There is no such thing as a perfect seal. The well know statement “Nature Abhors a Vacuum” is the standard. When sealing a vacuum chamber of the object is to reduce the leak to less than the Minimum pressure you wish to operate at. The first requirement of a sealant is “to do no harm”. Meaning that anything inside the vacuum chamber must be free of lighter molecular weight substances that will slowly evaporate and increase the pressure inside the vessel. Celvaseal is a silicone resin developed to be used inside vacuum chambers that will not out gas in a High Vacuum (Low pressure) environment. It will not trap impurities that that can out gas and cause contamination problems inside the chamber. It will cure at room temperature or curing times can be reduced by applying heat. It will seal to most materials Kovar, steel, Stainless steel, glass and form a seal bond. It can be used to repair a known leak or applied to thread, gaskets and sealing areas at time of assembly to reduce any chance of vacuum leak at time of assembly. It is best applied to the atmosphere side of a chamber under vacuum to allow material to be drawn into the leak and cure for increased strength and seal integrity. Application can be done vis brush direct to area of a known leak or onto a seal surface or applied with aerosols spray to a larger area (Spray and Pray).
It will seal leaks to the 2 m Torr range but can be effective for larger holes is applied at atmosphere and cured before vacuum is drawn.
It is useful as a cement for sealing all kinds of optical windows and glass to wire feed thru’s. It will substantially reduce the IR reflectivity of metals and will produce higher emissivity levels for better heat transfer. And it can be used for applications such as the repairing of gauge tubes and also vacuum feed thru’s. When sprayed on a surface, “dries” to a film that is optically transparent and exhibiting optical properties characteristic of clear silicone polymers.
It has been used as an adhesive at cryogenic temperatures and has good radiation resistance. It is used by NASA and has been used on more than a few projects that have gone into space. It will survive the environment of space without adverse effect on the product or the spacecraft itself.
Although shelf life is typically longer it is recommended that material be rotated/replaced after 12-15 months to insure product effectiveness when used. The usage life on chamber when applied and cured is infaninate and does not have to be replaced unless problems are encountered.
Some typical uses for Celvaseal® for suspect leak areas
- Glass tube sensor pin feed troughs. Occasionally the glass to metal seal becomes suspect due to movement of the pins when plugging on or changing the tube cable socket. Be sure to keep the sealant off of the electrical contact points.
- Glass-Kovar joints sometimes start to leak in the Kovar due to crystallization.
Some UHV systems with metal gaskets and/or high penetration welds “open up”. The sealant fluid carrier will draw into the suspect area and can be cured with the system conditioning schedule. - Glass systems where fusing of glass joints is not thoroughly annealed and “pin prick holes” have developed.
- External exposed gasketed flanges where aging of gasket has caused small stress cracks. This would be a temporary fix until the gasket could be replaced.
- Welded steel where crystallization of the weld has occurred and a small hairline crack appears. The surface tension of the fluid will flow into the crack by capillary action before it starts to cure.
- Brazed connections of copper tubing to brass valve housings.
- Apply to pipe threads for mounting of sensors and other components to vacuum system.
Celvaseal® may be used at temperatures up to 300ºC continuously, and up to 400ºC for short periods.
Average Curing Temperature Schedule
400ºC – 20-30 minutes
250ºC – 60-70 minutes
230ºC – 75-90 minutes
Room Temperature – Days
Celvaseal® 2 oz. Bottle Brush-On: Part Number 271375
Click here to download MSDS/SDS in PDF Format
Celvaseal® 6 oz. Aerosol Spray Can: Part Number 271373-6
Storage stability at 25º C one year
Click here to download MSDS/SDS in PDF Format
Celvaseal® is a registered trademark of Myers Vacuum Repair Services Inc., Kittanning, PA. 16201.
The information contained here is believed to be accurate and reliable, however it is the responsibility of the user to determine the suitability of use.
