CN103700221B - Oil and gas pipeline torrential flood disaster monitoring method - Google Patents

Abstract

The invention discloses a method for monitoring mountain torrents disasters of an oil-gas pipeline based on a fiber grating sensing technology, and relates to the technical fields of linear velocity measurement, liquid level measurement, mechanical vibration measurement, general safety devices and pipeline systems. The process comprises the following steps: respectively monitoring the water level, the flow rate and the vortex-induced vibration of the pipeline of the mountain torrents and the water regime; demodulating, collecting and preprocessing wavelength signals; remote transmission and reception of signals; further analysis and processing of the signals; dynamically displaying peak flow change and pipeline vortex-induced vibration frequency; forecasting the flood peak flow of the torrential flood and analyzing the fatigue state of the pipeline; mountain torrent forecast, pipeline safety precaution. The invention has high spatial resolution, low cost, safety and effectiveness.

Description

A kind of oil and gas pipes mountain flood monitoring method

Technical field

The present invention is a kind of oil and gas pipes mountain flood monitoring method based on fiber grating sensing technology, relates to the measurement of linear velocity, the measurement of liquid level, the measurement of mechanical vibration, general safety feature and piping system technical field.

Background technology

Mountain flood refers to flood, rubble flow and landslide disaster that Mountainous Areas is caused by rainfall.Along with global warming causes extreme weather abnormal in recent years, do not meet heavy rain even not seen once in a hundred years decades and happen occasionally.China's middle and small river is numerous, and drainage area is at 100 ~ 1000km ²river have more than 50,000; China is located in Over East Asia Monsoon Area simultaneously, Mountain Area heavy rain takes place frequently, ravines and guillies criss-cross, topographic and geologic complicated condition, add increasingly sharpening of Human dried bloodstains (indiscriminate felling of trees, cut into a mountain and cut slope, water conservancy irrigation), initial landform, landforms are formed larger disturbance and destroyed, causes mountain flood to occur frequent.

Long-distance oil & gas pipeline is the same with railway, highway etc., and be typical line-shape construction, these line-shape constructions are inevitably subject to the impact of river, raceway groove, and as washed away, river-bed deepened, embankment collapse, bank erosion and river diversion; In the area of topographic relief, these engineerings are also subject to the impact of the erosion caused by sloping surfaces caused by flowing water, and surface subsidence caused by domatic soil erosion, pipe trench are emptied, domaticly collapse, fort bank collapses; Mountain area and in front of the mountains district's middle and small river, the water catchment area caused because the slope of river is comparatively large is large, current anxious, wash away acutely etc., makes riverbed usually expose basement rock, boulder and cobble and erratic boulder.In this kind of river course during roughing-in, if pipeline does not have build-in in stable basement rock or when buried depth is inadequate, once Freshets roar down from the mountains, next plays motion in high-velocity flow effect for these block stones of top layer and erratic boulder, pipeline is very likely gone out by water, form the unsettled pipeline section directly do not contacted with ground surface, i.e. tube span.Under certain condition, when current flow through pipeline, the wake zone of pipeline produces vortex, and vortex is with the alternately release on rear side of pipeline of certain frequency, make pipeline be subject to a following current to wave making resistance and perpendicular to flow to fluctuating force, cause pipeline vibration, this phenomenon is commonly referred to vortex-induced vibration, and it affects one of the serviceable life of flood effect underground pipelines, the principal element causing tube span fatigue failure.

Flood damage brings huge risk and loss to China's oil and gas pipes industry.As the Ma Huining pipeline in loess plateau, after being constructed and put into operation, flood damage constantly occurs, unsettled, disconnected event of running affairs once occurs for several times.The puckery peaceful blue gas pipe line mountain flood of the Northwest is also very frequent, often causes pipeline to expose with unsettled.In July, 2004, area, Ledu, Qinghai Province bust heavy rain, stone ditch breaks out mountain torrents, and pipeline is gone out by surging flood, makes pipeline be the unsettled state of naked pipe, the large erratic boulder intense impact pipeline that flood is carried secretly.In July, 2010, area, loyal military pipeline bulky level ground meets with heavy showers and attacks.Heavy rain makes Lang Ping river, and the flood swelled in volume, and dangerous situation appears in the military pipeline many places of the loyalty of laying along river course, wherein two place's pipe long-distance drift pipes, place's dew pipe, separately has 30 many places water conservancy project protection barricades to be destroyed by rush of water.In August, 2010, the flood swelled in volume for Shi Ting river, Deyang, Sichuan, causes river levee to be destroyed by rush of water, occur that large area inrushes, and causes the unsettled 400m of blue Chengdu-Chongqing Products Pipeline branch line, be exposed to completely under current scour.In March, 2011, there is flood in Hei Wa gully, the second west to east gas pipeline project Hutubi County, cause incision bottom this section of coombe, about 140m pipeline is rushed out, and pipeline dew occurs empty floating, in critical condition.

In the face of numerous middle small watershed mountain floods; China's pipeline operator often takes positive Hydraulic Protection Project safeguard procedures; but also there is the drawback of some in these measures; first be that cost is high; next is protection works is not " putting things right once and for all " yet; the uncertain factor of design and construction is more, moreover the cycle of casing pipe protection is long and improvement is not easily grasped opportunity.Monitoring is then a kind of prophylactico-therapeutic measures of efficient, low cost.

At present, China's middle and small river mountain torrent monitoring early warning technology is also in the starting stage, because most of middle and small river network density is less than normal, adds that the short stream in middle and small river source is anxious, mountain torrents have intensity large, last the features such as short, difficult forecast.Traditional mountain flood water regime monitoring many employings mechanical type or electromagnetic sensor, for the former, its technology relative maturity, common are float type level meter, differential pressure water level gauge, mechanical rotor formula velocimeter etc., but owing to limiting by physical construction self, its measuring error is large, precision is low; For the latter, common are radar type liquid-level gauge, ultrasonic current metre, acoustic Doppler velocimetry etc., measuring accuracy is higher, easy to use, but cost is high, and easy electromagnetic wave interference.In addition, monitoring to body ess-strain is more paid close attention to for the safety monitoring of buried pipeline under the extensive soil body migration such as landslide, avalanche, surface collapse, frozen swell and melt settlement, movable causative fault, and the failure mode main manifestations of pipeline is that the vortex-induced vibration that Coupling effect of seepage rock deformation causes causes pipeline generation fatigue failure under mountain torrents effect, simple monitoring pipe body stress strain can not meet the requirement of pipe safety protection under mountain torrents effect.For the vibration monitoring of hardware, traditional mechanical type, electric class vibration transducer (as piezoelectricity, magnetoelectricity and electric vortex type etc.) exist that sensitivity is low, measurement range is little, transmission range is near and the shortcoming such as fault in material, are not suitable for the long-term remote real time monitoring of heavy construction.The Distributed Optical Fiber Sensing Techniques (taking BOTDR as representative) risen in recent years has certain application in mechanical vibration monitoring, but there is not yet report Fiber Bragg Grating technology being applied to the monitoring of mountain torrents effect underground pipelines vortex-induced vibration.

Current mountain flood monitoring and warning technology is applied to engineering and the urban flood defence System Constructions such as highway, railway, power station, dam more, also the buried oil and gas pipes under mountain torrents and impact thereof is not carried out to the combined monitoring of system.Carry out pipeline mountain flood combined monitoring, can not only judge in advance mountain torrents formed before water level, flow velocity and crest discharge, can also find out that current scour is to the influence mode of pipeline and degree, the more important thing is and can grasp condition and the Changing Pattern that vortex-induced vibration occurs steel pipe under flood percussive action, judge the safe condition of pipeline, for the determination preventing and treating opportunity provides foundation.Comprehensive above information, just can carry out safe early warning to the pipeline of valley floor, stream, mountain area section, forecast the precarious position of the formation time of mountain torrents, scale and pipeline in advance, and the design for scheme of disaster reduction is implemented to provide foundation.

Fiber grating is fiber optic passive device with the fastest developing speed in recent years.It is a kind of space periodicity index distribution utilizing the light sensitive characteristic of fiber optic materials to set up on the fibre core of optical fiber, its role is to change or control the dissemination mode of light in this region.Except having ordinary optic fibre electromagnetism interference, size is little, lightweight, intensity is high, except the feature such as high temperature resistant, corrosion-resistant, fiber grating also has the characteristic of its uniqueness: be easy to little with optically-coupled, coupling loss, be easy to wavelength-division multiplex etc.Thus fiber grating is made to have wide prospect in the field such as optical-fibre communications and Fibre Optical Sensor.As a kind of emerging technology of photon research field, be that the sensing technology of pedestal sensor part is subject to common concern in recent years with fiber grating, various countries researcher actively develops relevant research work.At present, the physical quantity that the fiber-optic grating sensor reported can be monitored has: temperature, strain, pressure, displacement, pressure, torsional angle, moment of torsion (twisting stress), acceleration, electric current, voltage, magnetic field, frequency, concentration, thermal expansivity, vibration etc., wherein a part of fiber grating sensing system practical application.

Fiber Bragg Grating FBG (FiberBraggGrating) be the most simply, the most general a kind of fiber grating.It is one section of refractive index is periodically variable optical fiber, and its refractive index modulation depth and screen periods are all generally constants.The change of temperature, strain can cause the cycle of Fiber Bragg Grating FBG and the change of refractive index, thus the reflectance spectrum of Fiber Bragg Grating FBG and transmission spectrum are changed.By the reflectance spectrum of detection fiber Bragg grating and the change of transmission spectrum, just can obtain the information of corresponding temperature and strain, Here it is by the ultimate principle of Fiber Bragg Grating FBG measuring tempeature and strain.

From coupled mode theory, wherein transmit guided mode can be coupled to another guided mode transmitted in opposite direction and form narrowband reflection, peak reflectance wavelength (bragg wavelength) λ by uniform Fiber Bragg Grating FBG _bfor:

λ _B＝2n _effΛ（1）

In formula: λ _bfor bragg wavelength; n _efffor the effective refractive index of spread fiber pattern; Λ is grating pitch.

The centre wavelength of grating and the relation of temperature and strain can be obtained to formula (1) differential:

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}+(1-P_e)\mathrm{\ϵ}---\left(2\right)$

In formula: α _ffor the thermal expansivity of optical fiber; ξ is the thermo-optical coeffecient of fiber optic materials; P _efor the elasto-optical coefficient of fiber optic materials.From formula (2), strain stress is because the flexible of Fiber Bragg Grating FBG cycle and elasto-optical effect cause the change of bragg wavelength, and temperature T is because Fiber Bragg Grating FBG thermal expansion effects and thermo-optic effect cause the change of bragg wavelength.

Fiber grating can be made into various senser element, is used widely at sensory field.Compared with traditional electric transducer, fiber-optic grating sensor has the advantage of oneself uniqueness: (1) transducing head structure is simple, volume is little, lightweight, shape variable, be applicable to imbedding in various large scale structure, the stress of inside configuration, strain and structural damage etc. can be measured, stability, reproducible; (2) and between optical fiber, there is natural compatibility, easily and Fiber connection, light loss is low, spectral characteristic good, reliability is high; (3) have non-conducting, on measured medium impact little, there is again feature that is anticorrosive, electromagnetism interference, be adapted at working in rugged surroundings; (4) lightly soft, multiple grating can be write in an optical fiber, form sensor array, combine with wavelength-division multiplex and time division multiplex system, realize distributed sensing; (5) metrical information is with Wavelength-encoding, and thus fiber-optic grating sensor is by the impact of the light-intensity variation of light source, Fiber connection and the factor such as coupling loss, optical polarization change, the antijamming capability that tool is stronger; (6) high sensitivity, high degree of resolution.

Compared with widely used Brillouin light domain reflectometer BOTDR, the advantage of fiber-optic grating sensor has: (1) can accurately locate measurement point, and resolution is high; (2) cost is low; (3) can process transducing part, encapsulate, make it be more suitable for on-the-spot rugged surroundings.

Due to these advantages, in Geotechnical Engineering field, fiber-optic grating sensor is easy to imbed in Rock And Soil and carries out high resolving power and large-range measuring to the strain of its inside and temperature, technical advantage clearly, especially be embodied in and can obtain long-term, Rock And Soil deformation data reliably, yet there are no the report of fiber grating sensing technology for mountain stream River Valley Region mountain torrents rainwater feelings and flood percussive action underground pipelines vortex-induced vibration frequency combined monitoring.

Summary of the invention

The object of the invention is to invent that a kind of spatial resolution is high, cost is low, safely and effectively based on the oil and gas pipes mountain flood monitoring method of fiber grating.

The present invention proposes a kind of oil and gas pipes mountain flood monitoring and pre-alarming method based on fiber grating sensing technology.System adopts fiber grating sensing technology, carries out combined monitoring to the pipeline under mountain stream River Valley Region mountain torrents regimen and flood percussive action, and Contents for Monitoring comprises the monitoring of river water level, mountain torrents flow velocity and pipeline vortex-induced vibration.And construct monitoring system, achieve the real-time automatic collecting of data, remote transmission and automatic analysis.

The oil and gas pipes mountain flood monitoring method based on fiber grating sensing technology that the present invention proposes, its Contents for Monitoring comprises three parts: water level monitoring, flow monitoring and pipeline vortex-induced vibration are monitored, adopt fiber-optic grating sensor real time on-line monitoring respectively, fiber grating early warning content comprises the early warning of crest discharge to mountain torrents and pipeline vortex-induced vibration frequency.

Based on fiber grating sensing technology oil and gas pipes mountain flood monitoring method monitoring method principle flow chart as shown in Figure 1, monitoring method is as shown in Figure 2.Metal plate 1 bolt 2 is fixed on bank, river course, metal plate 1 is installed protection cylinder 3, and protection cylinder 3 is placed in river course downwards, with bolt, fiber grating level sensor 4 is fixed in protection cylinder 3 wall, in bottom of river channel reference for installation stake 5, fixed fiber grating flow sensor 6 in stake, installing optical fibres grating vibration sensor 8 on the monitoring cross section of oil and gas pipes 7, then by level sensor 4, flow sensor 6 and vibration transducer 8 introduce optical Fiber Closure 9 in the lump, be connected with the optical cable 10 causing monitoring station, in monitoring station, optical cable 10 is connected with photoswitch 11, photoswitch 11 is connected with fiber Bragg grating (FBG) demodulator 12, (FBG) demodulator 12 is connected with slave computer 13, the pretreated data of slave computer 13 are transmitted by wireless communication module 14, wireless communication module 15 receives host computer 16, with said apparatus, oil and gas pipes mountain flood is monitored.

Mountain torrents water level, flow velocity of river and pipeline vortex-induced vibration signal are passed to photoswitch 11 through optical cable I 10 by fiber grating level sensor 4, optical fiber optical grating flow speed sensor 6 and optical fiber raster vibration sensor 8; slave computer 13 is reached through (FBG) demodulator 12 demodulation after photoswitch 11; slave computer 13 calls self-editing program; control photoswitch 11 and (FBG) demodulator 12, realize the collection of data and pre-service is carried out to data; Pretreated data are transmitted by wireless communication module I 14, wireless communication module II 15 receives host computer 16, host computer 16 pairs of data carry out further analyzing and processing, the crest discharge of mountain torrents is obtained by river water level and mountain torrents flow relocity calculation, judge whether the crest discharge in this region has reached forecast warning value, and the comparative analysis of the natural vibration frequency of connecting pipe line vortex forcing frequency and pipeline self, judge the safe condition of pipeline under mountain torrents percussive action.The process of data completes primarily of software, and software flow as shown in Figure 3.The optical wavelength data transformations of fiber Bragg grating (FBG) demodulator collection is mainly strain data by slave computer data prediction, host computer after receiving the data, first by Data classification, according to rainfall, water level and flow relocity calculation mountain torrents total amount and flood peak, and it is combined with pipeline vortex-induced vibration signal, judge the safety case of pipeline under time that mountain torrents are formed, scale and flood erosion effect.

Based on the oil and gas pipes mountain flood monitoring method of fiber grating sensing technology flow process as shown in Figure 1, for:

Mountain torrents regimen and pipeline carry out the monitoring of water level monitoring, flow monitoring and pipeline vortex-induced vibration respectively;

The demodulation of wavelength signals, collection, pre-service;

The remote transmission of signal and reception;

The further analysis and treament of signal;

The display of crest discharge change tread, the display of pipeline vortex-induced vibration frequency dynamic;

Mountain torrents Flood Peak Forecasting, pipeline Analysis of Mental Fatigue;

Mountain torrents forecast, pipe safety prewarning.

Wherein:

Water level monitoring method water level monitoring method adopts the fiber grating level sensor of designed, designed, and its structure as shown in Figure 4.Fix a right cylinder 18 in the center of upper and lower two end faces of stainless steel containment housing 17, a fiber Bragg grating strain sensor I 19 is pasted on right cylinder 18 surface, and by optical cable II 20, signal is caused monitoring station, its principle is as follows:

According to hydrostatics principle, the hydrostatic pressure P at depth of water h place, river course is

P＝P ₀+γh(3）

Wherein: P ₀for atmospheric pressure, γ is the unit weight of water.

In the diagram, containment housing 17, owing to deforming by the impact of outside surface hydraulic pressure P, causes inner connected right cylinder 18 to produce axial strain ε, according to Elasticity, has:

P＝Eε(4）

Wherein: E is the elastic modulus of right cylinder 18.

When river water level changes, outside under surperficial effect of water pressure, casing 17 and the inner right cylinder 18 be connected thereof deform, thus cause the temperature compensating type fiber Bragg grating strain sensor I 19 be pasted on right cylinder 18 to produce axial strain ε, cause bragg wavelength to produce drift, its variation relation is shown in formula (2).

Association type (2), (3), (4), can obtain:

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=(1-P_e)\frac{P_0+\mathrm{\γh}}{E}+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}---\left(5\right)$

Known by formula (5), the wavelength variations Δ λ of fiber grating _blinear with the change of river water level h, fiber grating level sensor is based on formula (5) indirect inspection river water level h, utilize containment housing 17 and inner the stressed of right cylinder 18 be connected thereof that hydrostatic pressure is converted into axial strain amount, and then be converted into the bragg wavelength change of fiber grating, utilize the knots modification Δ λ of (FBG) demodulator determined wavelength _bjust can know water level height by inference.

Flow monitoring method flow monitoring method adopts optical fiber optical grating flow speed sensor, and be made up of venturi-type choker-line 21, conduit I 22, conduit II 23 and fiber bragg grating pressure sensing mechanism, as shown in Figure 5, fluid flows through its structure from left to right.When flux density one timing, the Bernoulli equation of incompressible fluid is

$P_1+\frac{1}{2}{\mathrm{\ρv}}_1^2=P_2+\frac{1}{2}{\mathrm{\ρv}}_2^2---\left(6\right)$

By fluid continuity equation,

$\mathrm{\π}{\left(\frac{1}{2}{d}_1\right)}^2{v}_1=\mathrm{\π}{\left(\frac{1}{2}{d}_2\right)}^2{v}_2---\left(7\right)$

The pressure difference being obtained cross section I and cross section II by formula (6), (7) is

$\mathrm{\ΔP}=P_1-P_2=\frac{\mathrm{\ρ}}{2}[{\left(\frac{d_1}{d_2}\right)}^4-1]v_1^2=\frac{\mathrm{\ρ}}{2}[{\left(\frac{d_1}{d_2}\right)}^4-1]v^2---\left(8\right)$

Wherein, d ₁, d ₂be respectively the large round tube inside diameter of venturi-type choker-line 21, little pipe (throat) internal diameter, (v ₁, P ₁) and (v ₂, P ₂) be respectively flow velocity on conduit I 22 and conduit II 23 midline cross section and pressure.ρ is fluid density, v=v ₁for the flow velocity of liquid.As can be seen from formula (8), the flow velocity of fluid is directly proportional to the pressure difference Δ P on conduit I 22 and conduit II 23 midline cross section, and pressure difference Δ P records by fiber bragg grating pressure sensing mechanism, and concrete grammar is as follows:

Fiber bragg grating pressure sensing mechanism is made up of organic glass seal box 24, airtight aluminum foil pipe 25, steel pin 26, equi intensity cantilever 27, temperature compensating type fiber Bragg grating strain sensor II 28 and optical cable III 29 etc.Airtight aluminum foil pipe 25 is rigidly connected by the free end of steel pin 26 with semi-girder 27, a temperature compensating type fiber Bragg grating strain sensor II 28 is pasted onto semi-girder 27 surface.

For semi-girder 27, according to the mechanics of materials, have

$\left\{\begin{array}{c}\mathrm{\ϵ}=\frac{\mathrm{Mh}}{2E{I}_y}\\ \frac{M}{I_y}=\frac{12\mathrm{Fl}}{{\mathrm{bh}}^3}\end{array}\right.---\left(9\right)$

In formula: E, h, l and b are the elastic modulus of semi-girder 27, thickness, length and width respectively, and ε is the strain of beam, I _yfor the cross sectional moment of inertia of beam, M is semi-girder moment of flexure, and F is the pressure that semi-girder is subject to.

Because aluminum foil pipe can only stretch vertically, and elasticity coefficient is very little, and the relational expression of the pressure F that semi-girder is subject to is as follows

$F=\mathrm{\ΔPSg}=(P_1-P_2)\mathrm{\π}{\left(\frac{d}{2}\right)}^{2}g---\left(10\right)$

In formula: Δ P is the inside and outside pressure difference of aluminum foil pipe 25, and S is the cross-sectional area of aluminum foil pipe 25, and g is acceleration of gravity, and d is the diameter of aluminum foil pipe 25,

The pressure of the unequal generation of inside and outside pressure of aluminum foil pipe 25 acts on semi-girder 27 by steel pin 26, result in the distortion of semi-girder 27, and then causing the bragg wavelength of temperature compensating type fiber Bragg grating strain sensor II 28 to drift about, its variation relation is shown in formula (2).

Association type (2), (8), (9), (10), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=\frac{3(1-P_e)\mathrm{\π}{\mathrm{ld}}^2\mathrm{\ρg}}{4E{\mathrm{bh}}^2}[{\left(\frac{d_1}{d_2}\right)}^4-1]v^2+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}---\left(11\right)$

Known by formula (11), the wavelength variations Δ λ of fiber grating _bwith the square of tested flow velocity v, utilize this optical fiber optical grating flow speed sensor can measure mountain torrents flow velocity v.

The computing method of crest discharge are according to knowledge of hydraulics, and the crest discharge calculation formula in river course is as follows

Q=ΔhLv（12）

In formula: Q is the crest discharge in river course, Δ h is the changing value of river water level, L is river width, and v is mountain torrents flow velocity.Therefore, the river water level obtained according to monitoring and mountain torrents flow velocity, utilize formula (12) can calculate the crest discharge of mountain torrents.

Pipeline vortex-induced vibration frequency monitoring method current are when washing pipe section, often discharge along with periodic vortex, cause washing pipe section periodic vibration, this washing pipe section periodic vibration evoked due to vortex shedding becomes vortex-induced vibration, the fatigue accumulation damage that this vibratory response causes causes pipe across the main cause of fatigue failure.Therefore the safe condition of pipeline can be judged preferably to the measurement of the pipeline vortex-induced vibration that flood erosion causes.

Pipeline vortex-induced vibration frequency monitoring method adopts the optical fiber raster vibration sensor of designed, designed, and its structure as shown in Figure 6.Pedestal 30 side inwall fixes a Metallic rod 31, the free end of bar fixes a derby 32, a temperature compensating type fiber Bragg grating strain sensor III 33 is pasted on Metallic rod 31 surface, and by optical cable IV 34, signal is caused monitoring station, its principle is as follows:

In figure 6, as Metallic rod 31 is equivalent to a semi-girder, according to the mechanics of materials, have

$\left\{\begin{array}{c}\frac{\mathrm{\σ}}{x\left(t\right)}=\frac{{\mathrm{Ebh}}^3}{6l^3}\\ \mathrm{\σ}=\frac{{\mathrm{Ebh}}^2}{6l}\mathrm{\ϵ}\end{array}\right.---\left(13\right)$

In formula: E, h, l and b are the elastic modulus of semi-girder, thickness, length and width respectively, and σ is the stress of beam, and x (t) is the amount of deflection of beam free end, according to formula (13),

$x\left(t\right)=\frac{l^2}{h}\mathrm{\ϵ}---\left(14\right)$

When the derby 32 that the free end of Metallic rod 31 is installed vibrates together along with external environment condition, due to the effect of inertial force, make the temperature compensating type fiber Bragg grating strain sensor III 33 pasted produce axial strain, cause bragg wavelength to produce drift, its variation relation is shown in formula (2).

Association type (2), (14), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=(1-P_e)\frac{h}{l^2}x\left(t\right)+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}---\left(15\right)$

Optical fiber raster vibration sensor is based on formula (15) indirect inspection component Vibration Parameter, utilize the stressed of Metallic rod that the parameter such as amplitude, acceleration is converted into axial strain amount, and then be converted into the bragg wavelength change of fiber grating, utilize the vibration survey that the knots modification of (FBG) demodulator determined wavelength just can realize component.

Suppose under external force, pedestal 30 does that amplitude is A, angular frequency is the simple harmonic oscillation of ω, and its vibration displacement can be expressed as

x(t)=Acos(ωt-θ)（16）

Second derivative is asked to x (t), can vibration acceleration a (t) be obtained

a(t)＝x(t)″＝-Aω ²cos(ωt-θ)（17）

Association type (16), (17), have

a(t)=-ω ²x(t)（18）

Association type (15), (18), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=-(1-P_e)\frac{h}{{\mathrm{\ω}}^2{l}^2}a\left(t\right)+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}---\left(19\right)$

Wherein ω is the natural frequency of optical fiber raster vibration sensor, can be represented by the formula

$\mathrm{\ω}=\sqrt{\frac{{\mathrm{Ebh}}^3}{6m{l}^3}}---\left(20\right)$

Wherein m is the quality of derby 32, and association type (19), (20), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=-(1-P_e)\frac{6\mathrm{ml}}{\mathrm{Eb}{h}^2}a\left(t\right)+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\ΔT}---\left(21\right)$

Known by formula (21), the wavelength variations Δ λ of fiber grating _bchange linear with vibration acceleration a (t) of vibration source, the measurement to vibration acceleration just can be realized by the change of the wavelength of measuring optical fiber grating, FFT(FastFourierTransform is carried out to vibration acceleration a (t), fast fourier transform) calculate after, the rumble spectrum of component can be obtained, thus obtain the vibration period; By the wave number in 1/4th cycles, amplitude and the frequency at measuring point place can be obtained, and the amplitude-time-history curves of structural member can be drawn.

Oil and gas pipes mountain flood monitoring system

Devise oil and gas pipes mountain flood monitoring system according to the method described above.As shown in Figure 7, this system is divided into collection in worksite emission coefficient and long-range receiving and analyzing system, specifically comprises the receiving terminal (host computer) of Level monitor, flow monitoring device, pipeline vortex-induced vibration monitoring device, field monitoring station, office.

The overall formation of oil and gas pipes mountain flood monitoring system as shown in Figure 2.Metal plate 1 bolt 2 is fixed on bank, river course, metal plate 1 is installed protection cylinder 3, and protection cylinder 3 is placed in river course downwards, with bolt, fiber grating level sensor 4 is fixed in barrel, in bottom of river channel reference for installation stake 5, fixed fiber grating flow sensor 6 in stake, installing optical fibres grating vibration sensor 8 on the monitoring cross section of oil and gas pipes 7, then by level sensor 4, flow sensor 6 and vibration transducer 8 introduce optical Fiber Closure 9 in the lump, be connected with the optical cable I 10 causing monitoring station, in monitoring station, optical cable I 10 is connected with photoswitch 11, photoswitch 11 is connected with fiber Bragg grating (FBG) demodulator 12, (FBG) demodulator 12 is connected with slave computer 13, the pretreated data of slave computer 13 are transmitted by wireless communication module I 14, wireless communication module II 15 receives host computer 16, with said apparatus, combined monitoring is carried out to oil and gas pipes mountain flood.

River water level, mountain torrents flow velocity and pipeline vortex-induced vibration signal are passed to photoswitch 11 through optical cable I 10 by fiber grating level sensor 4, optical fiber optical grating flow speed sensor 6 and optical fiber raster vibration sensor 8; slave computer 13 is reached through (FBG) demodulator 12 demodulation after photoswitch 11; slave computer 13 calls self-editing program; control photoswitch 11 and (FBG) demodulator 12, realize the collection of data and pre-service is carried out to data; Pretreated data are transmitted by wireless communication module I 14, wireless communication module II 15 receives host computer 16, host computer 16 pairs of data carry out further analyzing and processing, the crest discharge of mountain torrents is obtained by river water level and mountain torrents flow relocity calculation, judge whether the crest discharge in this region has reached forecast warning value, and connecting pipe line vortex forcing frequency and its natural frequency comparative analysis result, judge the safe condition of pipeline under mountain torrents souring.

The electric principle of this system as shown in Figure 8, monitor water level respectively, three type optical fiber grating sensors--the fiber grating level sensor 4 of flow velocity and pipeline vortex-induced vibration, optical fiber optical grating flow speed sensor 6 is connected with the PC joint of light switch 11 with optical cable I 10 with the PC joint of optical fiber raster vibration sensor 8, the R232 of light switch 11 connects the R232 interface of slave computer 13, the CH1 end of the PC joint connecting fiber grating demodulation instrument 12SM125 of light switch 11, the LAN port of fiber Bragg grating (FBG) demodulator 12SM125 connects the LAN port of slave computer 13, the R232 port of slave computer 13 connects the R232 port of GPRS wireless communication module I 14 Siemens MC 35i, GPRS wireless communication module I 14 is through antenna GSM, GPRS network, received the R232 of host computer 16 by R232 after being received by GPRS wireless communication module II 15 antenna GSM, the output of host computer 16 is held by the VGA of VGA termination display.

The output signal of three type optical fiber grating sensors of water level, flow velocity and pipeline vortex-induced vibration through photoswitch one by one conducting transfer to fiber Bragg grating (FBG) demodulator 12, the centre wavelength displacement that fiber Bragg grating (FBG) demodulator 12 demodulates each fiber-optic grating sensor transfers to slave computer 13, and the cycle of photoswitch 11 Continuity signal is controlled by slave computer 13.Slave computer 13 pairs of data carry out pre-service, and the data after process are defeated by GPRS wireless communication module I 14, each monitoring variable that slave computer 13 calculates by GPRS wireless communication module I 14 is transferred to the host computer 16 being positioned at office by public's cordless communication network, host computer carries out analyzing and processing by self-programmed software to data, is shown by display.

Wherein:

River water level monitoring device as shown in Figure 4.A right cylinder 18 is fixed in the center of upper and lower two end faces of stainless steel containment housing 17, a fiber Bragg grating strain sensor I 19 is pasted on right cylinder 18 surface, and by optical cable II 20, signal is caused optical Fiber Closure 9, optical Fiber Closure 9 is connected with optical cable I 10, and finally causes monitoring station.

Described fiber Bragg grating strain sensor I 19 selects temperature compensating type fiber Bragg grating strain sensor.

Mountain torrents flow monitoring device as shown in Figure 5.Be made up of venturi-type choker-line 21, conduit I 22, conduit II 23 and fiber bragg grating pressure sensing mechanism, fiber bragg grating pressure sensing mechanism is made up of organic glass seal box 24, airtight aluminum foil pipe 25, steel pin 26, equi intensity cantilever 27, temperature compensating type fiber Bragg grating strain sensor II 28 and optical cable III 29 etc.Airtight aluminum foil pipe 25 is rigidly connected by the free end of steel pin 26 with semi-girder 27.A temperature compensating type fiber Bragg grating strain sensor II 28 is pasted onto semi-girder 27 surface, and by optical cable III 29, signal is caused optical Fiber Closure 9, optical Fiber Closure 9 is connected with optical cable I 10, and finally causes monitoring station.

Described fiber Bragg grating strain sensor II 28 selects temperature compensating type fiber Bragg grating strain sensor.

Pipeline vortex-induced vibration monitoring device as shown in Figure 6, pedestal 30 side inwall fixes a Metallic rod 31, the free end of bar fixes a derby 32, a fiber Bragg grating strain sensor III 33 is pasted on Metallic rod 31 surface, and by optical cable IV 34, signal is caused optical Fiber Closure 9, optical Fiber Closure 9 is connected with optical cable I 10, and finally causes monitoring station.

Described fiber Bragg grating strain sensor III 33 selects temperature compensating type fiber Bragg grating strain sensor.

Field monitoring station is arranged on the valve chamber near river course, comprises following a few part:

(1) monitoring station and each sensor optical Fiber Closure and be connected optical cable, for by water level, flow velocity and pipeline vortex-induced vibration sensor signal concentration of transmissions to monitoring station;

(2) light switch, because pipeline mountain flood monitors sensor used a lot, signalling channel is numerous, cannot once be connected on fiber Bragg grating (FBG) demodulator, changes to (FBG) demodulator analysis with light switch successively by each channel signal;

(3) fiber Bragg grating (FBG) demodulator, for demodulating the centre wavelength displacement of each sensor;

(4) computing machine and program, for controlling the frequency of (FBG) demodulator demodulation, and the centre wavelength displacement demodulated by (FBG) demodulator is calculated as each monitoring variable automatically, and these monitoring variables are sent to GPRS wireless communication module, and the signal receiving GPRS wireless communication module controls;

(5) GPRS wireless communication module, for each monitoring variable of computer calculate is transferred to the server being positioned at office by cordless communication network, also can accepts the signal of server, send to computing machine.

The principle of work of this system for: when monitored region, mountain stream river valley occurs to continue rainfall, pipeline river water level along the line, river flow all change, monitored the amount of increase change of river water level by level sensor 4, measured by flow sensor 6 pairs of mountain torrents flow velocitys, the crest discharge of mountain torrents can be calculated based on river water level, mountain torrents flow velocity, meanwhile, the effect of mountain torrents continuous erosion can cause pipeline 7 and produce vortex-induced vibration, measures its vibration frequency by the vibration transducer 8 on body, by connecting optical cable I 10, by the sensor signal concentration of transmissions of each position in pipeline mountain torrent monitoring region to light switch 11, each channel signal is changed to fiber Bragg grating (FBG) demodulator 12 by light switch 11 successively, fiber Bragg grating (FBG) demodulator 12 demodulate each sensor wavelength centre wavelength displacement and sensing to on-site computer 13, the centre wavelength displacement that (FBG) demodulator demodulates by on-site computer 13 is calculated as each monitoring variable automatically, and monitoring variable is sent to on-the-spot GPRS wireless communication module I 14, GPRS wireless communication module I 14 is by cordless communication network signal transmission, terminal server 16 is sent to GPRS wireless communication module II 15, each crest discharge and pipeline vibration frequency and alarm threshold value contrast by terminal server 16, warning is provided time necessary.

The advantage of effect this method of invention shows:

(1) method of mountain stream river valley area Storm Flood and the lower oil and gas pipes of impact thereof being carried out to combined monitoring is proposed, disclose river water level change, mountain torrents change in flow and and flood erosion effect underground pipelines vortex-induced vibration and optic fiber grating wavelength change between linked character; The safe early warning of the lower oil and gas pipes of mountain stream river valley area Storm Flood impact is carried out with multi objective;

(2) fiber grating sensing technology is applied to pipeline mountain flood monitoring, this technology is anti-interference, corrosion-resistant, to be easy to networking etc. with the obvious advantage; This technology is easy to realize automatic real time on-line monitoring, and cost is lower;

(3) water level monitoring, adopts the fiber grating level sensor of designed, designed, river water level is changed the movement that the variation in water pressure caused is converted into sensor internal fiber bragg grating center wavelength; Test wavelength moves size, can know water level height by inference; Compared with traditional float-type, bubble type, differential pressure type level sensor, this monitoring method has the advantages such as highly sensitive, measurement range is wide, long transmission distance, and available minimum monitoring point realizes the remote real time monitoring to long-distance oil & gas pipeline mountain torrents water level along the line;

(4) flow monitoring, adopt the optical fiber optical grating flow speed sensor of designed, designed, based on venturi-type choker-line, mountain torrents change in flow is converted into pressure change, and by equi intensity cantilever, pressure difference is converted into the movement of sensor internal fiber bragg grating center wavelength; Test wavelength moves size, can calculate the size of mountain torrents flow velocity; This optical fiber optical grating flow speed sensor take fiber grating as sensing primitive; without any rotary part; compared with traditional mechanical rotor formula velocimeter and ultrasonic current metre, acoustic Doppler velocimetry; this monitoring method has that precision is high, anti-electromagnetic wave interference, can the advantages such as multiple spot is distributed, available minimum monitoring point realizes the remote real time monitoring to long-distance oil & gas pipeline mountain torrents flow velocity along the line;

(5) pipeline vortex-induced vibration monitoring, adopt the optical fiber raster vibration sensor of designed, designed, utilize the stressed of built-in metal bar that the parameter such as amplitude, acceleration is converted into axial strain amount, and then be converted into the bragg wavelength change of fiber grating, utilize the measurement that the knots modification of (FBG) demodulator determined wavelength just can realize mountain torrents effect underground pipelines vortex-induced vibration; Compared with traditional mechanical type, electric class vibration transducer, this monitoring method has the advantages such as highly sensitive, measurement range is wide, long transmission distance, available minimum monitoring point realizes the remote real time monitoring to long oil/gas pipe line, save cost, decrease the set-up time of equipment and the damage to body, control for pipeline mountain flood provides effective foundation, ensure that the safety of pipeline.

The present invention extensively can use the monitoring and warning of the common pipeline flood damages such as the damaged or destroyed by flood of road, stream, domatic damaged or destroyed by flood, raised fields ground damaged or destroyed by flood, has good application prospect.

Accompanying drawing explanation

Fig. 1 oil and gas pipes mountain flood monitoring method principle flow chart

Fig. 2 oil and gas pipes mountain flood monitoring method figure

Fig. 3 software flow pattern

Fig. 4 level sensor monitoring device pie graph

Fig. 5 flow sensor monitoring device pie graph

Fig. 6 vibration transducer monitoring device pie graph

Fig. 7 oil and gas pipes mountain flood Fundamentals of Supervisory Systems

Fig. 8 oil and gas pipes mountain flood monitoring system electrical schematic diagram

Wherein

1-metal plate, 2-bolt

3-protection cylinder, 4-fiber grating level sensor

5-spud pile, 6-optical fiber optical grating flow speed sensor

7-pipeline, 8-optical fiber raster vibration sensor

9-optical Fiber Closure, 10-optical cable I

11-photoswitch, 12-(FBG) demodulator

13-slave computer, 14-wireless communication module I

15-wireless communication module, II 16-host computer

17-stainless steel containment housing, 18-right cylinder

19-fiber Bragg grating strain sensor, I 20-optical cable II

21-venturi-type choker-line, 22-conduit I

23-conduit, II 24-organic glass seal box

25-airtight aluminum foil pipe 26-steel pin

27-equi intensity cantilever, 28-fiber Bragg grating strain sensor II

29-optical cable, III 30-pedestal

31-Metallic rod, 32-derby

33-fiber Bragg grating strain sensor, III 34-optical cable IV

Embodiment

Embodiment. this example is a kind of monitoring method, and the formation of system for use in carrying is as Figure 1-Figure 8.And carried out site test respectively in blue Chengdu-Chongqing products pipeline Pu Bahe, loyal military natural gas line Lang Ping river; these two test sections all belong to road, Typical Small Watershed stream, mountain area mountain torrents; flood season Mountainous Heavy Rainfall intensity large, produce that conflux networks is fast, river flood rises suddenly to fall suddenly, source, river section stream is anxious; mountain torrents have the advantages that intensity is large, flood peak is high, magnanimity is concentrated; incision and lateral erosion ability by force, protect facility destructive strong to companion's walking along the street, pipeline, water conservancy project.Wherein blue Chengdu-Chongqing Products Pipeline Pu Ba river is positioned at Tan river township, Cheng County, Longnan City, Gansu Province, and influenced duct length is about 10km, and drainage area is about 25km2; Loyal military pipeline Lang Ping river is positioned at Lang Ping town, Changyang, hubei Province county, and influenced duct length is about 16km, and drainage area is about 100km2.

Oil and gas pipes mountain flood monitoring system

This system is divided into collection in worksite emission coefficient and long-range receiving and analyzing system, specifically comprises the receiving terminal (host computer) of river water level monitoring device, mountain torrents flow monitoring device and pipeline vortex-induced vibration monitoring device, field monitoring station, office.

The overall formation of oil and gas pipes mountain flood monitoring system as shown in Figure 2.Metal plate 1 bolt 2 is fixed on bank, river course, metal plate 1 is installed protection cylinder 3, and protection cylinder 3 is placed in river course downwards, with bolt, fiber grating level sensor 4 is fixed in barrel, in bottom of river channel reference for installation stake 5, fixed fiber grating flow sensor 6 in stake, installing optical fibres grating vibration sensor 8 on the monitoring cross section of oil and gas pipes 7, then by level sensor 4, flow sensor 6 and vibration transducer 8 introduce optical Fiber Closure 9 in the lump, be connected with the optical cable I 10 causing monitoring station, in monitoring station, optical cable I 10 is connected with photoswitch 11, photoswitch 11 is connected with fiber Bragg grating (FBG) demodulator 12, (FBG) demodulator 12 is connected with slave computer 13, the pretreated data of slave computer 13 are transmitted by wireless communication module I 14, wireless communication module 15 receives host computer 16, host computer carries out Treatment Analysis to pretreated data, the safe condition of comprehensive descision pipeline.

The electric principle of this system as shown in Figure 8, monitor river water level respectively, three type optical fiber grating sensors--the fiber grating level sensor 4 of mountain torrents flow velocity and pipeline vortex-induced vibration, optical fiber optical grating flow speed sensor 6, the PC joint of optical fiber raster vibration sensor 8 is connected with the PC joint of light switch 11 with optical cable I 10, the R232 of light switch 11 connects the R232 interface of slave computer 13, the CH1 end of the PC joint connecting fiber grating demodulation instrument 12SM125 of light switch 11, the LAN port of fiber Bragg grating (FBG) demodulator 12SM125 connects the LAN port of slave computer 13, the R232 port of slave computer 13 connects the R232 port of GPRS transmission module I 14 Siemens MC 35i, GPRS transmission module I 14 is through antenna GSM, GPRS network, received the R232 of host computer 16 by R232 after being received by GPRS wireless communication module I 15 antenna GSM, the output of host computer 16 is held by the VGA of VGA termination display.

The output signal of three type optical fiber grating sensors of river water level, mountain torrents flow velocity and pipeline vortex-induced vibration through photoswitch one by one conducting transfer to fiber Bragg grating (FBG) demodulator 12, the centre wavelength displacement that fiber Bragg grating (FBG) demodulator 12 demodulates each fiber-optic grating sensor transfers to slave computer 13, and the cycle of photoswitch 11 Continuity signal is controlled by slave computer 13.Slave computer 13 pairs of data carry out pre-service, and the data after process are defeated by GPRS wireless communication module I 14, each monitoring variable that slave computer 13 calculates by GPRS wireless communication module I 14 is transferred to the host computer 16 being positioned at office by public's cordless communication network, host computer carries out analyzing and processing by self-programmed software to data, is shown by display.

Wherein:

Level monitor as shown in Figure 4, a right cylinder 18 is fixed in the center of upper and lower two end faces of stainless steel containment housing 17, a temperature compensating type fiber Bragg grating strain sensor 19 is pasted on right cylinder 18 surface, and by optical cable II 20, signal is caused optical Fiber Closure 9, optical Fiber Closure 9 is connected with optical cable I 10, and finally causes monitoring station.

In above-mentioned monitoring device:

Fiber grating level sensor: select the fiber-optic grating sensor that designed, designed encapsulates;

Temperature compensating type fiber Bragg grating strain sensor: BGK-FBG-4150;

Light switch selects the grand SUM-FSW of light;

SM125 selected by grating demodulation instrument.

Flow monitoring device as shown in Figure 5, pedestal 30 side inwall fixes a Metallic rod 31, the free end of bar fixes a derby 32, a temperature compensating type fiber Bragg grating strain sensor III 33 is pasted on Metallic rod 31 surface, and by optical cable IV 34, signal is caused optical Fiber Closure 9, optical Fiber Closure 9 is connected with optical cable I 10, and finally causes monitoring station.

In above-mentioned monitoring device:

Optical fiber optical grating flow speed sensor: select the fiber-optic grating sensor that designed, designed encapsulates;

Temperature compensating type fiber Bragg grating strain sensor: BGK-FBG-4150;

Light switch selects the grand SUM-FSW of light;

SM125 selected by grating demodulation instrument.

Pipeline vortex-induced vibration monitoring device as shown in Figure 6, pedestal 17 side inwall fixes a Metallic rod 18, the free end of bar fixes a derby 19, a temperature compensating type fiber Bragg grating strain sensor I 19 is pasted on Metallic rod 18 surface, and by optical cable II 20, signal is caused monitoring station; The slave computer 13 of monitoring station calls self-editing program, controls fiber Bragg grating (FBG) demodulator 12, realizes the real-time automatic collecting of data.

In above-mentioned monitoring device:

Optical fiber raster vibration sensor: select the fiber-optic grating sensor that designed, designed encapsulates;

Temperature compensating type fiber Bragg grating strain sensor: BGK-FBG-4150;

Light switch selects the grand SUM-FSW of light;

SM125 selected by grating demodulation instrument.

Field monitoring station is arranged on selected pipeline mountain stream river valley along the line monitoring field, as shown in Figure 2, comprises optical Fiber Closure 9, connects optical cable I 10, light switch 11, fiber Bragg grating (FBG) demodulator 12, lower seat in the plane 13, GPRS wireless communication module I 14; The signal of each fiber-optic grating sensor collection receives the photoswitch 11 of monitoring station by optical cable I 10, photoswitch 11 exports and connects fiber Bragg grating (FBG) demodulator 12, and fiber Bragg grating (FBG) demodulator 12 exports and connects lower seat in the plane 13, and lower seat in the plane 13 exports and connects GPRS wireless communication module I 14.

The signal of each fiber-optic grating sensor collection receives the photoswitch 11 of monitoring station by optical cable 10, each channel signal is changed to fiber Bragg grating (FBG) demodulator 12 by light switch 11 successively, fiber Bragg grating (FBG) demodulator 12 demodulates the centre wavelength displacement of each fiber-optic grating sensor to lower seat in the plane 13, lower seat in the plane 13 automatically calculates each monitoring variable and is defeated by GPRS wireless communication module I 14 and the signal accepting GPRS wireless communication module I 14 controls, each monitoring variable that lower seat in the plane 13 calculates by GPRS wireless communication module I 14 is transferred to by the public's cordless communication network receiving terminal host computer 16 being positioned at office and is further analyzed and process, same seat in the plane 13 at present also accepts by GPRS wireless communication module II 15 signal receiving host computer 16.

Wherein:

Light switch: select the grand scientific and technological SUM-FSW of light;

Fiber Bragg grating (FBG) demodulator: select SM125;

Host computer and program: select and grind magnificent IPC-610, program is self-editing;

GPRS transmission module 14: Siemens MC 35i

The receiving terminal being positioned at office comprises following 2 parts:

(1) GPRS receiver module 15, for receiving the monitoring variable that field monitoring station GPRS wireless communication module I 14 sends, and is transferred to host computer 16, sends feedback command also can to on-the-spot GPRS wireless communication module I 14;

(2) host computer 16 and program, for the signal of download terminal GPRS wireless communication module II 15, and calling program carries out automatic analysis, analysis result and alarm threshold value is contrasted, and implements to report to the police time necessary.

The principle of work of this system for: when monitored region, mountain stream river valley occurs to continue rainfall, pipeline river water level along the line, river flow all change, the amount of increase change of river water level is monitored by Level monitor 4, measured by flow monitoring device 6 pairs of mountain torrents flow velocitys, then according to the crest discharge of water level and flow relocity calculation mountain torrents, namely report to the police once exceed mountain torrents warning value; Simultaneously, the effect of mountain torrents continuous erosion can cause pipeline 7 and produce vortex-induced vibration, measure its vibration frequency by the vibration transducer 8 on body, and contrast with the natural frequency of pipeline self, judge that the possibility of fatigue failure occurs pipeline under mountain torrents wash away continuous erosion effect.

By connecting optical cable I 10, by the sensor signal concentration of transmissions of each position in pipeline mountain torrent monitoring region to light switch 11, each channel signal is changed to fiber Bragg grating (FBG) demodulator 12 by light switch 11 successively, fiber Bragg grating (FBG) demodulator 12 demodulate each sensor wavelength centre wavelength displacement and sensing to on-site computer 13, the centre wavelength displacement that (FBG) demodulator demodulates by on-site computer 13 is calculated as each monitoring variable automatically, and monitoring variable is sent to on-the-spot GPRS wireless communication module I 14, GPRS wireless communication module I 14 is by cordless communication network signal transmission, terminal server 16 is sent to GPRS wireless communication module II 15, the crest discharge of mountain torrents and pipeline vortex-induced vibration frequency and alarm threshold value contrast by terminal server 16, warning is provided time necessary.

Wherein:

GPRS wireless communication module II 15: select Siemens MC 35i;

Host computer 16 and program: host computer is selected and ground magnificent IPC-610; Program is self-editing.

When monitoring with said method, when monitored area occurs to continue rainfall, the river water level change of fiber grating level sensor 4 to each monitoring point is adopted to measure, optical fiber optical grating flow speed sensor 6 is adopted to measure the mountain torrents flow velocity of each monitoring point, based on river water level and these two measured values of mountain torrents flow velocity, utilize formula (12) just can calculate the crest discharge of mountain torrents, and then the mountain torrents reaching warning value are forecast; Simultaneously, buried pipeline can be gone out by the mountain torrents that mountain area continues heavy showers initiation, form the unsettled pipeline section directly do not contacted with ground surface, pipeline generation vortex-induced vibration is caused under water flow fluctuation drag effect, measured by body optical fiber raster vibration sensor 8 pairs of pipeline vortex-induced vibration frequencies, and be analyzed with the natural frequency of pipeline self, judge the possibility of pipeline generation fatigue failure.

Through for a long time monitoring, this example is easy to build monitoring system, is easy to the real-time automatic collecting analysis of pipeline combined monitoring data under mountain area Typical Small Watershed regimen and mountain torrents souring and long-range issue, long-range real-time automatic alarm.Avoid loaded down with trivial details artificial image data, improve the precision of early warning, decrease time of fire alarming, accurately can also locate warning place simultaneously, this to pipeline emergency measure take most important.

Claims (6)

1. an oil and gas pipes mountain flood monitoring method, it is characterized in that monitoring equipment therefor is: metal plate (1) bolt (2) is fixed on bank, river course, metal plate (1) is installed protection cylinder (3), and protection cylinder (3) is placed in river course downwards, with bolt, fiber grating level sensor (4) is fixed in protection cylinder (3) wall, in bottom of river channel reference for installation stake (5), fixed fiber grating flow sensor (6) in stake, installing optical fibres grating vibration sensor (8) on the monitoring cross section of oil and gas pipes (7), then by level sensor (4), optical Fiber Closure (9) introduced in the lump by flow sensor (6) and vibration transducer (8), optical Fiber Closure (9) is connected with the optical cable I (10) of monitoring station, in monitoring station, optical cable I (10) is connected with photoswitch (11), photoswitch (11) is connected with (FBG) demodulator (12), (FBG) demodulator (12) is connected with slave computer (13), slave computer (13) pretreated data are transmitted by wireless communication module I (14), host computer (16) is transferred to after wireless communication module II (15) receives pretreated data,

Mountain torrents water level, flow velocity of river and pipeline vortex-induced vibration signal are passed to photoswitch (11) through optical cable I (10) by fiber grating level sensor (4), optical fiber optical grating flow speed sensor (6) and optical fiber raster vibration sensor (8), photoswitch (11) reaches slave computer (13) by (FBG) demodulator (12) demodulation, slave computer (13) calls self-editing program, control photoswitch (11) and (FBG) demodulator (12), realize the collection of data and pre-service is carried out to data; Pretreated data are transmitted by wireless communication module I (14), wireless communication module II (15) is transferred to host computer (16) after receiving pretreated data, host computer (16) carries out further analyzing and processing to data, the crest discharge of mountain torrents is obtained by river water level and mountain torrents flow relocity calculation, judge whether crest discharge has reached forecast warning value, and the comparative analysis of the natural vibration frequency of connecting pipe line vortex forcing frequency and pipeline self, judge the safe condition of pipeline under mountain torrents percussive action; The optical wavelength data transformations of fiber Bragg grating (FBG) demodulator collection is mainly strain data by slave computer data prediction, host computer after receiving the data, first by Data classification, according to rainfall, water level and flow relocity calculation mountain torrents total amount and flood peak, and it is combined with pipeline vortex-induced vibration signal, judge the safety case of pipeline under time that mountain torrents are formed, scale and flood erosion effect.

2. a kind of oil and gas pipes mountain flood monitoring method according to claim 1, is characterized in that idiographic flow is:

Mountain torrents regimen and pipeline carry out the monitoring of water level monitoring, flow monitoring and pipeline vortex-induced vibration respectively;

The demodulation of wavelength signals, collection, pre-service;

The remote transmission of signal and reception;

The further analysis and treament of signal;

The display of crest discharge change tread, the display of pipeline vortex-induced vibration frequency dynamic;

Mountain torrents Flood Peak Forecasting, pipeline Analysis of Mental Fatigue;

Mountain torrents forecast, pipe safety prewarning.

3. a kind of oil and gas pipes mountain flood monitoring method according to claim 2, it is characterized in that the method for described water level monitoring adopts the fiber grating level sensor of designed, designed, a right cylinder (18) is fixed in the center of upper and lower two end faces of stainless steel containment housing (17), a fiber Bragg grating strain sensor I (19) is pasted on right cylinder (18) surface, and by optical cable II (20), signal is caused monitoring station; Its computing method are as follows:

The hydrostatic pressure P at depth of water h place, river course is

P＝P ₀+γh3)

Wherein: P ₀for atmospheric pressure, γ is the unit weight of water;

Containment housing (17), owing to deforming by the impact of outside surface hydraulic pressure P, causes inner connected right cylinder (18) to produce axial strain ε, has:

P＝Eε4)

Wherein: E is the elastic modulus of right cylinder 18;

When river water level changes, outside under surperficial effect of water pressure, casing (17) and the inner right cylinder (18) be connected thereof deform, thus cause the temperature compensating type fiber Bragg grating strain sensor I (19) be pasted on right cylinder (18) to produce axial strain ε, cause bragg wavelength to produce drift, its variation relation is shown in formula 2);

Association type 2), 3), 4), can obtain:

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=\left(1-P_e\right)\frac{P_0+\mathrm{\γ}h}{E}+\left({\mathrm{\α}}_f+\mathrm{\ξ}\right)\mathrm{\Δ}T---5)$

By formula 5) know, the wavelength variations Δ λ of fiber grating _blinear with the change of river water level h, fiber grating level sensor is based on formula 5) indirect inspection river water level h, utilize containment housing (17) and inner the stressed of right cylinder (18) be connected thereof that hydrostatic pressure is converted into axial strain amount, and then be converted into the bragg wavelength change of fiber grating, utilize the knots modification Δ λ of (FBG) demodulator determined wavelength _bjust can know water level height by inference.

4. a kind of oil and gas pipes mountain flood monitoring method according to claim 2, it is characterized in that the method for described flow monitoring adopts optical fiber optical grating flow speed sensor, be made up of venturi-type choker-line (21), conduit I (22), conduit II (23) and fiber bragg grating pressure sensing mechanism, fluid flows through from left to right; When flux density one timing, the Bernoulli equation of incompressible fluid is

$P_1+\frac{1}{2}{\mathrm{\ρv}}_1^2=P_2+\frac{1}{2}{\mathrm{\ρv}}_2^2---6)$

By fluid continuity equation,

$\mathrm{\π}{\left(\frac{1}{2}{d}_1\right)}^2{v}_1=\mathrm{\π}{\left(\frac{1}{2}{d}_2\right)}^2{v}_2---7)$

By formula 6), 7) the pressure difference of cross section I and cross section II is

$\mathrm{\Δ}P=P_1-P_2=\frac{\mathrm{\ρ}}{2}\[{\left(\frac{d_1}{d_2}\right)}^4-1\]v_1^2=\frac{\mathrm{\ρ}}{2}\[{\left(\frac{d_1}{d_2}\right)}^4-1\]v^2---8)$

Wherein, d ₁, d ₂be respectively the large round tube inside diameter of venturi-type choker-line (21), little pipe throat internal diameter, (v ₁, P ₁) and (v ₂, P ₂) be respectively flow velocity on conduit I (22) and conduit II (23) midline cross section and pressure; ρ is fluid density, v=v ₁for the flow velocity of liquid; As can be seen from formula 8), the flow velocity of fluid is directly proportional to the pressure difference Δ P on conduit I (22) and conduit II (23) midline cross section, and pressure difference Δ P records by fiber bragg grating pressure sensing mechanism, and concrete grammar is as follows:

Fiber bragg grating pressure sensing mechanism is made up of organic glass seal box (24), airtight aluminum foil pipe (25), steel pin (26), semi-girder (27), temperature compensating type fiber Bragg grating strain sensor II (28) and optical cable III (29); Airtight aluminum foil pipe (25) is rigidly connected by the free end of steel pin (26) with semi-girder (27), a temperature compensating type fiber Bragg grating strain sensor II (28) is pasted onto semi-girder (27) surface;

For semi-girder (27), according to the mechanics of materials, have

$\left\{\begin{array}{c}\mathrm{\ϵ}=\frac{Mh}{2{\mathrm{EI}}_y}\\ \frac{M}{I_y}=\frac{12Fl}{{\mathrm{bh}}^3}\end{array}\right.---9)$

In formula: E, h, l and b are the elastic modulus of semi-girder (27), thickness, length and width respectively, and ε is the strain of semi-girder, I _yfor the cross sectional moment of inertia of semi-girder, M is semi-girder moment of flexure, and F is the pressure that semi-girder is subject to;

Because aluminum foil pipe can only stretch vertically, and elasticity coefficient is very little, and the relational expression of the pressure F that semi-girder is subject to is as follows

$F=\mathrm{\Δ}PSg=\left(P_1-P_2\right)\mathrm{\π}{\left(\frac{d}{2}\right)}^{2}g---10)$

In formula: Δ P is the inside and outside pressure difference of aluminum foil pipe (25), and S is the cross-sectional area of aluminum foil pipe (25), and g is acceleration of gravity, and d is the diameter of aluminum foil pipe (25);

The pressure of the unequal generation of inside and outside pressure of aluminum foil pipe (25) acts on semi-girder (27) by steel pin (26), result in the distortion of semi-girder (27), and then cause the bragg wavelength of temperature compensating type fiber Bragg grating strain sensor II (28) to drift about, its variation relation is shown in formula 2);

Association type 2), 8), 9), 10), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=\frac{3\left(1-P_e\right){\mathrm{\πld}}^2\mathrm{\ρ}g}{4{\mathrm{Ebh}}^2}\[{\left(\frac{d_1}{d_2}\right)}^4-1\]v^2+\left({\mathrm{\α}}_f+\mathrm{\ξ}\right)\mathrm{\Δ}T---11)$

By formula 11) know, the wavelength variations Δ λ of fiber grating _bwith the square of tested flow velocity v, utilize this optical fiber optical grating flow speed sensor can measure mountain torrents flow velocity v.

5. a kind of oil and gas pipes mountain flood monitoring method according to claim 2, is characterized in that described mountain torrents crest discharge calculation formula is as follows:

Q＝ΔhLv12)

In formula: Q is mountain torrents crest discharge, Δ h is the changing value of river water level, L is river width, and v is mountain torrents flow velocity; Therefore, the river water level obtained according to monitoring and mountain torrents flow velocity, utilize formula 12) crest discharge of mountain torrents can be calculated.

6. a kind of oil and gas pipes mountain flood monitoring method according to claim 2, is characterized in that the method for described pipeline vortex-induced vibration frequency monitoring adopts the optical fiber raster vibration sensor of designed, designed; Pedestal (30) side inwall is fixed a Metallic rod (31), the free end of Metallic rod (31) fixes a derby (32), a temperature compensating type fiber Bragg grating strain sensor III (33) is pasted on Metallic rod (31) surface, and by optical cable IV (34), signal is caused monitoring station, its computing method are as follows:

As Metallic rod (31) is equivalent to a semi-girder, have

$\left\{\begin{array}{c}\frac{\mathrm{\σ}}{x\left(t\right)}=\frac{{\mathrm{Ebh}}^3}{6l^3}\\ \mathrm{\σ}=\frac{{\mathrm{Ebh}}^2}{6l}\mathrm{\ϵ}\end{array}\right.---13)$

In formula: E, h, l and b are the elastic modulus of semi-girder, thickness, length and width respectively, and σ is the stress of semi-girder, and x (t) is the amount of deflection of semi-girder free end, according to formula 13), have

$x\left(t\right)=\frac{l^2}{h}\mathrm{\ϵ}---14)$

When the derby (32) that the free end of Metallic rod (31) is installed vibrates together along with external environment condition, due to the effect of inertial force, the temperature compensating type fiber Bragg grating strain sensor III (33) pasted is made to produce axial strain, cause bragg wavelength to produce drift, its variation relation is shown in formula 2);

Association type 2), 14), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=\left(1-P_e\right)\frac{h}{l^2}x\left(t\right)+({\mathrm{\α}}_f+\mathrm{\ξ})\mathrm{\Δ}T---15)$

Optical fiber raster vibration sensor is based on formula 15) indirect inspection component Vibration Parameter, utilize the stressed of Metallic rod that amplitude, acceleration parameter are converted into axial strain amount, and then be converted into the bragg wavelength change of fiber grating, utilize the vibration survey of knots modification realization to component of (FBG) demodulator determined wavelength;

Suppose under external force, pedestal (30) does that amplitude is A, angular frequency is the simple harmonic oscillation of ω, and its vibration displacement is expressed as

x(t)＝Acos(ωt-θ)16)

Second derivative is asked to x (t), can vibration acceleration a (t) be obtained

a(t)＝x(t)″＝-Aω ²cos(ωt-θ)17)

Association type 16), 17), have

a(t)＝-ω ²x(t)18)

Association type 15), 18), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=-\left(1-P_e\right)\frac{h}{{\mathrm{\ω}}^2{l}^2}a\left(t\right)+\left({\mathrm{\α}}_f+\mathrm{\ξ}\right)\mathrm{\Δ}T---19)$

Wherein ω is the natural frequency of optical fiber raster vibration sensor, can be represented by the formula

$\mathrm{\ω}=\sqrt{\frac{{\mathrm{Ebh}}^3}{6{\mathrm{ml}}^3}}---20)$

Wherein m is the quality of derby 32, association type 19), 20), have

$\frac{{\mathrm{\Δ\λ}}_B}{{\mathrm{\λ}}_B}=-\left(1-P_e\right)\frac{6ml}{{\mathrm{Ebh}}^2}a\left(t\right)+\left({\mathrm{\α}}_f+\mathrm{\ξ}\right)\mathrm{\Δ}T---21)$

By formula 21) know, the wavelength variations Δ λ of fiber grating _bchange linear with vibration acceleration a (t) of vibration source, the measurement to vibration acceleration is realized by the change of the wavelength of measuring optical fiber grating, after the calculating of FastFourierTransform fast fourier transform is carried out to vibration acceleration a (t), the rumble spectrum of component can be obtained, thus obtain the vibration period; By the wave number in 1/4th cycles, amplitude and the frequency at measuring point place can be obtained, and the amplitude-time-history curves of structural member can be drawn.