Sample Conditioning Systems
Gas samples generally require some form of sample conditioning before they are suitable for gas analysis. Many types of portable and continuous gas analyzers have various forms of built-in sample conditioning and sample motivation.
Here are a few examples from the Nova product line:
If an instrument is portable, this usually implies that the gas analysis will be temporary or intermittent, such as a spot-check application. This reduces the need for extensive sample conditioning components. A portable instrument also has limited space in which to integrate sample conditioning components.
Probe & Flexible Hose
Many portable Nova analysers come equipped with a 35cm (14″) stainless steel probe and flexible hose. This allows the user to extract a sample from a duct or enclosed area. The probe and hose are a small diameter to ensure fast sample transport time. The connection of the flexible hose to the sample inlet of the analyzer is usually via a compression-style or barbed fitting. In some cases, a quick-connect style of fitting might be used if the sample is under some pressure.
Engine Exhaust Probe & Hose
The portable engine exhaust analyzers are shipped with a special probe to ensure that particulate and oil vapors are removed before the gas sample cools down and develops condensate. The probe body has a tail-pipe retainer clip which will help position and anchor it to the exhaust pipe of the automobile. The standard probe tip is flexible, with an optional straight tip being optionally available.
Many gas samples contain condensable moisture which can be removed and contained using a condensate filter and bowl which is sometimes located at the sample inlet on Nova portable analyzers. A variation on this configuration may be located inside the analyzer with a condensate pump being used to drain the water out of the analyzer on a continuous basis.
Gas samples that are hot or excessively moist can be pre-treated before they are sent to the gas analyzer. Nova has two options for this purpose.
The first is a simple ice bath style pre-cooler in which the sample is directed through a tube that is immersed in a small reservoir filled with ice-water. The ice-cooler cools the sample gas and causes the condensable moisture to accumulate in the collection bowl located at the outlet of the cooler. The cool dry sample gas continues on to the analyzer.
The second option is the Model 2000 Portable Thermoelectric Cooler which filters the gas and then cools it and drains the condensed moisture. This device can treat a sample gas with a temperature as high as 100C (212F). It will deliver 1-2 liters of filtered sample gas controlled to 4C (40F). It is ideal for use with portable flue gas analyzers where long term unattended testing is required.
Continuous gas analyzers comprise a significant portion of the Nova Analytical product line. These types of instruments are generally used for continuous gas analysis of an individual sample point in a facility. Because these analyzers are intended for permanent exposure to the sample gas, they must be equipped with suitable sample conditioning components. This also means that continuous analyzers are bigger than portable analyzers, and they are almost always permanently mounted to a wall or other vertical surface.
Probe and heated filter
The Nova Model 7240 Probe & Heated Filter system is designed to be mounted at the sample extraction point on a pipe with flange. The pipe flange is mated with the cabinet flange and anchors the whole assembly securely to the process duct. The probe passes through the flange into the duct and is suitable for gas temperatures as high as 1000C (1830F). The purpose of the Model 7240 is to remove the dust and other particulate from the sample as close to the extraction point as possible. This maximizes filter efficiency and prevents the dust from mixing with condensate and causing sample line blockage.
Probe & Un-heated Filter
In some applications where the sample gas has little or no dust or soot, a probe-mounted un-heated pre-filter may be suitable enough to extract a gas sample. Some combustion applications that have natural gas as a fuel can be configured with a probe and un-heated filter.
Nova continuous analyzers can be equipped with moisture removal systems that are tailored to the requirements of the application. Some applications require continuous condensate removal, while others require aggressive cooling and moisture removal. We can offer both options in the same basic footprint inside the gas analyzer. This prevents our designs from diverging widely from our standardized layout. It also allows the customer to easily extract the moisture removal system and replace it if there is a problem. Some of our customers keep a spare moisture removal system in stock to allow quick replacement. In applications where there is a known abundance of moisture, an external version of the moisture removal system is available. It is mounted in its own cabinet and can be used to pre-treat the gas before it enters the analyzer cabinet.
Some combustion applications, such as incinerators, may produce acidic sample gas which can corrode the analyzer or interfere with accurate gas measurement. The Nova 7300 Water Wash system takes advantage of the fact that many acids are water-soluble. The sample gas is aspirated into the preparation system by a flow of fresh water. The gas is then bubbled through the fresh water and is stripped of any soluble acids and by-products. The water is re-circulated by a pump. A small amount of input water must be continuously added to the water wash system to prevent it from becoming too acidic. The excess water is automatically drained out of the system. The clean sample gas is then sent to the gas analyzer for analysis.
Some applications require a single analyzer to be time-shared over several sample points. The Nova 402 Series Auto-Sampler system can receive up to 24 sample lines and direct one at a time to a gas analyzer. The system is fully programmable to allow the customer to vary the time or order of the sample points being analyzed. The inactive sample points are still extracted using bypass pumps to ensure that the gas remains fresh when it is sent to the analyser. A simplified version of this system is available for dual point applications that only require a timer and a toggle mechanism between the two points.
If you have a requirement for continuous gas analyzers, or for sample conditioning systems, we can assist you. Please inquire here or here to see if your requirements can be met.