JPS63229343A - Method for testing blow-out of safety valve - Google Patents

Abstract

PURPOSE:To shorten a testing time, by respectively measuring the operation pressures of hydraulic oil when a piston displaces in mutually reverse directions and estimating blow-out pressure on the basis of the average measured value. CONSTITUTION:When a hydraulic pump 30 is driven to raise the internal pressure of the cylinder 12 of the first hydraulic jack 11, a piston 14 rises and the second jack 21 is pushed up. A safety valve 1 is opened resisting against a valve spring 5. The cylinder internal pressure P1 of the jack 11 and the internal pressure P2 of the jack 21 are read by pressure gauges 17, 27 and the pressure P0 on the inlet side 2 of the safety valve is read by a pressure gauge 3. Blow-out pressure Pa is calculated from these pressures P1, P2 according to formula I (wherein As is the pressure receiving area of the safety valve main body, A] is the piston pressure receiving surfaces of the hydraulic jacks, f14 is the friction force between the cylinder and piston of the first hydraulic jack, f24 is the friction force between the cylinder and the piston of the second hydraulic jack, and P0 is base pressure).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for testing the blowout of a safety valve, particularly to a method for testing the blowout of a safety valve using a jack test method.

This invention is used for blowout tests of safety valves installed in boilers and other pressure vessels.

(Conventional technology) Conventionally, the blowout test for safety valves installed in boilers, etc.
Actual tests were conducted in which safety valves were attached to boilers and other equipment, and the safety valves were activated under actual operating conditions. However, recently, the jack test method has been widely adopted as an alternative to actual tests due to thermal economy and noise pollution concerns.

(For example, see Japanese Utility Model Application Publication No. 56-33542.) In the jack test method, an auxiliary force in the direction of opening the safety valve is applied to the valve stem by a hydraulic jack, and the pressure is gradually lower than the normal setting pressure (for example, the normal setting pressure is lower than the normal setting pressure). 80t) to open the safety valve. Then, the blowout pressure is estimated from the pressure oil operating pressure of the hydraulic jack when the safety valve opens. In the jack test method, as mentioned above, the test is performed at a low blowing pressure, so less fuel is consumed to increase the pressure, and the noise generated when the safety valve blows out is also reduced. In addition, in the case of a safety valve for a boiler, the error in the blow-off pressure due to the jerk test is required to be 1 to 2 times the blow-off pressure in the actual test.

In addition, in the jack test method, the magnitude of the frictional force between the cylinder and piston of the hydraulic jack (mainly the frictional force between the inner peripheral surface of the cylinder and the rubber O-ring) is such that it cannot be ignored with respect to the above error. It's the size. Therefore, when estimating the safety valve blowout pressure from the pressure oil working pressure, this frictional force is subtracted to obtain the blowout pressure.

(Problems to be Solved by the Invention) In the conventional jacking test method, the frictional force was corrected as described above. Therefore, the magnitude of the frictional force can be determined accurately, that is, the error of the blowing pressure by the jacking test is 1 to 2.
Measurements had to be made with an accuracy within 96 degrees. To this end, conventionally, friction force has been measured using an expensive measuring device (for example, several million yen). Moreover, this measurement required several hours.

Therefore, the present invention seeks to provide a safety valve blowout test method that can accurately estimate the safety valve blowout pressure without measuring the frictional force between the cylinder and piston of a hydraulic jack.

(Means for Solving Problems) The safety valve blowout test method of the present invention involves supplying pressure oil to the cylinder of a hydraulic jack and applying force in the valve opening direction to the valve stem of the safety valve. Estimate the safety valve blowout pressure based on the pressure oil operating pressure. At this time, a first pressure oil working pressure when the piston is displaced in a first direction with respect to the cylinder, and a second pressure oil working pressure when the piston is displaced in a direction opposite to the first direction. Measure. Then, the blowout pressure is estimated based on the average value of the first and second pressure oil working pressures.

In order to apply a force in the valve opening direction to the valve stem of the safety valve using the hydraulic jack, the valve stem is pushed up by the piston or cylinder of the hydraulic jack via a nut attached to the valve stem.

In this invention, two pressure oil working pressures, the first and second, are measured, but the two pressure oil working pressures may be measured simultaneously in one operation test, or the operation test is performed twice, and the first and second pressure oil working pressures are measured.
and the second two hydraulic oil operating pressures may be measured separately. To measure two hydraulic oil working pressures simultaneously in one operation test, connect two sets of hydraulic jacks in series so that the pistons move in opposite directions, and measure the hydraulic oil working pressure of each hydraulic jack. Just measure it. Further, when measuring the two hydraulic oil working pressures separately, only one set of hydraulic jacks is required. In this case, for example, in the first operation test, the piston is pushed up by hydraulic pressure, and in the second operation test, the piston is pushed down by another piston or a spring mechanism with the cylinder filled with pressure oil.

In addition, the working pressure of the two hydraulic oils combined as above,
The blowing pressure can be estimated by at least one set. However, in order to estimate the blowout pressure with high accuracy, it is desirable to estimate the blowout pressure using a plurality of sets of these pressure oil working pressures, that is, to perform a blowout test several times.

(Operation) In the present invention, the blowout pressure is estimated based on the average value of two pressure oil working pressures when the pistons are displaced in mutually opposite directions. When these two hydraulic pressures act on the piston, the frictional forces are in opposite directions. Furthermore, if the machining accuracy of the cylinder and piston of the hydraulic jack is high, the magnitudes of these two frictional forces are approximately equal. Therefore, by taking the average of the two pressure oil operating pressures, the frictional forces cancel each other out, and the effects of the frictional forces can be removed.

That is, accurate blowing pressure can be obtained without considering frictional force.

(Example Work) FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the present invention together with a safety valve.

A first hydraulic jack 11 and a second hydraulic jack 21 are attached in series to the top of the safety valve 1. That is, the second
As shown in the figure, a cylinder 12 of a first hydraulic jack 11 is fixed to the upper end of the blowout pressure adjusting screw 6 of the safety valve 1 via a spacer 7, and a second jack is further fixed to the upper end of the piston 14 of the first hydraulic jack 11. 21 cylinders 22
is placed. The pressure receiving area of the piston 14.24 of both hydraulic jacks 11.21 is the same, and the pressure receiving area of the piston 14.24 of both hydraulic jacks 11.21 is the same.
Between 22 and piston 14.24 is an O-ring 15.18.
．． 25.28 ensures airtightness.

On the other hand, the valve rod 4 of the safety valve 1 passes through the blowout pressure adjusting screw 6, and an auxiliary threaded rod 8 is connected to the upper end thereof by a nut 9. The auxiliary threaded rod 8 passes through the first hydraulic jack 11 and the second hydraulic jack 21, and a support nut IO is fitted onto the top of the rod.

Further, as shown in FIG. 1, a hydraulic pump 30 is connected to the first hydraulic jack 11 and the second hydraulic jack 21 through stop valves 16 and 26, respectively. Each hydraulic jack II, cylinder 12.22 has a pressure gauge 17.27.
is connected.

Here, using the device configured as described above, the safety valve 1
This section explains how to perform a balloon test.

First, a constant air pressure (hereinafter referred to as pace pressure P0) is applied to the inlet side 2 of the safety valve 1, and the hydraulic pump 30
to drive both hydraulic jacks 11. and 21 cylinders 12.
22 is filled with pressure oil. Once the cylinders 12, 22 of both hydraulic jacks 11, 21 are filled with pressure oil, the stop valve 26 of the second hydraulic jack 21 is closed. The base pressure P0 is a value lower than the blowout pressure PR, for example, 80 zero of the blowout pressure, and therefore the safety valve 1 is in a closed state. Further, the pressure of the pressure oil in the cylinder 12.22 is zero. At this time, the lower surface of the support nut 10 is attached to the second jack 21.
The upper surface of the piston 24 is lightly touched.

When preparations for the test are completed as described above, the hydraulic pump 30 is driven to gradually supply pressure oil to the first hydraulic jack 11. When the pressure inside the cylinder 12 of the first hydraulic jack II increases, the piston 14 thereof rises. 1st
As the piston 14 of the hydraulic jack 11 rises, the valve stem 4
The second jack 21 is pushed up against the force of the valve spring 5 applied to the valve spring 5. Finally, the force of the valve spring 5 is overcome and the safety valve 1 opens. At this time, the pressure gauges 17 and 27 read the cylinder internal pressure P of the first hydraulic jack 11 and the cylinder internal pressure P2 of the second jack 2I, and the pressure gauge 3 reads the pressure P of the safety valve inlet side 2. Read.

The blowing pressure PB is determined from the pressures P1 and P2 obtained as described above in the following manner.

The balance of the force applied to the valve stem 4 when the safety valve 1 opens is As Pa = As PO + AJ (P + - f + 4) for the first hydraulic jack 11.
−(1) becomes.

Similarly, regarding the second jack 21, A, PB=A9Po+A.

X(P2 fz+) ”・(2).

Here, A5; pressure receiving area of the safety valve body AJ: pressure receiving area of the piston of the hydraulic jack f, a: first
Frictional force between the cylinder and piston of the hydraulic jack f2↑: Frictional force between the cylinder and the piston of the second jack Also, the subscripts ↑ and ↓ indicate the piston 14° and 24°, respectively.
The rise and fall of cylinder 12.22 is shown.

Adding both the left and right sides of the above equations (+) and (2), we get 2AsPB=2AsPo+AJ ,
If the size of the f-th and the size of fo are equal, then fl
Since the directions of the forces at J and f2t are opposite, equation (4) becomes as follows. Therefore, the blowing pressure PB can be determined regardless of the frictional force f IJ+ f 24. That is, the blowout pressure PB is based on the frictional force f, ↓+f2+
There is no need to correct it. As is clear from the experimental examples described below, if the machining accuracy of the cylinder and piston of the hydraulic jack is high, fI&=f2. However, there is no practical problem.

EXPERIMENTAL EXAMPLE A blowout test was conducted using the apparatus shown in FIG. 1 with an Ebase pressure of 20 kg and 7 cm2 as a reference. The results are shown in Table 1.

Note that the symbols in Table 1 are the same as those in formula (5) above, and k indicates AJ/2As.

Table 1 k LTO, 841 In addition, the blowout pressure in the actual test of this safety valve was 68
．． It was 5 kg/cm2. Therefore, the error due to the jacking test is 0.28 $, which sufficiently satisfies the accuracy required for the jacking test.

(Example 2) In the above example, two sets of hydraulic jacks were used, but in the next example 2, a blowout test of a safety valve was performed using one set of hydraulic jacks. FIG. 3 explains this embodiment (2) and shows a sectional view of the hydraulic jack. In addition, the same reference numerals are attached to the same members as those in the example construction, and the explanation thereof will be omitted.

As shown in the drawing, a cylinder 32 of a hydraulic jack 31 is fixed to the upper end of the blowout pressure adjusting screw 6 of the safety valve 1 via a spacer 7. Cylinder 3 of hydraulic jack 31
2 and the piston 34 are kept airtight by an O-ring 35. A thrust ball bearing 39 is inserted between the piston and a support nut 10 that fits onto the top of the auxiliary threaded rod 9. Further, similar to the device shown in FIG. 1, a hydraulic pump (not shown) is connected to the hydraulic jack 31 via a stop valve 36. Cylinder 32 of hydraulic jack 31
A pressure gauge 37 is connected to. Note that a spanner 41 is fitted into the support nut 10.

Here, using the device configured as described above, the safety valve 1
This section explains how to perform a balloon test.

Prepare for the test in the same manner as in the example.

Next, the hydraulic pump is driven to supply pressure oil to the hydraulic jack 3I. When the pressure inside the cylinder 32 of the hydraulic jack 31 rises, the piston 34 thereof rises. As the piston 34 of the hydraulic jack 31 rises, the valve stem 4 is pushed up against the force of the valve spring 5 applied thereto. and,
Finally, the force of the valve spring 5 is overcome and the safety valve 1 opens. At this time, the first hydraulic oil operating pressure is read.

Next, after lowering the pressure of the hydraulic jack 31, the stop valve 36 is closed, and the wrench 41 is rotated to tighten the support nut IO. This allows the hydraulic jack 3
The piston 34 of No. 1 is pushed down and the pressure increases. Finally, the safety valve 1 opens, and at this time the second pressure oil operating pressure is read. Using these two measured values, the blowing pressure is estimated in the same manner as in Example I.

Experimental Example (2) A blowout test was conducted using the apparatus shown in FIG. 3 with a base pressure of 40 kg/am2 as a reference. The results are shown in Table 2.

In Table 2, the pressure P1 shows the value when the piston is pushed up by hydraulic pressure, and the pressure P2 shows the value when the piston is pushed down by tightening the support nut.

In addition, the blowout pressure in the actual test of this safety valve was 68
．． It was 5 kg/cm2. Therefore, the error due to the jacking test is 0.44%, which fully satisfies the accuracy required for the jacking test.

The present invention is not limited to the above-mentioned embodiments; for example, the two sets of hydraulic jacks of Embodiment I may have different piston diameters. In this case, the pressure receiving area must be corrected. Furthermore, instead of tightening the support nut 10 in Embodiment H, another set of additional hydraulic jacks may be used to push down the pistons of other hydraulic jacks.

(Effects of the Invention) According to the method of the present invention, the blowout pressure of the safety valve can be accurately estimated without measuring the frictional force between the cylinder and the piston of the hydraulic jack. therefore,
Blowout test work has become easier, instead of taking about 2 hours in the past.
This reduces the work time required to approximately one hour, allowing the test to be completed in a short time. Further, the blow test can be performed economically without requiring an expensive friction force measuring device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a device for carrying out the present invention together with a safety valve 1, FIG. 2 is a sectional view showing details of the hydraulic jack of the device, and FIG. 3 is an illustration of another embodiment of the present invention. This is a sectional view of a hydraulic jack. 1...Safety valve, 4...Valve stem, 5...Valve spring, lO
...Support nut, 11.2+, 31...Hydraulic jack, 12,22.32...Cylinder, 14,24.3
4-...Piston, 15,25.35...0 ring,
+ 6, 26, 36--Stop valve, 30--Hydraulic pump, 41--Spanner.

Claims (1)

[Claims] In this method, pressure oil is supplied to the cylinder of a hydraulic jack to apply force in the valve opening direction to the valve stem of the safety valve, and the blowout pressure of the safety valve is estimated from the pressure oil operating pressure when the safety valve opens. a first pressure oil working pressure when the piston is displaced in a first direction and a second pressure oil working pressure when the piston is displaced in a direction opposite to the first direction; A blowout test method for a safety valve, characterized in that the blowout pressure is estimated based on the average value of two-pressure oil operating pressures.