Downloaded from https://www.everyspec.com .,~., ,, . ~ MIL–STD-81OB 15 J un e 1967 M E T H OD 518 . . : . T E M P E R A T U R E - H U M I D I T Y -A LT ~ U D E 1. P u r p o s e . T h e t e m p e r a t u r e - hu m i d i t y - a l - t i t u d e t e s t i s co n d u c t e d t o d e t e r m i n e t h e e f- f e c t s of c y c li n g b e t w ee n 10* t e m p e r a t u r e / l Ow Step 7—Maintain t e m p e r a t u r e a n d co n d i t i o n s fo r 6 humidity h o u r s . p r e ss u r e a n d h i g h t e m p e r a t u r e f ii g h hu m i d - Step 6 - D u r i n g t h e n e x t 8 h o u r s , r e - e q u i p m e n t b e t w , ee n e x t r e m e e n v i r o n m e n t s .
i t y a s m a y b e o b t a i n e d i n s e r v i c e b y f l y i n g d u c e t h e c h a m b e r t e m p e r a t u r e a t a un i fo r m r a t e t o s t a n d a r d a m b i e n t t e m p e r a t u r e w h il e 2. A pp a r a t u s . T e m p e r a t u r e - hu i d i t y - a l t i - t u d e c h a m b e r . N o r u s t o r co rr o s i v e co n t a m i n - m a i n t a i n i n g hu m i d i t y a t 95 p e r c e n t R H . S t e p 9 M a i n t ii n s t a n d a r d a m b i e n t t e m p e r a t u r e a t 95 p e r c e n t R H a n t s s h a ll b e i m p o s e d o n t h e t e s t i t e m b y t h e t e s t f a c ili t y . hu m i d i t y fo r 2 h o u r s . Note:
S t e p s 2 through 9 constitute one cycle a~ showncm figure618-1. 3. P r oc e d u r e I . S t e p l P l a c e t h e t e s t i t e m i n t h e t e s t c h a m b e r i n a cco r d a n c e w i t h Step 10—Repeat steps2 through 9 three m o r e t i m e s . s e c t i o n 3, p a r a g r a p h 3.2.2. S t e p n - R e t u r n t o s t a n d a r d a m b i e n t co n d i t i o n s . S t e p 2 R e d u c e t h e c h a m b e r t e m p e r a - t u r e t o ° C ( ° F ) w i t h i n 2 h o u r s . S t e p 12 R e d u c e t h e c h a m b e r t e m p e r a - t u r e t o ° C ( F ) S t e p 3 R e d u c e t h e c h a m b e r p r e ss u r e w i t h i n 2 h o u r s . m i n .
t o 50,000 f ee t a l t i t u d e a t a r a t e of 1,000 to 1,500 f t . / S t e p 13 R e d u c e t h e c h a m b e r p r e ss u r e a t a . r a t e of 1,000 t o 1,500 f t . / w h il e m a i n t a i n i n g t h e s p e c i - f i e d 54 ° C 65 F ) t e m - m i n . t o 50,000 f ee t a l t i t u d e p e r a t u r e . T h e t i m e f r o m t h e w h il e m a i n t a i n i n g t h e s p e c i - f i e d 54 ° C ( ° F ) t e m - 3 s h a ll b e 21 A h o u r s . s t a r t t o t h e co m p l e t i o n of s t e p p e r a t u r e .
T h e t i m e f r o m t h e s t a r t t o t h e co m p l e t i o n of s t e p S t e p 4 W i t h i n 30 m i nu t e s , r a i s e t h e c h a m b e r p r e ss u r e t o s t a n d a r d 13 s h a ll b e 2 + 4 h o u r s . a m b i e n t p r e ss u r e , r e t u r n t h e c h a m b e r t e m p e r a t u r e t o s t a n d - S t e p 14 W i t h i n 30 minutes, return the chamber to standard ambient conditioirs.’( Do not add humi- dity.) a r d a m b i e n t t e m p e r a t u r e , a n d t h e n , r a i s e t h e c h a m b e r hu m i - Step 15—After stabilization of the test item, operate the item and compare the results with the data obtained in accordance with section 3, paragraph 3.2.1.
During this period, special attention shall be giv- en to electrical and electronic test items for erratic Opera- d i t y t o 95 p e r c e n t R H . S t e p 5 M a i n t a i n t e m p e r a t u r e a n d hu m i d i t y co n d i t i o n s fo r 21 / z S t e p & D u r i n g t h e n e x t 30 m i nu t e s , h o u r s . i n c r e a s e t h e t e m p e r a t u r e t o 65 C ( 149 F ) a n d m a i n t a i n hu m i d i t y a t 95 p e r c e n t R H . L . - 518 - 1 M E T HOD 518 .