1. Connectors and Fittings

Two of the three speakers foreseen to give presentations did not turn up to
the meeting.
Ray Gregory listed some limitations regarding the installation of pipework.
Piping can be obtained in lengths up to 6 m and is only bendable up to about
22mm diameter on site. All the LEP gas piping was butt welded and this was
very successful. Joints can also be made by braising or gluing and the
lifetimes of such joints are normally good, being greater than 20 years.  Glue
joints are easy to prepare on site but the effects of radiation on glue would
have to be considered. Braising always leaves flux within the pipe and so
might not be suitable for thin pipes which might later develop leaks, as
improper cleaning can leave small quantities of flux which can burn through
the material.
Ray explained the sealing methods of different types of connectors and listed
some of their limitations. Slide fitting O-ring seals will not work on rolled
and welded tubing. Screwed joints with Teflon seals may eventually leak as
Teflon creeps. They are normally conical.  Metal to metal joints are only
practicable down to 1mm wall thickness. He mentioned the advantages of CPV
connectors over the more traditional Gyrolock connection. The former have an
aluminium joint.
It was agreed that O-ring materials would have to be lifetime tested if used
with performance fluids. H. Postema referred to NBR materials as being the
preferred O-ring material for perfluorocarbons.  It was agreed that I. Zorin
would be approached to arrange irradiation tests of NBR in fluids, as well as
of the crimp connectors with epoxy being considered for use by CMS. Locktite
was later added to the list of materials to be tested.
There was a lengthy discussion of the merits of welding and braising st. steel
tubes, but those present had little experience of the equivalent for
aluminium.
Bob MacKenzie mentioned a Thermite process for making joints but he had found
information on this hard to obtain as it appeared it was used almost
exclusively by the military.

2. ALICE Cooling Plans

Ray explained that ALICE planned to use performance fluids for their inner
detectors and water for everything else. The inner detector will produce up to
8 KW in a very small volume. He had found a commercial source of cooling units
with ±0.2C stability and available over a cooling power range of 0.5 KW to 10
KW. The units are small and can be used with water, glycol and performance
fluids, but they will not work in strong magnetic fields. They can themselves
be water cooled and they dissipate less than 400 W. ALICE was about to buy
such a unit from Applied Thermodynamics for a cost below 10 KCHF. Antti and
Hans believed that Lauda could also supply such units.

Conclusion : A. Smith will e-mail the CCG about materials for the next
irradiation tests and will speak to Ilie Zorin about planning these tests.

3. Subjects for the next meeting

Hans wondered whether the two missing speakers would make a presentation at a
later meeting. Alasdair recalled that we had planned to return to the question
of ST-CV’s need for up to date information for their forthcoming tender for
the cooling installations in the underground service caverns.

 
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