Safety valve on-line verification device

Abstract

The utility model relates to an on-line verification device for a safety valve, and belongs to the technical field of valve verification devices. The diaphragm type pressure cylinder comprises a supporting frame, a diaphragm type pressure cylinder, a connecting screw rod, a connecting screw sleeve, a gland and a nut, the supporting frame comprises a lower supporting ring, an upper supporting plate and a supporting column, the upper supporting plate is provided with a first screw rod via hole, the upper end of the connecting screw sleeve is rotationally connected with the lower end of the connecting screw rod, and the axis of the diaphragm type pressure cylinder is vertically arranged. The ends, provided with piston column feet, of the diaphragm type pressure cylinders are placed on the upper surface of the upper supporting plate, a second screw through hole allowing the upper end of the connecting screw to penetrate through is formed in the middle of the gland, the upper end of the connecting screw penetrates through the second screw through hole and then is in threaded connection with the nut, and the multiple diaphragm type pressure cylinders are evenly arranged around the connecting screw at intervals. And pressure heads in one-to-one correspondence with cylinder covers of the diaphragm type pressure cylinders are arranged on the periphery of the gland. According to the utility model, the existing equipment and data are fully utilized, the development cost is reduced, and the development and improvement period is shortened.

Description

Technical Field

[0001] This utility model relates to an online calibration device for safety valves, belonging to the technical field of valve calibration devices. Background Technology

[0002] Safety valves are currently calibrated in two ways: offline calibration and online calibration. Offline calibration involves disassembling the safety valve and calibrating it on a test bench. Online calibration, on the other hand, does not require disassembly. Instead, an online calibrator's lifting device applies external force to the valve stem to assist in opening the safety valve. Then, based on parameters such as the applied lifting force, the pressure of the medium, and the area of ​​the valve disc subjected to the force of the medium, calculations are performed to determine the actual opening pressure of the safety valve.

[0003] The specific calculation principle is as follows: When the upward lifting force applied by the lifting device + the upward force of the medium on the valve disc equals the downward pressing force of the spring on the valve disc, the valve begins to open, that is: Fs = F + P × S. Fs: The downward pressing force of the spring on the valve disc; F: The upward lifting force of the lifting device; P: The pressure of the medium inside the safety valve (commonly referred to as pressure in the industry, but essentially as pressure intensity); S: The area of ​​the valve disc subjected to the force of the medium; Pt: The opening pressure of the safety valve. The formula for calculating the opening pressure of the safety valve is: Pt = Fs / S.

[0004] There are currently two main types of lifting devices for online verification equipment:

[0005] The first method uses a piston-type pressure cylinder with a force sensor for lifting. Because this type of cylinder has high and unstable resistance and friction, a force sensor is necessary to accurately obtain the auxiliary lifting force applied to the valve stem. It also requires electrical computer equipment for receiving, converting, and calculating the force. The advantage of this method is that the lifting force can be very large, but the disadvantages are its complex structure, high probability of failure, and high cost.

[0006] The second method uses a diaphragm-type pressure cylinder to apply the lifting force. Because the frictional resistance of the diaphragm-type pressure cylinder is very small and stable, the pressure of the medium entering the cylinder can be directly read from the pressure gauge, and the lifting force applied to the safety valve can be calculated by combining this with the force-bearing area of ​​the diaphragm piston. Then, the opening pressure of the safety valve can be calculated by combining this with the safety valve parameters. Of course, in practical applications, for greater accuracy, we don't rely solely on this theoretical calculation. We also need to conduct experimental tests and correct the data for various types of safety valves, so that the device has a precise corresponding coefficient for each type of safety valve. This coefficient is a precise value obtained through theory and experimentation, and it has already corrected for various influencing factors as much as possible. In actual use, we only need to substitute this coefficient with the pressure gauge reading for a simple calculation to obtain the accurate opening pressure value of the safety valve. Each valve corresponds to a coefficient. The advantage of this method is that the equipment structure is simple and reliable, and the price is low. The disadvantage is that the lifting force is relatively small because, with current technology, the diaphragm cannot withstand excessive pressure, otherwise it will rupture.

[0007] The principle by which a diaphragm pressure cylinder is used to lift a safety valve is as follows:

[0008] Pressure cylinders are divided into pneumatic and hydraulic types. Since most are hydraulic and operate on the same principle, they will be analyzed as diaphragm-type hydraulic cylinders. Figures 1 to 3 As shown, when a hand-cranked hydraulic pump injects pressurized oil into the diaphragm chamber of the diaphragm hydraulic cylinder through a hydraulic pipe, the piston body will push downwards, and the piston rod feet will follow suit. At the same time, the cylinder body and cylinder head will be pushed upwards in the opposite direction, which will then drive the connecting screw and connecting sleeve to pull upwards. If the connecting sleeve is connected to the valve stem of the safety valve through the valve stem connector, it will apply an upward auxiliary opening lifting force to the safety valve.

[0009] In recent years, as the operating pressure of pressure vessels such as industrial boilers has gradually increased, the opening pressure of corresponding safety valves has also increased. Sometimes, older diaphragm hydraulic cylinders are no longer sufficient for current tasks due to insufficient lifting force. There are only two conventional ways to increase the lifting force. The first is to increase the pressure of the hydraulic medium injected into the cylinder. This method is currently not feasible due to diaphragm technology limitations and will only be possible once high-pressure, lightweight diaphragms with sufficiently high pressure resistance are available on the market. The second method is to increase the hydraulic force-bearing area of ​​the diaphragm and piston. This method is feasible but also very complicated, requiring the development of larger diaphragms and the overall design and manufacture of larger diaphragm hydraulic cylinders. Furthermore, for accuracy, all safety valves must be re-tested and new coefficient sets obtained, resulting in a significant workload. Additionally, excessively large cylinders have large errors when used to calibrate smaller safety valves and are inconvenient to install on smaller valves. Utility Model Content

[0010] The technical problem to be solved by this utility model is to provide an online calibration device for safety valves that is easy to implement and can multiply the lifting force.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: an online safety valve calibration device, including a support frame, a diaphragm pressure cylinder, a connecting screw, and a connecting sleeve. The support frame includes a lower support ring, an upper support plate, and a support column. The upper end of the support column is fixedly connected to the upper support plate, and the lower end of the support column is fixedly connected to the lower support ring. The lower support ring and the upper support plate are both horizontally arranged. A first screw through hole is provided in the middle of the upper support plate for the upper end of the connecting screw to pass through. The lower end face of the connecting sleeve has an internal thread hole coaxial with it. The upper end of the connecting sleeve and the lower end of the connecting screw form a rotational connection. The rotation axis between the two is collinear with the axis of the connecting screw and the axis of the connecting sleeve. The axis of the diaphragm pressure cylinder is vertically arranged. The end of the diaphragm pressure cylinder with the piston pin is placed on the upper surface of the upper support plate. The online calibration device for the safety valve also includes a gland and a nut. The middle of the gland has a second screw through hole for the upper end of the connecting screw to pass through. After the upper end of the connecting screw passes through the second screw through hole, it is threadedly connected to the nut. The diaphragm pressure cylinder is configured as multiple pieces evenly spaced around the connecting screw. The outer periphery of the gland has pressure heads that correspond one-to-one with the cylinder heads of the diaphragm pressure cylinder.

[0012] A further preferred embodiment is that the cylinder head of the diaphragm pressure cylinder has a raised screw end at the center of the upper surface, and the lower surface of the pressure head has a positioning clearance groove that matches the screw end.

[0013] A further preferred option is to have two or three diaphragm pressure cylinders.

[0014] A further preferred embodiment is that multiple support columns are evenly spaced around the lower support ring in the circumference, and all support columns are set vertically.

[0015] The beneficial effects of this utility model are as follows: In specific implementation, the lower support ring is placed flat on the testing platform of the safety valve under test in a conventional manner, and the connecting sleeve is threadedly connected to the valve stem connector. This utility model can gather the upward thrust generated by multiple diaphragm pressure cylinders (usually two or three), and then transmit it to the safety valve stem through the intermediate connecting screw, connecting sleeve, and valve stem connector. During the verification process, we only need to multiply the original coefficient by two or three times (corresponding to two or three diaphragm pressure cylinders), and other operations remain unchanged. The influence of the weight of the gland, nut, connecting screw, and diaphragm hydraulic cylinder itself can be ignored, because the weight is several kilograms, while the lifting force is several tons, and the influence error is only within one-thousandth, with an allowable error requirement of one percent or more. This utility model makes full use of existing equipment and data, reduces development costs, and shortens the development and improvement cycle. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a diaphragm-type hydraulic cylinder in the prior art.

[0017] Figure 2 yes Figure 1 A schematic diagram of the AA cross-section.

[0018] Figure 3 This is a schematic diagram of the structure of a safety valve for online detection using existing technology.

[0019] Figure 4 This is a schematic diagram of the structure of an online detection safety valve according to Embodiment 1 of this utility model.

[0020] Figure 5 yes Figure 4 The front view of the embodiment shown.

[0021] Figure 6 yes Figure 4 A schematic diagram of the gland structure of the embodiment shown.

[0022] Figure 7 This is a schematic diagram of the structure of a safety valve applied to online detection according to Embodiment 2 of this utility model.

[0023] Figure 8 yes Figure 7 The front view of the embodiment shown.

[0024] Figure 9 yes Figure 7 A schematic diagram of the gland structure of the embodiment shown.

[0025] Component markings in the diagram: support frame 10, lower support ring 11, upper support plate 12, support column 13, diaphragm pressure cylinder 20, piston pin 21, cylinder head 22, screw end 23, hydraulic pump 24, pressure gauge 25, hydraulic pipe 26, cylinder body 27, diaphragm chamber 28, diaphragm 29, piston body 210, piston body guide sleeve 211, fixing bolt 212, connecting screw 30, connecting screw sleeve 40, pressure cap 50, pressure head 51, positioning clearance groove 52, nut 60, valve stem connector 71, safety valve stem 72. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] like Figures 4 to 9As shown, this utility model includes a support frame 10, a diaphragm pressure cylinder 20, a connecting screw 30, and a connecting sleeve 40. The support frame 10 includes a lower support ring 11, an upper support plate 12, and a support column 13. The upper end of the support column 13 is fixedly connected to the upper support plate 12, and the lower end of the support column 13 is fixedly connected to the lower support ring 11. The lower support ring 11 and the upper support plate 12 are both horizontally arranged. The middle part of the upper support plate 12 is provided with a first screw through hole for the upper end of the connecting screw 30 to pass through. The lower end face of the connecting sleeve 40 has an internal thread hole coaxial with it. The upper end of the connecting sleeve 40 and the lower end of the connecting screw 30 are rotatably connected, and the axis of rotation between the two is the same. The axis of the diaphragm pressure cylinder 20 is vertically aligned with the axis of the connecting screw 30 and the axis of the connecting sleeve 40. The end of the diaphragm pressure cylinder 20 with the piston pin 21 rests on the upper surface of the upper support plate 12. The online calibration device for the safety valve also includes a pressure cap 50 and a nut 60. The pressure cap 50 has a second screw through-hole in its center for the upper end of the connecting screw 30 to pass through. After the upper end of the connecting screw 30 passes through the second screw through-hole, it is threadedly connected to the nut 60. The diaphragm pressure cylinder 20 is configured as multiple components evenly spaced around the connecting screw 30. The outer periphery of the pressure cap 50 has pressure heads 51 corresponding to the cylinder heads 22 of the diaphragm pressure cylinder 20. The diaphragm pressure cylinder 20 can be a diaphragm pneumatic cylinder or a diaphragm hydraulic cylinder, generally a diaphragm hydraulic cylinder. Both diaphragm pneumatic cylinders and diaphragm hydraulic cylinders are existing complete sets of equipment. This utility model preferably uses a diaphragm hydraulic cylinder, the specific structure of which can be found in [reference needed]. Figure 1 and Figure 2 The number of diaphragm pressure cylinders 20 is generally preferably two or three. In specific implementation, it is sufficient to ensure that the multiple diaphragm pressure cylinders 20 operate synchronously and have equal output force, which is common knowledge in the field. For example, this utility model preferably uses diaphragm hydraulic cylinders, which only require the corresponding hydraulic pipes to be connected in parallel. This utility model can gather the upward thrust generated by multiple diaphragm pressure cylinders 20 (usually two or three), and then transmit it to the safety valve stem 72 through the intermediate connecting screw 30, connecting sleeve 40, and valve stem connector 71. During the verification process, we only need to multiply the original coefficient by two or three times (corresponding to two or three diaphragm pressure cylinders 20).

[0028] To ensure a simple and reliable structure, the cylinder head 22 of the diaphragm pressure cylinder 20 typically has a protruding screw end 23 at its center on the upper surface, and the lower surface of the pressure head 51 is correspondingly provided with a positioning clearance groove 52 that matches the screw end 23. The positioning clearance groove 52 only needs to be able to avoid the screw end 23, and a circular groove can generally be used. Of course, for more accurate positioning, a regular hexagonal groove can also be used.

[0029] To ensure a simple and reliable structure, multiple support columns 13 are arranged at even intervals around the lower support ring 11, and all support columns 13 are vertically positioned.

Claims

1. A safety valve online calibration device, comprising a support frame (10), a diaphragm pressure cylinder (20), a connecting screw (30), and a connecting sleeve (40). The support frame (10) includes a lower support ring (11), an upper support plate (12), and a support column (13). The upper end of the support column (13) is fixedly connected to the upper support plate (12), and the lower end of the support column (13) is fixedly connected to the lower support ring (11). The lower support ring (11) and the upper support plate (12) are both arranged horizontally. A connection point is provided in the middle of the upper support plate (12). The upper end of the connecting screw (30) passes through the first screw through hole, and the lower end face of the connecting screw sleeve (40) has an internal thread hole coaxial with it. The upper end of the connecting screw sleeve (40) and the lower end of the connecting screw (30) form a rotatable connection, and the axis of rotation between the two is collinear with the axis of the connecting screw (30) and the axis of the connecting screw sleeve (40). The axis of the diaphragm pressure cylinder (20) is vertically arranged, and the end of the diaphragm pressure cylinder (20) with the piston pin (21) is placed on the upper surface of the upper support plate (12). The characteristic is that: It also includes a pressure cap (50) and a nut (60). The pressure cap (50) has a second screw through hole in the middle for the upper end of the connecting screw (30) to pass through. After the upper end of the connecting screw (30) passes through the second screw through hole, it is threadedly connected to the nut (60). The diaphragm pressure cylinder (20) is configured as multiple pieces evenly spaced around the connecting screw (30). The outer periphery of the pressure cap (50) has a pressure head (51) that corresponds one-to-one with the cylinder cover (22) of the diaphragm pressure cylinder (20).

2. The safety valve online calibration device as described in claim 1, characterized in that: The cylinder head (22) of the diaphragm pressure cylinder (20) has a raised screw end (23) at the center of the upper surface, and the lower surface of the pressure head (51) has a positioning clearance groove (52) that matches the screw end (23).

3. The safety valve online calibration device as described in claim 1, characterized in that: The number of diaphragm pressure cylinders (20) is two or three.

4. The safety valve online calibration device as described in any one of claims 1 to 3, characterized in that: Multiple support columns (13) are evenly spaced around the lower support ring (11) in the circumference, and all support columns (13) are set vertically.

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