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In most bulk powder handling applications, sliding doors are mainly used to fully close or fully open the material flow. In some cases, it may be necessary to limit the amount of material allowed through the gate. When controlling the flow of dry bulk solid materials, different controls can be used to measure the volume and flow rate.
Flow control is a component that can be added to pneumatic actuators to help control material flow. Pneumatic actuators are more cost-effective than electric actuators and can quickly reposition the blade. Pneumatic actuators are composed of cylinders, pistons/diaphragms, rods and valve stems, and can also be modified to include material flow control devices to help provide accurate material metering.
Whether filling small bags and/or containers or filling trucks on a scale, the implementation of material flow control and accessories can improve accuracy through precise batch weight calculations. Other benefits include reduced filling time between workstations and flow control when processing immersable materials that can be filled quickly.
The most commonly used and customizable material flow control component is AVP, so it is the most common option for material flow control. Unlike other options, AVP can control the flow of opening and closing strokes. AVP is a very cost-effective option that provides high precision positioning up to 3/16 inches.
AVP can accommodate many intermediate positions. The number of intermediate positions is determined by the number of reed switches mounted on the (pneumatic) actuator. The number of AVP intermediate positions is only limited by the size of the reed switch, the available space along the lever of the pneumatic actuator, and ensuring that the sensing range of the reed switch does not overlap. AVP requires a programmable logic controller (PLC).
In contrast to other material flow control options, IVP allows full control of the variable positioning of opening and closing strokes. IVP relays blade position feedback along the entire stroke of the blade by using linear output sensors. One of the main advantages of IVPâ????s instant feedback capability is that the door can be moved to any position at any time.
The control box or PLC is used to operate the gate, which can be manually operated on the valve or synchronized with the PLC to realize automatic operation. The variable position of IVPâ????s is adjusted using a different technology from other material flow control components.
Common applications of IVP are those that require the most precise material flow accuracy. In these cases, reaching the exact weight of the bag or container is critical, as reducing a small amount can be costly for the company.
In the VPO configuration, the gate can start from the closed position, start to the variable position during the opening stroke, and then return to the fully closed position or continue to the fully open position. VPO is not backward compatible. If the blade is in the fully open position, it cannot be driven to the variable position during the closing stroke. It must first be driven back to the fully closed position before it can be reopened to the variable position. If required, VPO also allows traditional full-open to full-close drive, and vice versa. VPO is very useful in applications involving trickle metering.
The improved CVPO is very suitable for applications that need to limit the fully open position to avoid overflow in the downstream process. A threaded rod is included at the end of the cylinder housing, and the cylinder itself has a CVPO modification. The threaded rod can be manually adjusted to limit the opening stroke of the blade. When using the CVPO option, the fully open position of the blade becomes the set point established by the threaded rod.
CVPO is only used for applications where customers need to limit the opening stroke. Due to the manual nature of this material flow control, there are few changes.
In a VPC configuration, the gate can start from the open position, drive to a variable position during the closing stroke, and then return to the fully open position or continue to the fully closed position. Like VPO configuration, VPC is not backward compatible. If the blade is in the fully closed position, it cannot be driven to the variable position during the opening stroke. First, it must be driven back to the fully open position before it can be reclosed to the variable position. VPC also allows traditional full-open to full-close driving, and vice versa. This is another flow control device that can be used for trickle metering.
The VPO-VPC configuration is used for applications that need to control the open and closed positions of the blades to achieve material dribbling feed. This component combines all aspects of VPO and VPC control, allowing manual adjustment of the middle blade position by implementing an air control solenoid valve and a pneumatic travel switch.
The two-stage cylinder is designed with a magnetic piston to accommodate a magnetic switch for position indication. It is most suitable for applications where the blade needs to stop at the same exact middle position every time. The combined cylinder provides blade positioning in three positions: blade open, blade partly open and blade closed. Two-stage cylinders are usually used with three-way splitters, where the stroke needs to be precise to accommodate the middle position.
The manufacturer of the sliding door can help evaluate which material flow control options are best for your specific application. Many details need to be evaluated to determine the best option, including the characteristics of the processed material and the location of the gate control in the system.
Austin Anderson is the content marketing manager for Vortex Global USA (Salina, Kansas). For more information, please call 888-829-7821 or visit www.vortexglobal.com.
Post time: Nov-11-2021
