Vaisala HMK15 - Manual (Page 33)

Chapter 5 ________________________________________________ Maintenance
VAISALA _________________________________________________________ 31
CHAPTER 5
MAINTENANCE
Depending on the frequency of use and the general
operating conditions, the salt solutions maintain their
characteristics for 6 … 12 months. After that, they must be
replaced. A visual check should be performed at intervals of
2 … 3 months. There must be a minimum of approximately
10% of undissolved salt at the bottom of the chamber
(max. 90 %) and the salt must be clean, otherwise it must be
reprepared. Please, note that the LiCl solution may
crystallize on the surface. However, there may still be
solution under the surface. Therefore, in such cases stir the
solution and check it again the next day. It is advisable to
keep a maintenance log which shows the dates of salt
replacements and other maintenance procedures.
For correct calibration it is essential that salt chambers are
tightly closed. Check the O-rings at each salt replacement. If
they are damaged, replace them with new ones. The O-rings
used are of the following types:
O-ring location dimensions type
measurement hole
12 mm 12 × 2.5 mm NBR70
measurement hole
13.5 mm 13.5 × 2.5 mm NBR70
measurement hole
18.5 mm 18.3 × 2.4 mm NBR70
transit cover 41.2 v 3.0 mm NBR70
chamber 50.0 × 2.0 mm NBR70