To remove broken capillary that is glued into tip of needle, I hold the needle assembly in the nozzle of a compressed air gun while heating for several seconds in a burner flame. This might be a bit hard on the needle (loss of temper?) but I haven't got a better way.
The new capillary is threaded through, a dob of epoxy resin applied just beyond the tip of the needle, then the cap. pulled back into the needle a few mm. Both capillaries are similarly sealed at the top of the needle with epoxy. Trim off any excess capillary when the glue has set.
Also make your silica capillary about a foot longer than the metal capillary (if you have that type) so that metal takes any strain.
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> Behalf Of Jonathan Wynn
> Sent: Thursday, 5 November 2009 4:50 a.m.
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] Gasbench needle capillary repair
> Hello all,
> 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.
> Jonathan Wynn
> Department of Geology
> University of South Florida
> 4202 E Fowler Ave, SCA 528
> Tampa, FL 33620
> Tel. +1 (813) 974-9369
> Lab. +1 (813) 974-5278
> Fax. +1 (813) 974-2654
> [log in to unmask]