54
December
2014
HYDROCARBON
ENGINEERING
requirements allow these systems to be
powered by integrally mounted solar
panels and rechargeable battery packs;
resulting in them being totally self
contained.
There are many valve automation
applications in which totally SCEH systems
are preferable or even the only viable
solution; the most common of these being
the on/off control of mainline valves
situated in gas transmission pipelines. Often
these pipelines are hundreds of miles long
and traverse areas in which there is little to
no existing infrastructure. Traditionally,
mainline valves in gas transmission lines
have been actuated by two types of
systems; gas over oil (GOO) and direct gas
(DG) systems. Both of these systems use
the high pressure gas in the pipeline as the
motive power source for the actuators and,
while being proven and reliable
technologies, they suffer from one
significant drawback; this being that natural
gas is vented from the systems to
atmosphere whenever a mainline valve is
actuated.
With increasing focus on environmental
responsibility and the threat of global
warming, many countries including the UK have now banned GOO
and DG systems for greenfield sites and so there has been
increasing pressure on the valve automation industry to identify
replacement technologies. SCEH systems give operators all the
functionality available fromGOO and DG systems, but with
numerous additional benefits including the non-venting of natural
gas during operation and the ability to operate on biodegradable
fluid. With the most advanced SCEH systems now being able to be
powered from integral solar panels and rechargeable battery packs;
pipeline operators can start replacing their existing GOO and DG
systems with ones that create no carbon footprint during
operation.
SCEH systems have already been designed and installed in the
harshest operating conditions on the planet, including Gazprom’s
South Stream and Bovanenkovo-Ukhta pipelines in which the
project specifications required systems to be able to operate in
temperatures as low as -65 °C.
With SCEH systems often being installed in extremely remote
locations, the next challenge was determining how best to
communicate with them to provide on/off or positional valve
control. The majority of current systems typically incorporate
both wireless communications to provide remote valve control
and local control is provided via infrared keypad controllers. The
most advanced systems on the market have recently started
using Bluetooth enabled tablets and smartphones for local
control.
Although communications for on/off valve applications are
relatively straightforward and can be met with traditional wireless
remote control methods and locally via infrared keypad
controllers, positioning/modulating systems or those with smart
partial valve stroke testing capabilities require more advanced
communication methods.
Several valve actuator manufacturers
have for many years used infrared keypad
controllers to communicate locally with
numerous makes and models of smart valve
positioners and partial valve stroke test
systems for valve control, fault diagnostics
and condition monitoring. Conditioning
monitoring has become increasingly popular
in valve automation systems as it allows
operators to diagnose faults in their systems
before they negatively impact process
productivity or employee safety and allow for
the implementation of cost effective
preventive maintenance programs.
Although infrared keypad controllers
have been well adopted by end users and
adequately met their operational needs, the
recent advances in the capabilities of valve
positioners and partial valve stroke test
devices have highlighted their limitations. The
main limitation of infrared keypad controllers
is that communication is unidirectional, only
transferring data from the infrared keypad
controller to the positioner or partial valve
stroke testing device.
During development of a condition
monitoring version of one of Paladon Systems’
smart positioner models, it became clear that
an infrared keypad controller used in conjunction with the
positioner’s LCD display was simply inadequate to capture all the
data from the SCEH system and hence another form of
communication had to be found.
Bluetooth proved to be the ideal solution for many reasons,
including the fact that the technology is already well developed,
proven and used in many industries on a global basis. The
communication set up is also extremely straightforward, only
requiring a one time preliminary ‘pairing’ between the Bluetooth
enabled controller and a smart positioner or partial valve stroke
test device. More critically, since the radiated power of Bluetooth
systems is limited to 10 MW, which is well below the acceptable
threshold of electrical devices operating in Zone 0, 1 and 2
hazardous locations; it allows the technology to be used for all
valve applications in the oil and gas industry.
Once Bluetooth communication was selected, a standardised
operating system platform also had to be selected. Paladon
Systems elected to standardise on Android tablets and
smartphones for developing the graphical user interface (GUI) on
these devices as they are relatively low cost and, being open
source, relatively easy to program. While most Android devices
are not suitable for use in hazardous locations, certified tablets
and smartphones do already exist. As a further benefit, the
Android operating system makes applications totally
transportable between SCEH installations.
During Paladon Systems’ development of the GUI, it became
obvious that it would have to be split into three distinct sections:
n
n
An exact copy of the infra red keypad controller on the
tablet/smartphone screen giving a one to one replacement of
the keypad.
n
n
A means of downloading, inspecting, editing and uploading
operational parameters to the smart positioner or partial valve
Figure 1.
Double acting hydraulic
linear actuator mounted to a 4 in.
Class 600 gate valve.