Installing Marine Carbon Steel Pipes
2.1 Installation of carbon steel pipes and their accessories
1) Installation of pipelines
Before installing the pipe, it is necessary to confirm the reference coordinates of the pipe. The basic installation method is to determine the installation position of the piping system according to the distance from the deck surface, the frame, the midline surface or the size of the corresponding structure. In the installation process, the piping system cannot be under stress and the flange connection surface should be perpendicular to the center line of the pipeline; the two adjacent flanges should be kept parallel to each other, and the centers of the two flange holes should be aligned as much as possible, with a deviation of no more than 3 mm. The bolt holes on the two flanges should ensure that the screws can enter freely. In the installation process, the bolts should not be used to forcefully pull the pipes to eliminate the tilt of the pipe.
2) Installation of the sealing gasket
The selection of the sealing gasket should be in strict accordance with the gasket’s material specified in the pipeline. The size of the sealing surface of the gasket is not less than that of the flange, and only one gasket can be placed between a pair of flanges. The gasket should be uniformly stressed at the flange part, and the inner diameter of the gasket should not be smaller than that of the pipe, but not greater than that of the flange sealing surface, avoiding throttling or poor sealing caused by the gasket. In the process of installing the paper gasket, butter can be applied to the surface of the gasket to soften the gasket and expand the oil immersion to achieve a better sealing effect.
3) Installation of fasteners
The selection of fasteners such as bolts, nuts and pipe codes for installation of fasteners should be in strict accordance with the requirements of the drawings, and the correct materials and specifications should be selected. The flange should use bolts with the same specification, and the installation direction should be consistent. When the flange face is parallel to the hull baseline, the hexagonal head of the bolt is installed on the flange face, and the nut is below. In the process of tightening the bolts, they should be tightened evenly and gradually according to the distribution of the bolts and the principle of diagonal tightening. When the connecting flange finally reaches the corresponding tightening torque, the bolts should be in close contact with the flange without gaps, and 3 to 5 threads of the nut should be exposed for the tightened bolts.
4) Installation of the pipe bracket
When installing the pipe supports, the pipes should not be under stress. The supports should be installed on the hull’s strong supporting structures such as the hull girder and the hull frame as far as possible, and the pipe supports should not be directly welded to the hull plate. When the foot end of the bracket is on the deck or dry compartment, the bottom of the bracket should be welded with a backing plate, and the welding between the backing plate and the hull should be continuous full welding; the welding between the bracket and the backing plate should be a continuous fillet welding. The direction of the back edge of the bracket angle steel is towards the stern or outboard in principle, and the direction of the vertical pipe should be downward. When the pipe is installed, it should be fixed with brackets or hanging brackets. The position of the bracket and hanging bracket should be correct, and the installation should be firm. Anti-corrosion materials such as lead rubber and polyvinyl fluoride should be provided between the pipe and the support surface to avoid direct contact, but the contact between the pipe and the support should be firm. When installing pipelines, try not to use or don’t use temporary brackets and hanging brackets, and do not weld temporary brackets and hanging brackets on the pipes. After the pipeline is installed, formal brackets and hanging brackets should be replaced in time.
5) Installation of pipe parts
Before installing the valves and filters, the specifications and models should be checked according to the drawings. When installing the valve, the flow direction arrow on the valve is consistent with the flow direction of the medium in the pipe. For the installation of the straight-through globe valve, globe check valve, anti-wave valve, and solenoid valve, the inlet and outlet of the valve body should be kept horizontal. The handwheel should face upward when it is under the cast iron plate. When the installation is performed in a place with a narrow space, it is necessary to consider whether the structure of hulls and piping systems have an influence on the lifting and lowering of the handwheel. When the valve and pipeline are connected by flanges or threads, the valve should be installed in a closed state. When the valve and pipeline are connected by welding, the valve should be in an open state. The installation of the filter should consider the uninstallation and washing of the filter screen in the filter later, and there should be no pipes above the filter.
When a ship sails, any small hidden danger may cause serious consequences. The piping system is easy to be ignored due to its simple structure, slow corrosion, and difficulty in troubleshooting. Therefore, in the construction process, it is necessary to follow the construction process of the piping system, not to miss any small link to eliminate potential safety hazards from the source, and to ensure the safe navigation of the ship.
1) Installation of pipelines
Before installing the pipe, it is necessary to confirm the reference coordinates of the pipe. The basic installation method is to determine the installation position of the piping system according to the distance from the deck surface, the frame, the midline surface or the size of the corresponding structure. In the installation process, the piping system cannot be under stress and the flange connection surface should be perpendicular to the center line of the pipeline; the two adjacent flanges should be kept parallel to each other, and the centers of the two flange holes should be aligned as much as possible, with a deviation of no more than 3 mm. The bolt holes on the two flanges should ensure that the screws can enter freely. In the installation process, the bolts should not be used to forcefully pull the pipes to eliminate the tilt of the pipe.
2) Installation of the sealing gasket
The selection of the sealing gasket should be in strict accordance with the gasket’s material specified in the pipeline. The size of the sealing surface of the gasket is not less than that of the flange, and only one gasket can be placed between a pair of flanges. The gasket should be uniformly stressed at the flange part, and the inner diameter of the gasket should not be smaller than that of the pipe, but not greater than that of the flange sealing surface, avoiding throttling or poor sealing caused by the gasket. In the process of installing the paper gasket, butter can be applied to the surface of the gasket to soften the gasket and expand the oil immersion to achieve a better sealing effect.
3) Installation of fasteners
The selection of fasteners such as bolts, nuts and pipe codes for installation of fasteners should be in strict accordance with the requirements of the drawings, and the correct materials and specifications should be selected. The flange should use bolts with the same specification, and the installation direction should be consistent. When the flange face is parallel to the hull baseline, the hexagonal head of the bolt is installed on the flange face, and the nut is below. In the process of tightening the bolts, they should be tightened evenly and gradually according to the distribution of the bolts and the principle of diagonal tightening. When the connecting flange finally reaches the corresponding tightening torque, the bolts should be in close contact with the flange without gaps, and 3 to 5 threads of the nut should be exposed for the tightened bolts.
4) Installation of the pipe bracket
When installing the pipe supports, the pipes should not be under stress. The supports should be installed on the hull’s strong supporting structures such as the hull girder and the hull frame as far as possible, and the pipe supports should not be directly welded to the hull plate. When the foot end of the bracket is on the deck or dry compartment, the bottom of the bracket should be welded with a backing plate, and the welding between the backing plate and the hull should be continuous full welding; the welding between the bracket and the backing plate should be a continuous fillet welding. The direction of the back edge of the bracket angle steel is towards the stern or outboard in principle, and the direction of the vertical pipe should be downward. When the pipe is installed, it should be fixed with brackets or hanging brackets. The position of the bracket and hanging bracket should be correct, and the installation should be firm. Anti-corrosion materials such as lead rubber and polyvinyl fluoride should be provided between the pipe and the support surface to avoid direct contact, but the contact between the pipe and the support should be firm. When installing pipelines, try not to use or don’t use temporary brackets and hanging brackets, and do not weld temporary brackets and hanging brackets on the pipes. After the pipeline is installed, formal brackets and hanging brackets should be replaced in time.
5) Installation of pipe parts
Before installing the valves and filters, the specifications and models should be checked according to the drawings. When installing the valve, the flow direction arrow on the valve is consistent with the flow direction of the medium in the pipe. For the installation of the straight-through globe valve, globe check valve, anti-wave valve, and solenoid valve, the inlet and outlet of the valve body should be kept horizontal. The handwheel should face upward when it is under the cast iron plate. When the installation is performed in a place with a narrow space, it is necessary to consider whether the structure of hulls and piping systems have an influence on the lifting and lowering of the handwheel. When the valve and pipeline are connected by flanges or threads, the valve should be installed in a closed state. When the valve and pipeline are connected by welding, the valve should be in an open state. The installation of the filter should consider the uninstallation and washing of the filter screen in the filter later, and there should be no pipes above the filter.
When a ship sails, any small hidden danger may cause serious consequences. The piping system is easy to be ignored due to its simple structure, slow corrosion, and difficulty in troubleshooting. Therefore, in the construction process, it is necessary to follow the construction process of the piping system, not to miss any small link to eliminate potential safety hazards from the source, and to ensure the safe navigation of the ship.
