Download Skin Effect Heat Management System

S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
Cairn India Limited.
Skin Effect Heat
Management System
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Cairn India is building the world’s longest
continuously heated and insulated
pipeline (~700 km) to evacuate the crude
from the Mangala field in Rajasthan. The
export pipeline route from source at
the Mangala Production Terminal to the
Gujarat coast at Bhogat via Salaya, passes
through the states of Rajasthan and
Gujarat covering eight districts and more
than 250 villages. In addition, there are 4
branch lines ranging in length from 2.5 km
to 21 km delivering crude to customers
enroute. Currently, 600 km section from
Mangala to Salaya, along with four branch
lines if fully operational.
The necessity of evacuating the Rajasthan
crude, which is waxy in nature and needs
to be maintained above 65 °C to ensure
its flow, resulted in customizing existing
heating technology into the Skin Effect
Heat Management System (SEHMS), an
innovative system by far the longest of its
kind in the world today. SEHMS technology
has traditionally been most often applied
to shorter above ground applications.
There were many innovations required to
apply this technology to an underground
cross country pipeline system. The crude
oil pipeline is insulated with 90 mm Poly
Urethane Foam (PUF) to arrest the heat
loss from pipeline to the surrounding soil;
this is further enclosed with a 5 mm HDPE
jacket for protection and to make it water
SEHMS technology also known as
the Skin Trace System (STS) or Skin
Electric Current Tracing (SECT), are all
dependent on the same principles of skin
and proximity effect for operation. They
are all established and proven electrical
heating technologies used for long
distance piping and pipelines.
SEHMS generates heat on the inner
surface of a carbon steel heat tube that
is welded to the carrier pipe to be heat
traced, which in our case is the 24”
crude pipeline. An electrically insulated,
high specification temperature-resistant
conductor is installed inside the heat
tube and connected to the tube at the
circuit end. The tube and conductor are
connected to an AC voltage source in a
series connection. This method of heating
is called skin-effect heating because the
return path of the circuit current is pulled
to the inner surface (approximately 1 mm)
of the heat tube by both the skin effect
and the proximity effect between the
heat tube and the conductor. The outside
surface of the heat tube is at ground
potential, and completely safe, while
the inner surface of the tube carries full
current. The heating circuit impedance
AC VOLTS
(Outside Surface
to Earth)
AC VOLTS
(Inside Surface
to Earth)
Heat Tube
(with insulated
wire inside
Carrier Pipe
Fluid
Thermal
Insulation
STSTM System
is mainly resistive, generating heat in the
heat tube wall and, to a lesser extent, in
the insulated conductor. Additional heat
results from eddy currents induced in the
heat tube wall by the current flow through
the insulated conductor. The allowable
circuit length is determined by the power
output; heat tube size; conductor size;
and the carrier pipe temperature. SEHMS
‘s advantage over other electrical trace
heating systems is that extremely long
circuit lengths are possible – typically a
pipeline of up to 20 km may be heated
from a single electric supply point (2
circuits of 10 km each).
In ideal situations the SEHMS heating
system is not required on the MangalaBhogat Pipeline as the 90 mm of PUF
pipeline insulation will be good enough to
keep heat losses within acceptable limits.
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Tyco Thermal Controls LLC
However, certain operational situations,
such as low flows or a stoppage, could lead
to wax formation at lower temperatures
(<65 °C), and for this reason SEHMS is
a critical system because without it there
would be no way to re-melt the crude oil
and keep the pipeline operational.
The key SEHMS elements are
transformers, heat tube, pull boxes, end
boxes and temperature sensors.
For this project, and in a first for India,
an insulation plant was set up at the pipe
manufacturers Mill using cutting edge
spray applied insulation techniques.
Fuel for the gas engines producing
the power for the pipeline heating
system comes from an 8 inch diameter
pipelinelaid parallel to the main 24 inch
Cairn India Limited
Cairn India Limited
Necessity, as they say, is the mother of
invention, and in the case of Cairn it was
the same for this innovation of technology.
tight. Above ground heating stations
with maximum 1 MW power generating
units installed at every 20 km along the
pipeline route supply power to SEHMS.
In addition, 2 intermediary terminals and
a total of 36 heating stations are installed
along the pipeline route.
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
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STSTM System
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
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Termination
Power Source
and Temperature
Monitoring
RTD’s
Heat Tube
Tyco Thermal Controls
LLC
W
A
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Cairn India Limited
Cairn India Limited
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S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
A view of the Mangala development pipeline showing the SEHMS and the Raageshwari Gas Pipeline
crude pipeline. The primary gas source
is from Cairn’s Raageshwari field in
Rajasthan.
Skin Effect Heat Management System
was chosen as a suitable solution due to
the following advantages:
The details of the Power Source and
Temperature Monitoring are as follows:
•
•
•
• Safe
• Custom engineered
• Easy to maintain
• Rugged and reliable
• Provides built in redundancy
• Cold re-start capability
• Successfully used in similar conditions
•
•
•
Mangala Development Pipeline Project
is unique as it is believed to be by far
the longest such continuously heated
and insulated pipeline in the world.
Currently, the longest pipelines using this
technology are in Russia (160 km) and
Indonesia (115 km).
Cairn India Limited
Cairn India Limited
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Power requirement – 40 W / m
Voltage – Approx. 4000 V
No current flow on outside skin of
tube
System earthed & grounded with
earth fault automatic trip
Remote emergency shut-down
capability
Current flows through center
conductor
Current returns through inside skin
of outer tube
Since the start of pipeline operations in
2010, the SEHMS system has performed
capably and contributed importantly
to the pipeline, achieving world-class
availability levels and has proven to be a
robust and reliable technological solution
to effectively solve flow assurance issues
with waxy Mangala crude oil. This is
the largest scale application of this
technology.
S K I N E F F E C T H E AT M A N A G E M E N T S Y S T E M
CAIRN INDIA LIMITED
Cairn India is one of the largest independent oil and gas exploration and
production companies in India with a market capitalisation of ~US$ 10 billion
and the fastest-growing energy company in the world as adjudged by the Platts
2012 and 2013 Rankings. Cairn India operates more than 25 per cent of India’s
domestic crude oil production.
Through its affiliates, Cairn India has been operating for more than 15 years
playing an active role in developing India’s oil and gas resources. To date, Cairn
India has opened 4 frontier basins with over 40 discoveries, 28 in Rajasthan alone.
The Mangala field in Barmer, Rajasthan, discovered in January 2004, is the largest
onshore oil discovery in India in more than two decades. Mangala, Bhagyam and
Aishwariya fields – major discoveries in Rajasthan block – have gross ultimate
oil recovery of over 1 billion barrels from primary, secondary and enhanced oil
recovery (EOR) methods.
Cairn India has a portfolio of 9 blocks - one block in Rajasthan, two on the west
coast and four on the east coast of India, and one each in Sri Lanka and South
Africa. Oil and gas is currently being produced from Barmer, Ravva and Cambay.
Cairn India Limited.
Cairn India Limited
3rd & 4th Floors, Vipul Plaza, Sun City, Sector 54,
Gurgaon 122 002, India +91 124 459 3000
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