Within process industries, one of the most common process control elements is the control valve. Control valves regulate process media, such as gas, steam, water, or chemical compounds, to keep a process regulated as close as possible to the desired set point conditions.
Control valves work by opening or closing in response to a signal. The signal is typically sent from a control mechanism that compares a selected process set-point to the actual process conditions. The control mechanism signal then triggers the valve actuators, which then open or close the valve by the amount needed to restore the process conditions to the chosen set-point.
Because they do not require human intervention to activate them, control valves are an increasingly important feature of manufacturing and facility operations. At the same time, because they do their work unattended and without direct human control, control valves may leak or generate fugitive emissions which can go unnoticed. Choosing an appropriate compression packing for control valves may therefore require consideration of a wider array of factors than that for standard valves.
Typically, control valves have a packing box with the compression packing held in place and adjusted by bolting. Depending upon service conditions, a choice of compression packing materials can be used in control valves. A critical aspect to consider in any application is whether or not compliance to environmental regulations is required.
PTFE and Graphite Packing for Control Valves
PTFE compression packing works well in many control valve applications. PTFE packing is resistant to most chemicals, except molten alkali metals, and the packing services application temperature ranges from -40°F to +450°F. A notable exception to the use of PTFE packing is nuclear applications where PTFE is easily destroyed by radiation.
Laminated and filament graphite compression packing is suitable for control valves in nuclear applications, or where a low chloride content is desirable. Graphite packing is impervious to most aggressive media, and it services application temperature ranges from cryogenic temperatures to +1200°F.
Certified Low Leak Packing
For control valve applications where compliance to environmental regulations is concerned, a certified low leak packing will be the preferred choice. According to the US Environmental Protection Agency (EPA), valves may account for as much as 60 per cent of all fugitive emissions. Using a certified low leak packing can reduce the fugitive emissions coming from control valves and bring the valve into compliance with EPA directives covering “Certified Low-Leaking Valve Packing Technology”.
Canada Rubber Group Inc. supplies a wide range of Teadit compression packing suitable for control valves. We can supply Teadit PTFE and graphite compression packing, as well as style 2236 certified low leak packing. Recently, Teadit style 2236 was submitted for ISO 15848-1 testing on a NPS 3 Class 600 Globe Control Valve, and came away with a Class A rating – a rating which is typically achieved with a bellow seal.
To view our full range of Teadit compression packing, download our Teadit Compression Packing PDF or contact our sales department at email@example.com.