Christo-Lube Oxygen Compatible Lubricant
Christo-Lube III is for the lubrication of all breathing apparatus, pressure regulators and pure oxygen systems.
For many years the diving industry has used lubricants such as Krytox GPL 205 as the lubricant for its breathing systems.
However, verification testing indicated that limitations exist with these current lubricants. Due to the extremely low temperatures that are reached in the breathing apparatus under peak flow conditions, which have been calculated at lower than minus 50OC.
Most of the lubricants in common use provide acceptable performance down to – 30OC and so Divex has undertaken a review of the commonly available lubricants in order to identify a more suitable material. We considered products marketed under the trade names of Krytox, Christo-Lube, Fomblin and Halocarbon and in each case gave the original supplier a performance specification to quote against.
There is however, a conflict of requirements noted by all the manufacturers. In order to achieve the low temperature performance there is usually a sacrifice at higher temperatures, which is reflected in the higher volatility of the base oils from which the lubricant is formulated.
In order for the lubricated part to remain lubricated in service, it is desirable to have as wide an operating temperature range as possible so that it does not readily evaporate under high gas velocities.It is also desirable to have some dry film lubrication capability which is achieved by adding PTFE particles into the matrix.
Lubricants made under the name Krytox, Christo-Lube and Fomblin are generically the same, being perfluorinated polyethers. Halocarbon’s are polychlorotriflu-oroethylene.
More than one version of their lubricants were put forward for evaluation and samples were supplied for the most appropriate formulations. These were used in the unmanned verification of Underwater Breathing Apparatus (UBA) for practical evaluation.
All of the lubricants under review must be handled with care and not contaminated. As they all contain materials which breakdown to
form highly toxic substances at temperatures in excess of 300OC, they should not be heated or burnt. Christo-Lube, Krytox and Fomblin are compatible with the common rubbers and polymers used in UBA, However, Halocarbon is not recommended by the manufacturer for use with BUNA-S, silicone rubbers and natural rubbers. As these materials are frequently used in UBA for diaphragms and ‘O’ rings, Halocarbon is not recommended. All of the materials have a similar level of oxygen compatibility.
After studying the data given, it showed that the Christo-Lube MCG-III had the widest temperature range and the lowest evaporation
rate. The single grade meets three different categories of US MIL Spec and is also competitively priced.
From the review and tests conducted at Divex we have adopted and now recommendChristo-Lube MCG-III as the only grease for
use in breathing apparatus and associated pressure regulators.