CN109990142B - Research method for anti-leakage and anti-blocking scheme of pipeline sleeve in fabricated building structure - Google Patents
Research method for anti-leakage and anti-blocking scheme of pipeline sleeve in fabricated building structure Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L5/00—Devices for use where pipes, cables or protective tubing pass through walls or partitions
- F16L5/02—Sealing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L5/00—Devices for use where pipes, cables or protective tubing pass through walls or partitions
- F16L5/02—Sealing
- F16L5/025—Sealing the pipe being movable
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/18—Protection of pipes or pipe fittings against corrosion or incrustation specially adapted for pipe fittings
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
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- G06F30/20—Design optimisation, verification or simulation
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Abstract
The invention discloses a method for researching a leakage and blockage prevention scheme of a pipeline sleeve in an assembly type building structure, which belongs to the technical field of optimization of a solenoid coil magnetic field, and comprises the following steps: s1: selecting a proper pipeline sleeve leakage prevention scheme, S2: selecting any form of casing according to the specific situation on site, S3: designing a plugging scheme for sealing the sleeve end, and S4: selecting a proper sleeve plugging scheme, S5: the influence of the sleeve on the cathodic protection potential of the metal pipeline is numerically simulated. The research method of the invention can prevent the corrosion of the outer wall of the pipeline connecting part, reduce the leakage rate and the maintenance cost of the medium in the pipeline, ensure the integrity of the plugging end, simultaneously make up the defects of theoretical calculation and empirical estimation to a certain extent, and reduce the heavy measurement work and expensive measurement cost brought by actual measurement.
Description
Technical Field
The invention relates to the field of leakage and blockage prevention of a pipeline sleeve, in particular to a research method of a leakage and blockage prevention scheme of the pipeline sleeve in an assembly type building structure.
Background
With the rapid development of cities and towns, building pipelines become an indispensable part of urban infrastructure, the building pipelines are laid in large numbers at each corner of a building structure, and corresponding matched sleeves become non-negligible components of the infrastructure.
In a building structure, in order to avoid damage to pipelines from the outside, the pipelines are usually protected by a method of laying the pipelines in the sleeves, the main pipelines in the sleeves are prevented from being damaged by a third party and external acting force, but the existence of the sleeves shields cathodic protection current, the external corrosion probability of a main pipeline is increased, the pipelines have certain external corrosion hidden dangers due to the particularity of the sleeve environment, the steel sleeves are usually adopted for ensuring the effective safety of the pipelines when the pipelines pass through a floor slab in the building structure, a plurality of specifications and standards related to the sleeves are published at home and abroad, the requirements of design, installation, construction and the like of the pipeline sleeves are specified in detail, and a plurality of scholars also perform a great deal of research on the problems of a sleeve strength calculation method, a cathodic protection measure, integrity evaluation and the like, and obtain abundant results. According to the statistics data related to the building department, about 80% of the reinforced concrete structures which are built in the related regions for more than 2 years have leakage problems at the pipeline sleeve part, the domestic water seeps out due to the fact that the pipeline sleeve part is not tightly sealed, and the corresponding peripheral valves, pipelines and other equipment are soaked in a humid environment for a long time to cause serious corrosion, so that the valves are out of order, the service lives of the pipelines are shortened, the peripheral structures are damaged, the use of building functions is seriously influenced, the pipelines generate leakage due to the fact that the pipelines are corroded and broken under the stress action, even underground water and the surrounding environment are polluted, in addition, the pipeline leakage passing through the floor slab part is difficult to treat and high in cost, and huge economic loss is caused.
Therefore, a research method for the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure is provided.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problems in the prior art, the invention aims to provide a research method of an anti-leakage and anti-blocking scheme of a pipeline sleeve in an assembly type building structure, which can prevent the corrosion of the outer wall of a pipeline connecting part and reduce the leakage rate and the maintenance cost of a medium in the pipeline by adopting a closed elastic corrugated pipe compensation type sleeve technology, can prevent the relative displacement between a main pipeline and the sleeve by adopting flexible blocking and reserving the expansion allowance of the pipeline, thereby ensuring the integrity of a blocking end, simultaneously utilizes numerical simulation to analyze various influence factors and protection states of the cathode protection of the pipeline in the sleeve, can make up the defects of theoretical calculation and empirical estimation to a certain extent, and reduces heavy measurement work and expensive measurement cost brought by actual measurement.
2. Technical scheme
In order to solve the above problems, the present invention adopts the following technical solutions.
The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure comprises the following steps of:
s1: selecting a proper pipeline sleeve leakage prevention scheme, adopting a closed elastic compensation type sleeve, sleeving the sleeve on the pipeline, connecting the end of the sleeve and the pipeline in a closed manner by using a corrugated pipe elastic element, fixing a water stop plate on the sleeve, embedding the sleeve in a floor slab to form a whole with the pipeline, and performing anticorrosive treatment on the outer surface of the corrugated pipe at the same level as that of the pipeline so as to form a closed cavity between the pipeline and the sleeve;
s2: selecting any form of sleeve according to the specific situation of a site, and selecting the specification form and the connection mode of the sleeve according to the outer diameter, the material and the length of the pipeline, the thickness and the material of a floor slab before the installation of the closed elastic compensation type pipeline sleeve for a newly-built project; for maintenance projects, connecting corrugated pipe compensation elements at two ends by using the original sleeve;
s3: designing a plugging scheme for sealing the sleeve end, analyzing the stress and displacement levels of a main pipeline in the sleeve under an operating condition according to production experience, two types of sleeve end plugging schemes commonly used in engineering and combining a pipeline constraint rule, comprehensively judging the adaptability of two plugging modes, and recommending a proper pipeline sleeve end plugging scheme;
s4: selecting a proper sleeve plugging scheme, and using a flexible plugging sleeve as a method for sealing a sleeve port when a pipeline passes through, so that the material characteristics of an end sealing sleeve can adapt to the pipeline conveying temperature and the environmental temperature during construction, the adhesion of the end sealing sleeve material and a conveying pipe (or an anticorrosive material) can be stable for a long time, meanwhile, on the premise of ensuring the strength of the end sealing sleeve (according to the requirements of related technical specifications), a fold type installation method is adopted to provide a telescopic margin for the expansion and contraction of the pipeline in operation, and if an exhaust pipe is required to be arranged, a flexible plugging sleeve with double openings is adopted;
s5: the influence of the numerical simulation sleeve on the cathodic protection potential of the metal pipeline is as follows:
firstly, establishing a model, including a mathematical model and boundary conditions and solving a physical model and a model, simplifying the model, then determining the boundary conditions, and finally calculating the cathode protection potential of the pipeline and analyzing the result of the established model according to related steps;
secondly, summarizing the sleeve, whether two ends of the sleeve are sealed, the coating quality, electrolyte in the sleeve, whether a sacrificial anode sleeve is arranged in the sleeve or not, and the influence of the coating defect points of the inner and outer pipelines on the cathode protection potential of the pipeline;
thirdly, concluding that after the sleeve is installed on the pipeline, the longer the sleeve is, the greater the influence on the cathode protection potential of the pipeline is; the sealed sleeve can prevent impurities such as soil, underground water, silt and the like from entering the sleeve to cause corrosion of a pipeline; the better the coating quality is, the less the electric energy consumed by the forced current method is, and the longer the service life of the sacrificial anode is; the larger the conductivity of the internal electrolyte is, the more negative the protection potential of the pipeline is, so that under the condition that the sleeve is filled with the electrolyte, the good conductivity of the electrolyte material is required to ensure that the pipeline in the sleeve can obtain the sufficient cathodic protection effect; the sacrificial anode is arranged inside the special section, so that the cathode potential of the special section can be guaranteed; when the coating defects of the inner and outer pipelines of the sleeve are more serious, the positive deviation of the cathode protection potential of the pipeline is larger.
Furthermore, the bellows elastic element in S1 has reliable quality, zero leakage, low cost and long service life, can prevent the corrosion of the outer wall of the pipeline connecting part and reduce the leakage rate of the medium in the pipeline.
Further, the connection mode in S2 may be welding, clamping, or flange connection.
Further, the two types of sleeve end plugging schemes in the step S3 are respectively rigid plugging based on insulating materials such as broken red bricks, cement mortar and asphalt hemp, and flexible plugging based on end sealing sleeves.
Furthermore, fine sand or fine soil is used for backfilling around the end sealing sleeve in the S4, so that sharp objects are prevented from being carried in the backfilling.
Further, the related step in S5 is to divide the generated model by using a freely subdivided tetrahedral mesh, then set a solver to make the precision meet the requirement, and finally perform post-processing to obtain data and graphs required by subsequent comparative analysis by using the post-processing function of the software itself.
Further, the solver is a steady state solver.
Further, the accuracy requirement is less than 0.001.
3. Advantageous effects
Compared with the prior art, the invention has the advantages that:
the scheme adopts the technology of the closed elastic corrugated pipe compensation type sleeve pipe by comparing and selecting the leakage reason of the crossing part of the pipeline and utilizing the elastic corrugated pipe to compensate the expansion amount of the pipeline, so that a space is formed between the pipeline and the sleeve pipe, thereby achieving the purposes of zero leakage and corrosion prevention of the pipeline sleeve pipe, preventing the corrosion of the outer wall of the connecting part of the pipeline, reducing the leakage rate of media in the pipeline, protecting the pipeline and the valve in the valve well, reducing the maintenance cost, prolonging the service life of the pipeline and the valve, protecting the water environment of a building, adopting the method of using the flexible plugging sleeve as the port sealing of the sleeve pipe when the pipeline passes through, enabling the material characteristics of the end sealing sleeve to adapt to the pipeline conveying temperature and the environmental temperature during the construction period, and enabling the adhesion of the end sealing sleeve material and the conveying pipe (or the anti-corrosion material), under the condition that rigid plugging cannot provide enough anchoring force, relative displacement between a main pipeline and a sleeve can be prevented by reserving pipeline expansion allowance through flexible plugging, so that the integrity of a plugging end is ensured, meanwhile, each influence factor and protection state of pipeline cathode protection in the sleeve are analyzed by utilizing numerical simulation, the defects of theoretical calculation and empirical estimation are overcome to a certain extent by the numerical simulation technology, heavy measurement work and expensive measurement cost brought by actual measurement are reduced, and the protection potential and current density of each point on the surface of a protected object can be obtained through numerical calculation.
Drawings
FIG. 1 is a schematic overall flow diagram of the present invention;
FIG. 2 is a diagram of an electric field infinitesimal model according to the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention.
Example 1:
referring to fig. 1-2, a method for researching a leakage-blocking prevention scheme of a pipe sleeve in an assembly type building structure, as shown in fig. 1, includes the following steps:
s1: the method is characterized in that a proper pipeline sleeve leakage prevention scheme is selected, a closed elastic compensation type sleeve is adopted, the sleeve is sleeved on the pipeline, the end head of the sleeve is connected with the pipeline in a closed mode through a corrugated pipe elastic element, a water stop plate is fixed on the sleeve and embedded in a floor slab to be integrated with the pipeline, the outer surface of the corrugated pipe is subjected to anti-corrosion treatment in the same grade as the pipeline, so that a closed cavity is formed between the pipeline and the sleeve, the waterproof and anti-corrosion effects are achieved, the corrugated pipe elastic element is reliable in quality, zero in leakage, low in cost and long in service life, the outer wall of a pipeline connecting part can be prevented from being corroded, the leakage rate of media in the pipeline is reduced, pipelines and valves in a valve well are protected, the maintenance cost is reduced, the service lives of the pipelines and;
s2: selecting any form of sleeve according to the specific situation of a site, and selecting the specification form and the connection mode of the sleeve according to the outer diameter, the material and the length of the pipeline, the thickness and the material of a floor slab before the installation of the closed elastic compensation type pipeline sleeve for a newly-built project; for maintenance projects, the original sleeve can be utilized, and corrugated pipe compensation elements are connected to two ends of the sleeve; in order to save materials and cost, under the condition of lower water pressure, a corrugated pipe compensation element can be arranged on one side of the sleeve contacting water to seal one side; in the aspect of material selection, for weldable metal pipelines, in order to facilitate connection, a closed elastic compensation type pipeline wall bushing made of metal materials is selected; for the non-metal pipeline, a closed elastic compensation type pipeline sleeve made of a metal material can be selected, and the non-metal pipeline can also be adopted; the connection mode can be selected from welding, clamping and flange connection; the static sealing points can be increased by selecting the clamping and flange connection modes, but the sealing effect of the sleeve is not influenced; the external compensation type welded sleeve structure is simple to install and is suitable for preventing leakage of wall penetrating positions of most metal pipelines; the external compensation type flange connecting sleeve is suitable for the condition that the material of the pipeline is different from that of the compensation element, and the pipeline is connected with the compensation element through a flange, a bolt and a gasket; the built-in compensation type welded sleeve structure is suitable for the conditions that the requirement on the internal structure space of buildings and structures is concise and attractive, is suitable for the leakage prevention of most metal pipeline parts, and can be freely adjusted in length by adopting a mode of freely connecting the sleeve and an adjustable stepped sleeve for the convenience of installation; the built-in compensation type flange connecting sleeve is suitable for the conditions that the requirement on the internal structure space of a building and a structure is concise and attractive, is suitable for the leakage prevention of the pipeline part under the condition that the materials of the pipeline and the compensation element are different, and can be selected according to the specific condition of the environment or adopt other combination forms; the sleeve is installed according to relevant specifications, so that the requirement on the installation precision of the sleeve can be met; for materials which are easy to corrode, the corrosion prevention treatment which is the same as the grade of the pipeline or the asphalt corrosion prevention is needed to be carried out on the sleeve close to the underground water side;
the key links for applying the technology on the pipeline are calculation of the expansion amount of the pipeline and selection of a corrugated pipe compensation element; firstly, the thermal expansion and cold contraction variation of the pipeline is calculated according to a formula, wherein the formula is as follows:
ΔX＝0.012×(t1-t2)×L
in the formula:
t1 is the temperature of heating medium, DEG C;
t2 is the temperature at which the pipe is installed, DEG C;
l is the calculated length of the pipeline, m;
0.012 is the linear expansion coefficient of steel, mm/(m ℃);
because the pipeline is under the action of the resistance of the floor in the expansion process caused by the temperature change, the expansion amount of circulating water, fresh water (fire water) and sewage pipelines is less than 25mm and the expansion amount of the buried heat supply pipeline is less than 50mm by taking the friction coefficient into consideration and calculating and practical experience; then, selecting a corrugated pipe compensation element according to the thermal expansion and cold contraction variation of the pipeline and the outer diameter of the pipeline, wherein the corrugated pipe is selected according to the standard because the size specification of the corrugated pipe is serialized according to the inner diameter standard; finally, determining the length of the straight pipe section of the sleeve according to the material and the thickness of the floor slab;
for the assembled steel structure floor hole, a straight pipe section and a water stop plate of a sleeve are omitted, an elastic compensation element is directly welded on the wall of a steel well, and the position of the outer surface, which is easy to corrode, is subjected to corrosion prevention treatment in the same grade as the pipeline; for a concrete structure floor hole, a straight pipe section of a sleeve and a water stop plate are installed according to a construction method and a sequence required by specifications, an elastic compensation element is welded on a pipeline and the straight pipe section of the sleeve, and the part with the easily corroded outer surface is subjected to corrosion prevention treatment in the same grade as the pipeline; during the installation process, determining the precompression amount of the corrugated pipe according to the expansion amount of the pipeline and the compensation amount of the corrugated pipe; because the water pressure is far less than the compressive strength of the steel corrugated pipe, the pressure of water on the elastic compensation type pipeline sleeve can be ignored;
s3: designing a plugging scheme for sealing the sleeve end, according to production experience, commonly using two types of sleeve end plugging schemes in engineering, based on rigid plugging of insulating materials such as broken red bricks, cement mortar and asphalt hemp and based on flexible plugging of end sealing sleeves, combining a pipeline constraint rule, analyzing the stress and displacement level of a main pipeline in the sleeve under an operating condition, comprehensively judging the adaptability of two plugging modes, and recommending a proper pipeline sleeve end plugging scheme; in the running state of the pipeline, the pipeline generates stress and strain due to the action of temperature, pressure and the like on a pipeline system, so that the stability of the plugging end of the sleeve is also restricted by the movement of the pipeline under the operation condition (mainly considering the influence of the deformation of the pipeline on the plugging end), and the complete restriction of the pipeline is roughly divided into two modes, namely rigid restriction of a floor slab; a is for the natural anchorage of the floor, most long straight pipelines can be regarded as in the complete anchorage and restrained the state, go in and out the place and some pipelines near the line bend are in half the half-anchorage and half-restrained the state, under the complete anchorage state, the pipeline because deformation that temperature difference, pressure, etc. produce is restrained by the friction that the floor component, etc. provided, so the pipeline presents the state of high axial stress, no bending stress, no deformation; in a semi-anchoring and semi-active state, the deformation of the pipeline caused by temperature difference, pressure and the like can only be partially restrained by the friction force provided by the floor slab, so that the pipeline is in a state of low axial stress, high bending stress and large deformation, generally, the length of the non-anchoring section of the pipeline is more than 2.4m, and for the pipeline passing through the floor slab, in order to adjust the passing angle and meet the specification requirement, related constructional measures are generally arranged at the two ends of the passing section; meanwhile, no constraint is provided in the sleeve, and the natural anchoring section is also interrupted; therefore, according to the analysis, the pipeline at the crossing section is almost completely in a semi-anchoring and semi-active state, the pipeline at the crossing section can be qualitatively considered to be in an active state in the casing according to the analysis of the active section rule of the pipeline, and for rigid plugging, if enough anchoring force can be provided, the pipeline in the casing can be completely constrained; otherwise, the pipeline in the casing pipe is subjected to thermal displacement, so that the sealing end of the main pipeline is inevitably subjected to relative movement, and the integrity of rigid sealing is damaged; generally, a stress model recommended in ASME B31.8 is adopted to calculate axial stress under different working conditions, the axial stress mainly comprises axial component force caused by internal pressure, temperature difference and bending moment, and the straight pipe section is completely constrained at two ends according to the specification of ASME B31.8, and the axial stress calculation method comprises the following steps:
in the formula:
μ -poisson coefficient;
t is the wall thickness of the pipeline, mm;
p is the pressure in the pipeline, MPa;
d, the outer diameter of the pipeline is mm;
α -coefficient of thermal expansion of the pipe, 1/deg.C;
t 1-temperature of pipe installation and mouth collision, DEG C;
t 2-ultimate operating temperature of the pipeline, DEG C;
e, the elastic modulus of the steel pipe is MPa;
meanwhile, considering the thrust additional effect of the pipe end, the total axial thrust of the pipeline can be expressed as:
in the formula:
f, thrust, N;
aip — internal cross-sectional area of pipe, m 2;
apipe-cross sectional area of tube wall, m 2;
in order to confirm the accuracy of the formula, the CAESARII is used for carrying out complex check on the calculation result of the formula to obtain an example table; therefore, an anchoring thrust calculation formula deduced according to the stress basic rule is very close to a software simulation value, the error is mainly caused by factors such as iteration, piping system relation and the like, and the software calculation is more rigorous;
generally, after the pipeline is provided with the anchoring piers, enough anchoring force can be provided for the pipeline, pipeline movement is reduced, and stress concentration is prevented; the force is generated by the friction between the anchoring pier and the floor slab so as to overcome the thrust transmitted to the anchoring flange by the thermal expansion of the pipeline and the like; for the rigid plugging end, the inner wall of the sleeve and the outer wall of the main pipeline are both not provided with bulges, and the sleeve can only provide restraint by means of mutual friction; thus, if the friction force F is greater than the pipe axial thrust force F, it indicates that the pipe can be anchored, as follows:
f＝F
if flexible plugging is adopted, the pipeline can be allowed to axially move to a certain degree under the operation condition, so that the allowable expansion amount of the sealing sleeve is larger than the free expansion amount of the pipeline under the working condition of extreme displacement; according to the classical Hooke's law, under a certain temperature difference, the expansion amount of the pipeline is as follows:
ΔL＝α·(T1-T2)·L
in the formula:
Δ L-the telescopic length of the pipeline, m;
l is the original length of the pipeline, m;
in fact, the amount of expansion and contraction of the pipeline is smaller than the corresponding calculation result, because the pipeline is constrained and cannot move freely, the calculation result is conservative and reliable as the maximum allowable displacement; therefore, the adopted flexible plugging material is required to reserve an extension allowance (generally realized by folds at the transition part of the sleeve and the main pipe section) according to the maximum displacement of the pipeline so as to avoid the plugging sleeve from being pulled apart when the main pipeline expands and ensure the pipeline sealing effect;
s4: selecting a proper sleeve plugging scheme, adopting a method for sealing a sleeve port when a flexible plugging sleeve passes through a pipeline, enabling the material characteristics of an end sealing sleeve to adapt to the pipeline conveying temperature and the environmental temperature during construction, enabling the adhesion of the material of the end sealing sleeve and a conveying pipe (or an anticorrosive material) to be stable for a long time, simultaneously adopting a fold type installation method to provide a telescopic allowance for the expansion and contraction of the pipeline in operation on the premise of ensuring the strength of the end sealing sleeve (according to the requirements of related technical specifications), and preventing the relative displacement between a main pipeline and the sleeve when the pipeline cannot provide enough anchoring force in rigid plugging so as to ensure the integrity of a plugging end and further thoroughly avoid the plugging failure caused by the operation working condition, adopting fine sand or fine soil to backfill around the end sealing sleeve to avoid sharp objects carried in backfill from puncturing the sealing sleeve, if the exhaust pipe is required to be arranged, a flexible plugging sleeve with double openings is adopted, and field cutting is reduced as much as possible;
s5: the influence of the numerical simulation sleeve on the cathodic protection potential of the metal pipeline is as follows:
firstly, establishing a model, including solving a mathematical model and boundary conditions with a physical model and a model, simplifying the mathematical model, uniformly and consistently arranging the surrounding floor slab media where the pipeline is located, keeping a cathode protection system in a stable state, keeping cathode protection current in an ohm law, keeping the floor slab concrete medium in an electric neutral principle, and enabling a infinitesimal body model in the floor slab medium to be as shown in figure 2;
according to the classical electric field theory, the medium around the floor follows the ohm law, see the formula;
in the formula:
qc is the amount of charge that flows through a boundary in the electric field, C;
sigma is the conductivity, S/m;
a is the area of the boundary region, m 2;
phi is the potential at a certain point in the electric field, V;
x is unit length, m;
t is time, s;
when the source point and the sink point are not contained in the micro-element to be inspected, the charge quantity flowing in from the left side of the micro-element is the same as the charge quantity flowing out from the right side; deducing potential distribution in the obtained floor electrolyte region to satisfy the following equation
Namely, it is
The equation is a control equation for representing the distribution of the cathodic protection potential;
determining boundary conditions, wherein the anode surface gives a fixed anode open circuit potential, and the pipeline surface and the inner and outer surfaces of the sleeve give protection current densities required by the coating; the ground is insulated, and the two ends of the sleeve are sealed, if the two ends of the sleeve are sealed, the current cannot flow in, otherwise, the current flows in; setting infinite sizes for the lower surface of the floor slab and the surface of the floor slab in the direction parallel to the pipeline; the current for the remaining boundary conditions is zero, and the zero current boundary condition can be defined as: ∑ j ═ 0; based on the corrosion and protection requirements of metal material pipelines, adopting a coating method and cathode protection for the pipelines, and selecting the pipeline protection current densities of good, medium and poor coatings to be 0.01mA/m2, 0.05mA/m2 and 0.1mA/m2 respectively according to the selection principle of a protection current anti-corrosion layer in the standard; the simulation scheme is to change a plurality of test working conditions to seek the influence of the test working conditions on the pipeline potential;
solving a physical model and a model, namely taking a pipeline with the length of 2000m and the pipe diameter of 610mm, arranging a sacrificial anode at the middle position in the length direction of the pipeline, wherein the sacrificial anode is a cylinder, and has the length of 5m and the diameter of 0.2 m; sleeves with the length of 20m and the length of 10m are respectively arranged at the positions 300m away from the left and the right of the sacrificial anode, the diameter of each sleeve is 813mm, and the wall thickness is 10 mm; the bracelet sacrificial anode in the sleeve is a circular ring with a main radius of 0.31m and a small radius of 0.05 m; the floor slab area is a cuboid, and the size is 2200m (length) x 50m (width) x 20m (height); respectively establishing a sleeve, a pipeline, an anode and two end sealing models, and then establishing a floor slab environment; the buried depths of the pipeline and the sacrificial anode are both 2m, and the distance between the sacrificial anode and the center of the pipeline is 3 m; wherein the sacrificial anode material is a zinc anode, and the open-circuit potential is-1.05V; taking the soil resistivity as 20 omega-m;
and finally, calculating the cathodic protection potential of the pipeline and analyzing the result of the established model, wherein the method comprises the following steps: mesh subdivision is carried out firstly, the generated model is divided by adopting a freely subdivided tetrahedral mesh, the pipeline, the sleeve and the anode boundary mesh are divided into extremely-refined meshes, solution domains of other floors are divided into special-refined meshes, and the solution cost is reduced; secondly, setting a solver, solving by adopting a steady state solver, setting the precision requirement to be less than 0.001, resetting the configuration parameters of the solver if the precision requirement is not met, increasing iteration times, repeatedly modifying until the precision of the solved result meets the final requirement, then performing post-processing, and obtaining data and graphs required by subsequent comparative analysis by utilizing the self-contained post-processing function of software;
secondly, summarizing the influence of the sleeve on the cathode protection potential of the pipeline, the influence of whether two ends of the sleeve are sealed on the cathode protection potential of the pipeline, and the influence of the coating quality on the cathode protection potential of the pipeline, wherein the coating quality comprises the coating quality on the surface of the sleeve and the coating quality on the outer surface of the pipeline, the influence of electrolyte in the sleeve on the cathode protection potential of the pipeline, the influence of whether a sacrificial anode is arranged in the sleeve on the cathode protection potential of the pipeline, and the influence of the defect point of the coating of the inner and outer pipelines of the sleeve on the cathode protection potential of the pipeline;
thirdly, concluding that the cathode protection current cannot smoothly flow into the pipeline due to the shielding effect of the sleeve on the cathode protection current, and the longer the sleeve is, the more obvious the shielding effect is, so that the cathode protection potential of the sleeve section is influenced by the sleeve after the sleeve is installed on the pipeline, and the longer the sleeve is, the larger the influence is; the sealed sleeve can prevent impurities such as soil, underground water, silt and the like from entering the sleeve to cause corrosion of a pipeline; the better the coating quality, the more negative the cathodic protection potential, the less cathodic protection current required by the pipeline, the less electric energy consumed by the forced current rule, and the longer the service life of the sacrificial anode; the larger the conductivity of the internal electrolyte is, the more negative the protection potential of the pipeline is, so that under the condition that the sleeve is filled with the electrolyte, the good conductivity of the electrolyte material is required to ensure that the pipeline in the sleeve can obtain the sufficient cathodic protection effect; because the cathode protection current of the pipeline in the casing is shielded, the sacrificial anode is arranged in the pipeline, so that the cathode protection potential of the special section can be realized, the cathode protection effect is achieved, the good sealing performance of the casing is ensured while the sacrificial anode is arranged, and the service life of the sacrificial anode in the casing can be effectively prolonged; when the defects of the coating of the inner and outer pipelines of the sleeve are more serious, the positive deviation of the cathode protection potential of the pipeline is larger, and the defect points in the pipeline are not only seriously damaged but also difficult to detect, so that the pipeline coating in the sleeve needs to be protected in an enhanced level in engineering, and the defect points are avoided as much as possible.
The technical scheme adopts the closed elastic corrugated pipe compensation type sleeve technology by comparing and selecting the leakage reason of the pipeline crossing part and the technical scheme, utilizes the elastic corrugated pipe to compensate the expansion amount of the pipeline, so that a space is formed between the pipeline and the sleeve, thereby achieving the purposes of zero leakage and corrosion prevention of the pipeline sleeve, preventing the corrosion of the outer wall of the pipeline connecting part, reducing the leakage rate of media in the pipeline, protecting the pipeline and the valve in a valve well, reducing the maintenance cost, prolonging the service life of the pipeline and the valve, protecting the water environment of a building, adopting the method of using the flexible plugging sleeve as the sleeve port sealing when the pipeline passes through, enabling the material characteristics of the end sealing sleeve to adapt to the pipeline conveying temperature and the environmental temperature during the construction period, and enabling the adhesion of the end sealing sleeve material and the conveying pipe (or the anti-corrosion material) to be stable for a long time, under the condition that rigid plugging cannot provide enough anchoring force, relative displacement between a main pipeline and a sleeve can be prevented by reserving pipeline expansion allowance through flexible plugging, so that the integrity of a plugging end is ensured, meanwhile, each influence factor and protection state of pipeline cathode protection in the sleeve are analyzed by utilizing numerical simulation, the defects of theoretical calculation and empirical estimation are overcome to a certain extent by the numerical simulation technology, heavy measurement work and expensive measurement cost brought by actual measurement are reduced, and the protection potential and current density of each point on the surface of a protected object can be obtained through numerical calculation.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (6)
1. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure is characterized by comprising the following steps of:
s1: selecting a proper pipeline sleeve leakage prevention scheme, adopting a closed elastic compensation type sleeve, sleeving the sleeve on the pipeline, connecting the end of the sleeve and the pipeline in a closed manner by using a corrugated pipe elastic element, fixing a water stop plate on the sleeve, embedding the sleeve in a floor slab to form a whole with the pipeline, and performing anticorrosive treatment on the outer surface of the corrugated pipe at the same level as that of the pipeline so as to form a closed cavity between the pipeline and the sleeve;
s2: according to the specific situation on site, the casing is selected: for a newly-built project, before the closed elastic compensation type pipeline sleeve is installed, the specification form and the connection mode of the sleeve are selected according to the outer diameter, the material and the length of the pipeline and the thickness and the material of a floor slab; for maintenance projects, connecting corrugated pipe compensation elements at two ends by using the original sleeve;
s3: designing a plugging scheme for sealing the sleeve end, wherein two types of sleeve end plugging schemes which comprise a rigid plugging scheme and a flexible plugging scheme are commonly used in engineering according to production experience, analyzing the stress and displacement levels of a main pipeline in the sleeve under an operation condition by combining with a pipeline constraint rule, comprehensively judging the adaptability of the two plugging schemes, and recommending a proper pipeline sleeve end plugging scheme;
s4: selecting a proper sleeve end plugging scheme, and adopting a method that a flexible plugging sleeve is used for sealing a sleeve port when a pipeline passes through, so that the material characteristics of an end sealing sleeve can adapt to the pipeline conveying temperature and the environmental temperature during construction, the bonding of the end sealing sleeve material and the pipeline can be stable for a long time, meanwhile, on the premise of ensuring the strength of the end sealing sleeve, a fold type installation method is adopted to provide a telescopic allowance for the telescopic movement of the pipeline in operation, and if an exhaust pipe is required to be arranged, the flexible plugging sleeve with double openings is adopted;
s5: the influence of the numerical simulation sleeve on the cathodic protection potential of the metal pipeline is as follows:
firstly, establishing a model, including a mathematical model and boundary conditions and solving a physical model and a model, simplifying the model, then determining the boundary conditions, and finally calculating the cathode protection potential of the pipeline and analyzing the result of the established model according to related steps;
the mathematical model is as follows: according to the classical electric field theory, the medium around the floor follows the ohm law, see the formula;
in the formula:
qc is the amount of charge that flows through a boundary in the electric field, C;
sigma is the conductivity, S/m;
a is the area of the boundary region, m 2;
phi is the potential at a certain point in the electric field, V;
x is unit length, m;
t is time, s;
boundary conditions: the surface of the anode gives a fixed anode open circuit potential, and the surface of the pipeline and the inner and outer surfaces of the sleeve give protection current density required by the coating; the ground is insulated, and the two ends of the sleeve are sealed, if the two ends of the sleeve are sealed, the current cannot flow in, otherwise, the current flows in; setting infinite sizes for the lower surface of the floor slab and the surface of the floor slab in the direction parallel to the pipeline; the current for the remaining boundary conditions is zero, and the zero current boundary condition can be defined as: φ i = 0; based on the corrosion and protection requirements of metal material pipelines, adopting a coating method and cathode protection for the pipelines, and selecting the pipeline protection current densities of good, medium and poor coatings to be 0.01mA/m2, 0.05mA/m2 and 0.1mA/m2 respectively according to the selection principle of a protection current anti-corrosion layer in the standard; the simulation scheme is to change a plurality of test working conditions to seek the influence of the test working conditions on the pipeline potential;
physical model and model solution: taking a 2000 m-long pipeline with the pipe diameter of 610mm, arranging a sacrificial anode at the middle position in the length direction of the pipeline, wherein the sacrificial anode is a cylinder, is 5m long and has the diameter of 0.2 m; sleeves with the length of 20m and the length of 10m are respectively arranged at the positions 300m away from the left and the right of the sacrificial anode, the diameter of each sleeve is 813mm, and the wall thickness is 10 mm; the bracelet sacrificial anode in the sleeve is a circular ring with a main radius of 0.31m and a small radius of 0.05 m; the floor slab area is a cuboid, and the size is 2200m in length, 50m in width and 20m in height; respectively establishing a sleeve, a pipeline, an anode and two end sealing models, and then establishing a floor slab environment; the buried depths of the pipeline and the sacrificial anode are both 2m, and the distance between the sacrificial anode and the center of the pipeline is 3 m; wherein the sacrificial anode material is a zinc anode, and the open-circuit potential is-1.05V; taking the soil resistivity as 20 omega-m;
and (4) analyzing results: mesh subdivision is carried out firstly, the generated model is divided by adopting a freely subdivided tetrahedral mesh, the pipeline, the sleeve and the anode boundary mesh are divided into extremely-refined meshes, solution domains of other floors are divided into special-refined meshes, and the solution cost is reduced; secondly, setting a solver, solving by adopting a steady state solver, setting the precision requirement to be less than 0.001, resetting the preparation parameters of the solver if the precision requirement is not met, increasing iteration times, repeatedly modifying until the precision of the solved result meets the final requirement, then carrying out post-processing, and obtaining data and graphs required by subsequent comparative analysis by utilizing the post-processing function of CAESARII software;
secondly, summarizing the sleeve, whether two ends of the sleeve are sealed, the coating quality, electrolyte in the sleeve, whether a sacrificial anode sleeve is arranged in the sleeve or not, and the influence of the coating defect points of the inner and outer pipelines on the cathode protection potential of the pipeline;
thirdly, concluding that after the sleeve is installed on the pipeline, the longer the sleeve is, the greater the influence on the cathode protection potential of the pipeline is; the sealed sleeve can prevent impurities from entering the sleeve to cause corrosion of the pipeline; the better the coating quality is, the less the electric energy consumed by the forced current method is, and the longer the service life of the sacrificial anode is; the larger the conductivity of the internal electrolyte is, the more negative the protection potential of the pipeline is, so that under the condition that the sleeve is filled with the electrolyte, the good conductivity of the electrolyte material is required to ensure that the pipeline in the sleeve can obtain the sufficient cathodic protection effect; the sacrificial anode is arranged inside the sleeve, so that the cathode protection potential in the sleeve can be realized; when the coating defects of the inner and outer pipelines of the sleeve are more serious, the positive deviation of the cathode protection potential of the pipeline is larger.
2. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure according to claim 1, wherein the method comprises the following steps: the connection mode in the S2 can be selected from welding, clamping and flange connection.
3. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure according to claim 1, wherein the method comprises the following steps: and in the S3, the two sleeve end plugging schemes are respectively rigid plugging based on broken red bricks, cement mortar and asphalt hemp insulating materials and flexible plugging based on end sealing sleeves.
4. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure according to claim 1, wherein the method comprises the following steps: and fine sand or fine soil is used for backfilling the periphery of the end sealing sleeve in the S4, so that sharp objects are prevented from being carried in the backfilling.
5. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure according to claim 1, wherein the method comprises the following steps: and the related steps in the S5 are that firstly, freely-split tetrahedral mesh division is adopted for the generated model, secondly, a solver is arranged to enable the precision to meet the requirement, and finally, post-processing is carried out, and data and graphs required by subsequent comparative analysis are obtained by utilizing the post-processing function of CAESARII software.
6. The method for researching the anti-leakage and anti-blocking scheme of the pipeline sleeve in the fabricated building structure according to claim 5, wherein the method comprises the following steps: the solver is a steady state solver.
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