Teledyne 4220 Reactivation of the Desiccators, Regenerating, Internal Case, Desiccant

4220 Flow Meter

Section 6 Maintenance and Service

6.2Reactivation of the Desiccators

The 4220 has a reusable desiccant canister held by a steel clamp on the inside of the case lid. There is also a tubular desiccant car- tridge on the top of the case next to the connectors. The canister contains silica gel that adsorbs moisture trapped inside the flow meter's case when it is closed. This keeps the inside of the case completely dry during shipment, storage and use. If you leave the case open, the desiccant will quickly absorb moisture from the surrounding air and will soon be saturated. It will no longer be able to protect the flow meter. Both desiccators use a color indicator that changes from blue to pink or from yellow to green when saturated. The external desiccant cartridge vents the ref- erence port of the pressure transducer.

6.2.1 Regenerating the	Look at the desiccant canister each time you open the case. The
Internal Case	canister has a window on its side that appears blue or yellow
Desiccant	when the desiccant is dry. As the desiccant absorbs moisture, the
	window will turn pale pink or green. When the window is pink or
	green, you need to regenerate the desiccant, or replace it with the
	spare canister provided in the flow meter accessory package.
	Remove the canister from the flow meter by pulling outward on
	the spring clamp, releasing its hold on the canister.
	Remove the canister and heat it in a vented oven in a well-venti-
	lated room at 300°F (150°C) for about three hours, or until the
	blue color returns. Do not use a microwave oven; the metal case
	of the canister could cause arcing. After cooling, reinstall the can-
	ister in the flow meter. Make sure the window on the side of the
	canister remains visible.

Figure 6-1 Location of the Desiccant Canister

6-2