1. Operating errors
The water injection pressure is high and the impact is large, and the glass steel pipe cannot be impacted by the load. After being put into use, the operator mistakenly reversed the process and held the pressure, and the operation was unbalanced, which would cause the leakage of the glass steel pipe line.
2. Prevention measures
According to SY/T6267-1996 “High Pressure Fiberglass Pipeline”, J/QH0789-2000 Buckle FRP Pipe Construction and Acceptance Specification. Harbin Star FRP Co., Ltd. “Instructions for Installation of Threaded Fiberglass Pipe Line System”, and refer to GB1350235-97 “Code for Construction and Acceptance of Industrial Metal Piping Engineering”, to prevent common quality defects, grasp the construction of each process, and ensure the quality of construction. In view of the above 6 reasons for leakage, preventive measures are proposed (see Table 1).
After the leakage of the glass steel pipe line occurs, measures must be taken immediately to prevent environmental pollution. The most effective construction method is to cut the taper and use the steel adapter to connect. The main processes are suspending production → finding leaks → excavation → recycling sewage → on-site thread installation → installing steel transfer → welding → pressure test → pipe trench backfilling → commissioning. Connection mode of construction pipe fittings (see Figure 1)
(1) Before cutting and making cones, according to the construction requirements of the HSE system, a warning tape should be pulled in the central area, and warning signs must be placed when entering the construction section. After the leakage occurs, the water injection source is cut off to reduce the pressure to zero, and the sewage is recovered in time after the excavation to prevent the collapse of the pipe trench and hurt people.
(2) After sawing the FRP pipe, the lifting height should not exceed 1m, and the angle should not exceed 10℃. When cutting and making cones, it is safe and convenient to construct on the ground. The maximum difference is more than 2m (the pipeline is buried 1m deep). Excavate both sides from the leakage point. At least 20m above.
(3) On-site thread installation
On-site thread installation process: cutting → taper cutting → bonding on-site threads → heating and curing. The cutting leakage point is better than 0.3m. Choose a suitable ratcheting grinder (manufacturer is equipped with special tools). The cone must be clean, free of grease, dust, moisture, and the adhesive must be evenly mixed. The end plating is bonded to drive out the air bubbles on the bonding surface, and then turn it by hand to tighten. The curing time of the adhesive is determined according to the ambient temperature. The ambient temperature and curing time are shown in Table 2.
In winter, the construction temperature is low, and the water injection stop time cannot exceed 24 hours. The electric heating and curing method can be used to shorten the construction time. According to the construction experience and the characteristics of the adhesive, the best curing effect can be achieved within 3-4 hours, and the total time of construction shutdown is controlled within 8 hours. The heating of the electric heating belt is controlled at 30-32℃, the time is 3 hours, and the cooling time is 0.5 hours. Tropical power requirements (see Table 3).
(4) Install the steel conversion joint. The on-site external thread and the steel conversion internal thread must be clean, and the sealing grease must be evenly applied. There is no torque with a wrench. After tightening by hand, tighten it for two more weeks. If there is a torque with a wrench, press Tighten the approximate rotation torque table (see Table 4).
(5) Welding workers should be certified. During the welding process, the steel conversion joint should be cooled down, and the temperature should not exceed 40°C, otherwise the on-site snail mosquito will be burnt out and leakage will occur.
(6) Pipe trench backfilling. Within 0.2m around the pipeline, it is 0.3m higher than the natural ground after backfilling with sand or soft soil.
4. Conclusions and recommendations
(1) The high-pressure glass steel pipe line is used in the production of water injection wells and part of the water injection trunk line in Jianghan Oilfield, which solves the corrosion and perforation of the pipeline, reduces the pollution, extends the service life of the pipeline, and saves investment.
(2) Through implementation, the construction technology for leak-mending high-pressure glass steel pipe lines has been standardized, the water injection time rate has been increased, safe production has been ensured, and civilized construction has been achieved. Since 2005, the average leakage has been repaired 47 times, and the annual crude oil output has increased by more than 80 tons.
(3) At present, for medium and high-pressure fiberglass steel pipe lines (0.25 MPa ~ 2.50 MPa), taper-making and steel conversion joints are used to repair leakage, which takes a long time and is non-corrosive. With the advancement of science and technology, high-strength resins, initiators, curing agents, accelerators and reinforcing materials continue to be produced. The use of adhesive interfaces for medium and high-pressure fiberglass steel pipe lines requires further research.
Solution to problems of winding product series
After the production of FRP winding products, there will be various problems in the quality of the products. These problems can be effectively eliminated and avoided after specific analysis of raw materials, additives, process and other factors. The following introduces a common problem in winding products-voids.
Basic types of voids
1. The bubbles are inside the fiber bundle, wrapped by the fiber bundle, and formed along the direction of the fiber bundle.
2. The voids mainly appear in the pits between the layers and where the resin accumulates.
Analysis of the cause of the gap
1. The reinforcing material is not completely impregnated with the matrix resin, and a part of the air remains in the fiber material, which is enclosed by the solidified resin around it.
2. The problem of glue itself. First, the glue was mixed with air during the preparation process, which could not be completely eliminated in time; in addition, when the glue was gelled and solidified, small molecules were produced due to chemical reactions, and these low-molecular substances could not escape in time.
Measures to reduce gaps
1. Preferred materials
According to the characteristics of the raw materials, select raw materials that match each other.
2. Strengthen impregnation
Impregnation is an important part of the composite material molding process, and it is the key to the process of bubbles or voids. Therefore, the impregnation must be strengthened to reduce bubbles and improve product quality.
3. Control mixing
Before the resin is used, initiators, accelerators, crosslinking agents, powdered fillers, flame retardants, antistatic agents and pigments will be added. When adding and mixing, a lot of air will be brought in, and measures must be taken to eliminate it.
4. Adjust the glue
Glue dipping is an important process for manufacturing FRP/composite materials. If the glass fiber roving is not impregnated well or the glue is insufficient, white silk will be produced after passing through the glue tank.
5. Rolled products
When white silk yarn is wound on the core mold, this phenomenon can be eliminated only by the core mold rotation element method. It must be eliminated by the rolling of the factory roll. Rolling is not only good for dipping, but also can make the product compact, so that the excess glue flows to or away from the lack of parts, reduces voids or bubbles, makes the product more fit, denser, and has better performance.
6. Reduce bridging
The so-called bridging refers to the phenomenon that the glue yarn of the product is overhead, and this phenomenon exists both at the end and the barrel.
(1) If the equipment is rough in manufacturing, poor in precision, unstable in operation, the yarns are arranged suddenly tightly, overlapping and separated suddenly, the original regular wiring cannot be realized, and the fiber overhead is easy to occur. At this time, maintenance and equipment improvement should be carried out in time.
(2) The actual yarn piece width must be adjusted to be equal to or close to the designed yarn piece width.
(3) Control the amount of glue.
(4) Fiber number, twist, resin viscosity and fiber surface treatment all have a certain effect on the overhead of winding fiber.
(5) The ambient temperature also has a certain influence on the overhead of the fiber.
Inspection and repair of filament wound products
Inspection of filament-wound composite products
For fiber-wound composite products, generally pay attention to the following inspections.
1. Appearance inspection
(1) Air bubbles: The maximum allowable bubble diameter on the surface of the corrosion-resistant layer is 5mm. If there are less than 3 bubbles with a diameter of not more than 5mm per square meter, they can not be repaired. Otherwise, the bubbles should be scratched and repaired.
(2) Cracks: There shall be no cracks above 0.5mm in depth on the surface of the corrosion-resistant layer. The surface of the reinforcement layer must have cracks with a depth of 2 mm or more.
(3) Concave and concave (or wrinkle): The surface of the corrosion-resistant layer should be smooth and flat, and the thickness of the convex and concave part of the reinforcement layer should be no more than 20% of the thickness.
(4) Whitening: The corrosion-resistant layer should not have whitening, and the maximum diameter of the whitening area of the reinforcement layer should not exceed 50mm.
2. Dimensional inspection
In accordance with the requirements of the drawings, the dimensions of the products shall be inspected with measuring tools with appropriate accuracy and range.
3. Inspection of curing degree and lining micropores
(1) On-site inspection
a) There is no sticky feeling when touching the surface of the composite product.
b) Dip clean cotton yarn with acetone and place it on the surface of the product to observe whether the cotton yarn has changed color.
c) Is the sound produced by hitting the product with your hand or coin vague or crisp?
If the hand feels sticky, the cotton yarn is discolored, and the sound is blurred, the surface curing of the product is considered unqualified.
(2) Simple inspection of curing degree of furan composite material
Take a sample and immerse it in a beaker containing a small amount of acetone, seal it, and soak for 24 hours. The surface of the sample is smooth and complete, and the acetone does not change color as a sign of curing.
(3) Inspection and testing of product curing degree
The Barcol hardness test is used to indirectly assess the degree of curing of the composite material. A Barcol hardness tester is used. The model can be HBa-1 or GYZJ934-1, and the measured Barcol hardness is used to convert the approximate degree of curing. The Barcol hardness of wound composite products with ideal curing is generally 40-55. The curing degree of the product can also be accurately tested in accordance with the relevant regulations of GB2576-89.
(4) Detection of lining micropores
When necessary, the composite lining shall be sampled and inspected with an electric spark detector or a micro-hole detector.
4. Product performance inspection
Test the thermal, physical and mechanical properties of the product according to the test content required by the work instruction document and the prescribed test standard to provide a basis for the acceptance of the product.
5. Damage inspection
When necessary, non-destructive testing of products such as ultrasonic scanning, X-ray, CT, thermal imaging, etc. is required to accurately analyze and determine the internal defects of the product.
Product defect analysis, control measures and repair
1. The main reasons for the sticky surface of composite products are as follows:
a) High humidity in the air. Because water vapor has the effect of delaying and inhibiting polymerization of unsaturated polyester resin and epoxy resin, it can even cause permanent stickiness on the surface, and defects such as incomplete curing of the product for a long time. Therefore, it is necessary to ensure that the production of composite products is carried out when the relative humidity is lower than 80%.
b) Too little paraffin wax in the unsaturated polyester resin or the paraffin wax does not meet the requirements, resulting in the inhibition of oxygen in the air. In addition to adding a proper amount of paraffin, other methods (such as adding cellophane or polyester film) can also be used to isolate the surface of the product from the air.
c) The dosage of curing agent and accelerator does not meet the requirements, so the dosage should be strictly controlled according to the formula specified in the technical document when preparing the glue.
d) For unsaturated polyester resins, too much styrene volatilizes, resulting in insufficient styrene monomer in the resin. On the one hand, the resin should not be heated before gelation. On the other hand, the ambient temperature should not be too high (usually 30 degrees Celsius is appropriate), and the amount of ventilation should not be too large.
2. There are too many bubbles in the product, and the reasons are as follows:
a) The air bubbles are not completely driven. Each layer of spreading and winding must be rolled repeatedly with a roller, and the roller should be made into a circular zigzag type or a longitudinal groove type.
b) The viscosity of the resin is too large, and the air bubbles brought into the resin cannot be driven out when stirring or brushing. Need to add an appropriate amount of diluent. The diluent of the unsaturated polyester resin is styrene; the diluent of the epoxy resin can be ethanol, acetone, toluene, xylene and other non-reactive or glycerol ether-based reactive diluents. The diluent of furan resin and phenolic resin is ethanol.
c) Inappropriate selection of reinforcement materials, the types of reinforcement materials used should be reconsidered.
d) The operation process is improper. According to the different types of resins and reinforcing materials, appropriate process methods such as dipping, brushing, and rolling angle should be selected.
3. The reasons for the delamination of products are as follows:
a) The fiber fabric has not been pre-treated, or the treatment is not enough.
b) The tension of the fabric is insufficient during the winding process, or there are too many bubbles.
c) The amount of resin is insufficient or the viscosity is too high, and the fiber is not saturated.
d) The formula is unreasonable, resulting in poor bonding performance, or the curing speed is too fast or too slow.
e) During post-curing, the process conditions are inappropriate (usually premature thermal curing or too high temperature).
Regardless of the delamination caused by any reason, the delamination must be thoroughly removed, and the resin layer outside the defect area must be polished with an angle grinder or polishing machine to a width of not less than 5cm, and then re-layed according to the process requirements. Floor.
Regardless of the above defects, appropriate measures should be taken to completely eliminate them to meet the quality requirements.
Typical winding composite material specimen production and performance test
Composite materials are often anisotropic materials, and their design analysis methods are different from those of metal materials. The anisotropic properties of composite materials lead to the difference between the performance test methods of composite materials and metal materials. For traditional materials, designers can obtain performance data from the manual or the material specification provided by the manufacturer according to the material (or brand) while selecting the material. The composite material is not so much a material as it is a more precise structure. Its performance is related to many factors such as the resin matrix, reinforcement materials, process conditions, storage time and environment.
It is very necessary to test the performance of raw materials before the design of composite materials, but it cannot be said that the performance data necessary for the design is mastered. It can only be considered that the selection of raw materials has laid the foundation. At present, the prediction results of micromechanics methods are still limited and can only be estimated qualitatively. The performance data required for composite component design needs to be obtained by basic performance tests, which is crucial to the design work.
Composite material performance testing is the basis for material selection, evaluation of reinforcement materials, resin matrix, interface properties, molding process conditions and manufacturing technology levels, as well as product design.
1. Unidirectional fiber composite plate
The elastic properties of unidirectional composites are characterized by the tensile and compressive properties of 0 degrees, 90 degrees, and 45 degrees, and the interface properties between the fiber and the resin are characterized by bending and interlaminar shear tests. In order to evaluate the material properties, according to the specific requirements of the national standards GB3354-82, GB3856-83, GB3356-82, GB3357-82, GB3355-82, the production of the unidirectional fiber composite material plate is completed, and then the fiber composite material plate is processed into various The size and quantity of the specimen required by the test method.
1. Production of unidirectional fiber composite material plate
The winding method is to make the fiber drawn from the creel pass through the tensioner, the glue groove, the yarn guide roller, and the wire winding nozzle in turn to be wound on the surface of the core mold, and finally solidified and formed. The national standard stipulates that the size of the template is 270mm X 270mm. The template can be wound to make two flat plates (front and back) at a time, which can be processed for stretching, compression, bending, interlayer shearing, etc.
Post time: Aug-12-2021