O-RING LUBRICANT / GREASE

There are two areas where O-rings are generally used on Pyrex neon manifold systems: The connections between various components and the stopcocks. There are also different types of O-ring connections as well as stopcocks. However they all have the same function: To make a high vacuum seal. SVP utilizes a precision cut Threaded Glass Compression O-Ring Connector to obtain our modular designs and a standard Teflon plug, high vacuum O-ring sealed stopcock.

THREADED GLASS COMPRESSION O-RING CONNECTORS:

The O-ring of this type of connection should not be lubricated or greased. These connectors rely on the friction of the compressed O-ring to hold components in place and to function properly. If the O-ring were slippery from lubrication it would not work correctly.

“GREASELESS” O-RING STOPCOCKS:

The O-ring seal Pyrex stopcocks that are used on virtually all new Pyrex manifolds throughout today’s neon industry are often referred to as “greaseless”. Although they can be used as such, with no lubrication at all they can be difficult to use. Therefore, a small amount of lubrication is used, which allows the O-rings to slide more easily inside the glass barrel. However, the type of lubricant used is important to long-term performance and ease of maintenance.

SVP Neon Equipment strongly recommends not using silicone based stopcock grease, such as Dow Corning silicone stopcock grease, or fluorinated grease such as Krytox® or similar products. For reference Dow Corning silicone grease is typically supplied in a blue and white tube, while Krytox® is usually supplied in a small white tube.

Silicone based grease, when used in glass vacuum apparatus, will polymerize to the glass as a non-conducting film that can allow static charge build-up. This invisible film will migrate through the vacuum system, trapping contaminants as it does so and preventing efficient pump-downs. This polymerization also makes it extremely difficult to clean the silicone film off the glass when the system is dismantled for cleaning or repair, even though the contamination is not visible to the eye.

When a glassware repair is necessary the silicone film must be completely removed by chemical means if a long-term successful repair is to be expected. The often used method of attempting to burn off the silicone film in an annealing oven prior to repair only worsens the situation as many times the oven temperature is too high and will literally burn the film into the structure of the glass, thereby making any future repair questionable. If not removed by chemical means prior to repair and annealing, the silicone film will be sealed into the glass where the repair is made. This is sometimes evident by a “cloudy” area adjacent to the repaired section. An example of this can be seen Here. Glass that is repaired in this manner and fused together with a silicone film present will always be a potential leak in the area of the repair. The repaired area may or may not leak. If it does, the leakage and subsequent “pin hole” may not be evident for months, or even years after the repair is performed.

Fluorinated grease such as Krytox®, is extremely resistant to almost all solvents and chemicals, which is exactly what it was designed to be. This makes it very difficult to remove from glassware as well and, therefore, poses many of the same problems encountered with silicone when attempting to repair glassware that has been exposed to it.

SVP highly recommends using a hydrocarbon based high vacuum grease, such as the various Apiezon® blends or Lubriseal®. These products are available from SVP Neon Equipment as well as other suppliers.

Hydrocarbon based grease or lubricant, such as the various Apiezon® blends, Lubriseal® and similar products, is easily removed from the glass surface with a number of different solvents when manifold components need to be cleaned. When a repair is required it is not necessary to chemically pre-clean the glassware prior to repair as it is with silicone or fluorinated based greases. Annealing the glassware prior to repair will completely remove all grease and residue without fear of compromising the surface of the glass, as in the case with silicone or fluorinated grease.
 

Proudly Made in the USA