Air Pumps and Accessories for LI-COR Gas Analyzers

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Air pumps and accessories for LI-COR gas analyzers.

The sample cells of LI-COR closed-path gas analyzers, such as the LI-800, LI-820, LI-840/A, LI-6251, LI-6252, LI-6262, and LI-7000, must be continually flushed while making measurements. The system time constant (T), a measure of how quickly the system responds, is determined by the cell volume and flow rate through the cells:

1T = Cell Volume / Flow Rate

The list of parts on the next page can be used to make a simple air flow system to move sample air streams through these analyzers. Parts available for sale through LI-COR are listed, as well as alternative vendors. Note the following precautions when designing your air flow system:

Always install an external air filter into the sample air stream before it enters the analyzer. Failure to do this will lead to contamination of the optical path.
Pressures of 15 kPa or more above ambient can cause damage to the source and detector windows. The safest mode of operation is to pull air through the optical bench.
Devices such as valve-actuated rotameters and T-fittings can be used to reduce flow rates. See parts listed in this document. Voltage regulators can also be used to reduce flow rates delivered from DC pumps.

For the LI-800, LI-820, LI-840, and LI-840A, the diaphragm pump (286-04198), flow meter, regulator, and vent can be used to restrict the flow rate to less than 1 liter/min. Alternatively, applying 3 VDC to the diaphragm pump (286-10198) reduces the flow rate to about 1 liter/min. For the LI-6251, LI-6252, LI-6262 and the LI-7000, either diaphragm pump (286-04198 or 286-10198) can be used directly without any flow splitting to reduce the flow rate. Similarly, if you are able to locate a pump that delivers less than 1 liter/minute, it can be used directly with the LI-800, LI-820, LI-840, and LI-840A analyzers without the need for a flow split. LI-COR does not offer DC power supplies or voltage regulators for use with these pumps. Several recommended suppliers are listed on the next page.

Pump and plumbing options

Recommended flow rates for LI-COR analyzers:

Model	Flow (LPM)
Model	Mininum	Maximum
LI-6251, LI-6252, LI-6262	0.25	10
LI-7000	0.25	~50
LI-800, LI-820, LI-840, LI-840A	0.25	1

Diaphragm air pumps for LI-COR gas analyzers:

Part #	Description
286-04198	Air pump; 12 VDC; maximum flow of 3.5 LPM
286-10198	Air pump; 6 VDC; maximum flow of 1.8 LPM

Plumbing example #1

The pump is on the intake side for large volumes of incoming air. This configuration is less prone to leaks due to positive pressure.

Plumbing example #2

The pump is on the outlet for injection measurements and small volumes of air. This configuration is more prone to leaks due to negative pressure.

Plumbing pieces, filters, scrub tubes, and flow meters available from LI-COR

Part #	Description
8150-250	Bev-A-Line tubing; ¼” OD; ⅛” ID; 15 meters
300-03123	Straight union quick connect
300-03125	Right angle union quick connect
300-03367	Y-union quick connect
300-07385	T-union quick connect
300-10471	Regulator quick connect
300-01961	Balston 0.01-micron air filter; recommended for the LI-800 and LI-820
9967-008	1-micron filter assembly; recommended for the LI-840/A, LI‑6251/52/62, and LI-7000
9960-093	Long chemical scrub tube assembly
294-03334	Rotameter; 2.5 LPM with valve. Requires two hosebarb fittings (part number 300-03388)