There are many types of pipeline construction and dredging maintenance blocking in municipal engineering, such as underwater wall blocking, steel plate blocking, dry mix blocking, retarded drawing mold bag blocking and so on. The sealing principle of the sewage pipe is based on the actual pipeline conditions and the strength of the water flow in the pipe. In order to avoid a certain threat to the downstream construction personnel caused by the water pressure generated by the upstream water after the sealing time is too long, the sealing distance is determined according to the actual situation, and each water inlet of the upstream and intersection Wells is blocked. Before plugging, open the well cover within the scope of all construction sections, place the fence or eye-catching signs, and use a gas detector to detect the gas in the well to ensure that there is no toxic gas before plugging the well. It must be equipped with oxygen for construction. Because there are many branch pipe water outlets in the pipeline, the rubber water blocking air bag assisted sealing technology is used in the diving plugging section (in the construction pipe section), which is convenient for the smooth development of the construction, and avoid the unsafe drainage caused by the elevation difference of some well locations, which affects the normal dredging. In this paper, the construction method of rubber water plugging technology is summarized by engineering practice, and the characteristics, process and operation key points of this technology are introduced, which can provide reference for similar projects.

1 Characteristics and scope of application of airbag plugging technology

1.1 Technical Features

(1) Safety: good sealing performance, can effectively control the anti-seepage requirements of the pipeline, ensure the safety of personnel operation of the construction surface, and improve the construction quality.

(2) Construction period: the construction speed is fast, regardless of the diameter of the pipeline, the installation is extremely convenient and fast, and the blocking of a pipe entrance only takes 2h, which greatly saves labor and construction costs.

(3) Economy: simple operation, high work efficiency and controllable quality; Strong applicability, less manpower and material resources required, shorten the plugging time, and directly reduce the construction cost.

(4) Environmental protection: the air bag does not deform, is not easy to age, can be reused many times, save construction costs, energy saving and environmental protection.

1.2 Scope of Application

The applicability of the technology is very wide, within the allowable range of pressure, the air bag can play a thorough section sealing effect on the pipeline of various materials, specifications and pipe diameters; It is also suitable for quickly blocking water flow in pipelines with different pipe diameters, different planes and positions, which is safe for personnel to operate in underground pipelines and improve construction

Quality.

(2) Construction period: the construction speed is fast, regardless of the diameter of the pipeline, the installation is extremely convenient and fast, and the blocking of a pipe entrance only takes 2h, which greatly saves labor and construction costs.

(3) Economy: simple operation, high work efficiency and controllable quality; Strong applicability, less manpower and material resources required, shorten the plugging time, and directly reduce the construction cost.

(4) Environmental protection: the air bag does not deform, is not easy to age, can be reused many times, save construction costs, energy saving and environmental protection.

1.2 Scope of Application

The applicability of the technology is very wide, within the allowable range of pressure, the air bag can play a thorough section sealing effect on the pipeline of various materials, specifications and pipe diameters; It is also suitable for quickly blocking water flow in pipelines of different diameters, different planes and positions, and is an ideal tool for underground pipelines to carry out drainage and silt treatment.

2. Airbag material performance and technology principle

2.1 Airbag material properties

Pipeline sealing air bag is a kind of multi-specification and multi-shape rubber product made by high temperature vulcanization of polymer synthetic materials such as rubber and fiber fabric, which is used for pipeline and culvert water transmission, sewage discharge and desilting maintenance. The models of the pipe sealing bag are: PVC air nozzle capsule, compound closed water plug, air nozzle type closed water plug, double different inflatable capsule. These products have good anti-expansion strength, but also elastic, flexibility, sealing air bag can meet the use of various working conditions, especially suitable for drainage pipe closed water test, closed air test, leak point search, pipeline maintenance temporary water plugging and other maintenance test work. It has the advantages of simple operation, good aging resistance and long service life.

2.2 Process Principle

The working principle of the pipe sealing bag water blocking is to use the rubber pipe sealing bag to expand it through the inflation method. When the gas pressure in the water blocking bag meets the specified requirements, the water blocking bag fills the entire pipe section and uses the friction generated by the pipe sealing bag wall and the pipe to block the water leakage, so as to achieve the purpose of no water seepage in the target pipe section.

3 Construction process and main construction methods

3.1 Construction process.

Construction preparation → plugging hole measurement -→ hole inspection and cleaning - + air bag placement - + air bag inspection - + air bag recovery.

3.2 Main construction methods

3.2.1 Construction Preparations

(1) Familiar with the drawings, carefully refer to the relevant underground pipeline layout, check the elevation and size of various pipelines, check the internal situation of the pipeline, if there is a problem, study and solve it with the relevant personnel in time, select the matching pipeline airbag parameters (see Figure 1). (2) Tool, pipe water blocking air bag, composed of air bag, pressure gauge, tee, 6m long special air pressure hose and air pump (see Figure 2).

3.2.2 Checking and Clearing

(1) Check whether the surface of the pipeline sealing bag is clean, whether there is dirt attached, whether it is intact, Fill a small amount of gas to check the parts and air bags for air leakage, check whether the pressure gauge pointer points to zero, carefully look at the unit of the pressure gauge (such as the conversion between MPa.bar and kPa. Pa), to avoid misreading the unit of the pressure gauge, so that the inflation pressure is too large leading to the rupture of the air bag. After confirming that it is normal, it can enter the pipeline for sealing operation.

(2) Before sealing, check whether the inner wall of the pipeline is smooth and smooth, and whether there are any protruding burrs should be placed horizontally, not twisted, so as to avoid sharp objects such as pits, glass, and stones. If there are any, remove them immediately, so as not to puncture the air bag. After the air bag is placed in the pipeline, it should be placed horizontally, not twisted, so as not to explode the air bag. (3) When the special sealing air bag for flammable and explosive medium pipelines needs to be opened, it should be noted that the diameter of the opening hole must be larger than the diameter of the unfoldable part of the air bag to facilitate insertion and removal.

3.2.3 Installation of air bags

The sealing air bag is put into the pipe mouth to be blocked, the length is the length of the sealing air bag pipe, and then the compressed air is charged to the specified pressure through the air intake valve, and the construction can be carried out. After completion of construction, open the intake valve to release air and take out the sealing bag.

Operation steps :(1) Construction preparation: First assemble the accessories of the round pipe stopper inflation device to check the leakage of tools. Use the air pump to inflate the air bag, the air pressure shall not exceed 0.15MPa, and check whether the air bag leaks.

(2) Open the pipe mouth, place the airbag slowly into the required position from the mouth, and then inflate it into the airbag, and inflate it to the appropriate pressure. The comparison table of airbag parameters is shown in Table 1.

(3) In order to prevent the air bag and the hose from coming off, the air bag and the hose interface should be tightened with iron plates and screws or tied by other means.

(4) When the air pump inflates the air bag, it should be slowly inflated to keep the pressure inside the pipe blocking the air bag uniform, and observe whether the pressure gauge rises or not, such as the pressure gauge is fast. The rise indicates that the inflation is too fast, at this time should slow down the inflation speed, the air check valve is slightly tightened to reduce the speed of the air intake, otherwise the speed is too fast, quickly exceed the pressure is likely to blow the airbag, because the power of the air pump is different from the brand quality, the inflation speed has a certain difference, so it is necessary to calculate the time required for the air bag to fill up when inflating on the ground.

(5) In the engineering operation, we should always pay attention to the pressure value of the air bag, if the pressure value of the air bag is falling slowly, it is unnecessary to stop the operation and continue to use gas. Pump the air bag to the standard air pressure, and then check where the air bag or accessories leak after the completion of the job.

3.2.4 Air bag Recovery

After use, the surface of the pipe sealing bag should be cleaned immediately with water, and the gas in the bag should be slowly released. Special cleaning agent must be used for air bag cleaning. After cleaning, the air bag can be stored only after checking that there is no attached material on the surface. The storage must be kept ventilated and dry, and should be away from corrosive chemicals or fire sources.

3.2.5 Construction precautions

(1) The pipe stopper should be avoided at the joint of the pipe fitting, where the inner wall has a joint, which affects the tightness of the water plugging, so as to avoid the pipe stopper expanding to one side, the air pressure can not be played up, if it continues to inflate, the pipe stopper will be broken.

(2) During the handling of the airbag, the airbag shall not be dragged to prevent damage to the outer wall of the airbag.

(3) For municipal drainage pipes, the sand is required to be clean, the inner wall is smooth, and no burrs are allowed, otherwise it will affect the sealing of water plugging and even puncture the air bag.

(4) Various specifications of the pipeline stopper must be used in the corresponding pipeline, can not be small to large.

4 Technical Requirements

(1) The temperature is too high (above 50°C) or too low (below 0C) will have a certain impact on the air bag. When the temperature is relatively high, the hardness of the rubber surface of the air bag will be reduced and softened, then the air bag may become very thin according to the usual pressure, the strength will be reduced, and it is easy to burst, then it can be inflated by 2/3 of the usual inflation. When the temperature is too low, the rubber surface hardness of the air bag will increase, and the inflation will be slightly larger than usual about 1/7. (2) When the air bag with flange is inflated. Be sure to straighten the flange horizontally to avoid skew and damage to the airbag. When used for sewage pipes, the air bag with flange can be tied to the hanging ring with a rope not lower than 15 on the side of the water to prevent the displacement of the air bag in the pipeline, because the main role of the air bag is the sealing effect, rather than the pressure effect, so when the sewage pressure is very large, it must be pulled by the rope. (4) When there are unknown chemicals suspected of flammable gas in the sewage pipe, check with the instrument first, and when the concentration is suitable for construction within the safety value, the air bag must be filled with nitrogen, because the proportion of nitrogen is larger than the air, so it must be inflated by 1/2-2/3 of the air pressure to avoid blowing the air bag. (5) When the air bag is filled with water, because the ratio of water is significant, the pressure gauge should be replaced with a water pressure gauge, and the pressure of filling water can be mastered according to the actual situation on the site. Ordinary air bags generally can not be filled with water, must be customized to fill water special air bags. (6) When used in pipelines with oil and corrosive liquids or gases with ski solvents, ordinary air bags must be applied in such pipelines, and corresponding products must be specially customized. (7) The various types of air bags are used according to the corresponding pipe diameter, and only the air bags of one pipe diameter can be used in other pipe diameters; Suitable for various types of airbags, must be used within the pipe diameter of the use instructions.