5　Pipe Installation

5.1　General Requirements

5.1.1　Pipe installation shall meet the following requirements.

1　The elevation,coordinate,slope angle,bedding of pipes shall meet drawing requirements when excavating channels for buried pipes.Drainage measures shall be taken if necessary.

2　Embedded parts in the trench of underground pipes shall be buried in line with drawing requirements.

3　Embedded parts and preserved holes in concrete columns,beams,walls and floors shall meet drawing requirements.

4　Specifications for embedded casing pipes and the location of connectors shall meet drawing requirements.

5　Installation qualities of the pipe-related steel structure shall meet drawing requirements.

6　Equipment connected with pipe shall be aligned and fixed.

7　Pipes,pipe fittings,pipe accessories and valves shall be qualified after the inspection.

8　Proper processing such as sandblast,exterior and interior anti-corrosion,pipe inner cleaning and degreasing shall be performed before pipe installation.

5.1.2　In case of assembly and installation of pipes,the assembly shall have adequate rigidity and no permanent deformation after being hoisted.It shall remain firm when fixed temporarily.

5.1.3　During installation of pipes and pipe components,the internal pipe shall be cleaned without sundries.The pipe shall be temporarily blocked during installation.

5.1.4　Slope direction and slope of the pipe shall meet design requirements.Without specific design requirements,the direction of pipe slope shall facilitate water drainage and air venting.

The slope shall meet requirements of DL/T 5054 Design Code for Steam and Water Piping in Thermal Power Plants.The direction of pipe fittings and valves installed on pipes shall be the same with the direction of the pipe slope.

5.1.5　The weld position of the pipe shall meet design requirements.Without specific design requirements,it shall meet the following requirements.

1　The distance between the welds and the initial curving point of the bend shall be no shorter than the outer diameter of the pipe and no less than 100mm with exception of setting pipes.

2　The distance between neighboring welds of the pipe shall be greater than the diameter of the pipe and greater than 150mm.

3　The distance between the welds and the edge of supports and hangers shall be greater than 50mm or greater than 100mm in case of weld joint requiring the postweld heat treatment.

4　The distance between the welds and the edge of openings for drain discharge pipes and instrument tubes shall be greater than 50mm and shall be no smaller than the bore diameter.

5　Pipes passing through walls and floor slabs shall have pipe casing in the wall bushing.There shall be no welds in the pipe segment inside the partition and floor slabs.

5.1.6　A short pipe shall be attached between two pipe fittings.They shall not be welded directly.

5.1.7　Except for cold spring and hot tight requirements in the design,when connecting pipes,the gaps,deflections and offset shall not be eliminated by fitting up,heating pipes or multi-layer pads.Pipes and equipment shall be connected in the nature position after pipe installation,the adjustment of anchors and the positioning of installed equipment.

5.1.8　The groove type and the size of pipes without design requirement should meet the requirements of Appendix E.

5.1.9　The fit-up of pipes or pipe fittings shall meet the following requirements.

1　Before fitting up,the surface of the grooves and the nearby base metal shall be cleaned until the metallic luster comes out.The cleaning scope shall meet the following requirements.

1)Butt joint:15mm~20mm at each side of the groove.

2)Butt joint of submerged-arc welding:15mm~20mm at each side of the groove.

2　During fitting up,the inside surface shall have the same leveling root.

The offset value shall meet the following requirements.

1)Local offset value of the single welded butt joint shall not surpass 10% of the wall thickness and be less than 1mm.

2)Local offset value of the double welded butt joint shall not surpass 10% of the thickness of the welded piece and be less than 3mm.

3　The pipe with nominal diameter over DN500mm can have fit-up gap with no more than 2mm.The total length of local excess part shall not surpass 20% of the total welds.

4　The groove and adjacent base metal within 20mm shall have no defects such as cracks,overlaps,damage of grooves or burrs.

5.1.10　The fit-up of pipes shall be aligned straight.The distortion of welding angle,except for special demands,shall be measured at location 200mm away from the center of the welded crater.The allowable deviation at the distortion area is shown as Fig.5.1.10.

For the pipe with nominal diameter less than DN100mm,a=2mm.

For the pipe with nominal diameter no less than DN100mm,a=3mm.

5.1.11　After meeting the fit-up requirement,pipes shall be avoided to move during welding or heat treatment.

5.1.12　Cold-spring pipes shall meet the following requirements.

1　The anchor of the cold-spring area shall be solidly installed.Except for cold-spring area,all the welded joints between the anchor shall be finished and accepted,heat treatment shall be carried out if required.

2　All the supports and hangers shall be installed,the adjustable allowance of the rods of hangers near the cold-spring area shall be reserved in advance.

3　The direction of the slope,the slope and the cold-spring value of the pipe shall meet the design requirements.

4　The connecting bolt linking the flange and the valve has been tightened.After welding of the pipe,the welded joint shall be qualified after inspection.

5　The loading tool for installing cold-spring area of pipes cannot be unloaded until the butt welding and heat treatment are completed.

5.1.13　The installation of the pipe compensator shall meet the specifications and design requirements.The limit supports shall be released or fastened after installing the pipe.When the inside of the pipe has sleeve,it shall be correctly installed in line with the flow direction of the medium.The pipe compensator linked to the equipment shall be linked after the final positioning of the equipment.

5.1.14　Installation of the flow measurement and throttle device shall meet the following requirements.

1　The installation direction and the angle of the pressure sampler shall meet the requirements of manufacturer.

2　Upstream and downstream straight pipes shall meet the requirements of manufacturer.Without the design requirements,DL/T 5190.4 Code for Electric Power Construction Part 4:Instrumentation and Control shall be followed.The surface of inside pipe shall be clean without dirt,roughness or sediments.

3　When installing the gasket,the inner edge shall not stretch into the interior wall of the pipe.The gasket of angle pressure sampler shall not block the pressure tapping opening or slot.

4　The installation of the orifice plates and the throttle pieces must be carried out after the flushing of pipes are qualified.

5.1.15　The whole process of the pipe and system installation shall be implemented in the clean way.

5.1.16　Allowable deviations of pipe installation shall meet the requirements of Table 5.1.16.

5.1.17　Supports and hangers shall be installed simultaneously with pipes.

5.1.18　Except for special measures in design,the hanger rod shall not run through the insulation layer.

5.1.19　The hanger rods of supports and hangers shall not pass through the cable bridge.

5.1.20　The drilling of holes on the pipes shall be completed before installing pipes.After drilling,the inside of the pipe shall be cleaned without drill chips or sundries.When the pore diameter is less than φ30mm,the openings shall be machined.