3.1.28 Encapsulated motors. - Motors encapsulated for severe environmental service conditions such
as exposure to condensate, steam leaks, flooding, salt spray, splashing or temporary submergence (see 6.1)
shall conform to the following:
220.127.116.11 Design. - All design requirements of this specification shall apply except as follows:
(a) The enclosure shall be as specified in contract or order (see 6.1) except test motors shall be
(b) Type. - The motor shall be squirrel-cage induction of a type as specified in contract or order.
(c) Temperature limits. - The motors shall not exceed the temperature values specified in table IX
by more than 5 `C. when operating in air or when tested submerged for dripproof protected
and for non-fan cooled, enclosed types of motors. Fan cooled, enclosed types of motors shall
not exceed the temperature value specified in table IX when operated in air only.
(d) Insulation resistance. - Insulation resistance of production motors (dry) shall be not less than
2000 megohms when measured in accordance with 40.4.1 of appendix II. For the suitability
test motors the insulation resistance shall be not less than 10 megohms (corrected to 25°C)
during any of the tests when measured in accordance with 40.4.1 of appendix If. For the
routine submergence test a minimum of 100 megohms shall be maintained.
(e) Corrosion. - The metal frame, end shields, terminal box assembly, rotor core, rotor ends
and exposed stator, iron parts shall be suitably protected to withstand the corrosive effects of
salt water. All hardware and shafts shall be made from corrosion resistant materials. A
design goal for corrosion protection shall be 40,000 hours life without retreatment.
(f) Insulation. - Class of insulation-shall be class B. The minimum material requirements of table
VIII need not apply to the insulating materials used in encapsulated motors.
(g) Submerged operation. - When specified in the contract or order, the motors shall be designed to
operate when submerged under the conditions specified.
18.104.22.168 Encapsulation. - By encapsulation is meant that the motor windings are completely sealed
from the terminal box connection end through the slots and return loop.
22.214.171.124 Random wound motors. - Stator windings shall be encapsulated after all winding is completed.
As a guide, the following points should be considered for encapsulated system:
(a) The resin or elastomer should be compatible with the insulation materials used.
(b) Bonding of the resin to the stator core should not be relied upon to give adequate sealing from
water. The encapsulated winding should float free in the slots and core.
(c) The core punchings should be sealed between laminations by use of a 100 percent solid resin.
(d) The winding should be so positioned during the encapsulation process that a minimum of 1/8 inch
thickness of material should encapsulate all end turn parts. Slot material shall be of the
moisture barrier type and approximately 0.015 thick.
(e) The leads should be of the non-wicking type and should not be braided. All connections at the
winding end should be embedded in the encapsulating material. Where the leads enter the
terminal box they should be sealed and encapsulated. The terminal box shall be watertight.
(f) The slot liners should be extended beyond the slot and should be folded over and bonded prior to
126.96.36.199 Form wound motors. - Stator coils shall be bonded and sealed prior to winding in the stator.
All connections after winding shall be bonded and sealed. As a guide, the following points should be con-
sidered for form wound motors:
(a) Coils should be preformed and preinsulated with a heat sealable or vulcanizing flexible plastic
or elastomeric material.
(b) Each coil should be insulated for full voltage to ground and be watertight.
(c) Leads should be of the non-wicking type and should not be braided. All connections and joints
should be sealed and watertight.
188.8.131.52 Repair of encapsulated motors. - Encapsulated motors shall be designed so that the motor may
be repaired (rewound) using encapsulating materials and methods suitable for normal repair shop usage and
also shall be designed for rewinding by using conventional rewinding materials and methods.
3.1.29 Class H and N insulation suitability tests. - Where class H or N insulation is used, insulation
suitability tests in accordance with the procedures detailed in MIL-E-917 shall be conducted and submitted
to the Bureau of Ships for approval. Bureau of Ships approval shall be obtained prior to manufacturing
class H or N insulated motors.