What is the difference between porous equilibrium orifice plates and ordinary orifice plates, and what are the differences in their application?

The structure of a multi-stage orifice plate should be similar to that of a single-stage orifice plate; in other words, a multi-stage orifice plate consists of several single-stage orifice plates connected together. Multi-stage orifice plates are used because the pressure behind the flow-limiting orifice plate (P2) cannot be less than 55% of the pressure before the plate (P1), in order to avoid flow blockage. When P2…

According to the introduction, balanced orifice plates have many advantages over standard orifice plates, such as higher precision, shorter straight pipe sections, and a wider range of applications. The balance orifice plate is not a standard throttling device and requires calibration with actual flow.

A porous element is not a single orifice string, but rather multiple pores on one plate; it is generally referred to as a balanced flow meter, and its accuracy level is higher than that of a standard orifice plate

This is a copy of the description from the product page of Huai’an Tianyi Instrument Manufacturer. I think the introduction is quite accurate and detailed. I’ve moved here to answer the original poster’s question. Product Overview: The balanced flow meter represents a significant improvement over traditional throttling devices, featuring prominent balanced rectification properties. Traditional throttling devices have only one flow aperture, which causes the fluid to lose its ideal state after throttling ； The balanced flow meter features multiple functional apertures, which can maximize the balancing and rectification of the flow field to achieve an ideal fluid state, thereby fully leveraging the advantages of the differential pressure flow meter. Balance flowmeters are suitable for almost all fluid measurement applications, representing a revolution in fluid measurement technology. Today, they are widely used in industries such as petroleum, chemicals, metallurgy, power generation, natural gas, and water treatment. Product Principle The balanced flow meter is a revolutionary differential pressure type flow meter. Its working principle is the same as that of other differential pressure flow meters, based on the principle of energy conversion in a sealed pipeline: in the case of an ideal fluid, the flow rate in the pipeline is proportional to the square root of the differential pressure ； The flow rate in the pipeline can be calculated using the measured differential pressure value and Bernoulli’s equation. A balanced flow sensor is a porous disc throttle regulator installed in the cross-section of a pipe; the size and distribution of each pore are customized based on specific formulas and test data, and these pores are known as functional pores. When the fluid passes through the functional holes in the disk, it is evenly directed, turbulence is minimized, resulting in a flow that is nearly ideal. A stable differential pressure signal can be obtained using pressure sensing devices, and the volumetric flow rate and mass flow rate can be calculated based on Bernoulli’s equation. Features of balanced flow meters: The measurement accuracy is 5 to 10 times that of standard orifice plates; the flow noise is 1/15 that of standard orifice plates; the permanent pressure loss is 1/3 that of standard orifice plates; pressure recovery is twice as fast as that of standard orifice plates; the minimum required straight pipe section can be less than 0.5D. First, they exhibit high linearity and good repeatability. Balanced flow sensors have a symmetric porous structure that enables balancing of the flow field, reducing eddies, vibrations, and signal noise. This improves the stability of the flow field, resulting in a linearity that is 5 to 10 times higher than that of orifice plates, and a repeatability of 0.15%. In terms of their overall performance, balanced flow meters belong to the category of high-end flow meters. At a ratio of 5:1, the linearity can reach ±0.3% ； At a range ratio of 7:1, the linearity can reach ±0.5% ； At a range ratio of 10:1, the linearity can reach ±1.0%. Second, the requirements for straight pipe sections are low; due to the stable flow field in balance flow sensors and the fact that pressure recovery occurs twice as fast as in orifice plates, **the requirements for straight pipe sections are reduced. The straight pipe sections before and after such sensors are typically 3D in length ahead and 1D behind, with a minimum length of less than 0.5D, which allows for significant savings in terms of straight pipe sections, especially in pipelines made of expensive materials. III. Reduction of permanent pressure loss: The porous and symmetric design reduces turbulent shear forces and the formation of vortices, thereby minimizing kinetic energy losses. Under the same measurement conditions, it reduces permanent pressure loss by 2.5 times compared to orifice plates, which saves significant amounts of energy costs. It is an energy-saving instrument that deserves widespread adoption. IV. Resistant to dirt and less prone to clogging: The porous, symmetrical design reduces turbulent shear forces and the formation of vortices, thereby **reducing the creation of dead zones where debris can accumulate. This allows dirty substances to pass through the various pores easily, minimizing the chances of those pores becoming blocked. V. It can directly replace orifice plates. Since it has the same usage method and shape as orifice plates, it can be replaced directly without any need for changes to the piping or related instruments; it is thus very suitable for replacing orifice plates with balanced flow meters in the EMS renovation for energy measurement across an entire plant. VI. Wide flow measurement range: Based on the test results, we found that the performance of the balanced flow meter allows its flow velocity to range from a minimum value up to the speed of sound ； Its minimum Reynolds number can be below 200, and its maximum Reynolds number is above 107 ； The β value can range from 0.25 to 0.90. VII. Good long-term stability: Due to the significant reduction in turbulent shear forces, the direct friction between the medium and the throttling element is greatly diminished. Its β value remains constant over time, and since the entire instrument has no moving parts, it can maintain stability for a long period. VIII. Measurable high-temperature and high-pressure media: Similar to throttle devices such as orifice plates, the operating temperature and pressure depend on the material and grade of the pipes and flanges; the operating temperature can reach 850°C, and the operating pressure can reach 42 MPa. IX. Media under complex measurable conditions: Due to its special structural design, it possesses unique properties. It can handle gas-liquid phases, various mixed gases (such as gas, biogas, coal gas, etc.), various low-temperature gases (such as LNG, liquid nitrogen, liquid oxygen, liquid argon, liquid hydrogen, liquid chlorine, liquefied ethylene, liquefied petroleum gas, etc.), gas-liquid phase media (such as humid air), slurries, multiphase water flows, vibrating water flows, electromagnetic interference-prone media, and two-way flows (since the balance flow meter is completely symmetrical on both sides).

You are referring to a multi-stage pressure-reducing orifice plate, not a porous orifice plate (balance flow meter).

Porous materials are being used quite a lot these days; I’m not sure about their actual performance, but it seems that they require fewer specifications regarding straight sections.