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Guard Gas Controller for Gas Chromatography

IP.com Disclosure Number: IPCOM000200987D
Publication Date: 2010-Nov-03
Document File: 6 page(s) / 129K

Publishing Venue

The IP.com Prior Art Database

Abstract

The present invention generally relates to a gas chromatography (GC) system. Modern GC system utilizes electronic pneumatics control (EPC) to precisely control the gas flow or pressure of columns, inlets and detectors, as shown in Fig. 1. EPC is also referred to as advanced flow control (AFC) or electronic flow control (EFC) by different GC manufactures. The electronic pneumatics controller usually consists of solenoid valves and/or proportional valves, which are designed to open fully or partially while voltage is applied and close completely without voltage. Therefore all gases are shutdown while the GC power is off.

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Guard Gas Controller for Gas Chromatography

 Yao, Wei-Jun

Jiang, Ling

The present invention generally relates to a gas chromatography (GC) system.  Modern GC system utilizes electronic pneumatics control (EPC) to precisely control the gas flow or pressure of columns, inlets and detectors, as shown in Fig. 1.  EPC is also referred to as advanced flow control (AFC) or electronic flow control (EFC) by different GC manufactures.  The electronic pneumatics controller usually consists of solenoid valves and/or proportional valves, which are designed to open fully or partially while voltage is applied and close completely without voltage.  Therefore all gases are shutdown while the GC power is off.

Figure 1  GC flow diagram (Prior Art)

Such a design has many disadvantages.  First, it is common to encounter a sudden power failure in some developing countries and areas.  If a power failure happens while a GC instrument is running at high temperature, the shutdown of carrier gas can cause atmosphere air/moisture to enter into a hot column and may damage the column solid phase.   Second, for some applications, such as those using molesieve columns to separate oxygen and nitrogen, it is required to always maintain a carrier gas flow in the columns, but for safety concern and/or for energy saving consideration, the GC instrument has to be powered off at night or during weekend.

The present invention was proposed to address the above issues and problems.  The invention is designed to maintain a guard gas flow in the columns and/or inlets and/or detectors from a guard gas source through a Guard Gas Controller (GGC) when the GC power is off.   When the power is on, the EPC supplies gases as normal while the GCC is closed.  When the power is off, the GCC supplies guard gas (an inert gas, such as helium or nitrogen) to the columns and/or inlets and/or detectors while the EPC is closed, thus ensuring there are always inert gases flowing through the protected columns/inlets/detectors.  As a result, the column lifetime is extended and the GC startup time is shortened.

Fig. 2A and Fig. 2B illustrate the conceptual diagram of the GC instrument in accordance with the present invention.  As shown in Figs. 2A and 2B, the GC instrument comprises an EPC unit to supply gas from a gas source to an inlet/column/detector, just like that in the prior art instrument.  The CG instrument differs from the prior art in that it further comprises a GGC unit, which comprises a Tee union (1), an adjustable or fixed restrictor (2) and a normal open solenoid valve (3).  

The inlet of the solenoid valve (3) is connected to an inert gas source (guard gas source), such as helium or nitrogen.  The outlet of the solenoid valve (3) is connected to the restrictor (2).  The purpose of the solenoid valve (3) is to provide or cut off the supply of inter gas from the inert gas source to the column/inlet/detector of the GC instrument.  The power of the solenoid valve (3) is supp...