AMC-240-1 Propulsion Shafts and Propellers.pdf

AMC-240-1

SEPTEMBER 1990

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION (NOAA)

ATLANTIC MARINE CENTER

STANDARD SPECIFICATION AMC-240-1

PROPULSION SHAFTS AND PROPELLERS

1. SCOPE. This specification contains the general requirements for inspection, repairs, and other work on propulsion shafts and propellers of 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.

3.1.2 All requirements of this specification may not apply

to all purchase orders or contracts. The extent of applicability will be stated in the detail specifications or other procurement document. Section 3.1 and 4 apply to all work referencing this specification.

3.2 Propeller Removal.

3.2.1 Whenever removing a fixed-blade propeller from a

tapered-end shaft, this procedure shall be followed. When removing a controllable-pitch propeller (CPP), follow the procedures in the CPP system manufacturer's technical manual.

3.2.2 Before removing a propeller or propeller nut, fit a

shore from the bottom of the dock to one propeller blade near the root to take the shock of driving the propeller nut.

3.2.3 If necessary to remove the propeller and nut, heat

may be applied to the propeller hub to a maximum of 500 degrees Fahrenheit, provided prior written approval of the COTR is obtained. Before applying heat, shield the shaft bearings from damage. When used, heat shall be applied by two soft gas torches on opposite sides of the hub; the flame shall be worked around the hub to heat and expand the hub uniformly. The temperature shall be continuously monitored by means of tempil sticks or contact pyrometer to insure the hub temperature never exceeds 500 degrees Fahrenheit.

3.2.4 Follow the following procedure:

a. Remove the fairwater cap (if installed). Remove the O-ring seal (if installed) from the forward face of the propeller hub.

b. Loosen the propeller nut a few turns but do not remove.

c. Insert drawbolts in tapped holes in the hub face if provided. Otherwise, hook drawbolts over the blade edges or screw them into pieces of metal laid across the forward edges of the blade roots.

d. Place a drawbolt clamp or strongback over the end of the shaft. Interpose a pair of steel wedges between the clamp (or strongback) and the shaft end. Tighten down on the clamp nuts as much as possible and drive the wedges until the propeller starts to move. A wooden maul may be used judiciously to release the hub.

e. Rig the propeller for handling, remove the nut, and carefully remove the propeller from the shaft taper.

3.3 Propeller Installation.

3.3.1 After verifying that the key is installed on the

shaft, carefully fit the propeller to the shaft as follows:

a. Thoroughly clean the shaft and propeller hub tapers to remove all grit, grease, oil, dirt, rust, lint, and other foreign particles.

b. Apply a thin even coat of prussian blue to the shaft taper with the palm of the hand. Do not use a rag to apply the prussian blue because it may leave lint.

c. Carefully install the propeller onto the shaft taper. The propeller is to be pushed firmly and snugly onto the shaft, but is not to be driven on.

d. Remove the propeller and inspect the hub taper for the bluing pattern transferred from the shaft taper. A pattern of 75 percent, evenly distributed around and over the entire hub, is required. If the contact pattern is slightly heavier over the large end of the taper, a 70-percent fit is acceptable. In any case, the contact must be evenly distributed around the circumference of the hub.

e. If an acceptable fit is not obtained, remove the propeller. Grind, machine, and polish the tapered surfaces as necessary to obtain an acceptable fit.

f. Repeat the above steps until an acceptable fit is obtained. The COTR shall witness the final fit to verify an acceptable fit is obtained.

3.3.2 Clean the prussian blue from the tapers and return

the propeller onto the shaft in the same position as when the acceptable fit was obtained. Do not apply any oil, grease, or other substance to the tapers. If an O-ring and retainer were previously installed, make sure they are inserted over the taper onto the shaft before installing the propeller.

3.3.3 Scribe a small reference mark on the shaft to mark

the propeller's location. The reference mark must be located such that it will be accessible while driving on the propeller.

3.3.4 Install the propeller nut and drive the propeller

until it is advanced forward on the taper a distance of 1/32-inch (0.031 inch) beyond the scribe mark. Do not apply heat to the hub while driving on the propeller. The COTR shall witness driving of the propeller onto the shaft.

3.3.5 Lock the nut in position with locking tabs, monel

lockwire, or other method acceptable to the COTR. The COTR shall verify adequacy of the locking method.

3.3.6 If applicable, install O-ring seal, seal retainer, and fairwater cap.

3.4 Propulsion Shaft Removal and Reinstallation.

3.4.1 During all handling of propulsion shafts, exercise

extreme care to prevent mechanical damage and provide adequate support to prevent bending the shafts.

3.4.2 When rigging a shaft for removal, do not allow wire

slings to contact the shaft surfaces. Instead, slings shall be isolated from the shaft using a material which will protect the shaft from mechanical damage.

3.4.3 After disconnecting the shaft flanges, rotate the

shaft in the ship's bearings prior to removal and measure the shaft runout at each end.

3.4.4 During reinstallation of the shaft, verify proper

alignment at the flange faces using "sag and gap" procedures.

3.5 In-shop Inspection of Propulsion Shaft.

This procedure covers inspections required after the shaft has been removed from the ship or boat. Unless otherwise specified elsewhere, actual removal and reinstallation of the shaft is not required.

3.5.1 Set the shaft up in a lathe, providing supports at

each bearing surface.

3.5.2 If the shaft has removable couplings (flanged or

muff), remove the couplings.

3.5.3 Conduct the following inspections in company of the

COTR:

a. Complete visual inspection for mechanical defects.

b. Measure bearing liners diameters. Three measurements, equidistant apart, shall be taken at each bearing surface of the shaft.

c. Measure the runout of the shaft at the taper ends, couplings, and each bearing surface.

d. Measure all dimensions of the coupling to verify conformance with the manufacturer's drawing.

e. Measure all keys and keyways.

f. Conduct a liquid penetrant inspection of all surfaces of shaft liners.

g. Conduct a magnetic particle or liquid penetrant inspection shaft of tapers and keyways.

h. Inspect fiberglass reinforced plastic (FRP) covering (if installed) for pinholes, porosity, and other defects by using a high frequency spark tester. Use 250-300 volts per mil of glass reinforcement (approximately 15,000 volts for a 4-ply covering). Pinholes will be evidenced by bright sparks as distinguished form the normal purplish corona.

i. Inspect the FRP covering (if installed) for proper adhesion to the shaft by tapping, at regular intervals of about 18 inches along the length of the covering, with a light hammer while holding the palm of one hand against the covering on the opposite side. Discernible vibration, movement of the covering, or audible hollow sound is evidence of probable loose bond.

3.5.4 Install the shaft couplings and measure the runout of

the flange. Also verify perpendicularity of the flange face with the shaft axis.

3.6 Fiberglass Reinforced Plastic (FRP) Shaft Covering Renewal.

3.6.1 Materials. When installing new FRP shaft covering, the following materials shall be used:

a. Fiberglass cloth, conforming to MIL-Y-1140, Class C, Form 4, fabric No. 7500. Volan A, Owens-Corning "Alraton", or Gustin-Bacon "Methacrylic" finish, 75 filaments, are acceptable.

For shafts less than six inches in diameter, use 3-inch wide cloth. For shafts six inches and greater in diameter, use 6-inch wide cloth.

b. Reinforcing filler for resin shall be milled glass fiber.

c. Coating resin and catalyst conforming to MIL-R- 23461, type I.

d. Paste resin shall be automobile body filler compound or a product equal to "Marine Tex".

e. Solvents shall be Xylol, Xylene, or Union Carbide Cellosolve", or equal.

3.6.2 Shaft Preparation.

a. Remove all existing shaft coverings and coatings in area to receive the new FRP covering by sandblasting or machining. Wash the shaft surface thoroughly with a solvent to remove all oil, grease, dirt, and other foreign particles.

b. Inspect the shaft for pitting, mechanical damage, and other conditions which may have an impact on the shafts reliability or which will interfere with the FRP installation.

Fill in small pits with polyester or epoxy paste repair compound which is to be mixed, applied and cured according to the manufacturer's printed instructions.

c. Verify that the shaft liners have been machined in according with the details on the applicable shaft drawing. If the liners are not machined according to the drawing, contact the COTR prior to proceeding.

d. When specifically required in the detail specifications or other procurement document, machine the shaft liners ends in accordance with attached Figure 1.

e. Apply paste to the junction of the bearing liner ends and the shaft, fairing it in evenly. Sand the paste smooth after it is fully cured.

3.6.3 Material Application.

a. Four plies (two overlapping runs) of fiberglass cloth covering are required. The approximate length of glass cloth needed for each wrap, allowing some excess, can be found from the following equation:

L=7 DH

W

Where: L= length of tape required for each wrap, in feet.

D= diameter of shaft, in inches.

H= length of shaft to be covered, in feet.

W= width of glass cloth, in inches.

The total length required for four plies is 2L.

b. Prepare a batch of resin and brush on one coat to the prepared shaft according to the manufacturer's printed instruction.

c. Apply the dry cloth, starting at one end of the shaft, on the taper of the liner or as close to the flange as possible. Wind the cloth in a spiral until the complete straight section of shaft is covered. Overlap the cloth half the width.

Wrap tightly to prevent the formation of wrinkles.

d. Impregnate the glass cloth by brushing the entire surface with catalyzed resin. Coat the cloth uniformly and generously so that a thorough wetting of the glass fibers is obtained.

e. Work out all entrapped air with a roller, squeegee, or other convenient method.

f. Apply a second wrap of cloth in a manner similar to the first, but start at the end of the shaft where the first wrap finished. Impregnate the second wrap with catalyzed resin and work out all entrapped air.

g. Using two short lengths of cloth, apply two circumferential turns to each end of the coated section of shafting, overlapping the bearing liner taper and impregnate each wrap separately. Coat the entire covering with an additional coat of resin and allow it to cure in accordance with the manufacturer's printed instructions.

h. Prepare a batch of resin containing 10 percent (by weight) of milled glass fibers. Coat all couplings and other discontinuities in the shafting not covered by cloth. Permit the coating to gel. Then apply three additional coats of this resin mixture, allowing each coat to gel before applying the next.

i. After the entire coating has cured, pass a high-frequency spark tester slowly over the entire covering, paying particular attention to couplings and bearing liner junctions with the shaft. Use 250-300 volts per mil of glass reinforcement (approximately 15,000 volts for a 4-ply covering). Pinholes will be evidenced by bright sparks as distinguished form the normal purplish corona.

j. If pinholes or other defects are found, lightly sand the surface of the coating. Prepare a small batch of resin without the fibers and paint the entire coating, paying particular attention to the the areas that showed sparking.

k. Repeat the preceding two steps until a no bright sparks are evident during the spark test.

4. QUALITY ASSURANCE.

4.1 Within 24 hours after completion of inspections and tests, prepare and submit to the COTR a condition report which contains the following:

4.1.1 A complete record of all measurements taken, compared

to the original dimension.

4.1.2 A record documenting the results of all visual and

other NDT inspections.

4.1.3 Recommendations of additional work and materials

deemed to be needed, if any, to return the shaft or propeller to good reliable condition.

4.2 The COTR shall be advised at least 8 hours in advance of all inspections, tests, and other work required herein to be witness by the COTR .

4.3 All NDT shall be in accordance with MIL-STD-271F, including compliance with the requirements for qualification of NDT personnel, procedures, and equipment. Workers performing NDT shall be certified as Level two craftsmen by the American Society of Non-Destructive Testing in accordance with Recommended Practice No. SNT TC-1A, 1980 edition.

END OF SPECIFICATION