A steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio

Abstract

The application discloses a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio, which comprises a cylinder, an inlet part, an outlet part and at least two sleeve type throttle orifice plates. The cylinder has opposite first and second ends. The inlet and outlet parts are respectively located at the first and second ends. The sleeve type throttle orifice plate comprises a wall part and a bottom part, the radial section of the wall part is annular, and the bottom part is connected to one end of the wall part. The wall part of each sleeve type throttle orifice plate is provided with a plurality of through holes, and the bottom part is away from the inlet part relative to the wall part. The at least two sleeve type throttle orifice plates are arranged in a step-by-step sleeve type manner from inside to outside and are spaced apart, and the total area of the through holes gradually increases from inside to outside, so that the pressure reduction ratios of the at least two sleeve type throttle orifice plates gradually increase. According to the steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio, the purposes of pressure reduction and noise reduction can be achieved at the same time, noise pollution is reduced, and the use environment of the equipment is safer.

Description

TECHNICAL FIELD

[0001] The present application relates to the mechanical technical field, and in particular to a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio. BACKGROUND

[0002] The pressure reducing device is widely used in the pressure relief pipeline, pressure reducing device and other equipment in the ship, power, petrochemical and other industries. It can reduce the pressure of high-pressure steam, so that the pressure parameter of the steam meets the production technical requirements.

[0003] The current market generally uses a throttling orifice plate or a pressure reducing valve to reduce the pressure of steam. If the pressure drop is large, multiple pressure reducing valves or throttling orifice plates will be used. However, if the pressure drop is too large, many problems will occur, such as insufficient compactness of the equipment, large volume, significant increase in cost, and most importantly, excessive noise.

[0004] Therefore, a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio is needed to at least partially solve the above problems. SUMMARY

[0005] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the specific embodiment section. The summary section of the present application does not mean to attempt to limit the key features and essential technical features of the claimed technical solution, nor to determine the protection scope of the claimed technical solution.

[0006] To at least partially solve the above problems, the present application provides a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio, comprising:

[0007] a cylinder body having opposite first and second ends;

[0008] an inlet portion located at the first end of the cylinder body;

[0009] an outlet portion connected to the second end of the cylinder body; and

[0010] at least two sleeve type throttling orifice plates, each comprising a wall portion and a bottom portion, the radial cross-section of the wall portion being configured as an annular shape, the bottom portion being connected to one end of the wall portion, the wall portion of each sleeve type throttling orifice plate being provided with a plurality of through holes, the at least two sleeve type throttling orifice plates being at least partially located in the cylinder body and the respective bottom portions being arranged away from the inlet portion relative to the respective wall portions, the at least two sleeve type throttling orifice plates being arranged in a step-by-step nested manner and spaced apart from each other in an inner to outer direction;

[0011] Among them, the innermost sleeve throttle orifice plate communicates with the inlet part, and the total area of the through hole of each sleeve throttle orifice plate gradually increases in the direction from inside to outside, so that the pressure reduction ratio of each sleeve throttle orifice plate gradually increases.

[0012] The steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio can reduce the pressure of high-pressure steam, can adapt to the working condition of large pressure difference and low pressure reduction ratio, and can achieve the purposes of reducing pressure and noise at the same time by designing the internal steam flow field, thereby reducing noise pollution and making the equipment use environment safer. The through hole is designed in the wall part of the sleeve throttle orifice plate, which can greatly change the steam flow field, make the steam distribution uniform, reduce the generation of vortex, and the design of gradually increasing pressure reduction ratio is also beneficial to reducing the overflow of noise.

[0013] Further, the cylinder body includes a body part and a head part arranged at one end of the body part, and the steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio includes a first-end sleeve throttle orifice plate, an end of the wall part of the first-end sleeve throttle orifice plate away from the bottom part penetrates through the head part and extends towards the inlet part, and the inlet part is in butt joint with the wall part of the first-end sleeve throttle orifice plate.

[0014] Further, the steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio includes:

[0015] a last-end sleeve throttle orifice plate, the last-end sleeve throttle orifice plate is sleeved outside the first-end sleeve throttle orifice plate and is spaced apart from the first-end sleeve throttle orifice plate, and an end of the wall part of the last-end sleeve throttle orifice plate away from the bottom part is connected to the head part; and

[0016] at least one intermediate sleeve throttle orifice plate, the at least one intermediate sleeve throttle orifice plate is located between the first-end sleeve throttle orifice plate and the last-end sleeve throttle orifice plate, and an end of the wall part of the intermediate sleeve throttle orifice plate away from the bottom part is connected to the head part.

[0017] Further, the bottom part of the last-end sleeve throttle orifice plate is provided with a through hole.

[0018] Further, the bottom part of the first-end sleeve throttle orifice plate is provided with a support part extending towards the outlet part, the support part penetrates through and is connected to the bottom part of each of the intermediate sleeve throttle orifice plate and the last-end sleeve throttle orifice plate; and / or

[0019] The cylinder body is provided with a reinforcing rib, and the reinforcing rib extends from the inner side surface of the body part to the wall part of the first-end sleeve throttle orifice plate.

[0020] Further, the steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio further comprises:

[0021] a first planar throttle orifice plate arranged at the inlet portion; and / or

[0022] a second planar throttle orifice plate arranged at the outlet portion. According to the above arrangement, the steam flow field can be affected at the inlet and / or outlet, the local disturbance can be reduced, the vortex can be eliminated, and the steam distribution is more uniform.

[0023] Further, the hole diameters of the through holes on each sleeve throttle orifice plate are the same; and

[0024] The number of through holes on the sleeve throttle orifice plate gradually increases in the direction from inside to outside.

[0025] Further, the number of through holes on each sleeve throttle orifice plate is equal; and

[0026] The hole diameters of the through holes on the sleeve throttle orifice plate gradually increase in the direction from inside to outside.

[0027] Further,

[0028] The variation amount of the pressure reduction ratio between two adjacent sleeve throttle orifice plates gradually increases and then decreases in the direction from inside to outside; and / or

[0029] The variation amount of the total area of the through holes between two adjacent sleeve throttle orifice plates gradually increases in the direction from inside to outside.

[0030] Further, the distance between two adjacent sleeve throttle orifice plates is not less than 40 mm; and / or

[0031] The through holes on two adjacent sleeve throttle orifice plates are staggered. According to the above arrangement, the steam can be stabilized, the steam flow field is further changed, the uniformity is improved, and the noise reduction effect is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] The following drawings of the present application are hereby incorporated as part of the present application for the purpose of understanding the present application. The embodiments of the present application and the description thereof shown in the drawings are used to explain the principles of the present application.

[0033] In the drawings:

[0034] Figure 1 A perspective view of a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio according to a preferred embodiment of the present application;

[0035] Figure 2 A perspective view of a steam noise reduction pressure reducing device with large pressure difference and low pressure reduction ratio according to a preferred embodiment of the present application; Figure 1A cross-sectional view of a steam noise reduction pressure reducing device with a medium pressure differential and a low pressure reduction ratio; and

[0036] Figure 3 For Figure 1 A cross-sectional view from another perspective.

[0037] Reference Signs List:

[0038] 100: steam noise reduction pressure reducing device with a large pressure differential and a low pressure reduction ratio

[0039] 111: body portion

[0040] 113: support portion

[0041] 115: reinforcing rib

[0042] 117: second end

[0043] 121: first planar orifice plate

[0044] 123: second inlet flange

[0045] 131: second planar orifice plate

[0046] 133: second outlet flange

[0047] 141: middle sleeve orifice plate

[0048] 143: wall portion DETAILED DESCRIPTION

[0049] In the following description, numerous specific details are set forth to provide a more thorough understanding of the present application. However, it will be apparent to one of ordinary skill in the art that the present application can be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present application.

[0050] For a thorough understanding of the present application, reference is made to the following detailed description. It is appreciated that the following examples are given for purposes of disclosure and that the present application is not limited to these examples. The skilled person will readily appreciate that the present application is susceptible to variations and modifications without departing from the scope of the present application.

[0051] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof.

[0052] The ordinal numbers such as "first" and "second" used in this invention are merely identifiers and do not have any other meaning, such as a specific order. Furthermore, for example, the term "first component" does not imply the existence of a "second component," and the term "second component" does not imply the existence of a "first component." It should be noted that the terms "upper," "lower," "front," "rear," "left," "right," "inner," "outer," and similar expressions used herein are for illustrative purposes only and are not intended to be limiting.

[0053] Now, refer to Figures 1 to 3 The exemplary embodiments of the present invention will be described in more detail below. A preferred embodiment of the present invention, a steam noise reduction and pressure reduction device 100 with a large pressure difference and low pressure reduction ratio, includes a cylinder 110, an inlet 120, an outlet 130, and at least two sleeve-type throttling orifice plates.

[0054] The inlet 120 and outlet 130 are located at opposite ends of the cylindrical body 110. Alternatively, the cylindrical body 110 has a first end 116 and a second end 117, with the inlet 120 located at the first end 116 and the outlet 130 connected to the second end 117. In this embodiment, the cylindrical body 110 includes a body 111 and a head 112. The body 111 is generally cylindrical, or its radial cross-section is annular. The head 112 is located at the end of the body 111. The head 112 is the first end 116 of the cylindrical body 110, and the opposite end of the body 111 is the second end 117 of the cylindrical body 110. Preferably, the inlet area of ​​the inlet 120 is smaller than the outlet area of ​​the outlet 130.

[0055] The sleeve throttle orifice plate comprises a wall portion 143 and a bottom portion 144. The radial section of the wall portion 143 is configured as an annular shape, and the bottom portion 144 is connected to one end of the wall portion 143. In other words, the sleeve throttle orifice plate can be configured in the form of an open one end and a closed other end. Among them, each sleeve throttle orifice plate is arranged in a manner that the respective bottom portion 144 is arranged away from the inlet portion 120 relative to the respective wall portion 143. And, at least two sleeve throttle orifice plates are arranged in a step-by-step sleeve manner and are spaced apart in the direction from inside to outside.

[0056] The wall portion 143 of each sleeve throttle orifice plate is provided with a plurality of through holes. Therefore, the steam entering in the axial direction can diffuse in the radial direction in the cylinder body 110, and then the steam can pass through a plurality of sleeve throttle orifice plates in turn, appropriately increasing the residence time of the steam in the cylinder body 110, improving the overall pressure reduction and noise reduction effect and uniformity, and avoiding the steam from flowing out quickly after entering the cylinder body 110. Preferably, the bottom portion 144 of the outermost sleeve throttle orifice plate is also provided with a plurality of through holes, so that the steam can be quickly discharged after being sufficiently reduced in pressure and noise.

[0057] Among them, the through holes on the two adjacent sleeve throttle orifice plates are preferably staggered, and the distance between the two adjacent sleeve throttle orifice plates is not less than 40mm. In this way, the steam flow field is further improved, and the noise reduction effect is improved.

[0058] Preferably, the innermost sleeve throttle orifice plate communicates with or abuts against the inlet portion 120. And the total area of the respective through holes on the at least two sleeve throttle orifice plates gradually increases in the direction from inside to outside, so that the respective pressure reduction ratios of the at least two sleeve throttle orifice plates gradually increase. Among them, the pressure reduction ratio refers to the ratio of the pressure on the two sides of the sleeve throttle orifice plate, or the ratio of the pressure in front to the pressure behind.

[0059] The steam noise reduction and pressure reduction device 100 with large pressure difference and low pressure reduction ratio according to the present application can reduce the pressure of high-pressure steam, can adapt to the working condition of large pressure difference and low pressure reduction ratio, and can design the internal steam flow field to achieve the purpose of reducing pressure and noise at the same time, reduce noise pollution, and make the equipment use environment more safe. And the through holes are designed on the wall portion of the sleeve throttle orifice plate, which can greatly change the steam flow field, make the steam distribution uniform, reduce the generation of vortex, and the design of gradually increasing pressure reduction ratio is also beneficial to reducing the overflow of noise.

[0060] Among them, the number and diameter of the through holes on the sleeve throttle orifice plate can be designed as needed. For example, when the diameters of the through holes on each sleeve throttle orifice plate are the same, the number of the through holes on the sleeve throttle orifice plate gradually increases in the direction from inside to outside.

[0061] When the number of through holes on each sleeve orifice plate is equal, the diameter of the through holes on the sleeve orifice plate gradually increases in the direction from the inside to the outside.

[0062] Preferably, the variation of the total area of the through holes between the two adjacent sleeve orifice plates increases in the direction from the inside to the outside, so that the variation of the pressure reduction ratio between the two adjacent sleeve orifice plates first increases and then decreases in the direction from the inside to the outside.

[0063] Specifically, the at least two sleeve orifice plates include a first sleeve orifice plate 140 and a last sleeve orifice plate 142. The end of the wall portion 143 of the first sleeve orifice plate 140 away from the bottom portion 144 extends through the head 112 and towards the inlet portion 120, and the inlet portion 120 is in abutment with the wall portion 143 of the first sleeve orifice plate 140. Alternatively, the wall portion 143 of the first sleeve orifice plate 140 extends out of the barrel 110, and the wall portion 143 is welded to the head 112 of the barrel 110.

[0064] The last sleeve orifice plate 142 is located inside the barrel 110 and is sleeved on the outside of the first sleeve orifice plate 140. The last sleeve orifice plate 142 is spaced apart from the first sleeve orifice plate 140. The end of the wall portion 143 of the last sleeve orifice plate 142 away from the bottom portion 144 is connected to the head 112, for example, by welding. Preferably, as shown in the drawings, the barrel 110 is also provided with a reinforcing rib 115 extending from the inner side of the body portion 111 to the wall portion 143 of the first sleeve orifice plate 140 to improve the structural strength. Figure 2

[0065] In an alternative embodiment, at least one intermediate sleeve orifice plate 141 is provided between the last sleeve orifice plate 142 and the first sleeve orifice plate 140. It is easy to understand that the intermediate sleeve orifice plate 141 is also located inside the barrel 110. The end of the wall portion 143 of the intermediate sleeve orifice plate 141 away from the bottom portion 144 is connected to the head 112, for example, by welding. The wall portion 143 of the first sleeve orifice plate 140 and the intermediate sleeve orifice plate 141 are provided with a plurality of through holes. The wall portion 143 and the bottom portion 144 of the last sleeve orifice plate 142 are provided with a plurality of through holes.

[0066] ​In the embodiment, three intermediate sleeve throttle orifice plates 141 are arranged, and the three intermediate sleeve throttle orifice plates 141 are arranged in a step-by-step nested manner and are spaced apart in the direction from the inside to the outside. That is, the front-end sleeve throttle orifice plate 140, the three intermediate sleeve throttle orifice plates 141, and the rear-end sleeve throttle orifice plate 142 are arranged in a step-by-step nested manner and are spaced apart in the direction from the inside to the outside. In an alternative embodiment, other numbers of intermediate sleeve throttle orifice plates 141 can be arranged as needed.

[0067] Exemplarily, in the embodiment, the pressure reduction ratios of the sleeve throttle orifice plates at different levels can be 0.546, 0.608, 0.682, 0.763, and 0.800 in sequence. The overall pressure reduction ratio can be less than 0.138. In addition, the flow rate of the steam needs to be controlled at 40-60 m / s to achieve the best noise reduction effect and to avoid the noise caused by supersonic speed during pressure reduction. That is, the pressure reduction ratio of the front-end sleeve throttle orifice plate 140 cannot be less than 0.546.

[0068] In order to improve the stability of the sleeve throttle orifice plates in the cylinder 110, a support portion 113 is arranged at the bottom 144 of the front-end sleeve throttle orifice plate 140. The support portion 113 extends towards the outlet portion 130. The support portion 113 penetrates and connects the bottoms 144 of the intermediate sleeve throttle orifice plates 141 and the rear-end sleeve throttle orifice plate 142. Alternatively, the bottoms 144 of the intermediate sleeve throttle orifice plates 141 and the rear-end sleeve throttle orifice plate 142 are welded on the support portion 113.

[0069] Further preferably, the inlet portion 120 is provided with a first planar throttle orifice plate 121, and the outlet portion 130 is provided with a second planar throttle orifice plate 131. In this way, local disturbance can be reduced, and vortex can be eliminated, thereby further improving the steam flow field. In addition, the space between the second planar throttle orifice plate 131 and the rear-end sleeve throttle orifice plate 142 is configured as a pressure stabilization chamber 114 to change the steam flow field, improve the pressure stability, and further improve the noise reduction effect.

[0070] The inlet portion 120 includes a first inlet flange 122 and a second inlet flange 123. The first inlet flange 122 is connected to the end of the wall portion 143 of the front-end sleeve throttle orifice plate 140, and is preferably welded. The second inlet flange 123 is bolted to the first inlet flange 122, and the first planar throttle orifice plate 121 is clamped between the first inlet flange 122 and the second inlet flange 123. The first inlet flange 122 is used to be connected to the high-pressure steam pipeline to receive high-pressure steam.

[0071] The outlet part 130 comprises a first outlet flange 132 and a second outlet flange 133. The first outlet flange 132 is connected to the end of the cylinder body 110 away from the head 112, preferably by welding. The second outlet flange 133 is bolted to the first outlet flange 132, and the second planar throttle orifice plate 131 is clamped between the first outlet flange 132 and the second outlet flange 133. The first outlet flange 132 is used to interface with a low-pressure steam pipeline to discharge the reduced-pressure steam.

[0072] The steam noise-reducing and pressure-reducing device 100 with large pressure difference and low pressure-reduction ratio according to the present application uses a combination of multiple-stage throttle orifice plates to reduce noise and pressure for steam. The main noise-reducing multiple-stage throttle orifice plates are designed in a sleeve type, having the feature of porous sound absorption. The first and last throttle orifice plates in the steam flow field are designed in a planar type, which can reduce local disturbance and eliminate vortex. In addition, in the sleeve-type throttle orifice plate design, the pressure-reduction ratio gradually increases from the inside to the outside, and the pressure drop borne by each stage of orifice plate gradually decreases. The main noise is in the innermost part, and the noise becomes smaller and smaller as it goes outward, reducing the overflow of noise.

[0073] In addition, the steam noise-reducing and pressure-reducing device 100 with large pressure difference and low pressure-reduction ratio according to the present application can reduce the pressure of high-pressure steam. It can also adapt to the working condition of large pressure difference and low pressure-reduction ratio, especially to achieve the purpose of reducing pressure and noise at the same time, reduce noise pollution, and make the steam use environment more secure. In addition, the multiple-stage throttle orifice plates can achieve a larger pressure reduction capacity, and the structure is very compact (i.e., small in size), avoiding the increase in equipment size, cost, and control difficulty caused by the use of multiple pressure-reducing valves, actuators, and monitoring systems, greatly improving the reliability and economy of the equipment.

[0074] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The features described in one embodiment can be applied to another embodiment, unless the features are not applicable or are otherwise stated.

[0075] The present application has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and illustration, and are not intended to limit the present application to the scope of the described embodiments. In addition, those skilled in the art can understand that the present application is not limited to the above-mentioned embodiments, and more variations and modifications can be made according to the teachings of the present application, which all fall within the scope of the present application claimed. The scope of protection of the present application is defined by the attached claims and their equivalent scope.

Claims

1. A large pressure difference low pressure reduction ratio steam noise reduction pressure reducing device, characterized by, The device comprises: a barrel having opposite first and second ends; an inlet part at the first end of the barrel; an outlet part connected to the second end of the barrel; and at least two sleeve-type orifice plates, each comprising a wall part configured in a radial cross-section as a ring and a bottom part connected to one end of the wall part, the wall part of each sleeve-type orifice plate being provided with a plurality of through holes, the at least two sleeve-type orifice plates being at least partially located in the barrel and each having the bottom part arranged away from the inlet part relative to the wall part, the at least two sleeve-type orifice plates being arranged in a step-by-step manner and spaced apart from each other in an inside-to-outside direction, wherein the innermost sleeve-type orifice plate is in communication with the inlet part, and the innermost sleeve-type orifice plate is a first-end sleeve-type orifice plate, the first-end sleeve-type orifice plate having a pressure reduction ratio greater than or equal to 0.546; the total area of the through holes of each of the at least two sleeve-type orifice plates gradually increases in the inside-to-outside direction, and the change in the total area of the through holes between two adjacent sleeve-type orifice plates gradually increases in the inside-to-outside direction, so that the pressure reduction ratio of each of the at least two sleeve-type orifice plates gradually increases, and the change in the pressure reduction ratio between two adjacent sleeve-type orifice plates gradually increases first and then decreases in the inside-to-outside direction. The barrel comprises a body part and a head part arranged at one end of the body part, an end of the wall part of the first-end sleeve-type orifice plate away from the bottom part penetrates through the head part and extends towards the inlet part, and the inlet part is in abutment with the wall part of the first-end sleeve-type orifice plate.

2. The large differential pressure, low pressure reduction ratio, steam noise reduction pressure reducing device, as claimed in claim 1, wherein, The device comprises:

3. The large differential pressure, low pressure reduction ratio, steam noise reducing pressure reduction device, as recited in claim 2, characterized by, a terminal sleeve-type orifice plate arranged outside and spaced apart from the first-end sleeve-type orifice plate, and an end of the wall part of the terminal sleeve-type orifice plate away from the bottom part is connected to the head part; and at least one intermediate sleeve-type orifice plate arranged between the first-end sleeve-type orifice plate and the terminal sleeve-type orifice plate, and an end of the wall part of the intermediate sleeve-type orifice plate away from the bottom part is connected to the head part. The bottom part of the terminal sleeve-type orifice plate is provided with a through hole.

4. The large differential pressure, low pressure reduction ratio, steam noise reducing pressure reduction device, as recited in claim 3, c h a r a c t e r i z e d b y, 5. The device according to claim 4, wherein the bottom part of the first-end sleeve-type orifice plate is provided with a support part extending towards the outlet part, the support part penetrates through and is connected to the bottom part of each of the intermediate sleeve-type orifice plate and the terminal sleeve-type orifice plate; and / or the barrel is provided with a reinforcing rib extending from an inner side surface of the body part to the wall part of the first-end sleeve-type orifice plate. The device further comprises:

6. The large differential pressure low pressure reduction ratio steam noise reduction pressure reducing device according to any one of claims 1 to 5, characterized by, a first planar orifice plate arranged at the inlet part; and / or a second planar orifice plate arranged at the outlet part. A second planar orifice plate is arranged at the outlet portion.

7. The large differential pressure low pressure reducing ratio steam noise reduction pressure reducing device according to any one of claims 1-5, characterized in that, the hole diameters of the through holes on each sleeve orifice plate are the same; and the number of through holes on the sleeve orifice plate gradually increases in the direction from inside to outside.

8. The large differential pressure low pressure reducing ratio steam noise reduction pressure reducing device according to any one of claims 1-5, characterized in that, the number of through holes on each sleeve orifice plate is equal; and the hole diameters of the through holes on the sleeve orifice plate gradually increase in the direction from inside to outside.

9. The large differential pressure low pressure reducing ratio steam noise reduction pressure reducing device according to any one of claims 3-5, characterized in that, the distance between two adjacent sleeve orifice plates is not less than 40 mm; and / or the through holes on two adjacent sleeve orifice plates are staggered.

Images