53
December
2014
HYDROCARBON
ENGINEERING
perational
O
ver the last five years, the versatility and operational
benefits of self contained electro hydraulic (SCEH)
valve automation systems have become increasingly
more recognised by both valve companies and end
users.
SCEH typically comprise as a minimum a mainline valve, an
external electrical power source, an electric motor/pump set, a
hydraulic reservoir, a hydraulic accumulator, a hydraulic control
system and a rotary or linear hydraulic valve actuator.
The electrical supply powers the electric motor/pump set to
draw hydraulic fluid from a non-pressurised hydraulic reservoir and
pressurise it. The pressurised hydraulic fluid is then stored in an
accumulator and the control system used to apply and remove the
hydraulic fluid from the valve actuator to achieve the required
mainline valve position.
By using the pressurised hydraulic fluid stored in the
accumulator to power the valve actuator rather than using
pressurised fluid coming directly from the motor/pump set, valve
actuator stroking speeds can be fast enough for critical applications
such as emergency shutdown (ESD) and blowdown valves (BDV)
while the motor/pump set size and power requirements can be
kept to a minimum. Once the hydraulic fluid in the accumulator
falls to a pre defined low set point, a signal is sent to operate the
motor/pump set until the accumulator is refilled to its high set
point. Accumulators can be sized to allow for multiple valve
strokes before requiring refilling via the motor/pump set.
Recent technical advances in low power electrical control
system components coupled with innovative control system logic
have nowmade these types of systems suitable for operation on
power supplies as low as 100W. Very low operating power
Matthew Shepherd, Paladon Systems, UK,
discusses the
operational advantages of self contained electro hydraulic valve
automation systems.
O
benefits
