Vacuum impregnation of castings

VACUUM Classified A b s t l a c t s

III

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Vacuum

Processing

Techniques

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III

Contd

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IMPREGNATION

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V a c u u m Impregnation of Castings Umted States P o r o s i t y in castings can be due to poor design, defects f r o m physmal or chemical causes, or ~mproper f o u n d r y practice I m p r e g n a t i n g the castings will appreciably reduce the n u m b e r of relects for poromty A good l m p r e g n a n t should be of low viscosity, low volatility, and should dry w i t h little or no loss of volume I t should allow for heat t r e a t m e n t of the c o m p o n e n t up to 300°F and should h a v e no effect on m a c h m e a b l h t y Satisfactory materials are resin and resin-oil combinations, such as styrene w i t h linseed oil or d e h y d r a t e d castor oil Five m e t h o d s of impregnation are mentioned (1) I m m e r s i n g the casting in the l m p r e g n a n t which is kept in a vessel to which pressure is applied (2) I n t e r n a l - p r e s s u r e method, b y which the c o m p o n e n t s are sealed off except for one p o r t (3) E x t e r n a l pressure m e t h o d (4) V a c u u m impregnation by b a t c h immersion followed b y pressure, and (5) t h e use of v a c u u m only Of all these, No (4) is the preferred m e t h o d at p r e s e n t The p a r t s are cleaned and degreased and t h e n heated to 250°F for a b o u t 2 h o u r s Aftel cooling down t h e y are loaded into the v a c u u m c h a m b e r and a v a c u u m is d r a w n to 29 inch or more This is maintained for 20 m i n u t e s The capillary ducts of the casting should now be free from air and moisture and should offer easy access to the l m p r e g n a n t The l m p r e g n a n t is fed into the t a n k until all c o m p o n e n t s are covered while t h e v a c u u m p u m p continues to d r a w T h e n the v a c u u m p u m p is stopped and pressure applied in the t a n k (approximately 60-100 p s 1 ) for a period of 20-40 m i n u t e s Finally, the l m p r e g n a n t is w i t h d r a w n and the castings are removed, drained and rinsed in an acetone solution Baking or air curing follows Magnesium castings require a s o m e w h a t different t r e a t m e n t Sommazre Les m6thodes connues d h m p r ~ g n a t l o n de pl~ces de fonderm m~talhque s e n t 6tudl6es et les m6rltes comparatlfs de l'lmpr~gnation sons vide s e n t m d l q u e s

Impregnation of Masts Denmark A description of the t w o m e t h o d s of i m p r e g n a t i n g fir with t a r oil, after r e m o v a l of bark, and drying m open air I n a boiler containing the oil u n d e r pressure, and in a boiler u n d e r low pressure and filled w i t h off after the air m t h e t i m b e r has been (partially) removed I n the case of spruce, t h e b a r k m n o t removed, as impregnation m u s t be carried out along the axis of the t r u n k The usual liquid Is copper sulphate, b u t recently N A F salt, a m i x t u r e of sodium, arsenic and fluorine compounds, has been employed E x a r m n a t i o n of m a s t s m the field is discussed and some p h o t o g r a p h s of fungus attacks are s h o w n (Science A bstrac, ts) ~,omn~a,re Mdthode d h m p r 6 g n a t l o n de bols sous vide

34 ~

FUMIGATION

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DRYING

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t95/III

Artmle b) L W Hull J Metals lan 1952 q0-32

] 9b/III

Altmle by V Hallund Elektrotekmkeren 48, 22 5 52 172-6

34

Study of V a c u u m Fumigation Techniques Umted K*ngdom A s h o r t note in the Annual R e p o r t of t h e Pest Infestation Research Board r e p o r t s on tests comparing the q u a h t y of various low pressure fumigation m e t h o d s w i t h t r e a t m e n t at atmospheric pressure A c h a m b e r of a b o u t 1,700 htres capacity was used situated in an air conditioned r o o m kept at 15°C and described in detail elsewhere m the report The f m m g a n t was m e t h y l bromide and the p r o d u c t s tested were bagged w h e a t and boxed dates Preliminary results seemed to indicate t h a t v a c u u m techniques offer no a d v a n t a g e s in the case of granular p r o d u c t s such as wheat, b u t in the case of dates penetration m v a c u u m was speedier t h a n at atmospheric pressure I n t r o d u c i n g only the f u m i g a n t after evacuation and keeping the c h a m b e r at c o n s t a n t low pressure for a period, resulted m b e t t e r penetration t h a n the m e t h o d of introducing a m i x t u r e of the f u m i g a n t and air into the evacuated c h a m b e r and, at the same time, b n n g m g it up gradually to atmospheric pressure The tests w i t h bagged w h e a t will be continued Sommazre Br~ve note sur la fumigation de matl~res alimentaires sous vide

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Abstract No. and References

197/III

Aun Rep by Pest lnfestatwn Res Board DSIR 1951 28

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Design Features of Modern V a c u u m Drying Plant See A b s t r a c t No 199/I

198/III

Frozen Concentrated Pineapple Jmce See A b s t r a c t No 216/III

199/III

October, 1952

Vacuum Vol I I No 4

430