FAQ - Fail-Safe Backup (ADC)

What is a Valvcon Fail-Safe actuator?

Valvcon Fail-Safe actuators are electric actuators that are capable of cycling a valve or damper after the loss of primary power.

What options are there for Fail-Safe electric actuators in the industry?

Mechanical springs, external battery packs, internal battery packs, and non-replaceable high energy storage devices such as super-capacitors are different technologies used to provide back-up power.  Valvcon is one of the only manufacturers providing fail-safe actuators employing internal battery back-up and high energy storage devices.

What is the advantage of an internal battery pack?

Battery packs can store enough energy to continue to modulate after power outages (provided the control signal remains) and provide multiple cycles of the valve or damper upon battery power.  Internal battery packs save space and are less expensive.

What is the advantage of non-replaceable high energy storage devices to provide back-up power?

High energy storage devices such as "super capacitors" never require replacement. They are lightweight, compact, and because of the extremely high cycle life, can allow true "two wire" control - apply power to open, remove power to close.

What does the Fail-Safe actuator do?

As long as external power is present, it drives the valve like a normal actuator.  Upon loss of power, it drives the valve to the "fail" position (full open or full closed).

How do you set the actuator to "Fail-Open" or "Fail-Closed"?

This can be done by the user by setting the position of a jumper switch on the back of the board.

How is a Fail-Safe actuator wired?

There are several options.  Generally, for 115 VAC, two wires (one neutral and on hot) constantly provide power to the actuator.  Two additional wires) one neutral and one hot) are used to control the actuator so that whenever the hot is energized, the valve opens and whenever the hot is de-energized, the valve closes.

Can a battery back-up Fail-Safe actuator operate like a solenoid?

No.  The limitation in recharging a battery quickly and the battery charge circuit design are not intended for such repetitive operation.  The ESR series (energy storage device) is an excellent choice for this type of operation.

What does the Valvcon Fail-Safe Positioner do?

The Valvcon control board provides modulating control from an analog signal (such as 4-20mA) with the battery available to drive to the fail position upon loss of power.

What are the two possible modes of operation for the actuator upon loss of power?

1) The actuator can be set to drive immediately to the designated "Fail" position, either full CW or full CCW.

2) It can be set to sense for an active control signal.  If the control signal is present, (often the controller is protected by a UPS system) the actuator will continue modulating.  If the signal can not be detected, the actuator will drive to the designated fail position.

How may complete cycles are normal to expect from a fully charged battery?

10-15 cycles

What types of batteries are used in Valvcon Battery back-up Fail-Safe actuators?

The ADC uses a Polaroid Flatpack battery or a sealed lead acid battery.

The LADC uses a sealed lead acid battery.

What is the recharging mechanism in Valvcon battery back-up Fail-Safe actuators?

Trickle charge (the battery is constantly recharging as long as power is applied to the actuator) with overcharging protection.

What is the shelf life of the batteries used in Valvcon Fail-Safe actuators?

Three years.

What is the recommended replacement schedule for batteries used in Valvcon Fail-Safe actuators?

For both ADC and LADC: 2-5 years depending on the environment and operating conditions.

Is it difficult to replace the battery in a Valvcon Fail-Safe actuator?

No!  Valvcon Fail-Safe electric actuators are designed to make battery replacement a simple task.  Remove the bracket, remove the battery, insert a new one and re-install the bracket.

If a Valvcon Fail-Safe actuator is modulating under battery power, could the batteries run out of power and stop in mid-stroke?

No.  The actuator is designed to sense battery power level and will drive to the designated fail position when battery power drops below a safe operating level.