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airn India Limited.

Skin Effect Heat Management System

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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 Mangala-

Bhogat Pipeline as the 90 mm of PUF

pipeline insulation will be good enough to

keep heat losses within acceptable limits.

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

AC VOLTS(Outside Surface

to Earth)

Heat Tube(with insulated

wire inside

Carrier PipeFluid

Thermal Insulation

AC VOLTS(Inside Surface

to Earth)

STSTM System Tyco Thermal Controls LLCC

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.

Necessity, as they say, is the mother of

invention, and in the case of Cairn it was

the same for this innovation of technology.

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

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.

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

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Power Source and TemperatureMonitoring

RTD’s

Termination

Heat Tube

STSTM System

Tyco Thermal Controls LLCC

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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:

• Safe

• Custom engineered

• Easy to maintain

• Rugged and reliable

• Provides built in redundancy

• Cold re-start capability

• Successfully used in similar conditions

A view of the Mangala development pipeline showing the SEHMS and the Raageshwari Gas Pipeline

The details of the Power Source and

Temperature Monitoring are as follows:

• 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.

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).

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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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