JP7536239B2 - Safety valve test equipment - Google Patents

Description

This invention relates to a safety valve testing device that measures the operating pressure of a safety valve.

Safety valves are installed in equipment such as pressure vessels used in all industries that handle pressurized fluids, and protect the equipment from destruction if the pressure in the equipment increases abnormally. When the pressure inside the equipment increases abnormally and reaches a predetermined pressure, the safety valve opens to release steam, gas, or other fluids from the equipment, and closes again when the pressure drops to a specified value. There is safety valve testing equipment that tests whether the valve body of such safety valves opens at a predetermined pressure.

For example, the safety valve testing method and safety valve testing device of Patent Document 1 are provided with a hydraulic cylinder that lifts the valve body of the safety valve, a measuring means that measures the valve inlet pressure, the internal pressure of the hydraulic cylinder, and the lift amount before and after the hydraulic cylinder lifts the valve body of the safety valve, respectively, and a calculation means that calculates the characteristics of the safety valve from the relationship between the lifting force of the safety valve operating width and the spring force from the values measured by the measuring means. The calculation results by the calculation means can be compared with the demonstration test results of a model valve to obtain the operation test results of the safety valve.

The safety valve operating pressure measuring device disclosed in Patent Document 2 has a hydraulic jack connected to the valve stem of the safety valve via a load cell. The hydraulic jack is driven by a hydraulic pump, and the signal from the load cell is displayed as a load-time graph on the display of an analyzing recorder. After the valve stem is lifted by the hydraulic jack, the hydraulic pump is relieved. The load applied to the load cell gradually decreases, and the rate of decrease in the load changes after the seat surface closes again. The operating pressure of the safety valve is calculated from the load at this inflection point.

JP 2001-165812 A Japanese Patent Application Publication No. 5-87261

In the case of the above background technology, a hydraulic jack and a hydraulic pump for it are required as a means of applying the load, making the equipment large and expensive. In addition, when loading hydraulically, there is also the problem that it is difficult to apply the load delicately. To measure the load, an expensive load cell is required, and a dedicated sensor must be made by attaching a strain gauge to the test spring and an amplifier for strain is required. In this respect, the equipment is large and complicated, and inconvenient to carry, making it difficult to test the operating pressure of safety valves attached to various devices on site.

This invention was made in consideration of the problems in the background art described above, and aims to provide a safety valve testing device that is simple in structure and easy to operate, and that measures the operating pressure of a safety valve.

The present invention is a safety valve testing device attached to a safety valve in which a valve body attached to a valve stem is biased closed by a safety valve spring and is activated to open when a pressure equal to or greater than a predetermined value is applied to the valve body in a direction opposite to the biasing direction of the safety valve spring, the valve stem is provided so as to protrude outward from the upper surface of the safety valve, a tension bolt is provided at the end of the valve stem protruding from the upper surface of the safety valve and is connected with the same axial direction, the tension bolt is provided with a pair of plates that are plate materials having insertion holes through which the tension bolt is inserted and that are movably attached to the tension bolt so as to intersect with the tension bolt, and a tension bolt is provided between the pair of plates and whose extension direction is the axial direction of the tension bolt. A load spring that is approximately parallel to the direction of the valve and a load nut that is screwed to the end of the tension bolt opposite the end to which the valve stem is attached and located on the outside of the plate are provided. By tightening the load nut, the distance between the pair of plates narrows, compressing the load spring. A force in the opposite direction to the biasing direction of the safety valve spring is applied to the valve stem of the safety valve by the load spring through the tension bolt, the valve body of the safety valve opens against the force of the safety valve spring, and the force of the load spring at the operating point when the valve body is opened is converted into pressure to measure the safety valve operating pressure of the safety valve.

The load nut is manually tightened, and the load spring is manually measured in length. During measurement, the load nut is manually tightened to manually measure the length of the load spring at the operating point when the valve body of the safety valve opens against the force of the safety valve spring. The force of the load spring is calculated from the spring constant of the load spring based on the amount of displacement between the length of the load spring before compression before tightening the load nut and the length of the load spring at the operating point. The force of the load spring at the operating point is converted into pressure, making it possible to measure the safety valve operating pressure of the safety valve.

The tension bolt has a thrust bearing between the load nut and the plate.

The safety valve testing device of the present invention has a simple structure and can measure the operating pressure of a safety valve with simple operations. Since the nut is tightened manually and the length of the load spring compressed by tightening the nut is measured manually, no large-scale equipment is required, and the device is lightweight and easy to carry. Since a load spring is used, it is inexpensive, and by replacing the load spring with one of a different strength, safety valves of various strengths can be measured.

FIG. 1 is a front view of a safety valve testing device according to an embodiment of the present invention and a vertical sectional view of a safety valve. FIG. 2 is a front view of the safety valve testing device of this embodiment. FIG. 2 is a perspective view showing a state in which the safety valve testing device of this embodiment is used.

The following describes an embodiment of the present invention with reference to the drawings. Figures 1 and 2 show one embodiment of the present invention, with Figure 1 showing a safety valve testing device 10 attached to a spring-loaded safety valve 101.

Here, the safety valve 101 will be described. The valve seat 102 of the safety valve 101 has an inlet 103 and an outlet 104. An apparatus such as a pressure vessel is connected to the inlet 103 via a gate valve (not shown) and is applied with a base pressure Pb during operation of the apparatus. The outlet 104 releases fluids such as steam and gas when the pressure applied to the inlet 103 becomes abnormally high beyond the base pressure Pb. A valve rod 107 is provided in a valve housing tube 105 attached to the valve seat 102 via a safety valve spring 106, and a valve body 108 is attached to the end of the valve rod 107 located within the valve seat 102. The valve body 108 is pressed with a predetermined force against a seat surface 109 between the inlet 103 and the outlet 104 of the valve seat 102 by the force of the safety valve spring 106, closing the inlet 103 and the outlet 104 and maintaining the base pressure Pb applied to the inlet 103.

The strength of the safety valve spring 106 is appropriately set by an adjustment screw 110 interposed between the valve housing tube 105 and the safety valve spring 106. When the pressure applied to the valve body 108 from the inlet 103 of this safety valve 101 exceeds the base pressure Pb by a certain value or more, the valve body 108 lifts and opens from the seat surface 109, allowing the fluid to escape from the outlet 104 and protecting the device from destruction. When the pressure at the inlet 103 drops to a predetermined value, the force of the safety valve spring 106 again closes the valve body 108 to the seat surface 109.

A valve stem 107 protrudes upward from the upper surface 105a of the valve housing cylinder 105 of the safety valve 101, and a lever (not shown) is attached to lift the valve stem 107 when necessary. A cap (not shown) that covers the valve stem 107 and the base end of the lever is attached to the upper surface 105a of the valve housing cylinder 105, and the tip of the lever protrudes from a hole provided in the cap. When measuring the operating pressure of the safety valve 101, the safety valve testing device 10 of this embodiment is attached to the upper surface 105a of the valve housing cylinder 105 with the lever and cap removed from the safety valve 101.

Next, the safety valve test device 10 will be described. The safety valve test device 10 is formed by assembling multiple components made of metals such as iron and aluminum. Aluminum is lighter and more suitable than iron. The safety valve test device 10 has a cylindrical leg 12 that contacts the upper surface 105a of the valve housing tube 105 of the safety valve 101, and a circular opening 13 is provided on the side of the cylindrical leg 12 for attaching it to the upper surface 105a of the valve housing tube 105. A bridge lower plate 14, which is a square plate material larger than the outer diameter of the cylindrical leg 12, is attached to one end of the cylindrical leg 12 in the insertion direction with a bolt or the like, closing the opening of the cylindrical leg 12.

Screw holes 16 are formed slightly inside the four corners of the bridge lower plate 14, and a pair of bridge side plates 18, which are rectangular plates, are attached to the screw holes 16 with bolts. The pair of bridge side plates 18 have the same shape, and screw holes 16 that communicate with the screw holes 16 in the bridge lower plate 14 are provided on the sides that intersect in the thickness direction. The pair of bridge side plates 18 are positioned at right angles to the bridge lower plate 14, and are fixed with bolts (not shown) by aligning the screw holes 16 in the bridge side plates 18 with the screw holes 16 in the bridge lower plate 14. The pair of bridge side plates 18 are attached to a pair of side edges of the bridge lower plate 14, and the pair of bridge side plates 18 face each other parallel to each other.

A bridge upper plate 20 of the same shape as the bridge lower plate 14 is attached to the top of the pair of bridge side plates 18. Screw holes 16 are formed slightly inside the four corners of the bridge upper plate 20, and are fixed with bolts (not shown) in line with the screw holes 16 of the bridge side plates 18. Screw holes 16 for guides 22 (described below) are provided near the middle of the four sides of the bridge upper plate 20. Four guides 22, which are rod members, are inserted into the screw holes 16 and screwed to the top of the bridge upper plate 20. One end of each guide 22 is formed with a male screw that screws into the screw hole 16 of the bridge upper plate 20, and the opposite end is not formed with a male screw.

A load plate 24 of the same shape as the bridge upper plate 20 is attached on top of the guide 22. Near the middle of the four sides of the load plate 24, through-holes 25 through which the guide 22 can be inserted are formed through the thickness. By inserting the guide 22 into the through-hole 25, the load plate 24 is positioned horizontally and can be moved up and down.

A through hole 26 is formed at the center of each of the bridge lower plate 14, bridge upper plate 20, and load plate 24, penetrating the thickness, and the three through holes 26 are aligned horizontally and spaced a predetermined distance apart vertically. A tension bolt 28 having approximately the same diameter as the valve stem 107 is inserted through the upper two of the three through holes 26, passing through the load plate 24 and bridge upper plate 20, and reaches between the bridge lower plate 14 and bridge upper plate 20, and a long nut 30 is attached to the end 28a that reaches between the bridge lower plate 14 and bridge upper plate 20. When the safety valve test device 10 is attached to the safety valve 101, the valve stem 107 of the safety valve 101 is inserted through the lower one of the three insertion holes 26, passing through the bridge lower plate 14 and reaching between the bridge lower plate 14 and the bridge upper plate 20, and the end 107a that reaches between the bridge lower plate 14 and the bridge upper plate 20 is coaxially connected to the end 28a of the tension bolt 28 by the long nut 30.

Between the bridge upper plate 20 and the load plate 24, there is provided a load spring 32, which is a coil spring with a known spring constant. The lower end of the load spring 32 abuts against the upper surface 20a of the bridge upper plate 20, and the upper end abuts against the lower surface 24a of the load plate 24, and the direction of expansion and contraction of the load spring 32 is the direction in which the bridge upper plate 20 and the load plate 24 are separated from each other. On the lower surface 24a of the load plate 24, there is provided a cylindrical spring center 34 coaxially with the insertion hole 26 outside the insertion hole 26, which is inserted inside the load spring 32 and limits the horizontal movement of the load spring 32.

On the upper surface 24b of the load plate 24, a tension bolt 28 is inserted through the insertion hole 26 so that the end opposite the end 28a protrudes, and a bearing center 38 is attached to the tension bolt 28 via a washer 36, and a thrust bearing 39 is provided along the circumference of the bearing center 38. Two more washers 36 are attached to the thrust bearing 39, and a load nut 40 is screwed and attached to the washer 36.

By rotating and tightening the load nut 40, the load plate 24 moves to a different position on the tension bolt 28, compressing the load spring 32. By compressing the load spring 32, a force can be applied in the lifting direction to the valve stem 107 connected to the tension bolt 28. A lever (not shown) is fixed to the end of the load nut 40 of the tension bolt 28 that protrudes upward to prevent co-rotation.

Next, we will explain how to use the safety valve testing device 10 of this embodiment. Here, the operating pressure is measured on-site with the safety valve 101 attached to a device such as a pressure vessel (not shown).

First, the gate valve (not shown) on the inlet 103 side of the safety valve 101 is closed. Next, the lever and cap (not shown) of the safety valve 101 are removed, and the safety valve test device 10 is attached as shown in FIG. 1. The cylindrical leg 12 is placed on the upper surface 105a of the valve housing tube 105 of the safety valve 101 and fixed with a bolt (not shown). The valve stem 107 is inserted inside the cylindrical leg 12 and further inserted into the insertion hole 26 of the bridge lower plate 14, protruding into the space between the bridge lower plate 14 and the bridge upper plate 20. The end 107a of the valve stem 107 is connected to the end 28a of the tension bolt 28 with a long nut 30. Once the setting is complete, the gate valve is opened, base pressure Pb is applied, and the test is started.

First, manually tighten the load nut 40, stopping when it is lightly tightened by hand. At this time, the load spring 32 is not compressed and no force is applied to lift the valve stem 107. The force of the load spring 32 is 0, and at this point before compression, the length l1 of the load spring 32 is measured with a digital caliper 44. For example, as shown in Figure 3, the length between the lower surface 24a of the load plate 24 and the upper surface 20a of the bridge upper plate 20 is measured. On the upper surface 24b of the load plate 24, four marks 42 consisting of the letters "A" to "D" are marked near the center of each side, and the measurement positions may be indicated.

Next, the load nut 40 is tightened with an adjustable wrench or similar. At this time, a lever (not shown) for preventing co-rotation is held to prevent the tension bolt 28 from rotating together with the load nut 40. As the load nut 40 is tightened, a downward force is applied to the load plate 24, and since the guide 22 is simply inserted slidably into the through hole 25, the load plate 24 easily descends and approaches the bridge upper plate 20. The load nut 40 is tightened by rotating it via the thrust bearing 39, so it can be rotated with a small torque.

The load plate 24 approaches the bridge upper plate 20, the load spring 32 is compressed, and a force is gradually applied in the lift direction to the tension bolt 28 and the valve rod 107 connected to the tension bolt 28. When the force in the lift direction of the valve rod 107 increases, the valve rod 107 lifts against the safety valve spring 106 of the safety valve 101, the valve body 108 opens from the seat surface 109, the fluid flows to the outlet 104, and the sound of air leakage is confirmed. This position is set as the operating point, and the length l2 of the load spring 32 at the operating point is measured with a digital caliper 44. The displacement amount D of the load spring 32 is obtained by subtracting the length l2 of the load spring 32 at the operating point from the length l1 of the load spring 32 before compression, and the displacement amount D of the load spring 32 is multiplied by the spring constant F to calculate the load value, and this load value is divided by the cross-sectional area of the inlet 103 to convert it to pressure e. The base pressure Pb plus pressure e is the safety valve operating pressure P of this safety valve 101. Then, it is determined whether the safety valve operating pressure P of the safety valve testing device 10 is normal. Adjustments are made if necessary.

The formula for calculating the safety valve operating pressure P is as follows.
P = Pb + e
e=(F×D)/A=(F×D)/{(a/2) ² ×π}
Therefore, P = Pb + [(F × D) / {(a / 2) ² × π}]
P: Safety valve operating pressure Mpa
Pb: base pressure Mpa
F: Spring constant kN/mm
D: Spring displacement (mm)
a: Pipe diameter of inlet 103 cm
A: Valve area ^cm2
e: Converted pressure Mpa

Note that here, the measurement is performed with the safety valve 101 connected to the device and base pressure Pb applied, but it can also be performed without being connected to the device. When the safety valve 101 is removed from the equipment for testing or when it is shipped from the factory, a pressure equivalent to the base pressure Pb is applied to the inlet 103 of the safety valve 101 using a compressor or the like. In this case, a companion flange and a pressure port are required at the inlet 103. Also, a large torque is required to rotate the load nut 40, but a thrust bearing is used to make this rotation smooth. This allows the load nut 40 to be easily tightened manually.

The lengths l1 and l2 of the load spring 32 may be measured with a micrometer other than the digital caliper 44. A rotary encoder may also be attached to the load nut 40 to convert the number of pulses into the displacement D of the load spring 32. Although the method of measuring the length with the digital caliper 44 or a micrometer is the simplest method, a sensor that can accurately measure the displacement may be used instead, and the use of a sensor makes it possible to perform automatic measurement. In the case of automatic measurement, a pressure transducer may be used to measure the base pressure Pb, a servo motor connected to a reducer may be used to rotate the load nut 40, and a mechanism combining a rotary encoder and a ball screw may be connected to the rotation of the servo motor. This allows the displacement D of the load spring 32 to be converted from the rotation pulse of the rotary encoder without the need for a displacement sensor. In addition, a servo motor requires a power source for operation, but by using a battery-powered electric drill as a substitute, loading can be easily performed even at a site without a power source. The load spring 32 may be something other than a spring, and may be a ball screw. By using a ball screw, a thrust bearing is not required, and the valve body 108 of the safety valve 101 can be pulled up more smoothly.

The spring constant F can be accurately measured using a standard spring calibration tester, and a calibration certificate and traceability certificate can be obtained. In addition, the safety valve operating pressure P can be easily calculated by inputting the measured lengths l1 and l2 of the load spring 32 and the base pressure Pb using a spreadsheet software or the like. By bringing a mobile terminal with a spreadsheet software to the site where the measurement is to be performed, the safety valve operating pressure P can be easily calculated on the spot.

Here, the actual test of the safety valve test device 10 will be described. As shown in FIG. 3, marks 42 consisting of alphabets "A" to "D" were marked on the upper surface 24b of the load plate 24 of the safety valve test device 10 near the center of each side, and the length of the load spring 32 was measured near the marks 42 of alphabets "A", "B", "C", and "D" with a digital caliper 44. The length l1 of the load spring 32 before compression and the length l2 of the load spring 32 at the operating point were measured, and the average of the four lengths "A", "B", "C", and "D" was calculated and listed in the following table. The length l2 of the load spring 32 at the operating point was measured for two types of base pressures Pb: 0.6 MPa and 1.0 MPa. The measurement results are shown in Table 1.

From Table 1, subtract the average length of the operating point at Pb 0.6 MPa, 78.45 mm, from the average length of the load spring 32 before compression, 87.99 mm, to obtain the spring displacement D of 9.54 mm at Pb 0.6 MPa. Enter the spring displacement D of 9.54 mm into the above formula to obtain the safety valve operating pressure P. Then, determine whether the safety valve operating pressure P of the safety valve 101 is normal at Pb 0.6 MPa. Similarly, subtract the average length of the operating point at Pb 1.0 MPa, 81.43 mm, from the average length of the load spring 32 before compression, 87.99 mm, to obtain the spring displacement D of 6.56 mm at Pb 1.0 MPa. Enter the spring displacement D of 6.56 mm into the above formula to obtain the safety valve operating pressure P. Determine whether the safety valve operating pressure P of the safety valve 101 is normal when Pb is 1.0 MPa. Note that the same test method can be used to measure Pb at values other than 0.6 MPa and 1.0 MPa.

According to the safety valve test device 10 of this embodiment, the safety valve operating pressure of the safety valve 101 can be obtained and the operating pressure can be tested with a simple structure and simple operation. The load nut 40 is manually tightened, and the length of the load spring 32 compressed by tightening the load nut 40 is manually measured with a digital caliper 44 or the like, so the operation is easy, manual fine adjustments can be made, and it is accurate. No large-scale device is required, and no power source or various devices are required, so it is lightweight and easy to carry. Since the load spring 32, which is a spring, is used, it is inexpensive, lightweight, and easy to carry. By replacing the load spring 32 with one of different strength, it is possible to measure safety valves 101 of various strengths. It can be used not only for testing the safety valve 101 connected to a device such as a pressure vessel and in operation, but also for testing the safety valve 101 removed from the device by using a compressor.

The safety valve testing device of this invention is not limited to the above embodiment, and the structure and shape of each component can be freely changed. The length of the load spring can be measured by a method other than micro calipers, and the force can be measured by a method other than calculation from the displacement of the load spring. For example, it can be measured by a load cell. However, load cells are expensive, and require a jack, amplifier, and display, making the device complex and expensive. In contrast, the method of calculation from the displacement of the load spring requires inexpensive load springs and is easy to carry.

10 Safety valve test device 20 Bridge upper plate 24 Load plate 26 Insertion hole 28 Tension bolt 28a End 32 Load spring 39 Thrust bearing 40 Load nut 101 Safety valve 105a Top surface 106 Safety valve spring 107 Valve stem 107a End 108 Valve body

Claims (3)

A safety valve testing device is attached to a safety valve in which a valve body attached to a valve stem is biased closed by a safety valve spring and is activated to open when a pressure equal to or greater than a predetermined value is applied to the valve body in a direction opposite to the biasing direction of the safety valve spring,
The valve stem is provided so as to protrude outward from an upper surface of the safety valve,
A tension bolt is provided at the end of the valve stem protruding from the upper surface of the safety valve, and the axial direction of the tension bolt is aligned with the end of the valve stem. The tension bolt is provided with a pair of plates that have an insertion hole through which the tension bolt is inserted and are movably attached to the tension bolt in a crosswise manner, a load spring that is provided between the pair of plates and whose extension direction is approximately parallel to the axial direction of the tension bolt, and a load nut that is screwed to the end of the tension bolt opposite to the end to which the valve stem is attached and located outside the plate.
a load nut for applying pressure to the valve stem of the safety valve, the load nut being pressed against the tension bolt of the load spring, the valve body of the safety valve being opened against the force of the safety valve spring, and the load nut being pressed against the tension bolt of the load spring, the valve body of the safety valve being opened against the force of the safety valve spring, and the force of the load spring at the operating point where the valve body is opened is converted into pressure to measure the safety valve operating pressure of the safety valve. The load nut is manually tightened, and the length of the load spring is manually measured.
2. The safety valve testing device according to claim 1, wherein, during measurement, the load nut is manually tightened to manually measure the length of the load spring at the operating point where the valve body of the safety valve opens against the force of the safety valve spring, the force of the load spring is calculated from the amount of displacement between the length of the load spring before compression before tightening the load nut and the length of the load spring at the operating point using the spring constant of the load spring, and the force of the load spring at the operating point is converted into pressure, making it possible to measure the safety valve operating pressure of the safety valve. The safety valve testing device according to claim 1, wherein the tension bolt is provided with a thrust bearing between the load nut and the plate.

Images