Vacuum traps or foreline vacuum traps on high vacuum and ultra-high vacuum systems are placed between the high vacuum pump and the backing pump. Vacuum traps are specifically designed to capture various contaminants from entering the vacuum pump. Types of vacuum trap media include metal sieve, molecular sieve, metal or fiberglass fiber and liquid nitrogen.
Metal sieves are used for the removal of hydrocarbons to prevent any backstream when mechanical pump oil reaches vapor pressure. Sieve traps are manufactured out of 304 stainless steel but can be swapped for copper upon request.
Molecular sieve traps use a desiccant material as the filter mechanism to remove vacuum oils, water vapor and other contaminants. This desiccant material is re-fillable. A heating assembly can be incorporated into the design to regenerate the filter.
Liquid nitrogen (vacuum cold traps) traps use liquid nitrogen cooled filter elements to trap water vapor coming from the system to keep the water vapor before it condenses in the vacuum pump.
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Metal Sieve Traps
Molecular Sieve Traps
Molecular Sieve Traps perform two functions simultaneously. One function is the removal of hydrocarbons that may backstream toward the chamber when desired pressure is reached. The other is to ensure that water vapor and other gasses can be removed from the atmosphere before reaching and contaminating the pump oil. To initialize or replace the sieve, heat needs to be injected into the system to remove all imperfections caught within the system by turning on the heater and allowing it to run for 4 hours with the ballast valve open.
Particulate Traps use a polyester felt filter to trap contaminants over 10 microns at a 98% efficiency. To clean and maintain the filter, simply clean with a vacuum cleaner. These are not recommended to systems exceeding 150C. Should a polyester filter not meet your needs, please contact Schoonover to find a more fitting filter material.
Liquid Nitrogen Pumps condense gasses in a system before they can reach and contaminate the oil. Conversely, they also ensure fumes from the oil do not contaminate the vacuum chamber. Dual-tube traps allow for the attachment to a Nitrogen source so one never has to refill the trap.