Controlling Pipe Pig Speed
Pipe pigging is a method used to clean pipes in a variety of industries: food, chemical and oil to name a few. Pigging systems are used to clean pipes and reduce the amount of product waste and environmentally harmful cleaning products used to clean pipes. Controlling pipe pig speed with a Proportion-Air mass flow controller, makes too much sense and works great! An example of pigs can be seen HERE.
If air is used, air pressure generates the force to propel the pig through the pipe; however, controlling speed of the pig through the pipe requires that flow of the air be controlled. Without speed control, pipe elbows can be damaged and the pig can exit the pipe too quickly and damage equipment or injure an operator.
The Proportion-Air closed-loop F-Series flow controller is the perfect pig speed controller. Supply pressure sufficient to generate the force required is plumbed to the F-Series flow controller and a command signal from the customer’s controller is given to the F-Series to control the speed of the pig through the pipe. Speed is linear and proportional based on the command signal input.
Since the flow controller is closed loop, it maintains the speed of the pig regardless of obstructions encountered. If an obstruction in the pipe is encountered which slows the pig’s travel, the F-Series servo valve opens further allowing more pressure to be used to overcome the slowed travel. Once past the obstruction it throttles back to the necessary speed.
A concept sketch of pig velocity control is shown here.
Flow can be monitored by adding a digital readout to the flow monitor when ordering the F-Series assembly. Flow can also be displayed at a controller by connecting to pin 5 on the F-Series servo valve main connector. This signal is an analog 0-10Vdc or 4-20mA equivalent of the flow the transducer is sensing in the pipe.
The F-Series comes in three sizes and can be calibrated for flows up to 250 SCFM. They are very repeatable and made for an industrial environment. The product is immune to shock and vibration up to 25G. More information on these mass flow controllers can be found here.