From: Jason Curtis - University of Florida
Subject: Re: [ISOGEOCHEM] Clearing blocked Valco valve in Gasbench
Date: September 9, 2009 10:00:48 AM PDT
We also had a clog in our valco in our gasbench. The valco valves are actually really easy to take apart and almost as simple to rebuild. I am 99% sure that the instructions to do this are on the valco site. Basically you remove the top nut without changing the set screw. Then cycle the valve while holding a magnet on the top of the rotor (I used a strong magnet from inside a broken hard drive, they suggest a pencil type magnet). This allows the "surface tension" to be broken and allows you to lift the rotor out. Then you can see the holes for each port. Shine a light in each port and see if you see light from the top. I blew out the junk that was blocking ours. You might have to use water. Whatever you do be careful not to scratch the inside of the valve - if this happens it must go back to valco to be reground. When putting it back together there is a mark on the rotor that goes to the correct port - see the manual as it is different for each type of valve.
A note on rotors. When we scratched a rotor I called valco to get a new one. They did not have the rotors in the web catalog in stock and it was going to be weeks. After trying to figure out how to get a new one short of buying an entire new valve the person from valco suggested that they have different rotors made of different materials. They are not in the catalog. Different rotors of different material are for different temperature ranges. The one that came in my gasbench was good to like 450°C. The one that I got was good to like 350°C. A little hotter than we need in the gasbench which sits at like 22°C!
Hope this helps. Let me know if you need further info. Jason
Making Bench Sample Needle
Jonathan Wynn wrote:
Has anyone out there successfully replaced the fused silica capillary in double-holed needles used by the Thermo Finnigan Gasbench? Suggestions or tips would be very welcome on how to extract the fused silica capillary from the needle's interior (what sort of glue is used?), and rethreading a replacement piece.
Rather than treat these as consumables at ~$400/ea., it would be great if there were a simple method of replacing the capillary, which is not only susceptible to clogging (relatively easily solved), but the occasional breakage.
Department of Geology
University of South Florida
We've been making our own for a while now.
A 19Ga needle, ~4" (10cm), with a hole in the side, ~ 1cm up from the tip, does the trick. We epoxy it in place--but there was mention on Isogeochem that if the hole is far enough away from the tip, you don't need to do that.
To drill the hole in the side yourself, clamp the needle between two boards, with a small groove in one to hold it in place and a guide hole in the other for the (dental) drill. It may take a little practice. You can buy a custom made needle--we got some from Popper and Sons in the states--but that only make sense if you buy in bulk.
The needle attaches to a standard 1/16" swagelok 3-way connector (or metric equivalent). The glass capillary feeds straight through the connector and down the needle. We still epoxy it in place at the bottom of the needle--push extra through then snap that off when the epoxy dries. You'll want a tight fit on the needle. We like to use a stainless steel connector since you have have to over tighten the standard 1/16" ferrules to get them to grip the needle. We'll use the Valco ferrules (longer) in the swagelok fitting, or sometimes use a brass swagelok ferrule with an extra backing ferrule. The capillary ferrules are the standard GC capillary ferrules.
For attaching to the PAL holder, we use a 1/16" to 1/8" swagelok reducing union. The key connection is the attachment to the needle. We use a metal ferrule to tightly hold the needle in place--usually by pre-swaging a steel valco ferrule in a valco union then sliding onto the needle, or even getting it swaged (is that a word?) onto the needle before starting anything else. On the 1/8" side, we'll use an 1/8" to 1/16" reducing ferrule as a guide only. Please note, when attached the needle tip should not be below the bottom of the PAL's bottom needle guide.
The side arm is for the He feed. We're still using the steel capillary originally from Thermo--but some are available from McMaster-Carr (cleaning needed?).
We make homemade acid needles by just sharpened the stainless steel capillary (from McMaster-Carr in the US). In this case were using a 1/16" to 1/8" adaptor to fit into the 1/8" swagelok union--use the parts you got...
Question: May I know how could you solve the problem of clogging of the needle?
Answer: We place the needle under a binocular microscope and clean out septum crumbs with a fine wire. Keeping the needle sharp with a file helps extend the life greatly.
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