1. De-waxing & Cleaning of 212Km
long Loop Line to make suitable for
Pumping Products.
2. SCHEMATIC DIAGRAM OF PROPOSED NSPL ROUTE
SRIRAMPUR
631 KM
NJP TERMINAL ASSAM RS 2
832 KM BORDER PS5 172 KM.
RS9 RS5 PS4 RS3 ROW
401 KM RS4
512.7 361 260 KM 214.3 194 KM
313.3
KM KM KM
KM
Existing
mainline
112 KM
14 KM. New ROW
100 KM.
RGP NRL
TERMINAL TERMINAL
204 KM 197 KM ASSAM
W.B.
3. The De-waxing and cleaning of 16” Loop Line
of Oil India Limited pipeline is required to be
carried out in view of joining the portion of
loop line to the newly constructed product
pipeline from Numaligarh Refinery to Siliguri
Terminal.
– Pipe size of the line 16” (406mm)
– Thickness of Pipe 7.9mm
– Pipe API 5LX-46,52
– Capacity of Product line 1.72 MMTPA
4. The job of cleaning and de-waxing was
entrusted to CPTDC (China Petroleum
Technology Development Corporation).
After preliminary ground work a piece of land
of area 3200m2 outside RS-3 Kaziranga was
rented to place equipment and machines
accordingly.
A water storage pond of approximately 800m3
was constructed.
6. Loop
Line
Main
Line
RS-3 Kaziranga
PS-4 Sekoni
Loop Line and Main line between RS3 and PS4
7. Steps involved in de-waxing and
cleaning process
Pigging with different types of pigs with crude oil as medium
Sweeping of Crude oil
Hot water Pigging
Chemical Cleaning
Self Check
Chemical Cleaning
Acceptance Test
8. Equipment:
1) Compressors – Ingersoll Rand (2 no's)
a) Capacity – 45m3/min, Pressure – 1.0 Mpa
b) Capacity – 30m3/min, Pressure – 2.4 Mpa
2) Water Pump – 4 no’s of various capacity
3) Chemical dosing pump – 2 no’s
4) Hot water boiler etc.
10. It was decided to start the work in the RS-3
Kaziranga to PS-4 Sekoni sector first.
The date of starting of the pigging operation
was decided as 22.02.07.
General pigging process is decided to be
carried out with combined and Bi-Di Pigs.
Pig Type :- a) Combined Pig (Brush, Cup & Plate)
b) Bi - Di Pig
Size :- 105% of I.D of Pipe
i.e. 409.7mm ( Pipe I.D 390.2mm)
11. Pigs Used
Foam Pig
Combined Pig
B.C.P
Bi – Di Pig
(Brush, Cup &
Plate)
12. Pigging with different types of pigs with
crude oil as medium
The first pig was launched at RS-3 Kaziranga for
PS-4 Sekoni with a trekking instrument on
22.02.07.
Pig was tracked at various locations.
Throughput in the line during pigging operation
was kept at 150Kls/Hr.
Series of pigging operations were carried out
subsequently between RS-3 Kaziranga to PS-4
Sekoni from 22.2.07 to 08.04.07
Wax collected & other related information are
17. Same process started for the sector PS-4
Sekoni to RS-4 Ghani on 26.02.07
Wax collected in this sector is much more less
than the previous sector.
Total quantity of wax collected in both the
sector is around 26400Kgs approx.
18. Sweeping of crude oil
Very critical job.
Compressed air is used.
Safety precautions to be taken
Static electricity / Earthing.
Nitrogen Purging.
19. Arrangements of Equipment in Sweeping
operation
Water
Pump
Air Compressor Air compressor
--1 --2
Loop
Line
Main
Line
RS-3 Kaziranga PS-4 Sekoni
20. M/L is isolated from the Loop Line.
M/L was kept pressurized at 35Kg/cm2.
The first pig was a combined pig, launched at
1210hrs.
The second pig was Bi-Di, launched at 1410hrs
The third pig was also Bi-Di, launched at 1610hrs
The fourth pig was also a Bi-Di launched at
1820hrs followed by 30Kl of water and again
followed by a Bi-Di pig, and the whole train of
pigs was driven by compressed air
21. Sweeping Operation
Bi – Di Bi – Di Bi – Di Bi – Di B.C.P
Pig Pig Pig Pig Pig
Crude
Water Crude Crude Crude
Air -30 Kls
22. The oil from the loop line was taken into the
balance tank at PS-4 and normal pumping
from PS-4 Sekoni was continued.
The fourth pig which was the last pig in
contact with the crude oil was received on
9.4.07 at 1855 hrs and sweeping operation
completed.
The line is immediately isolated from all the
crude oil connections.
23. Sweeping process
(PS-4 Sekoni to RS-4 Ghani)
In PS4 – RS4 sector the oil column in front of the
sweeping pig was very long which was from PS-4
Sekoni to PS-5 Noonmati of 140Km long.
The length of the oil column to be swept is only
53Km.
After completing sweeping operation in both the
sectors, multiple pigging with air started and
considerable amount of cleaning is achieved.
24. PS-4 Sekoni RS-4 Ghani
L/L
M/L M/L under
Pressure
Loop Line between PS4 Sekoni & RS4 Ghani
25. Hot water Pigging
Decided to carry out hot water pigging.
Hot water plug of 200mtrs was driven
between one combination pig and a Bi-Di pig
with the help of air.
The water temperature at the inlet is 80’C
This process continued for a few days and
foam pigs were also driven along with air until
certain level of cleaning is achieved.
26. Arrangement for Hot Water Pigging
16” Loop Line under
Hot cleaning
Water
4” Line
HOT
WATER
27. Chemical Cleaning
Chemical mixed with H.S.D in a ratio of 1:12 is
used.
The H.S.D and the chemical mixture is plugged
between two pigs, of which one is a
combination pig and other a Bi-Di pig, and the
plug is followed by 30Kl of water.
The whole train is driven by compressed air.
Initially 12Kl of H.S.D was mixed with 1Kl of
chemical.
28. Chemical Cleaning
Bi – Di Bi – Di B.C.P
Pig Pig Pig
WATER H.S.D (12Kl) +
Air 30 Kl CHEMICAL(1Kl)
Air
Same procedure was followed for the other sector also.
29. Self Check
After cleaning with chemical a self check was
required to be carried out and finally 200mtrs
of H.S.D was plugged between 350mtrs and
250mtrs of water with separating pigs and the
train was driven between RS-3 Kaziranga and
PS-4 Sekoni as shown in the figure.
30. Self Check
B.C.P B.C.P B.C.P B.C.P
Pig Pig Pig Pig
AIR water H.S.D water AIR
Air
Foam 200 m 200 m 350 m Foam
Pig Pig
31. The above process was also carried out in the
other sector and concentration of chemical
required is determined to 1:12 only, and the
chemical cleaning process is decided to be
taken up once again.
32. Acceptance test
The final acceptance test of the cleaning
process is decided to be taken up after self
check and the total cleaning process.
The process is carried out as follows
Bi – Di Bi – Di Bi – Di Bi – Di
Pig Pig Pig Pig
Water H.S.D Water
Air Air
200 m 300 m 100 m
33. H.S.D – Euro III was used for testing in the line.
When H.S.D reached PS-4 Sekoni various
samples were taken in presence of OIL, NRL
and CPTDC representatives and tested for
colour.
For conducting the process of colour test,
officers of chemical department of all the
three parties carried out the test with respect
to the colour code.
34. The colour code was established by
contaminating crude oil and wax with Euro III
– H.S.D in the laboratory and they were
observed in testing machine.
The colour code of Euro III – H.S.D was taken
as to be “0”.
37. It was found in the laboratory that sample
with colour code 7 (i.e. up to 500ppm
contamination)was within acceptable limit.
The following results of colour code were
found in the sectors RS3 – PS4 & PS4 – RS4.
– RS3 to PS4 0 –1
– PS4 to RS4 4–5
38. Precaution taken in respect of safety
While carrying out sweeping operation with
the help of air, nitrogen was purged into the
receiving trap at both the location i.e. PS4 and
RS4 in a regulated manner.
Utmost precautions were taken when
sweeping pig was near to the receiving trap to
avoid any collision of pig head with the barrel
door.
39. Cushioning materials were also placed near
the door of the receiving trap.
The line was completely earthed in three
places to discharge any static electricity that
may be generated due to numerous numbers
of pigging operations.
Flame proof equipment were only used inside
the repeater stations and pump stations to
avoid any incidents.
40. Precaution taken in respect of Environment
To avoid any pollution, spill of oil is totally
restricted in Pump Stations and Repeater
Stations.
Wax and other materials were dumped in a
location made with concrete and poly-
ethylene lined sheet.
41. Water and other liquids coming out of the line
is kept reserved in a poly-ethylene lined
concrete walled pond made at RS-4 Ghani.
An effluent treatment plant (portable) was
constructed by the contractor to treat the
effluent before disposal which is again tested
to avoid any pollution and it was kept under
10mg/Ltr.
H.S.D and other chemicals were recycled and
reused for the other sectors.
43. Benefits:
Construction of a new pipeline of 212Kms long
would have cost us Rs 250 crores but the cost
of cleaning and de-waxing of existing line was
only Rs 27 crores.
Construction of pipeline inside Kaziranga
sanctuary would have been a difficult job in
view of the environmental policy of the
Government.
