Process Control

Improving Performance of Stream Switching Systems Under Low Air Conditions

Parker Instrumentation Chromotography and Gas Generation - Process Controls and FiltrationAs a user of analytical equipment such as process analyzers or gas chromatographs, are you affected by the vagaries of your compressed air supply? How often does a drop in its pressure affect the performance of the switching system you use for selecting a sample stream of gas or liquid media for analysis? Even if this only occurs a few times a month, its knock-on effect can significantly impact production.

Challenges with air pressure supply

Many process plants make extensive use of compressed air for controlling and powering equipment, especially in hazardous areas. They are challenged with

  • Loss of pressure
  • Drop in pressure
  • Unreliable switching
  • Higher volume of carrier gas used
  • Expensive carrier gas

 If the air supply falls below the actuation pressure of the valves in a stream switching system, analysis will need to be suspended until full pressure is restored, otherwise measurement integrity may be compromised by unreliable switching.

Manufacturers and users of gas chromatography equipment in the life science market sometimes elect to use carrier gas instead of compressed air for valve actuation, to circumvent air supply issues. However, the downside of this approach is that it uses a higher volume of carrier gas – which in the case of helium, for example, is becoming increasingly expensive. And of course, the higher the required valve actuation pressure, the more gas that gets used.

 

Stream switching as a option

Stream Switching System - R MAX Process Controls - Parker HannifinStream switching is where the sample flow going to an analyzer with multiple sample streams can be switched between samples.  You may already be using stream switching systems such as Parker's R-max – they’re very popular in industries such as chemical and petrochemical processing – to control the flow of gas or liquid sample media to your analyzer stations. The valve modules in Parker's systems each contain two valve cartridges, configured in a double-block-and-bleed arrangement to prevent cross contamination of the sample streams, and can operate over a media pressure range of vacuum to 500 PSIG (34 bar).

 

Retrofit kit options to enhance performance

Until now, the actuator for each of these valves has taken the form of a single piston that requires a 65 PSIG (4.5 bar) supply of air or gas. To help users improve the reliability and efficiency of its stream switching systems, Parker has developed a new low pressure actuator that only requires an operating supply pressure of 35 PSIG (2.4 bar). Based on a patent-pending pneumatic design that uses two pistons to effectively double its power, the new actuator provides an ideal solution for applications that are affected by ‘low air’ conditions or high carrier gas costs.

You can specify low pressure actuators for any valves in the Gen II version of R-max stream switching systems at the time of ordering. Alternatively, you can enhance the performance of an installed R-max or Gen II R-max system with a field retrofit kit. The kit can be installed easily and quickly – much like changing a valve cartridge – simply by removing four screws on the valve module. There is no need to remove the module from its base plate or break any process line connections. For configuration flexibility, either or both valves in a valve module can be upgraded with the low pressure actuator, which has the same compact footprint as the 65 PSIG version and is only 1.9 cm taller.

Users of analytical and gas chromatography systems can now benefit from state-of-the-art stream switching technology and reliable low pressure valve actuation.

 

 

Charles Harris Marketing Manager Instrumentation Products Division Parker HannifinArticle contributed by Charles Harris, Marketing Manager for Instrumentation Products Division Europe, Parker Hannifin

Other articles for the life science market:

Is Hydrogen a Safe Gas Chromatography (GC) Carrier Gas? Part 2 of 3

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