction or wear reduction occasions
In the venting system, the sudden pressure drop may produce huge noise. By installing the restriction orifice plate, the fluid pressure can be reduced step by step, which can effectively reduce noise and wear.
Standards related to restriction orifice plates can be referred to: HG/T 20570.15 Setting of Pipeline Restriction Orifice Plates, GB/T 2624.2-2006 Measurement of Fluid Flow in Closed Conduits Using Differential Pressure Devices Installed in Circular Cross-Section Conduits - Part 2: Orifice Plates, and ISO 5167.
Restriction orifice plates and throttle orifice plates have certain similarities in structure, as both control fluid by changing the flow cross-section. However, their design purposes are different: restriction orifice plates mainly focus on limiting flow rate and reducing pressure, while throttle orifice plates are more used for flow measurement, calculating the fluid flow rate by measuring the pressure difference across the orifice plate.
In addition, in terms of structural design and precision requirements, throttle orifice plates are usually more demanding than restriction orifice plates to ensure measurement accuracy.
