Several Common Methods of Plugging When Leaking Flanges

 Due to the influence of temperature, pressure, and corrosive media in the petroleum and chemical industries, it is common for flanges of material pipelines and equipment to leak. To eliminate hidden troubles, you must stop and deal with them. The following briefly introduces leaking flanges. Non-stop pressurized plugging technology. Flange leakage can be determined according to the pressure, temperature of the medium, flange connection gap and other parameters.

There are five methods to be recommended:

1. Direct caulking

  When the connection gap between the two flanges is less than 1mm and the gap is relatively uniform, and the medium pressure is relatively low, the direct caulking method can be used. The so-called direct twist seam does not use a special clamp, but uses a flat punch and a hand hammer to twist the flange connection gap tightly to form a sealed cavity. The injection agent can be injected into the sealed cavity through a special bolt auxiliary joint to achieve leak prevention purpose. 

2. Copper wire caulking method

  This method is used when the medium pressure is not higher than 2MPa and the flange connection gap is not larger than 5mm. The so-called copper wire twist seam method is to use copper wire with a diameter equal to the flange gap, twist it into the gap with a certain amount of overlap, and use a flat punch to twist the gap to make it a new sealed cavity. Then use a special bolt injection joint to inject the sealant to achieve the purpose of leak prevention. The specific operation is to install a G-shaped clamp near the leak, loosen a nearby nut and unscrew, quickly install the special injection connector for the bolt, and tighten the nut. Remove the G-shaped clamp, move it farther from the leak point, repeat the above process, and install the second injection connector until the quantity is sufficient. Insert copper wire twice the flange circumference into the flange gap and strike it with a hand hammer so that it is completely embedded in the flange gap. Using a spherical punch, the flange connection gap is briefly punched out of the plastic deformation. After these tasks are completed, the sealant can be injected as required. The injection sequence is shown in the following photos (a) (b) (c) (d).

 

Attention:

When selecting and injecting sealants, attention must be paid to the effects of medium temperature and ambient temperature. When the ambient temperature is normal temperature and the medium temperature is higher than 40 ℃, no heating is needed; if the medium temperature is lower than 40 ℃ and the ambient temperature is lower than normal temperature, the agent gun should be heated to improve its fluidity. In order to control the amount of injection and avoid injection of the injection into the leakage system, the volume of the cavity of the fixture should be estimated in order to control the injection amount.

3. Steel band containment

 Install a G-shaped clamp near the leak, loosen the bolt closest to the G-shaped clamp, remove the nut, install the special injection connector for the bolt, and re-tighten the nut. Move the G-clamp to the farthest point from the leak and repeat the above procedure to install the second injection connector. This is repeated until the injection connector is installed. Use asbestos packing or metal wire to plug into the flange gap. The length should be greater than the outer circumference of the flange, and there should be a overlap margin of not less than 50 mm. The overlap is staggered at the leak point. Select a steel belt that meets the requirements in width and has a length greater than the circumference of the flange. Install the steel belt clip and tighten it with a belt tensioner to make the steel belt tightly fit on the outer surface of the flange. Screw, cut off the excess, the rest of the operation is the same as the copper wire containment method.

4. Convex flange fixture method

The convex flange clamp method has a wide range of applications, and can also be plugged in situations where the temperature and pressure are relatively high. The general procedure is as follows.

a. Each injection hole of the clamp is equipped with a number injection valve, and each injection valve is in an open position. When installing the fixture, place the injection hole between the two connecting bolts and ensure that there is an injection hole near the leak hole. In order to ensure the safety of leaking and blocking of flammable and explosive media, explosion-proof tools are used during operation.

b. Close the injection valve furthest from the leak point and connect the injection system to it to start the injection operation. The sequence of plugging injection is shown in the following figure  (a) (b) (c) (d). The remaining steps are the same as the copper wire containment method.

 

c. In the injection operation, the injection volume should be controlled according to the calculated volume of the fixture cavity. The injection pressure is generally that when the system medium pressure is less than 10MPa, the injection pressure should not be higher than 10MPa; when the medium pressure is higher than 10MPa, the injection pressure is the system pressure plus 10MPa.

5. Concave flange fixture method

The concave flange clamp method is mainly used in situations where the flange connection gap is relatively small. The reliability of the seal is not as good as the convex flange clamp. Because there is no boss, it is difficult to install and locate, that is, it is not easy to fully align the groove with the flange gap. The injection molding of this clamp is the same as the convex flange.

Attention:

a. The design of the fixture in the implementation of the plugging must meet the pressure vessel equipment specifications.

b. During the operation, the top pressure of the manual hydraulic pump must be calculated to ensure the injection pressure range.

c. When a glue injection hole is finished and the glue needs to be changed, the glue must be paid attention to the agent valve before disassembling the agent gun.

 

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