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Applying a Nitrogen Purge

The Cary 4000/5000/6000i instruments are fitted with connection points for purging the

optical system with nitrogen to enhance the performance of each instrument at extremes

of its range. More details are provided in the Cary Hardware operation manual (part

number 8510197200), supplied with the instrument.

Nitrogen supplies are not available from Varian but may be obtained from commercial

suppliers. Liquid nitrogen (in conjunction with a heat exchanger) is recommended

because it is generally less costly than compressed nitrogen and is of better quality.

Where compressed nitrogen must be used, the gas must be dry, oil–free and

uncontaminated. Do not use compressed nitrogen from a supplier who uses oil or water in

the compression process (these methods leave fine particles of oil or water suspended in

the nitrogen that may be deposited on the instrument optics). Only use nitrogen from a

supplier who fills containers from immersion pumps lubricated with liquid nitrogen.

Note

The instrument warranty will be void if damage is caused by the use of contaminated nitrogen.

Operating pressure at the pressure regulator (# 7 in figure 53) for the nitrogen purging

system is 83 to 172 kPa (12 to 25 psi). Use a suitable regulator and gauge assembly to

ensure that the nitrogen supply is maintained at the correct pressure.

Nitrogen supply tubing should be clean, flexible plastic tubing 6 mm (1/4“) inside

diameter (Tygon PVC or equivalent). Do not use rubber tubing as this is usually treated

internally with talc which will be carried into and contaminate the instrument optics.

The nitrogen system should include a manifold assembly with inlet from the supply and

two outlets for connection to the instrument. Manifold outlets should each be fitted with a

stop valve and flowmeter for control of gas flow to the instrument. Flow meters should be

adjustable for flow rates of 0 to 30 litres per minute (0 to 64 cubic feet per hour). Refer to

the figure below for more details.

Figure 53. The position of flowmeters when purging with nitrogen:

1 2 ... 68 69 70 71 72 73 74 75 76 77 78 ... 87 88

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Mantis 5000 Especificaciones Pagina 73