CN102392940A - Method and system for testing tightness of underground gas pipeline - Google Patents

Abstract

A method and system for testing tightness of underground gas pipeline, wherein the method includes measuring the tube outer wall temperature, converting the temperature into tube inner gas temperature via a formula, measuring the tube pressure, the tube wall temperature and the atmospheric pressure every half an hour, and calculating the corrected pressure drop, when the corrected pressure drop is more than 50% of the minimum scale value of the test pressure, the tightness test is unqualified; if not, the tightness test is qualified. The testing system includes a gas source, a thermometer, a temperature detecting transmitter, a pressure gage, a pressure detecting transmitter, a gas inlet valve, a gas draining valve and a computer detection platform. The method increases the measuring precision of the tube gas temperature by means of converting the tube outer wall temperature into tube gas temperature, takes 50% of the minimum scale value of the test pressure as the allowable value of the corrected pressure drop, and increases the correctness and feasibility of the tightness test of the underground gas pipeline.

Description

Bury ground gas pipeline leak test method and system

(1) technical field

The present invention relates to a kind of leak test method and system, particularly a kind of leak test method and system that is applied to bury the ground gas pipeline.

(2) background technique

Gas pipeline generally adopts buried-pipe laying, if it is improper because of leakage detection method to be embedded in underground pipeline, can cause the erroneous judgement of leak test conclusion, causes gas leakage and explosive accident.Buried pipeline is in underground about 1m depths, is difficult to detect if take place to leak.In pipeline long-time running process, the combustion gas of leak will near the soil leakage point be gathered or is spread along pipe trench, can breaking out of fire or blast when combustion gas reaches finite concentration and meets naked light.Therefore, accurately detect the buried pipeline leak-down rate, guarantee its leakproofness, safe operation is of great significance to buried pipeline.

Existing gas pipeline leak test adopts the regulation of the nation-building CJJ33-2005 of portion " engineering construction of city gas transmission & distribution and acceptance specification " to carry out; This regulation and stipulation leak test continued in 24 hours voltage stabilizing time, and it is qualified that the pressure of correction must not fall above 133Pa.

Not enough below existing gas pipeline leak test method exists:

(1) the medium temperature measuring accuracy is lower in the pipe.Thermometry at present commonly used generally is employed on the exhaust stack of valve well and installs thermometer; The temperature that records receives the influence of environment bigger; Perhaps directly thermometer is inserted in the soil of conduit upper; The temperature that records is the soil temperature around the pipeline, exists than big-difference with medium temperature in the pipe.

Calculating two states when only considering on-test and finishing falls in the pressure of (2) revising.Temperature variation can't be considered the influence of pressure in the process of the test, therefore can influence the reliability of test result.

(3) judge that whether tight pipeline is, adopt same correction pressure to fall 133Pa, lack rationality and actual operability.For different tests pressure; If adopt same correction pressure to fall 133Pa, be feasible for the situation of test pressure below 0.1MPa, if but test pressure surpasses 0.1MPa; Therefore manometric reading error will can't accurately judge the leakproofness of test pipe greater than 133Pa.

(3) summary of the invention

The present invention seeks to overcome the existing not enough problem of ground gas pipeline leak test precision of burying, provide a kind of accurately, simple and easy to do leak test method and system.

The ground gas pipeline leak test method of burying of the present invention, it is following to carry out step:

(1) bury the ground test section and lay, the installation of leak test system, and start the computer testing platform;

(2) in test section, add pressurized air, till manifold pressure reaches needed test pressure, record original tube internal pressure P ₀, tube wall temperature T ₀' and testing ground atmospheric pressure P _A0

(3) the regular detecting tube internal pressure of test platform P _i, tube wall temperature T _i' and testing ground atmospheric pressure P _Ai

(4) gas temperature in the computer tube: at first through tube wall temperature instrumentation buret wall temperature, be scaled gas temperature in the pipe through empirical correlation then, the formula that gas temperature calculates in the pipe is following:

$T=\frac{{\mathrm{\λ}}_1}{{\mathrm{\δ}}_1}[(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0}+\frac{{\mathrm{\δ}}_1}{{\mathrm{\λ}}_1})T_{\mathrm{out}}-(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0})T_{\mathrm{soil}}]$

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that (5) will regularly detect _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

${\mathrm{\ΔP}}_i=P_0+P_{a0}-(P_i+P_{\mathrm{ai}})\frac{273+T_0}{273+T_i}$

In the formula: Δ P _i---revise pressure and fall (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Leak test qualification determination standard: in 24 hours, if Δ P falls in the correction pressure that regularly detect per half an hour _iBe not more than 50% of the minimum scale division value of pressure gauge, leak test is qualified, otherwise is defective.

Further, in step (4), in order to eliminate the influence of gas temperature skewness in the long-distance pipe, adopt and arrange a plurality of temperature points along pipeline section, with its arithmetic mean value as tube wall temperature.

A kind ofly realize described system of burying ground gas pipeline leak test method, comprising:

(1) pressurization of test section and pressure relief system are made up of source of the gas, suction valve, outlet valve and respective line;

(2) pressure and temperature detects and transmitting system; Weld nipple on the terminal blind plate of test section; The setting pressure table; According to the measuring accuracy needs,, be standard signal input main control computer with the pressure and temperature signal conversion of measuring through transmitter at test section outer wall mounting temperature meter at a certain distance;

(3) main control computer is made up of computer, pressure and temperature signal data interface and signaling line, and described computer comprises that the gas temperature analog module falls computing module and judge module with correction pressure in the pipe,

The gas temperature analog module is scaled gas temperature in the pipe through tube wall temperature instrumentation buret wall temperature in the described pipe, and the formula of calculating is following:

$T=\frac{{\mathrm{\λ}}_1}{{\mathrm{\δ}}_1}[(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0}+\frac{{\mathrm{\δ}}_1}{{\mathrm{\λ}}_1})T_{\mathrm{out}}-(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0})T_{\mathrm{soil}}]$

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that computing module will regularly detect falls in described correction pressure _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

${\mathrm{\ΔP}}_i=P_0+P_{a0}-(P_i+P_{\mathrm{ai}})\frac{273+T_0}{273+T_i}$

In the formula: Δ P _i---revise pressure and fall (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Described judge module is judged according to preset leak test qualification determination standard, and the output judged result: in 24 hours, if Δ P falls in the correction pressure that regularly detect per half an hour _iBe not more than 50% of the minimum scale division value of pressure gauge, leak test is qualified, otherwise is defective

Advantage of the present invention is: degree of accuracy is high, simple and easy to do.

(4) description of drawings

Fig. 1 is a system architecture schematic representation of the present invention.

(5) embodiment

The present invention does further explain below in conjunction with accompanying drawing.

Referring to Fig. 1,

The ground gas pipeline leak test method of burying of the present invention, it is following to carry out step:

(1) bury the ground test section and lay, the installation of leak test system, and start the computer testing platform;

(2) in test section, add pressurized air, till manifold pressure reaches needed test pressure, record original tube internal pressure P ₀, tube wall temperature T ₀' and testing ground atmospheric pressure P _A0

(3) the regular detecting tube internal pressure of test platform P _i, tube wall temperature T _i' and testing ground atmospheric pressure P _Ai

(4) gas temperature in the computer tube: at first through tube wall temperature instrumentation buret wall temperature, be scaled gas temperature in the pipe through empirical correlation then, the formula that gas temperature calculates in the pipe is following:

$T=\frac{{\mathrm{\λ}}_1}{{\mathrm{\δ}}_1}[(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0}+\frac{{\mathrm{\δ}}_1}{{\mathrm{\λ}}_1})T_{\mathrm{out}}-(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0})T_{\mathrm{soil}}]$

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that (5) will regularly detect _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

${\mathrm{\ΔP}}_i=P_0+P_{a0}-(P_i+P_{\mathrm{ai}})\frac{273+T_0}{273+T_i}$

In the formula: Δ P _i---revise pressure and fall (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Leak test qualification determination standard: in 24 hours, be not more than 50% of the minimum scale division value of pressure gauge if Δ Pi falls in the correction pressure that regularly detects per half an hour, leak test is qualified, otherwise is defective.

Further, in step (4), in order to eliminate the influence of gas temperature skewness in the long-distance pipe, adopt and arrange a plurality of temperature points along pipeline section, with its arithmetic mean value as tube wall temperature.

A kind ofly realize described system of burying ground gas pipeline leak test method, comprising:

(1) pressurization of test section and pressure relief system are made up of source of the gas, suction valve, outlet valve and respective line;

(2) pressure and temperature detects and transmitting system; Weld nipple on the terminal blind plate of test section; The setting pressure table; According to the measuring accuracy needs,, be standard signal input main control computer with the pressure and temperature signal conversion of measuring through transmitter at test section outer wall mounting temperature meter at a certain distance;

(3) main control computer is made up of computer, pressure and temperature signal data interface and signaling line, and described computer comprises that the gas temperature analog module falls computing module and judge module with correction pressure in the pipe,

The gas temperature analog module is scaled gas temperature in the pipe through tube wall temperature instrumentation buret wall temperature in the described pipe, and the formula of calculating is following:

$T=\frac{{\mathrm{\λ}}_1}{{\mathrm{\δ}}_1}[(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0}+\frac{{\mathrm{\δ}}_1}{{\mathrm{\λ}}_1})T_{\mathrm{out}}-(\frac{1}{\mathrm{\α}}+\frac{{\mathrm{\δ}}_0}{{\mathrm{\λ}}_0})T_{\mathrm{soil}}]$

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that computing module will regularly detect falls in described correction pressure _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

${\mathrm{\ΔP}}_i=P_0+P_{a0}-(P_i+P_{\mathrm{ai}})\frac{273+T_0}{273+T_i}$

In the formula: Δ P _i-revising pressure falls (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Described judge module is judged according to preset leak test qualification determination standard, and the output judged result: in 24 hours, if Δ P falls in the correction pressure that regularly detect per half an hour _iBe not more than 50% of the minimum scale division value of pressure gauge, leak test is qualified, otherwise is defective

As stated, in conjunction with the content of accompanying drawing and embodiment, can derive the similar techniques scheme.In every case be not break away from the content of inventing technological scheme, any simple modification, equivalent variations and modification according to technical spirit of the present invention is done above mode of execution all still belong in the scope of technological scheme of the present invention.

Claims (3)

1. bury ground gas pipeline leak test method, it is following to carry out step:

(1) bury the ground test section and lay, the installation of leak test system, and start the computer testing platform;

(2) in test section, add pressurized air, till manifold pressure reaches needed test pressure, record original tube internal pressure P ₀, tube wall temperature T ₀' and testing ground atmospheric pressure P _A0

(3) the regular detecting tube internal pressure of test platform P _i, tube wall temperature T _i' and testing ground atmospheric pressure P _Ai

(4) gas temperature in the computer tube: at first through tube wall temperature instrumentation buret wall temperature, be scaled gas temperature in the pipe through empirical correlation then, the formula that gas temperature calculates in the pipe is following:

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that (5) will regularly detect _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

In the formula: Δ P _i-revising pressure falls (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Leak test qualification determination standard: in 24 hours, if Δ P falls in the correction pressure that regularly detect per half an hour _iBe not more than 50% of the minimum scale division value of pressure gauge, leak test is qualified, otherwise is defective.

2. buried pipeline combustion gas leak test method according to claim 1; It is characterized in that: in step (4); In order to eliminate the influence of gas temperature skewness in the long-distance pipe, adopt and arrange a plurality of temperature points along pipeline section, with its arithmetic mean value as tube wall temperature.

3. realize the described system of burying ground gas pipeline leak test method of claim 1 for one kind, comprising:

(1) pressurization of test section and pressure relief system are made up of source of the gas, suction valve, outlet valve and respective line;

(2) pressure and temperature detects and transmitting system; Weld nipple on the terminal blind plate of test section; The setting pressure table; According to the measuring accuracy needs,, be standard signal input main control computer with the pressure and temperature signal conversion of measuring through transmitter at test section outer wall mounting temperature meter at a certain distance;

(3) main control computer; Form by computer, pressure and temperature signal data interface and signaling line; Described computer comprises that the gas temperature analog module falls computing module and judge module with correction pressure in the pipe; The gas temperature analog module is scaled gas temperature in the pipe through tube wall temperature instrumentation buret wall temperature in the described pipe, and the formula of calculating is following:

In the formula: T---gas temperature in the pipe (℃);

T _Out---the pipeline outer wall temperature (℃);

T _Soil---the test site soil temperature (℃);

δ ₀, δ ₁---pipeline and thermal insulation layer wall thickness (mm);

λ ₀, λ ₁---pipeline and thermal insulation layer thermal conductivity (w/mK)

Thermal contact resistance (mm between α---pipeline outer wall and the thermal insulation layer ²K/w);

The pipe internal pressure P that computing module will regularly detect falls in described correction pressure _i, be scaled the pressure of test original state, and calculate correction pressure and fall Δ P _i

In the formula: Δ P _i-revising pressure falls (Pa);

P ₀, P _A0---gas pressure and atmospheric pressure (Pa) in the original tube;

P _i, P _Ai---the interior gas pressure of pipe and the atmospheric pressure (Pa) that regularly detect;

T ₀, T _i---gas initial temperature and regular detected temperatures in the pipe (℃);

Described judge module is judged according to preset leak test qualification determination standard, and the output judged result: in 24 hours, if Δ P falls in the correction pressure that regularly detect per half an hour _iBe not more than 50% of the minimum scale division value of pressure gauge, leak test is qualified, otherwise is defective.

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