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Several things you may not know about our Super-Clean Gas Filters

8 Oct 2015

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.decorative

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.



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. Over the years the design of the universal ring nut and replacement gas filters/traps have changed.  Older style universal ring nuts may not fit over the current Restek filters (or filters from a different manufacturer).  If you are not able to use your current universal ring nut to install a new filter, Restek may be able to help.  Contact Restek Customer Service and request custom item 569908, which is a universal ring nut that has a slightly larger opening.  This larger opening should allow the ring to slide over the filter and attach to the baseplate.

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.

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.