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|  MIL-C-13874K
3.15.4
Drive. T h e d r i v e s h a l l c o n s i s t o f m a t c h e d m u l t i p l e V - b e l t s a n d g r o o v e d
p u l l e y s on the power unit and compressor unit. A l l d r i v e b e l t s s h a l l c o n f o r m t o
MIL-B-1104O
A means for belt removal and adjustment shall be provided.
3 . 1 6 T y p e II
rotary
3.16.1 Compressor T h e t y p e I I c o m p r e s s o r s h a l l d e l i v e r t h e c a p a c i t i e s o f f r e e
a i r s p e c i f i e d i n t a b l e I a t a p r e s s u r e o f 175 psig as determined by the ASME
P e r f o r m a n c e Test Code 9. T h e components of the compressor shall be balanced so
that when the compressor is operating in conjunction with the electric motor,
vibration shall be minimized. The compressor shall produce rated capacity at
rated pressure for 500 hours in operating periods of not less than 4 hours (see
4 . 6 . 2 . 4 ) . O p e r a t i n g periods of not less than 4 hours during high and low
t e m p e r a t u r e t e s t s m a y b e c o u n t e d ( s e e 4 . 6 . 2 . 5 a n d 4 . 6 . 2 . 6 ) . T h e compressor shall
not exceed the contractor's recommended continuous operating speed The
c o m p r e s s o r u n i t s h a l l b e p o s i t i v e d i s p l a c e m e n t a n d a i r c o o l e d . A means shall be
p r o v i d e d to remove a n d r e c o v e r t h e o i l f r o m t h e d i s c h a r g e a i r . W h e n a f i l t e r - t y p e
separator is used, it shall be accessible for examination, cleaning and
r e p l a c e m e n t without removal of other parts or components. T o prevent hydraulic
lock upon starting, a means shall be provided in the stator assembly to allow
a c c u m u l a t e d oil to pass into the sump. T h e r o t o r s , s t a t o r s , a n d blades for any
o n e size compressor s h a l l b e i n t e r c h a n g e a b l e a m o n g a l l c o m p r e s s o r s o f t h a t t y p e ,
c l a s s , a n d s i z e f u r n i s h e d b y t h a t m a n u f a c t u r e r . A pressure gage shall be provided
between the compressor unit and the separator discharge to indicate the pressure
i n the compressor. A n o n r e t u r n v a l v e s h a l l b e p r o v i d e d e i t h e r i n t h e o i l
separator or in the discharge from the separator to prevent reverse flow of air
from the receiver.
3.16.2 Pressure tubing a n d f i t t i n g s . All pressure tubing and fittings shall be
rated to withstand 1-1/2 times their normal working pressure.
3 . 1 6 . 3 D r i v e . T h e type II compressor s h a l l b e e i t h e r d i r e c t d r i v e o r m u l t i p l e
V - b e l t d r i v e . T h e m u l t i p l e V - b e l t d r i v e s h a l l c o n f o r m t o 3 . 1 5 . 4 . W h e n a direct
drive is used, a flexible coupling shall be installed between the power unit and
c o m p r e s s o r u n i t . T h e mounting base f o r t h e p o w e r u n i t s h a l l h a v e a m e a n s f o r b e l t
r e m o v a l and adjustment when V-belt drive is used.
3.17 C l a s s 1 . t a n k - m o u n t e d
T h e compressor unit and power unit shall be
mounted on a base attached to the air-receiver tank.
3 . 1 7 . 1 A i r - r e c e i v e r t a n k The air-receiver tank for the class 1 compressor
shall be of the horizontal type and shall be constructed in accordance with the
A S M E Boiler and Pressure Vessel Code, Section VIII. T h e r e c e i v e r s h a l l b e a r t h e
A S K E stamp and no welding or other actions shall be permitted after the receiver
has been certified. Unless otherwise specified (see 6.2), the capacity of the
air-receiver tanks for the 5-cfm shall be not less than 20 gallons and for the 15-
c f m and 25-cfm compressors shall be not less than 80 gallons. U n l e s s o t h e r w i s e
specified (see 6.2), the air-receiver tank fittings shall include a globe
discharge valve, a drain cock and a 0-psig to not less than 250-psig pressure gage
having 10 psig or smaller increments. The air-receiver tanks shall include a
p r e s s u r e relief valve conforming to ASME Boiler and Pressure Vessel Code. The
receiver shall be provided with a steel base of not less than four q ounting feet
f o r h o r i z o n t a l m o u n t i n g . W h e n equipped with a steel base, openings shall be
p r o v i d e d t o p e r m i t i n s e r t i o n o f f o r k l i f t t i n e s . E a c h opening shall be not less
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