This presentation talks about procedure carried in laying steel pipe in CGD, various rules, regulations, methods.

1. LAYINGWORK OF
STEEL PIPELINE IN
CGD SECTOR
AkshayToraskar

2. Material & equipment used in Steel piping
■ Pipe material specification details:
– For pipe size up to & including 12’’ NB: Carbon steel pipe - API 5L gr. B
– For pipe size up to & including 18’’ NB: Carbon steel pipe - API 5L gr. X-
60
– For pipe size up of 18’’ NB: Carbon steel pipe - API 5L gr. X-52
■ Fittings such asTees, elbows etc. are of smooth surface & without joint i.e.
seamless joint
– Elbows & reducers made by hot forging seamless steel pipe.
– Tees made by hot extrusion.
– All butt welds are beveled.

3. ■ Ball valves (size: 4’’ to 18’’) used are of fully welded construction with stem
extension.
■ All lifting equipment including cranes, spreader bars, belts, slings etc. are
duly certified by competent authority. Every lifting accessories are
appropriately handled to safeguard no damaged caused to the coating of
pipe.
■ The material used for backfilling the trench is Soil which is stone free & have
maximum grit size of 12 mm.
■ PE warning sheet :
– Density: 925 kg/m3
– Size for Steel pipeline of 6’’ and below diameter: 250mm width x
1.5mm thickness
– Size for Steel pipeline of 6’’ and above : 400mm width x 1.5mm
thickness

4. REFERENCES
1. ASME B 31.8 – Code for gas transmission & distribution piping system
2. Petroleum & natural gas regulatory board (PNGRB) technical standards
3. Steel ISO processes & work instrunctions
4. UK IGE/TD/1

5. TRENCHING
■ Before starting trenching work, all necessary statutory clearances, licenses,
permissions are obtained & made available on site.
■ Hazard identification & risk assessment done by competent personnel.
■ Cable locating survey is carried before trench activity.
■ Trial pits are taken prior to starting of trenching work.Trial pits requirements:
– Depth is 200mm more than the depth of trench & suitable width at interval
of 25- 50 M.
■ Excavations below 2 meters have shuttering or trench protection & carried
out as per confined entry procedure compliance.
■ The proximity of pipeline is of at least 3 meters horizontal distance from the
building/permanent structure.

6. ■ Clear separation of minimum 500 mm is strictly maintained between
adjacent pipelines, while laying more than one new pipeline in the same
trench.
■ When pipeline is laid parallel to any existing underground cable, drain etc.,
it is laid with horizontal distance of 300 mm from existing utilities.
■ Trench is kept free of water. Pumps, shoring equipment etc., are provided
to maintained trench in good condition.
■ Continuous plastic barricades are provided on either side of trench with
ensuring no gap between them. Barricades have retro reflective stripes and
red light to make it visible in night time.
■ Excavated soil is piled at least 300 mm away from trench.

7. Trench protection system

9. Confined space work

10. ■ Trench plate, ladder & rope is provided for emergency access at a
distance of every 500 meters of excavated trench.
■ Welding of main joints is completed before lowering of pipes in trench.
Welding of tie-in joints is done inside trench.
■ Wherever rock is encountered, the pipeline in wrapped with rock shield
to protect pipe from coating damaged.

11. Rock shield for pipeline protection

12. Welding activity in trench

13. Excavation and trench hazards

14. Depth of cover for buried steel pipeline
Location Cover (m.)
Cased/uncased road crossing 1.2
Cased railroad crossing 1.7
Normal/rocky terrain 1.2
Nallah crossing 1.5
River crossing 2.5

15. ■ Cover is measured from top of coated pipe to top of the undistributed
surface of soil.
■ Clearance sufficiently large enough to avoid electrical fault current
interference is maintained among pipeline and grounding facilities of
electrical transmission lines.

16. LOWERINGOF STEEL PIPELINE
■ The trench is padded with minimum 150 mm with soft material or sand,
before lowering of pipeline in trench. After lowering, 450 mm soft
material is placed above it.
■ Both ends of pipeline is capped so as to prevent debris/ unwanted
foreign material from entering into pipeline during lowering activity.
■ Hydra machine is not used for transportation & lowering of steel pipe.
Required capacity of cranes/tripods with chain pulley blocks is used for
lowering .

17. Crane with chain pulley blocks

18.  Holiday detection test performed on coated pipes before lowering by
using full circle type holiday detector. Pipe is lowered only after
ensuring that trench is dried & clean. Holiday detection test is as
follows (photo is only for representation purpose):

19. BACKFILLING
■ Backfilling is followed immediately after lowering of pipe so that
coating is not exposed to undue temperature variation.
■ Before backfilling work, all activities belong to welding, NDT, blasting,
field joint coating, holiday testing is completed properly.
■ Backfilling material does not contained any irrelevant material or hard
lumps of soil.
■ Sand padding of 100 mm is done by covering all around the pipe.
■ Subsequent layers with protection tiles & warning sheets is placed
accordingly.

20. Difference between padding material &
backfill material

21. ■ Backfill material is compressed in 150 mm layers to prevent trench from
settling & causing depression in road surface.
■ After backfilling appropriate crowning with existing soil is done
considering settling of surface.
■ Steel pipeline is covered by PCC concrete slab in case it passed through
overhead high tension electric line.

22. INSTALLATIONOF SECTIONALIZING
VALVE
■ In steel piping, valve is installed below ground with valve operating
device readily reachable.
■ The maximum distance between two valve is 3 km in steel pipeline.
■ Every alternating mainline valve is compatible for remotely operated
structure through SCADA.

23. HANDLING & STOCKINGOF PIPES
■ BARE PIPES:
– Bare pipes is handled by using lifting hooks equipped with a bend
brass copper plate placed within each pipe end.
– The used of steel cables, chains wound round the pipes is strictly
prohibited.

24. ■ COATED PIPES:
– Coated pipes are handled by using twisted hemp, plastic or leather
straps, at least 100 mm wide & swing bar for limiting the flexion of
pipes.
– In stocking of coated pipes, the pipe is supported from the ground by
skids & wedges with neoprene strips of 25-30 cm wide.

25. STRINGING OF PIPES & ACCESSORIES
■ Pipes are strung along the edge of trench in such way that they cause no
inconvenience to road, street traffic & no damage to road.
■ Stringing of pipe is done at proper location in accordance with
construction drawings.
■ Strung coated pipes are kept clear from ground by padded skids.
■ Rolling, Dragging & sliding of pipes during stringing is not permitted.
■ End of pipes are protected with bevel protector.

26. ■ Pipes are stacked at slope so that during rain, water doesn’t collect
inside pipes.
■ Predamaged pipes are stacked separately & taken to work only after
repair.
■ Pipes are strung preferably on left side of trench in flow direction of
pipe.
■ Pipe no., pipe length, heat no. are transferred on above pipes after
stringing with paint wherever stenciling is not clearly visible.
References: All images in this presentation is from google.com

27. THANK YOU