300-2.pdf

AMC-300-2

AUGUST 1991

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION (NOAA)

ATLANTIC MARINE CENTER

STANDARD SPECIFICATION AMC-300-2

CIRCUIT BREAKER OVERHAUL

1. SCOPE. This specification contains the requirements and procedures to be used in overhauling electrical circuit breakers on and for NOAA ships.

2. REFERENCES.

None

3. REQUIREMENTS.

3.1 General.

3.1.1 The contractor shall provide all labor, material, services, tools, supervision, and technical expertise needed to accomplish the required work. All material and replacement parts used or installed shall be new and shall be equal or superior to the materials and parts used in the original manufacture.

3.1.2 The contractor shall notify the Contracting Officer's

Technical Representative (COTR) at least 24 hours in advance of performing each test and inspection. The COTR may witness all or any portion of the tests and inspections.

3.1.3 The contractor shall submit to the COTR a written

report of all inspection findings and test results, including a record of all measurements and readings taken.

3.1.4 To the extent possible, all work shall be

accomplished and all parts shall be in compliance with the applicable manufacturer's instruction manual.

3.2 Overhaul Requirements.

3.2.1 Remove each circuit breaker to be overhauled as

follows:

a. Verify that electric power has been secured and tag out the controller. Disconnect electric wiring and tag individual wires to aid in proper reinstallation. Protect exposed terminal connections and internal switchboard parts from dirt and damage.

b. Remove, matchmark and retain the mounting hardware and fasteners.

3.2.2 Disassemble each circuit breaker, and conduct the

following preliminary inspections and tests:

a. Inspect and test electrical and mechanical components, assemblies, subassemblies, internal circuitry, and hardware to design characteristics and for missing and defective parts.

b. Test internal wiring, coils and transformers for open and shorted circuits and insulation resistance to ground.

Record readings. Minimum acceptable resistance to ground is one megohm.

3.2.3 Clean each mechanical part with lint-free cloths

moistened in a suitable solvent to remove all dirt, lubricants, and other foreign particles. Do not let solvent come in contact with varnished surfaces.

3.2.4 Repair parts and components as follows:

a. Resilver copper contacts in accordance with QQ-S- 365.

b. Dress, burnish, adjust, and align arching and main contacts (contacts that experience arcing in functional duty).

1. Acceptance criteria for silver contacts is that wear shall be less than 50 percent of original thickness, contacts shall have no evidence of copper migration, and shall have no irregular, burnt, or pitted interface after dressing.

2. Acceptance criteria for non-silver contacts is that wear shall be less than ten percent of original thickness and contacts shall have no irregular, burnt, or pitted interface after dressing.

c. Replate cadmium-plated parts in accordance with

MIL-STD-870.

d. Dip and bake taped insulated coils and open transformers, using varnish conforming to MIL-I-24092, Class 155.

e. Remove existing and install new coil and transformer leads where insulation is defective.

f. Repair defective connections.

g. Free-up and adjust moving parts and latching mechanisms.

h. Lubricate the current-carrying parts (except for interrupting contacts) and sliding joints with NO-OX-ID, Type A (special) lubricant. Lubricate mechanical pivots, excluding latch roller face components, with MIL-G-24508 lubricant. Apply new lubricant sparingly and wipe off excess.

i. Test and inspect all molded parts to determine conformance with the following acceptance criteria:

1. Phase-to-phase dielectric strength of 2000 volts minimum.

2. Surface burn marks and hairline cracks are acceptable but shall not deteriorate the mold surface or impair physical strength. Cracks are not permitted in wall section between phase and a ground plane when there is a conducting part in contact with the wall section. Cracks are not to exceed 0.75 inches in length and are not to be greater than 50 percent of the length of the surface in which the crack occurs.

3. Surface cracks are not to exceed 1.5 inches in length and are not to be greater than 50 percent of the length of the surface in which the crack occurs.

3.2.5 Disassemble each motor operator and motor, and

perform the following:

a. Clean the equipment and windings free of foreign matter.

b. Test each winding for opens, shorts, and grounds.

c. Dip and bake windings in varnish conforming to MIL- I-24092, Class 155.

d. Remove existing and install new bearings and carbon brushes. Seat new brushes.

e. Polish the armature commutator to remove brush imprints and scoring.

3.2.6 Reassemble each motor operator and motor.

3.2.7 Perform a shop test on each motor operator and motor

to verify proper operation.

3.2.8 Reassemble each circuit breaker and perform

adjustments and settings as needed. Align and true each set of stationary and movable contacts to manufacturer's specifications.

3.2.9 Test, adjust, calibrate, and certify the trip units

of each circuit breaker for time delay and instantaneous trip settings. Attach a calibration label denoting the name and location of the calibration facility and date of calibration to the face of each circuit breaker.

3.2.10 Install and connect each circuit breaker.

3.2.11 Perform final adjustments and test operate each

circuit breaker, including the control and safety devices as follows:

a. Close and trip each circuit breaker electrically from the local and remote stations. The circuit breaker must operate correctly four consecutive times to be acceptable.

b. Repeat a. above manually from the local station.

END OF SPECIFICATION