Installation principle of FRP pipe

The pipeline installation sequence is  d on the principle of sub-area and sub-system, first large diameter and then small diameter, first lower   and then upper  , first difficult and then easy, first on the pipe gallery and then on the equipment. In principle, the pipeline connected to the machine is arranged from the inside to the outside to reduce the impact of welding stress on the installation accuracy of the machine. The joint between indoor and outdoor pipelines should be left outdoors.

1、 Installation requirements for FRP pipes

1. Before pipeline installation, equipment nozzle,  ded parts, reserved holes, steel structure and other contents related to pipeline installation shall be reviewed.

2. The slope of the pipeline shall be adjusted according to the requirements of the drawing. The adjustment method can use the support to meet the slope requirements. The weld shall be set at a place convenient for maintenance and observation.

3. The pipes connected to the transmission equipment shall be cleaned internally before installation. The welded fixed pipe orifice shall generally be far away from the equipment to avoid the impact of welding stress on the installation accuracy of the transmission equipment.

4. Before connecting the pipe with the machine, the relative strength should be prevented, and the parallelism and coaxiality of the flange should be checked under the free state.

5. The safety valve shall be installed vertically, and the safety valve shall be adjusted in time when it is put into trial operation. The final adjustment of the safety valve shall be carried out on the system, and the opening and reseating pressure shall comply with the provisions of the design documents.

6. Before the installation of the valve, check its model according to the design documents, and determine its installation direction according to the flow direction of the medium. When the valve and pipeline are connected by flange or thread, the valve shall be installed in closed state; If installed by welding, the valve shall not be closed.

7. Temporary replacement of instrument elements: When all instrument elements are installed, they shall be replaced by temporary elements. After the completion of pressure test, flushing and purging, they shall be formally installed before feeding.

2、 Installation of FRP pipes and composite pipes

① Before construction, the appearance and size of FRP pipes shall be inspected and accepted according to the factory certificate.

② The pipeline installation drawing is the basis of the pipeline installation project. The laying of FRP/PVC pipes (including the connection form, coordinates, elevation, slope, slope direction, etc.), the connection of FRP/PVC pipes and equipment, pipe accessories, and the installation position and support of pipe accessories should comply with the design drawings. Any change must be resolved through consultation with the design unit.

③ For pipe installation, the pipe accessories can be installed from one end of the pipe to the other end according to the pipe section divided in the pipe installation drawing, and then the support or support (temporary support is required during installation if necessary). During pipeline hoisting, protective measures must be taken on the outer wall surface, and direct contact with steel wire rope is prohibited to avoid local stress.

④ The connection point of FRP pipe is only allowed in the straight pipe part. The distance between the butt welding connection point and the edge of the pipe support shall be greater than the outer diameter of the pipe and not less than 100mm; The distance between the socket connection and the edge of the pipe support shall be greater than 150 mm.

⑤ There are three types of pipe connection structures: socket connection, flange connection (welded ring loop flange connection and composite flat welding flange connection) and butt welding connection. The installation method will be determined according to the specific requirements of the design documents.

⑥ The installation workers engaged in welding must hold the welder qualification certificate, be familiar with the adhesive performance and installation method of FRP/PVC pipes, and have skilled PVC welding operation ability.

⑦ Before the socket connection, the dirt on the inner wall of the PVC pipe at the joint shall be removed first, and then the socket shall be inserted into the socket. The socket shall be free of deflection, cracks and other defects. After the socket depth is reached, PVC welding can be carried out.

⑧ The socket part shall be reinforced with FRP, and the reinforced part shall be evenly coated with a   of R glue. The thickness of the coating shall be uniform, and there shall be no leakage and flowing. Then a   of glass cloth shall be coated, unsaturated resin shall be coated, and glass cloth shall be coated, and the process shall be repeated until the thickness meets the requirements.

⑨ When the socket and socket are unqualified and need to be repaired, the socket and socket must be remade, and the used socket and socket must not be used.

⑩ When the flange is connected with the pipe, both inside and outside sides must be welded with the pipe. The inclination between the flange surface and the pipe axis should be less than or equal to 1/100 of the pipe outer diameter. The flange connection shall be strictly aligned, and the maximum allowable axial deviation shall not be greater than 2mm. It is not allowed to eliminate the deflection by tightening the bolts. The bolts shall be tightened in two times, the first time evenly and symmetrically, and then the bolts.

3、 Fabrication and installation of pipe supports and hangers

① The pipe support fabricated on site shall be in strict accordance with the specifications and drawings, and shall be painted for protection. The lifting lug support of the pull rod hanger and spring hanger shall be welded and 100% penetrant or magnetic particle flaw detection shall be conducted according to the steel structure fabrication standards.

② The position of all pipe supports shall be indicated in the single line diagram.

③ During pipe installation, the support shall be fixed and adjusted in time. The position of the support shall be accurate, the installation shall be flat and firm, and the contact with the pipe shall be tight.

④ The fixed support shall be installed according to the requirements of the design documents and fixed before the pretension of the compensator.

⑤ The sliding surface of the guide bracket or sliding bracket shall be clean and flat, and shall not be skewed or jammed. The installation position shall be shifted from the center of the bearing surface to the opposite direction, and the offset shall be 1/2 of the displacement value or comply with the provisions of the design document. The thermal insulation   shall not hinder its displacement.

⑥ When the temporary support is used for pipeline installation, it shall not conflict with the position of the formal support and shall be clearly marked. The pipeline shall be removed after installation.

⑦ FRP/PVC pipes and pipe supports (including supports) shall not be directly bonded or welded. A rubber block or other soft pad with a thickness of not less than 3mm shall be placed between the pipe fitting (pipe clamp, pipe bracket or pipe clamp) of the FRP/PVC pipe fixed pipe rack and the outer wall of the pipe.

⑧ After the installation of the pipeline, the form and position of the support shall be checked one by one according to the provisions of the design document.

4、 Pressure test and flushing of FRP pipes

① In order to reduce the temporary pipeline added during purging, save the time of pressure test and purging, and improve the qualification rate of pressure test and purging, the pipeline pressure test and purging shall be carried out according to the system, area and pressure grade. Before pressure test and purging, a plan must be prepared to guide the construction.

② Clean water shall be used for pipeline pressure test. When testing and flushing the connected stainless steel pipeline, the chloride ion content in the water shall not exceed 25 × 10 (25ppm), the pipeline pressure test and flushing procedures shall comply with the provisions of the General Contractor.

③ During pressure test, irrelevant personnel shall not enter. After the pressure test, it is not allowed to repair the pipeline.

④ Before pressure test, the following conditions shall be met:

A. Except for painting and thermal insulation, the pipeline installation works within the test scope have been completed according to the design drawings, and the installation quality conforms to relevant regulations.

B. Welds and other parts to be inspected have not been painted and insulated.

C. The expansion joint on the pipeline has been set with temporary restraint device.

D. The pressure gauge used for the test has been calibrated, and its accuracy shall not be lower than level 1.5 within the cycle. The full scale value of the gauge shall be 1.5-2 times of the maximum pressure measured, and there shall be no less than two pressure gauges.

E. The liquid or gas meeting the pressure test requirements has been prepared.

F. According to the test requirements, the pipeline has been strengthened.

G. The pipeline to be tested has been separated from the unrelated system by blind plate or other measures.

H. The safety valve and instrument elements on the pipeline to be tested have been removed or isolated.

I. The test plan has been approved and the technical disclosure has been carried out.

⑤ The hydraulic test shall comply with the following provisions:

A. Before the test, the air shall be exhausted during liquid injection.

B. The ambient temperature during the test should not be lower than 5 ℃. When the ambient temperature is lower than 5 ℃, anti-freezing measures should be taken.

C. The pipeline test pressure is 1.5 times of the design pressure.

D. When the design temperature of the pipeline is higher than the test temperature, the test pressure is calculated as follows:

Ps=1.5P[ σ] 1[ σ] two

Where Ps - test pressure (gauge pressure) (MPa);

P --- design pressure (gauge pressure) (MPa);

[ σ] 1 --- allowable stress of pipe under test temperature (MPa);

[ σ] 2 --- allowable stress of pipe under design temperature (MPa).

When[ σ] 1[ σ] If 2 is greater than 6.5, take 6.5.

E. When the pipeline and equipment are tested as a system and the test pressure of the pipeline is equal to or less than the test pressure of the equipment, the test shall be conducted according to the test pressure of the pipeline; When the test pressure of the pipeline is greater than the test pressure of the equipment, and the test pressure of the equipment is not lower than 1.15 times of the design pressure of the pipeline, the test can be carried out according to the test pressure of the equipment with the consent of the construction unit.

F. For pipes with large level difference, the static pressure of the test medium shall be included in the test pressure. The test pressure of liquid pipeline shall be subject to the highest point, but the pressure at the lowest point shall not exceed the bearing capacity of pipeline components.

G. The hydraulic test pressure should be increased slowly. After reaching the test pressure, stabilize it for 10min, and then reduce the test pressure to the design pressure. Stop the pressure for 30min, and it is qualified if the pressure does not drop and there is no leakage.

H. After the test, the blind plate and expansion joint limit facilities shall be removed in time to drain the accumulated liquid. The negative pressure shall be prevented during liquid drainage, and it shall not be discharged anywhere.

I. When leakage is found during the test, it shall not be handled under pressure. After the defects are eliminated, the test shall be conducted again.

⑥ For the pipeline conveying toxic fluid, the leakage test must also be carried out, and the leakage test medium is air (that is, air tightness test). The air tightness test shall be conducted according to the following provisions:

A. The air tightness test pressure is the design pressure.

B. The air tightness test shall focus on the inspection of valve stuffing box, flange or threaded connection, vent valve, exhaust valve, drain valve, etc.

C. The air tightness test shall be checked by brushing soapy water or other foaming agent, and it is qualified if there is no leakage.

⑦ After the pipeline passes the pressure test, the purging or cleaning plan of the pipeline shall be organized according to the purging plan.