A welded orifice flowmeter for taking pressure from an annular chamber

Abstract

The present invention provides a novel welded orifice flowmeter for taking pressure from an annular chamber, comprising a measuring tube, a front clamping ring, a pressure taking tube, a rear clamping ring and an orifice plate; the front clamping ring and the rear clamping ring are connected by welding, a front annular chamber is arranged in the front clamping ring, a rear annular chamber is arranged in the rear clamping ring, an inclined surface is adopted at the connection between the orifice plate and the rear clamping ring, the back of the orifice plate is connected with the rear annular chamber through an annular gap and a slot on the orifice plate, the front of the orifice plate is connected with the front annular chamber through an annular gap and a slot on the orifice plate, and a pair of pressure taking tubes are arranged on the front clamping ring and the rear clamping ring, respectively, and are connected with the annular chambers of the front clamping ring and the rear clamping ring, respectively. The present invention adjusts the butt weld position of the front and rear clamping rings, can carry out weld quality inspection, adopts an inclined surface transition, and the slope of the inclined surface meets the requirements of the safety technical specifications for special equipment. Compared with the original structure, the local peak stress caused by the structural mutation is greatly reduced, and the safety performance of the flowmeter is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of special equipment component manufacturing, and in particular relates to a welded orifice flowmeter for taking pressure from an annular chamber. Background Art

[0002] Flowmeters have been studied by scholars from various countries since the last century. The American AGA (American Gas Association) and ASME (American Society of Mechanical Engineers) have been studying them since the beginning of the last century. The German Industrial Standard (DIN) and the International Organization for Standardization (ISO) also formulated corresponding standards in the 1960s and 1970s. At present, the commonly used reference manufacturing standards for flowmeters in China are GB / T2624.1~3-2006, ISO / TR12767, ASMEMFC-3M, etc. These standards stipulate the structure of orifice plates and nozzles to ensure the accuracy of flow measurement, but do not make corresponding provisions for the material, welding and quality requirements of welds of the flowmeter cylinder. Most of these flowmeters are used in pressure pipelines such as steam pipelines and chemical process pipelines, which pose serious safety hazards.

[0003] Existing welded orifice flowmeter for taking pressure from annular chamber (see Figures 1 to 3 )Problems:

[0004] 1. The butt weld of the front and rear clamping rings is just above the orifice plate. According to the technical specifications for special equipment, the weld must be tested by radiography or ultrasonic testing. However, due to the sudden change in the structure and the orifice plate below the weld, radiography cannot be carried out. Ultrasonic testing is also very difficult. The quality of the weld cannot be effectively evaluated. The welded orifice flowmeter is often used on high-temperature and high-pressure power station boiler pipelines or chemical pipelines with flammable, explosive, toxic and harmful media, which poses a great hidden danger.

[0005] 2. When welding the butt welds of the front and rear clamping rings, the orifice plate connected to them actually acts as a pad. The orifice plate is generally made of austenitic stainless steel, and the clamping ring is generally made of carbon steel or heat-resistant steel. Some manufacturing units use carbon steel or heat-resistant steel electrodes for the first layer of the weld, and there is a problem of dissimilar steel welding at the connection between the weld and the pad. Some manufacturing units use stainless steel electrodes for the first layer of welds and carbon steel or heat-resistant steel electrodes for other layers of welds. In both of the above situations, carbon steel or heat-resistant steel materials are welded on austenitic stainless steel materials, which is prone to cracks and other defects but cannot be detected, posing a hidden danger to manufacturing quality.

[0006] 3. There are many mutations in the original front and rear clamping rings and the connection between the clamping ring and the orifice plate, resulting in stress concentration. This structural form does not meet the requirements of special equipment safety technical specifications such as the "Steam Boiler Safety Technical Supervision Regulations".

[0007] 4. When the orifice plate is inserted into the clamping ring to a certain depth, the effective thickness of the clamping ring is reduced. In order to ensure the strength of the clamping ring, the thickness of the clamping ring can only be thickened.

[0008] 5. The orifice plate acts as a pad for the butt weld of the clamping ring, and there is discontinuous welding. For those that have been welded together, cracks and other defects are easily generated due to welding of dissimilar steels. For those that have not been welded together, there is a certain gap between the orifice plate and the clamping ring, which affects the accuracy of the flow meter. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a welded orifice plate flowmeter for taking pressure from an annular chamber (see Figures 4 to 7 ).

[0010] A welded orifice plate flowmeter for taking pressure from an annular chamber, comprising a measuring tube, a front clamping ring, a pressure taking tube, a rear clamping ring and an orifice plate;

[0011] The front clamping ring and the rear clamping ring are connected by welding, a front ring chamber is provided in the front clamping ring, and a rear ring chamber is provided in the rear clamping ring. The orifice plate is installed in the rear clamping ring, avoiding the butt welds of the front and rear clamping rings and maintaining a certain distance from the center of the weld. The butt welds of the front and rear clamping rings can be non-destructively tested. The gap between the orifice plate and the lower edges of the front and rear ring chambers is the annular gap. The back side of the orifice plate (along the flow direction of the medium) is connected to the rear ring chamber through the annular gap and the slots on the orifice plate, and the front side of the orifice plate (along the flow direction of the medium) is connected to the front ring chamber through the annular gap and the slots on the orifice plate. There is a pair of pressure taking pipes, which are respectively arranged on the front clamping ring and the rear clamping ring, and are respectively connected to the annular chambers of the front clamping ring and the rear clamping ring.

[0012] Furthermore, the connection between the orifice plate and the rear clamping ring is connected by an inclined surface, and the slope of the inclined surface at the connection between the orifice plate and the rear clamping ring is not greater than 1:3 (such as Figure 7 shown).

[0013] Furthermore, the two protruding parts at the lower edges of the front and rear annular chambers are connected with two of the eight slots at the front and rear of the orifice plate to position and prevent the orifice plate from rotating in an annular direction (such as Figure 5 Figure 6 shown).

[0014] Furthermore, the four corners of the front and rear annular chambers are rounded.

[0015] Further, the cross-sectional area of ​​the front annular chamber is larger than the cross-sectional area of ​​the rear annular chamber (e.g. Figure 4 shown).

[0016] The beneficial effects of the present invention are as follows:

[0017] After the modification, the orifice plate of the flow meter avoids the butt weld of the front and rear clamping rings. This weld is convenient for both X-ray and ultrasonic testing, so the quality of the weld can be effectively evaluated.

[0018] The modified structure eliminates the problem of structural mutation. For the inconsistent local wall thickness, a slope transition is adopted, and the slope of the slope meets the requirements of the safety technical specifications for special equipment. Compared with the original structure, the local peak stress caused by the structural mutation is greatly reduced, and the safety performance of the flowmeter is improved.

[0019] After the transformation, the orifice plate and the rear clamping ring are connected with a bevel, which reduces the stress. The orifice plate no longer needs to be inserted into the clamping ring, and the thickness of the clamping ring can be greatly reduced, thereby achieving lightweight flowmeter, saving metal materials, and reducing manufacturing costs.

[0020] After the transformation, the original four corners of the front and rear annular chambers were changed from right angles to rounded corners, and the stress concentration problem caused by the structural mutation was solved.

[0021] The clamping ring with an annular gap is used to take pressure, and the annular chamber can play a role in stabilizing the flow field;

[0022] After the transformation, the orifice plate and the clamping ring are connected by an inclined surface, and they are fitted first during installation. During use, due to the pressure on the orifice plate formed by the flow of the medium and the ambient temperature of use being above 400°C, the orifice plate is made of stainless steel, and the measuring tube is made of carbon steel or heat-resistant steel. The expansion coefficient of stainless steel is slightly higher than that of carbon steel or heat-resistant steel. The connection here will be more tight, and pins are no longer required for fixing. Due to the tight connection, the metering accuracy of the flow meter will be further improved.

[0023] The two protruding parts at 0° and 180° on the lower edges of the front and rear annular chambers of the modified flowmeter are connected with the two grooves at 0° and 180° among the eight grooves at the front and rear of the orifice plate, which play a role in positioning and preventing the orifice plate from rotating in an annular direction.

[0024] Before the modification, the cross-sectional areas of the annular chambers before and after the orifice plate were the same. After the modification, although the cross-sectional area of ​​the annular chamber in front of the orifice plate was larger than that behind the orifice plate along the flow direction of the medium, it met the requirements of 5.2.3.6 on the cross-sectional area of ​​the annular chamber in GB / T2624.2-2006 "Measurement of full pipe fluid flow rate by differential pressure device installed in circular cross-section pipes Part 2: Orifice plates"; after the modification, although the structures of the front and rear clamping rings are different, they also meet the requirements of 85.2.3.9 in GB / T2624.2-2006 "Measurement of full pipe fluid flow rate by differential pressure device installed in circular cross-section pipes Part 2: Orifice plates". BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figures 1 to 3 It is a schematic diagram of the structure of an existing flow meter;

[0026] Figures 4 to 7 It is a schematic diagram of the flow meter structure; DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0028] like Figures 4 to 7 As shown, a welded orifice flowmeter for taking pressure from an annular chamber comprises a measuring tube 1, a front clamping ring 2, a pressure taking tube 3, a rear clamping ring 4 and an orifice plate 6;

[0029] The front clamping ring 2 and the rear clamping ring 4 are fixed by welding, a front ring chamber is provided in the front clamping ring 2, and a rear ring chamber is provided in the rear clamping ring 4, wherein the rear clamping ring 4 is provided with an inclined surface for fixing the orifice plate 6, and the two are connected by an inclined surface with a slope of no more than 1:3. An annular gap is provided between the orifice plate and the lower edges of the front and rear annular chambers (where f is the thickness of the annular gap and also the thickness of the lower edges of the front and rear annular chambers, and a is the width of the annular gap). The two protruding parts of the lower edges of the front and rear annular chambers at 0° and 180° (the length is b+a, and the width is e) are connected with the two grooves at 0° and 180° (the depth is b, and the width is e) in the eight grooves of the front and rear of the orifice plate. The cross-sectional area gh1 (g is the length of the front and rear annular chambers, and h1 is the height of the front annular chamber) of the front clamping ring 2 is greater than the cross-sectional area gh (h is the height of the rear annular chamber) of the annular chamber of the rear clamping ring 4;

[0030] Furthermore, both ends of the front and rear clamping rings are connected to the measuring tube 1, and both ends of the measuring tube 1 are connected to the process pipe fittings 5, wherein the front and rear clamping rings are machined from forgings;

[0031] Furthermore, the original four corners of the front and rear annular chambers were changed from right angles to rounded corners;

[0032] Furthermore, the front and rear clamping rings are provided with pressure-taking ports with a diameter of j, and the pressure-taking pipe 3 is fixed thereon by welding;

[0033] Furthermore, the orifice plate is made of austenitic stainless steel, which can maintain cleanliness and will not oxidize at high temperatures, ensuring the size of the orifice plate as a standard metering element and the accuracy of the flow meter. The front and rear clamping rings and the measuring tube are made of carbon steel or heat-resistant steel, which can withstand high temperature and high pressure.

[0034] Figures 1 to 3 This is a schematic diagram of the existing flow meter structure.

Claims

1. A welded orifice flowmeter for taking pressure from an annular chamber, characterized in that: It includes a measuring tube, a front clamping ring, a pressure taking tube, a rear clamping ring and an orifice plate; The front clamping ring and the rear clamping ring are connected by welding, a front ring chamber is provided in the front clamping ring, a rear ring chamber is provided in the rear clamping ring, the orifice plate is installed in the rear clamping ring, avoiding the butt welds of the front and rear clamping rings and keeping a certain distance from the center of the weld, the butt welds of the front and rear clamping rings can be non-destructively tested, the gap between the orifice plate and the lower edges of the front and rear ring chambers is the annular gap, the back of the orifice plate is connected to the rear ring chamber through the annular gap and the slots on the orifice plate, the front of the orifice plate is connected to the front ring chamber through the annular gap and the slots on the orifice plate, there is a pair of pressure taking pipes, which are respectively provided on the front clamping ring and the rear clamping ring, and are respectively connected to the annular chambers of the front clamping ring and the rear clamping ring; The connection between the orifice plate and the rear clamping ring is connected by an inclined surface, and the slope of the inclined surface at the connection between the orifice plate and the rear clamping ring is not greater than 1:

3.

2. A welded orifice flowmeter for taking pressure from an annular chamber according to claim 1, characterized in that: Furthermore, two protruding parts on the lower edges of the front and rear annular chambers are matched and connected with two of the eight front and rear slots of the orifice plate to position and prevent the orifice plate from rotating in an annular direction.

3. A welded orifice flowmeter for taking pressure from an annular chamber according to claim 2, characterized in that: Furthermore, the four corners of the front and rear annular chambers are rounded.

4. A welded orifice flowmeter for taking pressure from an annular chamber according to claim 3, characterized in that: Furthermore, the cross-sectional area of ​​the front annular chamber is greater than the cross-sectional area of ​​the rear annular chamber.

5. A welded orifice flowmeter for taking pressure from an annular chamber according to claim 4, characterized in that: Furthermore, the orifice plate is made of austenitic stainless steel.

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