VACUUM

Classified Abstracts

O

O

II - - V a c u u m A p p a r a t u s a n d A u x i l i a r i e s - - II

zo - - P U M P S - - zo

High Vacuum Engineering See Abst rac t No 206/I

High Vacuum Equipment See Abst rac t No 205/I

The Measurement of the Pressure m the Determmatton of Pump Speed See Abst rac t No 209/I

Simple Safety Devine for Mercury Diffusion Pumps Umted States To prevent mercury vapours from reaching the vacuum sys tem if an accident should occur

and the cold t rap cease operating, a thermosta tmal ly operated switch is placed in series wi th the heater of the diffusion pump, which will s top the p u m p ff the t r ap tempera ture rises above a pre-set value The au thors have set the switch at -60°C and inserted the the rmos ta t th rough the cork cover of the Dewar flask, so t h a t the element was well immersed In the coolant The device can be used for any coolant and does not affect the evaporat ion rate of the coolant

Somma*re Description d ' un syst6me de sdcurlt6 qul coupe le chauffage d 'une pompe h diffusion au cas oh le plege refrigdr6 cesseralt d 'op6rer

Backstreammg of Oil Diffusion Pumps See Abst rac t No 210/I

Pumping Speed Fluctuations in the Off Diffusion Pump Umted K , ngdom Pressure f luctuations on the high pressure side and on the backing side of diffusion p u m p s

m a y haze an impor t an t bearing on the effectiveness of leak detection methods Details and results of measurements are given on such pressure var la tmns occurring in a small diffusion p u m p of 3-inch diameter fitted wi th two slightly va rym g let construct ions The f luctuations determined in the expenmen t s depend on var iat ions of the heater input The note concludes wi th a discussion of the results

Sommazre On a mesur6 les f luctuations de presslon exls tant du c6te vide pr~hmmalre et du c6t6 vide moldculalre dans les pompes k diffusion

Portable Laboratory Vacuum Pump Umted K~ngdom The mare disadvantages of pro~ldmg a vacuum service in the form of water jet p u m p s

m a radioactive labora tory are (a) Tha t the water m u s t be t reated for contaminat ion, and (b) the sys tem m u s t be s i tuated in the v lcmlty of a water supply Two alternative designs of a self-contained umt, mounted on a trolley, were developed to overcome these disadvantages The first, consisting of a ro ta ry mechamcal p u m p and auxil iary equ ipment facll l tatmg the circulation of the wate r in a closed clrcmt, was rejected on account of the cost The second sys tem makes use of a water jet p u m p mounted in a light alloy casing, the t a t e r being circulated th rough the let f rom a reservoir by means of a centrifugal p u m p If produced in reasonable number s the cost of the lat ter unl t is about ~50 Trials wi th pro to type units indicate a m a x i m u m service life, wi thout maintenance, of about 350 hours when operated cont inuously, the lowest pressures obtained were 74 cm Hg at room tempera ture and 68 cm Hg at water t empera tures of 70°C In t e rmi t t en t operat ion lengthened the serx me life In all cases, failure was due to worn brush gear The vacuum obtained at 70°C water tempera ture could be improved by charging the reservoir wi th equal quanti t ies of wate r and ethylene glycol Fro th ing occurred when the sys tem was opened to a tmosphere bu t could be eliminated by the addition of a silicon ant i - foam agent

5ommazre Ce rappor t decrlt le dd~elopement d 'une pompe A wde portable, a lnjecteur, pour ~tre employee dans les laboratolres a tomlques

Ultimate Vacuum in a Vacuum-Enclosed Iomsatton Gauge See Abstract No 143/II

Abstract No and References

133/II

134/II

135/II

136/II

Letter by W E S Spmdel &

McLaren Rev Se~ Instrum

25, As,u~0 1954

137/II

] 38/II

Letter by O S Martin &

J H Leck V~cz~um

4, Oct 1954 48o-489

139/II

Report by A Bury

A ~ R E Rep No

0-4/54 January 1954

1 lO/II

October, 1954 Vacuum 523 Vol I V No 4