A leak detection method for heat exchanger tube

Abstract

A method for detecting leaks in a heat exchanger tube, comprising: 1) a first valve is provided at the extended end of the tube inlet, and a second valve is provided at the extended end of the tube outlet; 2) a first connecting pipe is provided on the extended end of the tube inlet, located downstream of the first valve, and a third valve is provided; 3) a second connecting pipe is provided on the extended end of the tube outlet, located upstream of the second valve, and a fourth valve is provided; 4) the first connecting pipe is connected to a detection liquid source, the third valve is opened, and liquid drips out to the shell port, which is counted as time t1; 5) the second connecting pipe is connected to a detection liquid source, the fourth valve is opened, and liquid drips out to the shell port, which is counted as time t2; 6) the tube length is known, which is recorded as s, and the distance from the tube leakage point to the third valve is set as x, and the heat exchange tube with the leak hole is determined by calculation. The present invention is simple and convenient to operate, and the position of the leak point on the heat exchanger tube can be determined without disassembling the heat exchanger, which greatly improves the maintenance efficiency of the shell-and-tube heat exchanger.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to a leak detection method for a heat exchanger tube. Background Art

[0002] Shell-and-tube heat exchangers are commonly used heat exchange equipment in chemical companies. During the methanol synthesis process, chemical companies need to distill crude methanol, remove the water, and use it as wash water after cooling.

[0003] The water obtained from distillation contains trace amounts of methanol, which is corrosive. During the cooling process, this methanol-containing water can cause corrosion to the tubes of a shell-and-tube heat exchanger. After prolonged operation, a shell-and-tube heat exchanger can develop tiny leaks, which can contaminate the cooling medium. Due to the harmful effects of methanol, leaking heat exchange tubes require prompt inspection and replacement.

[0004] Since the exact location of the tube leak cannot be determined, the usual practice is to remove all the heat exchange tubes in the shell-and-tube heat exchanger, conduct airtightness tests in a water tank one by one, and replace the leaking heat exchange tube with a new one after confirming the leak. The remaining functioning heat exchange tubes, along with the replaced heat exchange tube, are then reinstalled into the shell-and-tube heat exchanger. This operation makes the maintenance of the shell-and-tube heat exchanger time-consuming and labor-intensive, and it is difficult to meet the actual needs of enterprises.

[0005] Therefore, how to efficiently and accurately determine the location of the leak on the tube side of the shell and tube heat exchanger and directly replace the leaking heat exchange tube without disassembling all the heat exchange tubes is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to address the deficiencies in the prior art and provide a method for detecting leaks in the tubes of a heat exchanger. The method is simple and convenient to operate and can locate the location of the leak on the tubes without disassembling the heat exchanger, making it easier for maintenance personnel to directly replace the heat exchange tubes with leaks. This greatly improves the maintenance efficiency of shell-and-tube heat exchangers and avoids missed detections and false detections.

[0007] The technical solution of the present invention is: a leak detection method for a heat exchanger tube, comprising the following steps:

[0008] 1) Turn off the process medium and heat exchange medium, open the end cover on the side of the heat exchanger to be tested for leaks, and drain the residual medium in the shell side until no liquid drips out of the shell side port;

[0009] 2) Install a first valve at the inlet and outlet of the heat exchanger tube to be tested for leaks, and install a second valve at the outlet and outlet of the heat exchanger tube to be tested for leaks;

[0010] 3) Install a first connecting pipe on the extended end of the inlet of the heat exchanger to be tested for leaks, located downstream of the first valve, and install a third valve;

[0011] 4) Install a second connecting pipe on the outlet of the heat exchanger to be tested for leaks, upstream of the second valve, and install a fourth valve;

[0012] 5) Close the first valve and the second valve, open the third valve and the fourth valve, connect the first connecting pipe or the second connecting pipe to the high-pressure gas source, discharge the residual medium in the shell side, remove the high-pressure gas source, and stop the liquid from dripping out of the shell side port;

[0013] 6) Close the third and fourth valves, connect the first connecting pipe to the test liquid source, open the third valve, start timing, and stop timing when liquid drips out of the shell-side port. This is time t1;

[0014] 7) Repeat step 5);

[0015] 8) Close the third and fourth valves, connect the second connecting pipe to the test liquid source, open the fourth valve, and start timing. When liquid drips out of the shell-side port, stop timing, which is recorded as time t2;

[0016] 9) The length of the heat exchanger to be tested for leaks is known, denoted as s. The distance from the leak point to the third valve is set as x. The flow rate of the test liquid in the pipe is the same in steps 6 and 8.

[0017] Then x / t1=(sx) / t2, and x=s t1 / (t1+t2) is calculated. Combined with the length of a single heat exchange tube, the heat exchange tube with a leak can be determined. After replacing it individually and resetting the end cover, the leak detection operation is completed.

[0018] Preferably, the high-pressure gas source in step 5) is a high-pressure nitrogen source.

[0019] Preferably, the detection liquid in step 6) and step 8) is added with pigment.

[0020] Furthermore, the flow rate of the detection liquid in step 6) and step 8) in the tube side is the same as the flow rate of the process medium in the tube side.

[0021] Furthermore, in step 2), the distance between the first valve and the pipe-side inlet is the same as the distance between the second valve and the pipe-side outlet.

[0022] Furthermore, the first connecting tube in step 3) and the second connecting tube in step 4) have the same size, and the distance between the connecting end of the first connecting tube and the pipe-side inlet is the same as the distance between the connecting end of the second connecting tube and the pipe-side outlet.

[0023] Furthermore, after step 8) is completed, step 5) is repeated.

[0024] The above technical solution has the following beneficial effects:

[0025] 1. The leak detection method of the present invention is aimed at detecting the location of leaks in a tube-in-tube heat exchanger whose tubes are connected by multiple heat exchange tubes and elbows. First, a first valve and a second valve are respectively set at the inlet and outlet of the tube to temporarily isolate the tube of the heat exchanger from the process medium. A first connecting pipe is set at the inlet and outlet of the tube, which is located downstream of the first valve. A second connecting pipe is set at the outlet of the tube, which is located upstream of the second valve. The two connecting pipes are connected at both ends of the tube, and the detection liquid is opened or closed by opening or closing the first valve, the second valve, the third valve, and the fourth valve. The liquid enters the tube from one end of the tube and leaks into the shell from the leak point, then drips out from one end of the shell to determine a time period. The detection liquid enters the tube from the other end of the tube and leaks into the shell from the leak point, then drips out from one end of the shell to determine another time period. The time difference formed by the two time periods, combined with the overall length of the tube, can more accurately determine the distance between the leak point and the tube inlet or outlet. Then, based on the known length of a single heat exchange tube, it can be determined on which heat exchange tube the leak point specifically appears. The corresponding heat exchange tube can be directly replaced to complete the maintenance of the heat exchanger. This makes leak detection and maintenance simple and efficient, and can effectively avoid missed detection and false detection. In addition, after completing steps 1) to 4), the tube of the heat exchanger can be quickly tested for liquid leakage during the maintenance interval of other equipment (distillation equipment), or according to actual needs, by controlling the opening or closing of the first valve, the second valve, the third valve, and the fourth valve, eliminating the potential leakage risk in advance without affecting the normal operation of the entire system, and effectively meeting the actual needs of the enterprise.

[0026] 2. Pigments are added to the detection liquid in steps 6) and 8) to facilitate maintenance personnel to observe the dripping situation.

[0027] 3. In steps 6) and 8), the flow rate of the test liquid in the tube is the same as the flow rate of the process medium in the tube, simulating the flow of the process medium in the tube to fit the working conditions of the heat exchanger to be tested for leaks.

[0028] 4. In step 2), the distance between the first valve and the pipe inlet is the same as the distance between the second valve and the pipe outlet. In step 3), the first connecting pipe and the second connecting pipe in step 4) have the same dimensions. The distance between the connecting end of the first connecting pipe and the pipe inlet is the same as the distance between the connecting end of the second connecting pipe and the pipe outlet. This design can effectively reduce leak detection errors, improve the detection accuracy of the leak point on the pipe, and accurately determine the heat exchange tube where the leak point is located.

[0029] Through routine maintenance on the currently used shell-and-tube heat exchangers, the applicant has achieved a 100% accuracy rate in determining the location of the leak point and the corresponding heat exchange tube.

[0030] The following is a further description with reference to the accompanying drawings and specific implementations. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the modified structure of the heat exchanger to be tested for leaks according to the present invention.

[0032] In the accompanying drawings, 1 is the first connecting pipe, 2 is the second connecting pipe, a is the first valve, b is the second valve, c is the third valve, and d is the fourth valve. DETAILED DESCRIPTION

[0033] Example 1

[0034] See also Figure 1 To simplify the process, the applicant conducted a leak test on the tube side of a heat exchanger with a tube side length of 2.67m*2 (U-shaped tube side), including the following steps:

[0035] 1) Turn off the process medium and heat exchange medium, open the end cover on the right side of the heat exchanger to be tested for leaks, and drain the residual medium (water) in the shell side until no liquid drips out of the shell side port;

[0036] 2) Install a first valve a at the extended end of the inlet of the heat exchanger tube to be tested for leaks, and install a second valve b at the extended end of the outlet of the heat exchanger tube to be tested for leaks. The distance between the first valve and the tube inlet is the same as the distance between the second valve and the tube outlet.

[0037] 3) Install a first connecting pipe 1 on the extended end of the inlet of the heat exchanger to be tested for leaks, located downstream of the first valve a, and install a third valve c;

[0038] 4) Install a second connecting pipe 2 on the extended end of the outlet of the heat exchanger tube to be tested for leaks, located upstream of the second valve b, and a fourth valve d. The second connecting pipe 2 and the first connecting pipe 1 have the same dimensions, and the distance between the connecting end of the first connecting pipe and the tube inlet is the same as the distance between the connecting end of the second connecting pipe and the tube outlet.

[0039] 5) Close the first valve and the second valve, open the third valve and the fourth valve, connect the first connecting pipe or the second connecting pipe to the high-pressure nitrogen source, discharge the residual medium in the shell side, remove the high-pressure gas source, and stop the liquid from dripping out of the shell side port;

[0040] 6) Close the third and fourth valves, connect the first connecting pipe to the test liquid source. Typically, a pigment, such as red pigment, is added to the test liquid source, and the pressure of the test liquid source is the same as the pressure of the process medium, but it can also be different. Open the third valve and start timing. When liquid drips out of the shell-side port, stop timing. The time is 8 seconds (5 seconds until the test liquid flows to the shell-side surface, and 3 seconds after the test liquid drips out of the port on the right side of the shell).

[0041] 7) Repeat step 5);

[0042] 8) Close the third and fourth valves, connect the second connecting pipe to the detection liquid source (the detection liquid source is the same as the detection liquid source in step 6), open the fourth valve, start timing, and stop timing when liquid drips out of the shell-side port. The time is 8 seconds (5 seconds after the detection liquid flows to the shell-side surface, and after 3 seconds after the detection liquid drips out of the port on the right side of the shell);

[0043] 9) The length of the heat exchanger to be tested for leaks is known, recorded as 2.67m*2. The distance from the leak point to the third valve is set as x. The flow rate of the test liquid in steps 6 and 8) is the same in the pipe.

[0044] Then x / t1=(sx) / t2, and x=s t1 / (t1+t2) is calculated. x is 2.67m. Combined with the length of a single heat exchange tube, it can be determined that the leak is located on the elbow between the two heat exchange tubes. After replacing them separately, it was found that there was indeed a leak on the elbow. Resetting the end cover completed the leak detection operation.

[0045] Example 2

[0046] See also Figure 1 To simplify the process, the applicant conducted a leak test on a heat exchanger tube with a tube length of 2.67m*2 (U-shaped tube). The other steps were performed according to Example 1, except that the timing of step 6) was 7s, and the time of step 8) was 15s. After calculation, x was 1.63m, that is, the length from the third valve was 1.63m. Since the length of the heat exchange tube was 2.67m, it can be determined that the leak point is on the heat exchange tube located at the bottom. After replacing it separately, it was found that there was indeed a leak hole on the lower heat exchange tube. The end cover was reset, and the leak test was completed.

Claims

1. A heat exchanger tube leak detection method, characterized in that: The following steps are involved: 1) Turn off the process medium and heat exchange medium, open the end cover on one side of the heat exchanger to be tested for leaks, and drain the residual medium in the shell side until no liquid drips out of the shell side port; 2) A first valve is provided at the inlet extension end of the heat exchanger tube to be tested for leaks, and a second valve is provided at the outlet extension end of the heat exchanger tube to be tested for leaks; 3) A first connecting pipe is provided on the extended end of the inlet of the heat exchanger tube to be tested for leaks, which is located downstream of the first valve, and a third valve is provided; 4) A second connecting pipe is provided on the extended end of the outlet of the heat exchanger tube to be tested for leaks, which is located upstream of the second valve, and a fourth valve is provided; 5) Close the first valve and the second valve, open the third valve and the fourth valve, use the first connecting pipe or the second connecting pipe to connect to the high-pressure gas source, discharge the residual medium in the shell side, remove the high-pressure gas source, and wait until no liquid drips out of the shell side port; 6) Close the third valve and the fourth valve, connect the first connecting pipe to the detection liquid source, open the third valve, start timing, and stop timing when liquid drips out of the shell port, which is counted as time t1; 7) Repeat step 5); 8) Close the third valve and the fourth valve, connect the second connecting pipe to the detection liquid source, open the fourth valve, start timing, and stop timing when liquid drips out of the shell port, which is recorded as time t2; 9) The length of the tube of the heat exchanger to be tested for leaks is known, recorded as s, and the distance from the leak point in the tube to the third valve is set to x. Steps 6 and 8) have the same flow rate of the test liquid in the tube. Then x / t1=(sx) / t2, and x=s t1 / (t1+t2) is calculated. Combined with the single tube length of the heat exchange tube, the heat exchange tube with a leak can be determined. After replacing it separately and resetting the end cover, the leak detection operation is completed.

2. The heat exchanger tube leak detection method according to claim 1, characterized in that: Step 5) The high pressure gas source is a high pressure nitrogen source.

3. The heat exchanger tube leak detection method according to claim 1, characterized in that: The detection liquid in step 6) and step 8) is added with pigment.

4. The heat exchanger tube leak detection method according to claim 1, characterized in that: The flow rate of the detection liquid in step 6) and step 8) in the tube is the same as the flow rate of the process medium in the tube.

5. The heat exchanger tube leak detection method according to claim 1, characterized in that: Step 2) The distance between the first valve and the pipe inlet is the same as the distance between the second valve and the pipe outlet.

6. The heat exchanger tube leak detection method according to claim 1, characterized in that: The first connecting tube in step 3) and the second connecting tube in step 4) have the same size, and the distance between the connecting end of the first connecting tube and the pipe inlet is the same as the distance between the connecting end of the second connecting tube and the pipe outlet.

7. The heat exchanger tube leak detection method according to claim 1, characterized in that: After step 8), repeat step 5).

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