Proper linkages of all the components that comprise automated valves are critical to the performance of process control operations.
By Bob Donnelly, Contributing Writer
Historically, when valve automation first began, mounting kits made up of brackets and couplers to mount an actuator on top of a valve had to be machined by custom bracket manufacturers. This process typically took time and required these manufacturers to have all the different dimensions of the bottoms of the actuators and the tops of the valves. Over time, this process of making customized mounting brackets has become costly and is still time consuming.
These days, as a result of valve and actuator manufacturers standardizing on the dimensions (FO patterns) of their valves and actuators standard ISO ‘mounting kits’ (Figure 5) have been developed. These EZ-Link bracket kits can be manufactured inexpensively for all the standardized dimensions of valves and actuators, and are available off-the-shelf.
This means that any end user or industrial valve distributor can do their own valve automation with simple tools. The savings in time and money can be considerable. Of course, every automated valve assembly using these EZ-Link kits also needs to be tested, which likewise should be a relatively simple process with the right equipment for testing.
Stem Extensions
Another valve accessory that has been developed are EZ-Link heavy duty investment cast stainless steel stem extensions. These stem extensions (Figure 2) provide additional height and distance between the valve and operator. This protects any automated valve assemble from dangerous temperature media that may be in any process control operation. These stem extensions are available in a variety of sizes from 1 inch to 6 inch lengths, and can be customized to any quarter-turn valve.
Figure 2 is an example of an automated valve package with a stem extension and an EZ-Link bracket kit.
Figure 1.
Figure 2.
Media Containment Devices
Fugitive emissions are dangerous in any process control operation, and especially, in high temperature severe service applications. Media containment devices that can be mounted on valves have been developed to provide an additional safety feature. These devices have a secondary set of graphite stem packing and live loaded Bellville washers that automatically compensate for temperature and pressure fluctuations. This combination maintains a leak proof seal thus extending the life cycle of the valve, and can be installed on valves in service, another time and cost savings feature.
Like stem extensions, these devices (Figure 1) provide added height, thus distancing the valve operator/actuator from dangerous high temperature media. Sensing and sealing devices as well as a positive displacement air line can be affixed to the media containment device for even greater protection.
Figure 3.
Figure 4.
Limit Switch Brackets
Limit switches are used for valve positioning with visual indicators. They are available with a wide variety of switches and sensors. Limit switches have become more and more a part of automated valve packages and need to be mounted on actuators with special limit switch brackets (Figure 3). Newer and smaller (low profile) limit switches are also available and need similar mounting brackets (Figure 3).
Electric and Electro-Pneumatic Positioners
Another type of positioner that requires a mounting bracket is one where there is a need to change from a Pneumatic Positioned to an Electro-Pneumatic Positioner. This is accomplished by adding a limit switch and/or position transmitter module, or gauges.
Solenoid Valves
Another valve automation component that is part of many automated valve packages is the solenoid valve. These devices come in a variety of 3 and 4 way Namur ratings, and more often than not are direct-mounted to pneumatic actuators these days.
Fusible Link Valve Assemblies
Fire control valves are crucial to any piping systems that handle flammable gases, liquids or even toxic fluids. These assemblies are designed to fail close in the event of a fire, terminating the flow, which may be adding to the intensity of any fire. In the event of a fire, the fusible link separates and allows the springs to drive the valve into a closed position. Fusible link assemblies can also be made to fail in the open position to feed a sprinkler system in the event of a fire (Figure 4).
Conclusion
In summary, proper linkages to all the possible valve automation components are available from “One Stop Shop” valve and actuator suppliers, and can be assembled and tested in-house before shipment to insure the proper functioning of the complete valve automation package. This is a very cost effective and time saving feature when considering the alternative of having all of these components sourced from different suppliers, and then needing another contractor to assemble and test the total automated valve package.
Figure 5.
ABOUT THE AUTHOR
Bob Donnelly is Vice President of Business Development for FloTite Valves & Controls. He has over 30 years of process control automation experience.
