Frequently Asked Questions

The most commonly asked questions (and answers) are assembled here.  If you prefer to download the file (42 pages, 1.4MB) in pdf format click here.

Torque

What is the difference between breakaway torque and stall (or running) torque?

Breakaway Torque is the amount of torque that an actuator can generate immediately when power is supplied — the torque generated from a standing start.

Stall torque is the actual amount of torque an actuator can generate — measured as the amount of torque required to stall the momentum of a running actuator.

For electric actuators in general, breakaway torque is a minimum of 20% less than the stall torque. This means that an actuator rated at breakaway torque actually provides at least 20% more stall or running than the label indicates.

Does Valvcon rate its actuators at Breakaway Torque or Stall Torque?

Breakaway torque because it is the most relevant way to measure torque in electric actuators for valves.  Some valves and dampers require a great deal more torque to "break" them from their seated postion than to move in mid stroke.

What does that mean to your customer?

Since many competitors rate their actuators at stall torque or tunning torque, a comparable torque actuator from Valvcon will actually provide approximately 20% more torque.  There is a hidden price and safety margin advantage for your customer.

What are the various torque sizes available for each Valvcon product?

inch pounds	150	300	600	1000	1500	2000	2500	3000
V Series
ADC Series
LC Series
ESR Series

How does Valvcon define duty cycle?

Duty cycle is the relationship between the time that an actuator may run and the time it must rest (cool).  If an electric actuator is run beyond its rated duty cycle, the actuator may trip out on thermal overload (at best), or burn up the motor (at worst).

Example: a 25% duty cycle means that the actuator can only run 25% of the time and needs to rest 75% of the time.

Question: for a 25% duty cycle, 10 second cycle time "open/close" actuator, how long must the actuator rest before initiating the next full cycle?

Answer: 30 seconds

Question: For a 75% duty cycle, 18 second cycle time "open/close" actuator, how long must the actuator rest before initiating the next full cycle?

Answer: 6 seconds

What are some of the factors that affect duty cycle?

Ambient temperature affects duty cycle:  The rated duty cycle for Valvcon actuators is specified at an ambient temperature of 104° F.  75% duty cycle at 104° F means more duty cycle than 75% duty cycle at 70 ° F or ambient.  Higher ambient temperature environments will decrease the duty cycle due to the decrease in the cooling rate of the motor.

Torque affects duty cycle: Requriring the actuator to operate in excess of teh rated torque will decrease duty cycle due to overheating the motor.

NOTE!: Make certain that the bracket and coupling between the valve and actuator is not adding extra torque to the package.  Misalignment, side loading, and exccessinf shaft length can raob a significant amount of torque.

What level of duty cycle is avalable on Valvcon electric actuators?

For V series actuators with aC motors, the standard duty cycle is 75%.

For DC motors, the standard is 80%  an ADC-series, which can use 115VAC (with a DC motor) input, still has 80% duty cycle due to the use of a DC motor.

For LC Series actuators with AC motors, the standard duty cycle is 25%.

What about 100% duty cycle AC actuators available from the competitors?

Some competitors publish a 100% duty cycle for actuators with AC motors.  READ THE FINE PRINT! Their "fine print" definition of 100% is qualified with language, such as "capable of operating continuously for up to 30 minutes, the de-rate cycle to (25% or 50%)".

Valvcon defines duty cycle as 24 hours per day, 7 days per week condition.  Valvcon believes that it provides the highest available AC duty cycle with standard V Series 75% duty cycle.  The "fine print" on Valvcon 75% duty cycle actuators is:

"Continuous operation for 15 minutes at an ambient temperature of 104° F after which the actuator will operate at 75% duty cycle"

How does duty cycle differ from "starts per minute"?

Duty cycle is often confused with high cycling.  Even a 100% duty cycle actuator has a limitation in the number of starts per minute.  The maximum number of starts per minute is limited by such things as the electrical saturation in the motor windings and in the drive circuit electronics.  The maximum duty cycle is limited by the safe operating temperature rise in the motor.  All Valvcon actuators are rated for a maximum of 30 starts per minute.