Recently one of the designers of the Super-Clean Gas Filters spent some time with technical service and we were able to ask him a few common questions we get asked by customers. I thought I would share this information with you.
A. The fittings used on the baseplates (and those for the inline filters) are not NPT (National Pipe Thread). He said the NPT threads do not seal well, so they decided to use fittings with parallel threads. If you need replacement fittings for your baseplate, we sell them as custom products (custom numbers are below in bold print). Contact Customer Service for pricing and availability. However, to make sure your baseplate remains leak free and functions perfectly, you should consider purchasing a new one instead of replacing the fittings. Note: PTFE tape is not recommended for use on parallel threads.
Restek # 558626 : Brass, for 1/4-inch OD (outside diameter) copper tubing
Restek # 560824 : Brass, for 1/8-inch OD copper tubing
Restek # 556389 : Stainless Steel, for 1/4-inch OD stainless steel tubing
Restek # 560702 : Stainless Steel, for 1/8-inch OD stainless steel tubing
B. Listed maximum flow rates were determined by measuring the outlet flow at the maximum pressure, and not the recommended gas flow through the trap/filter. To achieve the best results, keep the flow rate at or less than 2L/min (liters per minute) for the baseplate filters & inline filters, 8L/min or less for the Big Trap Filters, and 20L/min or less for the LC/MS Filter Systems.
C. A common reason that a new trap will become quickly spent (saturated) is because the check-valve O-rings are cracked/split and are leaking because they are not inspected and/or replaced when the filter is replaced.
You may also want to review What are these O-rings for that I received with my baseplate trap?
D. The lifetime of the trap/filter is largely dependent on the quality of the gas going into it. Keep in mind that a filter/trap does not remove 100% of a particular contaminant, it cleans the gas (generally speaking) an order of magnitude. For example, if the gas quality going in contains 10ppm (parts-per-million) of a particular contaminant, the quality of the gas leaving the filter/trap will contain approximately 1ppm of that contaminant if the gas flow rate is within recommended specifications (see B above).
E. Restek baseplate filters/traps may not work with another manufacturer’s baseplate. In some cases, the metal and/or plastic ring which connects the filter to the baseplate may not have a hole large enough to fit over a Restek filter. To check if our filters will fit, search the Restek website using the competitor’s catalog/part numbers (one time using the competitor's trap/filter catalog/part number and a second time using the competitor's baseplate catalog/part number). If both are found, the trap should fit onto the baseplate. If no search result is found, or just one result is found, it likely will not.
To look at this another way, the opening of the Restek gray plastic sealing ring is approximately 38mm inside diameter; some of our competitor’s sealing rings have a smaller ID (approximately 35mm to 36mm), and our traps/filters will not fit into a competitor's sealing ring. If the sealing ring you have will not fit over a Restek filter, we may have a fix, custom item 569908, which is a universal ring nut with an ID of approximately 38mm. Contact Restek Customer Service or your local Restek representative to request.
F. All of these traps/filters are designed to be installed right next to the instrument (point-of-use) for best performance. Using one trap/filter for multiple instruments is discouraged because this will increase the number of fittings downstream of the filter which will increase the possibility of leaks.
G. If using these filters with hydrogen, only 99.9999% and purer incoming gas quality was suggested, which you can only get from research-grade gas cylinders and hydrogen generators containing a palladium membrane (purifier). According to what we were told, if too much moisture is present in the incoming gas stream, it may actually strip some of the trapped contaminates from the filter's packing and release them back into the filtered gas stream.
To read more about choosing the correct H2 generator, please review Need some help choosing a hydrogen generator?
H. Excess moisture and oxygen (greater than 0.5%) will cause an exothermic reaction within the oxygen filter and the triple filter which may result in damage to the filter and possibly any sensitive equipment downstream of the filter.
I. It was strongly advised that a pressure relief valve (which opens below 11 bar and is connected to the outside environment or exhaust) be installed on each gas line.
I hope you have found this information helpful and that this clarifies some of the more common questions we are asked by our customers. Feel free to contact technical service for any additional questions you may have on these filters/traps.