CN102718005A - Leakage detection method for detecting tank bottom leakage through oil gas in tank base of oil tank - Google Patents

Abstract

A leak detection method for oil and gas in the tank base of an oil tank to detect tank bottom leakage, including marking more than 4 marks evenly along the outer wall of the oil tank on the tank base; For the detection hole of the cushion layer, the diameter of the detection hole is 10-13mm, and the depth is 200-300mm. The angle α between the axis of the detection hole and the upper surface of the cement cladding is 30o to 50o; Seal the detection hole with a silicone plug; measure and record the oil and gas concentration of each detection hole and tank chamber with an oil and gas concentration detector at regular intervals; judge the oil tank bottom plate according to the oil and gas concentration values in each detection hole obtained within a period of time Whether leakage occurs. The invention detects whether there is leakage on the bottom plate of the oil tank by drilling holes on the tank foundation to detect the concentration of oil and gas in the foundation. The invention does not affect the normal production of the oil tank and does not damage the foundation of the oil tank.

Description

Leak detection method for oil and gas detection of tank bottom leakage in tank base of oil tank

technical field

The invention belongs to the technical field of oil and gas detection and environmental protection, and in particular relates to a leak detection method for oil and gas detection of tank bottom leakage in the oil tank base of an oil tank with a sand cushion layer.

Background technique

As an important equipment in the petroleum industry, the safe operation of oil tanks has attracted more and more attention. Since the height from the tank bottom 1a to the tank body is covered by the tank foundation (refer to Figure 2, the tank foundation is composed of ring beam 2, sand cushion 3, asphalt sand cushion 4 and cement cladding 5, the bottom of the oil tank is filled sequentially from bottom to top Sand cushion (300mm～600mm) and asphalt sand cushion (not less than 100mm), the oil tank floor 1a is supported on the asphalt sand cushion, and the cement cladding closely covers the gap between the oil tank floor and the ring beam. The upper surface of the tank bottom plate is in contact with the water or sediment in the oil tank, which is very easy to corrode; while the lower surface is in an oxygen-rich humid environment, it is very easy to be electrochemically and chemically corroded, so the oil tank bottom plate is the most prone to hidden dangers in the oil tank In addition, factors such as uneven settlement of the tank foundation, weld seam and steel defects can easily cause leakage of the oil tank floor. Since the oil tank floor is buried in the tank foundation, it is usually impossible to directly observe the state of the oil tank floor, resulting in Oil tank bottom plate leakage is the most imperceptible hidden danger in the operation of oil tanks. This hidden danger will not only cause waste of oil resources and economic losses, but also cause serious pollution and damage to the ecological environment, and even cause fire and explosion accidents. Therefore It is of great practical significance to carry out real-time or regular inspection on the bottom plate of the oil tank, find leakage in time, and eliminate hidden dangers.

The leak detection technology of the oil tank bottom plate is divided into the stop production leak detection method and the non-stop production leak detection method. Production shutdown testing requires evacuating fuel and opening tanks for testing. On the one hand, it affects the daily production of the oil depot and damages the economy. On the other hand, it is labor-intensive and time-consuming. The non-stop production detection is the detection in the state of oil storage, which does not affect the normal production of the oil depot. The main leak detection methods include: robot tank detection system, acoustic emission detection, preset sensor detection and drilling sampling monitoring, etc. The robot tank detection system has high requirements on the safety, controllability and sealing of the equipment, the detection cost is high, and the reliability is low. It is still in the exploratory stage and is mainly used for the detection of ground storage tanks; This dynamic non-destructive testing technology has real-time and online features, is very economical, and the test results are intuitive and thorough. However, the field application has just started. Due to the difficulty in identifying the bottom plate corrosion or defect signals, and the lack of field data, this technology is used in the field. It will take some time; there are two methods for preset sensor detection: laying optical fiber and oil leakage sensing cable at the bottom of the tank. These two methods of oil leakage sensing cable and optical fiber can only be used once and cannot be used again, and the product price is also relatively expensive. , and generally the laying should be completed before the tank is built. After the tank is built, the explosion-proof requirements are high, the difficulty is high, and the cost is high.

Contents of the invention

In view of the above-mentioned technical problems, the object of the present invention is to provide a leak detection method for oil and gas in the tank foundation of the oil tank to detect the leakage of the bottom of the tank. Whether there is leakage is detected, the method of the present invention does not affect the normal production of the oil tank, does not damage the foundation of the oil tank, the required tools are easy to purchase, economical, labor-saving and time-saving, wide applicability, and reliable detection results .

The technical scheme that realizes the object of the present invention is as follows:

A leak detection method for detecting tank bottom leakage of oil and gas in a tank base of an oil tank comprises the following steps:

Step 1. Evenly mark more than 4 marks on the tank foundation along the outer wall of the oil tank;

Step 2. Use a manual drilling device to drill a detection hole directly to the sand cushion at each mark. The diameter of the detection hole is 10-13mm and the depth is 200-300mm. The distance between the axis of the detection hole and the upper surface of the cement cladding The included angle α is 30o to 50o;

Step 3. After drilling a detection hole, quickly seal the detection hole with a silicone plug;

Step 4. Measure and record the oil and gas concentration of each detection hole and tank chamber with an oil and gas concentration detector at regular intervals;

Step 5. According to the oil and gas concentration values in each detection hole obtained within a period of time, it is judged whether leakage occurs on the bottom plate of the oil tank.

The above scheme is adopted, since the asphalt sand cushion and the sand cushion supporting the oil tank floor are successively laid under the oil tank floor, and both the asphalt sand cushion and the sand cushion have pores, once the oil tank floor leaks, The oil will spread to the surroundings and the bottom. Generally, the sealing detection hole closest to the oil leakage point will be filled with oil and gas first. This is the basis for finding the leakage and judging the approximate location of the leakage point. Due to the narrow space of the tank room where the oil tank is installed, it is difficult to exchange the air in the tank with the outside air. Once the bottom plate of the oil tank leaks, there will be more or less oil and gas in the tank room, so the drilling method that will generate sparks cannot be used. The present invention Manual drilling is used to ensure the safety of drilling. When drilling is difficult, a little water can be poured on the drill bit to reduce the wear and tear of the drill bit and reduce the resistance of drilling. Since the oil and gas concentration detection hole goes deep into the sand cushion, and the sand cushion has many pores, if there is leakage in the oil tank and the detection hole is not sealed immediately, the leaking oil and gas will enter the tank chamber along the detection hole , First, it affects judgment, and second, it is very unsafe. After the oil and gas concentration detector is used to measure and record the oil and gas concentration of each detection hole and tank chamber, the process of whether the oil tank bottom plate leaks is as follows:

Because there is a layer of asphalt sand insulation layer in the oil tank foundation, and some oil tank foundations also use asphalt to seal the gap between the tank bottom and the foundation, and more or less volatile organic compound gases (VOC gases) remain in the asphalt, so The oil and gas concentration in the foundation of the oil tank is generally not zero, but field experiments have proved that the oil and gas concentration in the foundation of all non-leakage tanks has little difference, and the average oil and gas concentration value in the foundation of an oil depot without oil leakage can be obtained. When a certain oil tank When the oil and gas concentration value of one or more detection holes reaches dozens or even hundreds of times of the average oil and gas concentration value in the foundation of the non-leakage tank of the reservoir, it can be judged that the tank has leaked.

Further, in step 5, if the oil and gas concentration of a certain detection hole obtained is much higher than that of other detection holes, continue to drill the detection hole in the middle of the hole and the adjacent hole, repeat steps 3 to 4, and finally according to a period of time The oil and gas concentration values obtained in each detection hole can be used to judge the approximate position or orientation of the leakage point of the oil tank floor. In this way, it is beneficial to increase the accuracy of detection.

Further, the manual drilling device used in step 2 is a bow drill or a hand drill. A bow drill or a hand drill is good for protecting safety during drilling.

Further, in step 2, the detection hole has a diameter of 12mm and a depth of 250mm. The aperture of the detection hole is selected as 12mm, mainly based on these considerations: 1. If the aperture is too large, it will cause damage or damage to the tank foundation; 2. The manual drilling device can only install a drill with a diameter of 10mm at most, and a drill with a diameter of 10mm The completed aperture is 12mm; 3. The confined space of the detection hole is too small, and the pump-suction PID oil and gas concentration detector is easy to suck and shut down, thus affecting the measurement of oil and gas concentration. 4. It must match the size of the silica gel plug. The diameter of the lower end of the silica gel plug used in the present invention is 12mm, and the diameter of the upper end is 17mm. The plug also seals the probe hole. The depth of the detection hole is selected as 250mm, mainly based on the following considerations: 1. The asphalt sand cushion of the tank foundation is 100mm, if the inclination angle a of the detection hole is 45°, the depth of the hole passing through the asphalt sand cushion is 141.4mm , plus the thickness of the cement coating is 10mm, and the thickness of the sand cushion is at least 300mm, so the detection hole is selected as 250mm to ensure that the detection hole reaches the sand cushion; 2. The size of the drill bit is generally 300mm long, Longer ones need to be custom-made. Considering the convenience of purchase, choose a 300mm long drill bit; 3. The depth of the detection hole drilled by a 300mm long drill bit with a manual tool is 250mm, which fully meets the requirements of the actual measurement; 4. But if it is convenient to buy a longer drill bit, it is better to choose 500mm or 600mm.

Further, the angle α between the axis of the detection hole and the upper surface of the cement cladding is 45°. Drilling to the direction of the sand cushion at an included angle of 45o is beneficial to make the depth of the hole reach 250mm, and it is also more suitable for the selection of tools.

Further, the surface of the silicone plug in step 3 is coated with a sealant, which is vacuum silicone grease, Vaseline, etc. The silicone plug itself has good flexibility. If a layer of sealant can be applied around the plug, the sealing effect of the detection hole will be better.

Further, in step 3, after the detection hole is sealed with a silica gel plug, the detection hole is marked. After the label is beneficial to the measurement, recording and management of each detection hole, it is helpful for the judgment of the specific leakage point of the oil tank.

The oil and gas concentration detector is a PID oil and gas concentration detector. The detection of the concentration of oil and gas leaking in the tank foundation not only requires high precision and high sensitivity, but also requires the detection instrument to have certain directivity in the complex gas environment of the tank foundation. The PID oil and gas concentration detector (10.6eV photoionization detector) responds to the volatilized oil and gas (above butane in VOC gas) in the leaked oil in the tank foundation, but to other carbon monoxide, carbon dioxide, methane that may exist in the tank foundation There is no response to water vapor, etc., and the PID oil and gas concentration detector has better accuracy (as low as 1PPM) and sensitivity than other gas detectors, so we choose the PID oil and gas concentration detector as our instrument for measuring oil and gas concentration. Since the sampling method of the PID oil and gas concentration detector is the pump suction type, the sampling time cannot be too short when measuring the oil and gas concentration, and the sampling can only be completed after the reading is basically stable. later stability.

In summary, the present invention detects whether there is leakage on the bottom plate of the oil tank by drilling holes on the tank foundation to detect the concentration of oil and gas. The method of the present invention does not affect the normal production of the oil tank and does not damage the foundation of the oil tank. The required tools are easy to purchase, economical, labor-saving and time-saving, have wide applicability and reliable test results.

Description of drawings

Fig. 1 is the top view of oil tank;

Fig. 2 is a structural schematic diagram of the oil tank body installed in the tank foundation;

Fig. 3 is the schematic diagram of the oil tank and tank foundation installed with sealing plug;

1 is the oil tank, 1a is the bottom plate of the oil tank, 2 is the ring beam, 3 is the sand cushion, 4 is the asphalt sand cushion, 5 is the cement cladding, 6 is the detection hole, and 7 is the silica gel plug.

Detailed ways

With reference to Fig. 1 and Fig. 2, the leak detection method of oil gas detection tank bottom seepage in the tank base of the oil tank of the present invention, comprises the following steps:

Step 1. Evenly mark more than 4 marks on the tank foundation along the outer wall of the oil tank;

Step 2. Use a manual drilling device to drill a detection hole 6 directly reaching the sand cushion layer 3 at each mark. The manual drilling device used is a bow drill or a hand drill. The diameter of the detection hole is 10-13mm, and the depth is 200-300mm. The diameter of the detection hole is 12mm, and the depth is 250mm. The angle α between the axis of the detection hole and the upper surface of the cement cladding 5 is 30o to 50o; the axis of the detection hole The angle α with the upper surface of the cement cladding is 45o.

Step 3. After drilling a detection hole, quickly seal the detection hole with a silica gel plug 7; the surface of the silica gel plug in step 3 is coated with a sealant. After sealing the probe hole with a silicone plug, mark the probe hole.

Step 4. Measure and record the oil and gas concentration of each detection hole and tank chamber with an oil and gas concentration detector at regular intervals; the oil and gas concentration detector is a PID oil and gas concentration detector.

Step 5. According to the oil and gas concentration values in each detection hole obtained within a period of time, it is judged whether the oil tank bottom plate 1a leaks. In step 5, if the oil and gas concentration of a certain detection hole obtained is much higher than that of other detection holes, continue to drill the detection hole in the middle of the hole and the adjacent hole, repeat steps 3 to 4, and finally according to the obtained detection holes The oil and gas concentration value in the oil tank can be used to determine the approximate position or orientation of the oil tank floor leakage point.

Embodiment one

Taking a 1000m ³ soil-covered oil tank as an example, first measure the circumference of the oil tank to be 38.62 meters, and then determine the position of a leak detection hole every 9.66 meters in the counterclockwise direction from the 200mm on the right side of the oil inlet tank and mark it 1#, 2#, 3# and 4#. Bow drill or hand drill is used to drill detection holes at each mark. The drill bit needs to penetrate the cement coating, ring beam, and reach the sand cushion. The diameter of the detection hole is 12mm and the depth is 250mm. The formed detection hole The included angle α between the axis and the upper surface of the cement cladding is 45o. Immediately after the hole is completed, plug the detection hole with a silicone plug coated with vacuum silicone grease on the surface, and measure the tank chamber and 1# to 4# detection holes after 24 hours Primary oil and gas concentration. If the oil and gas concentration in the 2# detection hole is very high, drill 2 more detection holes in the middle of the 1# detection hole and 2# detection hole, 2# detection hole and 3# detection hole, which are marked as 1.5# detection hole and 2.5# detection hole. If the oil and gas concentration of 1.5# detection hole and 2.5# detection hole are both high, it means that the leak point is near the midpoint between 2# detection hole and the center O of the tank bottom; if the oil and gas concentration of 1.5# detection hole and 2.5# detection hole are normal, it means The leak point is near the 2# detection hole; if the 1.5# detection hole has a high oil and gas concentration, but the 2.5# detection hole has no abnormal oil and gas concentration, it means that the leakage point is near the connecting line between the 1.5# detection hole and the 2# detection hole.

Embodiment two

Taking a 5000m ³ oil tank as an example, its diameter is 24.8 meters according to the nameplate of the oil tank, and its circumference is calculated to be 77.87 meters. Mark the position of a detection hole every 8.65 meters counterclockwise on the edge plate of the outer wall of the oil tank, drill holes one by one with a bow drill and seal the detection holes with silica gel plugs. The detection holes need to penetrate the cement cladding, ring beam, and reach the sand cushion , the diameter of the detection hole is 12mm, the depth is 250mm, and the angle α between the axis of the formed detection hole and the upper surface of the cement cladding is 45o. After drilling the detection hole, quickly plug it with a silicone plug coated with vacuum silicone grease. Detection holes, after all the detection holes are completed, number the detection holes 1#~9# counterclockwise from the oil inlet pipe. After 24 hours, measure the oil and gas concentration in the tank chamber and 1# to 9# detection holes, make a record and record the measurement date, oil and gas concentration and other information. According to the judging method of Embodiment 1, it is judged whether the bottom plate of the oil tank is leaking, and the approximate location of the leaking.

Claims (8)

1. The leak detection method for oil and gas detection tank bottom leakage in the tank foundation of the oil tank is characterized in that, comprising the following steps: Step 1. Evenly mark more than 4 marks on the tank foundation along the outer wall of the oil tank; Step 2. Use a manual drilling device to drill a detection hole directly to the sand cushion at each mark. The diameter of the detection hole is 10-13mm and the depth is 200-300mm. The distance between the axis of the detection hole and the upper surface of the cement cladding The included angle α is 30o to 50o; Step 3. After drilling a detection hole, quickly seal the detection hole with a silicone plug; Step 4. Measure and record the oil and gas concentration of each detection hole and tank chamber with an oil and gas concentration detector at regular intervals; Step 5. According to the oil and gas concentration values in each detection hole obtained within a period of time, it is judged whether leakage occurs on the bottom plate of the oil tank. 2. The leak detection method for oil and gas detection tank bottom leakage in the tank foundation of the oil tank according to claim 1, characterized in that, in step 5, if the oil and gas concentration of a certain detection hole obtained is much higher than that of other detection holes , continue to drill dense detection holes in the middle of the hole and adjacent holes, repeat steps 3 to 4, and finally determine the approximate location of the leakage point of the oil tank floor according to the oil and gas concentration values in each detection hole obtained within a period of time. location or location. 3. The leak detection method for oil and gas detection tank bottom leakage in the tank base of the oil tank according to claim 1 or 2, characterized in that the manual drilling device used in step 2 is a bow radial drill or a hand drill. 4. The leak detection method for oil and gas detection tank bottom leakage in the tank base of the oil tank according to claim 1 or 2, characterized in that, in step 2, the diameter of the detection hole is 12 mm, and the depth is 250 mm. 5. The leak detection method for oil and gas detection tank bottom leakage in the tank foundation of the oil tank according to claim 1 or 2, characterized in that the angle α between the axis of the detection hole and the upper surface of the cement cladding is 45° . 6. The leak detection method for oil and gas detection tank bottom leakage in the tank base of the oil tank according to claim 1 or 2, characterized in that the surface of the silica gel plug in step 3 is coated with a sealant. 7. The leak detection method for oil and gas detection tank bottom leakage in the tank base of the oil tank according to claim 1 or 2, characterized in that, in step 3, after the detection hole is sealed with a silica gel plug, and the detection hole is labeled . 8. The leak detection method for oil and gas detection tank bottom leakage in the tank base of the oil tank according to claim 1 or 2, characterized in that the oil and gas concentration detector is a PID oil and gas concentration detector.

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