JPS62254032A - Method for detecting breakage of piping - Google Patents

Abstract

PURPOSE:To enhance safety, by providing a gap between the outer wall surface of piping and a heat insulating material and detecting the lowering in the internal temp. of the gap due to the thermal expansion or reduced pressure boiling of a fluid leaking at the time of breakage. CONSTITUTION:A gap 3 is provided between a piping wall 3 and a heat insulating material 2 and a temp. sensor 4 is arranged in the gap 3. When a high pressure fluid 5 leaks to the outside of piping, the leaked fluid adiabatically expands in the gap 3 low in pressure to lose internal energy by its expansion work and the temp. sensor 4 can detect the lowering in the temp. of the gap. Therefore, the breakage of the piping permitting the high pressure fluid to pass is detected without being affected by the disturbance of pressure and sound caused by peripheral machinery and safety can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a piping system for passing high-pressure fluid in boilers, chemical plants, nuclear reactors, etc., and a fL rupture release method particularly suitable for early detection. .

[Conventional technology]

Conventional devices are known for detecting pressure fluctuations due to leakage fluid or Senna technology, as described in Japanese Patent Application Laid-open No. 58-59437, pp. 60-63 of Vol. 3, No. 3 (1981). As described, pipe breaks are detected by detecting ultrasonic waves generated by the field flow.

[Problem that the invention seeks to solve]

In the above conventional technology, consideration is given to pressure and sound disturbances caused by equipment around the piping.When the temporary VC cross-sectional area is small, leakage flow and ultrasonic energy are small, so it is easy to use.
There was a gap in terms of detection.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pipe rupture detection device that is less affected by disturbances caused by peripheral equipment and can easily detect VC even when the rupture area is small.

[Means for solving problems]

For the above purpose, as shown in Fig. 1, a pipe wall 1 and a heat insulating material 2 are
A gap 3 is provided between the two, and a gap 3 is installed in the space.
This is achieved by detecting with the temperature sensor 41C that when the high-pressure fluid 5 leaks outside the piping, it adiabatically expands in the gap 3 where it leaks, loses internal energy due to its work, and the temperature decreases. be done.

[Effect]

Pressure P (Pa) and temperature T (C) in general fluids
, the specific volume v (m!/kg) is given by the following equation of state.

T=T(P,V) When the high-pressure fluid 5 is a gas, when it expands adiabatically in the low-pressure gap 3, thermodynamics teaches that it obeys the following constraint:

Pvγ=constant where rll is the adiabatic index. If we eliminate this constraint φ and the specific volume V from the above equation of state, we can obtain the fluid temperature as a function of pressure only.

When it is an ideal gas, the temperature decreases as the pressure decreases VC#.
! A3! 'l (When a two-phase fluid becomes a two-phase fluid, the subtitle ζ of a two-phase fluid, that is, the fluid has a type of 151 M fusion. If the fluid is water and freon, the absorbed vorticity is expressed as pressure It is shown in Figure 3 as a function of .

〔Example〕

Embodiment 2 of the present invention will be explained below with reference to FIG. 4. 4 A piping wall through which high-pressure water 6 passes l A heat insulation box 7 with a gap 3 on the outside
Set up. Gap 3 is maintained by spacer 8π. Outside the heat insulation box 7 (il is insulated and covered with 2 and thermally disconnected from the external atmosphere Vr:J, so the gap 3 is at the same temperature as the high temperature and high pressure water 6). Hold it and place it over the entire length of the piping as shown in the 5th page.

Both ends of the conductor 90 are connected to a resistance value fluctuation detector 10vC. The calming resistance fluctuation detector 10 has a circuit configuration shown in the sixth section. 4 electric body 9 is normal 44 electric body 9 and 1hJ
In series with the reference resistor 11 having the same resistance value (q constant l'E
Connected to power source 12Vc. In parallel with this, two standard resistors 11 with the same resistance 1- are connected in series and constant 1h, E t
Continued on 16i12. ′[ of the two resistor nodes 13
h, Compare with full comparator 14vc, 41 of conductor 9
11 resistor nodes 13 are at a predetermined threshold fi compared to the other
City higher than A: Breakage is detected by indicating the position.

In response to the rupture signal, valves are closed, alarms are issued, and other necessary measures are taken automatically.

When the pipe drop IK break 15 occurs, its area Aδ (m2
) and the subcooled water critical flow Gc (kg/mJ) and the leakage flow tW I kg/5) are given by the following formula.

W ” An (Jc Gc can be approximated by the following equation according to Zaloudek V).

Ge = (2ρt (Po P”')) where P
ofPa) nPressure inside the pipe, P(8)(Pa) n
The point at which the high-temperature, high-pressure water 6 starts boiling under reduced pressure, ρ4 (8' (kg
/m3) is the monohydric water density at the starting pressure π of the pressure reducing groove S.

If the heat insulation box 7 can be prevented from flowing into the heat insulation box 7 by natural convection, the heat insulation box 7 will not turn on due to its pressure-resistant structure. For this reason, the high-temperature, high-pressure water 6 produced by Uranami is depressurized to atmospheric l-E, and 1
It becomes a two-phase fluid of steam and water at 00C. This is a very rapid boiling phenomenon, and the time required to generate steam is 100 ms.
2 No.

Among the leakage points, the proportion xh of steam in the gap 3 is given by the following equation.

Here, (JAg) is the enthalpy of Takahoro water pressure water 6, h
t I J/kgf, hz (J/kgl are the enthalpy of saturated steam and saturated water at atmospheric pressure, respectively.

From the above ryt equation, the volume occupied by the generated steam after Δ seconds after rupture is determined as follows: Vs (m'')n.

Vi=AmGeXvsΔElectricity Here, Vyo(m'/+r) is the specific volume of saturated steam at atmospheric pressure. The total volume of the gap 3 in the heat insulation box 7 is Vy(
mJ), a portion of the conductor 9 approximately corresponding to Va/VTVc will be surrounded by vapor at 100'C.

If the conductor 9 has a cylindrical shape with an outer diameter d (mJ), the time factor τ(s) for fluctuations in external temperature is given by the following equation.

Here, (," (J/kg-K) i specific heat of conductor 9, ρ (in g/m') J"1m stable, b (W/rn"K)
It is the heat transfer coefficient of hti. The temperature difference between the atmosphere Y and the conductive body 9 is 36.8 mm at the initial stage after τ seconds, and 13.8 mm after 2τ seconds.
It decreases to 5%.

The temperature dependence of the electrical resistance of a material can be expressed as a general equation.

d where R(ΩITI)ia, 5 resistance value, a (1tl;”
l tl depth '17% number, T (C') is the temperature of the material.

When the temperature of only the VIl/Vt portion of the conductor 9 decreases by ΔT (C), the total resistance value of the conductor 9 decreases, and the middle division becomes like a chipping.

2!4 in Pikkyokan 14. Beat: The electric resistance change of the body 9 is the signal and the threshold value, so the smaller T is, the harder it is to detect it early.
It is not possible to make the threshold smaller.

According to the above calculation method from the uniformity delay, 2s'tJi, body 9
By calculating the reduction rate of the total resistance value of T, it is possible to set a necessary and sufficient value.

As a specific example, consider a pipe having an outer diameter of 0.1 m and a length of 10 m (Gr), through which high-temperature, high-pressure water 6 with a pressure cuff MPa and a subcool degree of 10 C flows. When the heat insulation box 72 is a cylinder with an inner diameter of 0.14 m and T, each of the gaps 3 is 0.075 m'.

mlJ 'Z minimum possible fracture surface area 1 n-' m”
+1 ml, 2), and the allowable time delay is 1 second. The amount of leakage during this period is estimated to be 0.038k. Atmospheric pressure 1
When the pressure is reduced at 37'16. i.e. 0.1114
kg turns into steam, its volume! * is 0.0086 m". If this steam occupies a gap of 3 Vr and only 1", then it is 0.1
It is 1. In this section, the height of the conductor 9 is 284
It decreases by 184C from C to 100C. Temperature usiμ, with large values in platinum and tungsten, 9% 3X l
Over 0-3C-1. At this time, the total resistance T value change allocation of the Buddha rectangle 9 is estimated to be 6 chis. The rate of change in potential at the resistor node 13 is a factor of 3, so this ++a P l, Kii I
I can see that B and ■Regekou.

The time delay for evaporation is 10rr+s. Also,
The heat transfer coefficient with the high-speed two-phase flow in the outward direction is l O'ν.
If we assume that V/m''・C is W, then the time of temperature change will be 65tα13 (118).It can be ignored compared to the till delay when the evaporation and electric conductor 9 become electric. I'm a good partner.

If you install this example VR, you will be able to avoid the effects of pressure and sound disturbances caused by peripheral equipment, and any pipe breakage will occur quickly.
It is possible to extract K.

Another embodiment will be described below with reference to FIG. guide body 9
0. Inside the gap 3, in a coil around the pipe wall] If
σ is falling.

Low-temperature gas or steam generated by the adiabatic expansion or decompression of the high-pressure fluid that leaked from the opening of the opening 9A is caused by the atmospheric gas in the gap 3) below the gap 3 or above μvc, 1. There is an okeruruai. pitch? , all the thorns [within gap 3?] The proportion of gas or steam occupied by low-carbon gas or steam should be set at 1.1 m3 or less in the upper 1C world.

According to the present twisting, the rupture rvt0 is the town Re regardless of the type fd of the arrangement 11 of the piping.

Another embodiment will be explained from the eighth point of view. l' of gap 3
The pff heating wheel pair 16 is placed in a high yield arrangement.In the interval between them, the detected fracture U1.
Set up a box with a size smaller than 9 f, which is occupied by waste or steam. The heat signal 16 is processed by the circuit of FIG. A comparator 14rc detects a change in temperature from the signal of each thermocouple 16, and a timer 17vcj
: The difference in Ifi3 at the time of ejection of the power supply shown in 1 indicates the time difference in which the low-temperature gas or electricity generated by the tL disconnection reaches the installation position of the pair 16. Arithmetic unit 18f:,
9. Installation position of thermocouple 16 that broke and showed temperature change quickly and each thermocouple] 6-11jI! III! Temperature tremor 2
Divide by the difference in pumping time and calculate the rate of generation of discharged gas or steam.
do. The position where the temperature change was the earliest was near the first page of the μ-rupture. In addition, since the generation of gas or electricity is proportional to the area of the 4 degree σ fracture opening, the fracture area can be determined. 11 This report will be displayed on the cathode ray tube 19, and the 4th and 8th will be notified of the situation. According to IIVC, not only does break #r come out, but break occurs -vj! si and [detecting the discontinuous product■ is the town i
It is the mouth.

〔Effect of the invention〕

Inventive VC engineering fL, trf, high pressure fluid? This has the effect of improving safety by exposing the rupture of the T-wire without being affected by external disturbances such as pressure and pressure caused by peripheral equipment.

FIG. 1 shows the basic theory "ki" according to an embodiment of the present invention.
FjXJ Fig. 1, J4 is a diagram of one embodiment in the mist, Fig. 5 is a diagram showing the distribution of conductors, Fig. 6 is a circuit diagram for detecting resistance clay fluctuations, Fig. 7 is a separate diagram of α An explanatory diagram of the practical example 11, an explanatory diagram of another embodiment in No. 8, and an explanatory diagram of another embodiment in Fig. 9, a circuit diagram for processing the heating signal.

l... Piping wall, 2... Insulating material, 3... Gap, 4...
...Temperature sensor, 6...Akanegori crystal pressure water, 8...Spacer, 10...Resistance I[fwj horizontal structure 11...Reference resistor, 12-1. Fixed pressure P

Claims (1)

[Claims] 1. Pipe rupture detection, which is characterized by providing a gap between the outer wall surface of the pipe and a heat insulating material in a pipe that passes high-pressure fluid, and detecting a temperature drop in the gap due to thermal expansion or reduced pressure boiling of the fluid that leaks when the rupture occurs. Method.