Hydraulics
for the nuclear age
NL
Soni, Saurabh Pandharikar, and RG Agrawal discuss the development of
the servo valve based on the rotary principle at BARC
The
Bhabha Atomic Research Centre (BARC), a Central Government institution,
has been at the forefront of scientific research and development in
the field of nuclear power technology in India. Fluid power plays an
important role in the nuclear reactors at the BARC, especially during
the various stages of the nuclear fuel cycle, such as nuclear fuel and
structure material fabrication, handling, reprocessing, installation
of facilities, and material evaluation.
Fluid power technology is poised to play an important role in developing
repair and decommissioning technology for many nuclear facilities where
large forces and torques must be developed with precise control of position
and velocities, at remote locations.
Various divisions at the BARC are actively involved in developing fluid
power technology for meeting their own requirements. The Fluid Power
and Tribology Section at BARC is developing fluid power technology in
the following fields:
Development of remote repair and decommissioning technology for BARC’s
nuclear facilities:
For addressing this need, BARC has developed a remotely operated
hydraulic trolley along with 6 DOF manipulator remotely operated hydraulic
trolley along with manipulator, which is an electro-hydraulic servocontrolled
robot capable of handling a 50 kgf pay load with a reach of 3 m and
it can handle a 500 kgf load without wrist operation.
The equipment is capable of carrying out various remote activities such
as cutting small pipes and tubing, handling vessels, heat exchangers
and valves. It can also be used for opening bolts and studs, dismantling
high pressure flange joints and butt nut splitters, sucking liquid and
power, and so on. All these operations may be carried out remotely (about
50 m away) with the help of various feedback controls and through a
closed circuit camera system. Various gadgets are also being developed
for handling heavy tools to cut concrete walls, chip floors and cut
vessels. Special purpose hydraulic tools are being developed indigenously
to carry out these activities
Development of water hydraulic components:
Water hydraulics is being used by the centre for purposes of fuel
handling in nuclear power, research reactors and underwater manipulating
activities. The BARC is developing different types of water hydraulic
components like pumping systems, water hydraulic servolinear and rotary
actuators, special purpose valves for controlling pressure, differential
pressure and flow, and self-actuated passive valves for safety systems
Development of a condition monitoring technique for fluid power:
A condition monitoring technique is being developed for complete
hydraulic systems using particle counting and ferrography. This technique
can easily pinpoint the defective components of a system v Development
of water hydraulic servo valve: A water hydraulic servo valve based
on the rotary principle is also being developed at the BARC. In this
regard, it should be noted that various innovative ideas are being employed
for developing this hi-tech component.
In this article we shall study the development of the water hydraulic
servo valve based on the rotary principal for use in the nuclear power
plants among the developmental activities mentioned above. To control
flow, various types of valves are used and most of the valves available
in the market are developed for oil hydraulic applications. Continual
development in hydraulic components and fluids, especially in the last
15 years, has led to the use of a mixture of oil and water – and
now, pure water - as working fluid for various applications in the food
and steel industries, the power sector and agricultural equipment sector.
The servo valve discussed above is a flow control valve designed for
1100 lpm at a differential pressure of 6 bar, at full opening. The valve
consists of two modules, the main valve(MV) and pressure compensator.
The main valve controls the flow area while the pressure compensator
maintains a constant differential pressure across the main valve, irrespective
of load pressure. The pressure compensator acts i series with main valve.
In the main valve, the flow area is controlled by the position of the
spool. This valve uses a new concept to maintain the position of the
spool. It is maintained by pressure balance on both sides of the spool.
The valve uses a rotary sleeve with a helical groove to open the pilot
port of the spool. The rotation of the rotary sleeve changes the opening
of two pilot ports on the spool. It also makes the spool unbalanced
and the spool moves in such a way that it tries to nullify the unbalanced
pressure. The spool ....
....CONTD
