Stern Rudder Bearings

Stern Rudder Bearings

Introduction Of Product

"Deyuan" DY-ⅢA brand ship (naval) bearings are the company's leading products, used for stern bearings and rudder bearings. It is a modified polymer material obtained through rare earth and nano-modification technology. It has excellent friction and wear characteristics under water lubrication conditions, high pressure bearing capacity, impact resistance and self-lubrication. The Shanghai Institute of Science and Technology Information has concluded that the product performance has reached the international advanced level and has obtained an invention patent. It has obtained type approval certificates from classification societies such as CCS, LR, BV, DNV·GL, NK, ABS and KR. It also has DNV and LR rudder bearing self-lubricating certificates. The maximum surface allowable stress of the rudder bearing approved by DNV Classification Society is 15MPa, which is the highest level at home and abroad.

In 2013, the company successfully developed the "DY-IV thermal insulation support pad" and obtained a utility model special certificate. The successful development of this project has filled the domestic gap. It is suitable for dry transportation of asphalt, coal tar and other goods that need to be transported at a high temperature below 230"C. The common specifications of products that have obtained CCS and BV type approval certificates are: 200X200 (mm), 300X300 (mm), 350X350 (mm), and can also be customized according to customer needs.

Comparision Of Wear Rate Between DY-IIIA And Othermaterialunder Water Lubrication

Technical Properties Of De Yuan IIIA Bearing Material

Design Essentials Of“DY” Bearing Materials

1. The structure adopts cylindrical shape.

2.The recommended formula for the minimum wall thickness of the bearing is:δ=0.0435D+(6~7) D is the calculated diameter of the propeller shaft (mm)

3. Bearing length L: (refer to the construction specifications of each classification society)

a. Oil-lubricated stern bearing: L/D=2:1

b. Water-lubricated stern bearing, the classification society generally stipulates: L/D=4:1 or L/D₁=3:1 D₁ is the actual diameter of the propeller shaft (mm). Since the DY-IIIA bearing material can work under higher pressure, when the bearing calculated specific pressure P<0.55N/mm², the bearing length can be appropriately reduced, but it should not be less than 2 times the actual shaft diameter D₁. That is, L/D₁=2:1

C. Rudder bearing:

Rudder stock bearing: L/D=0.9~1.8:1 Rudder pintle bearing: L/D=0.9~1.2:1

D is the diameter of the rudder stock and rudder pintle (mm)

4. Allowable design surface pressure:

a. Rudder bearing: P=15N/mm² (see the certificate approved by each classification society)

b. Stern bearing: P=0.6N/mm² (see the certificate approved by each classification society)

5. Stern bearing cooling water volume: Q≥16D liters/minute; D is the diameter of the propeller shaft (decimeters)

Measuring&Maching Bearing

Bearings are tough thermoplastic polymers that are easy to machine. They can be turned, drilled, planed, sawed, and milled, but cannot be ground. To achieve optimal bearing machining, the following points should be noted:

1. Because the material is soft and has a certain degree of elasticity, a metal bushing is generally installed in the inner bore of the lathe clamping end to minimize deformation. (The end face can also be fixed to the machine faceplate with bolts or a pressure plate.)

2. Correct tooling is crucial for machining bearings. The rake and relief angles of the turning tool should be slightly larger to facilitate chip removal from the surface. The turning tool should be sharp, typically with a carbide tip.

3. Maintain appropriate rotational speed and feed rate. A linear speed of 1.3 to 1.8 m/s is recommended. To achieve the desired size and surface finish, the final cut feed rate should be between 0.25 and 0.5 mm, and the blade edge should be as sharp as possible.

4. Machining Steps:

1) Install a metal bushing in the inner bore of one end of the bearing.

2) Clamp one end of the bushing with the lathe caliper, align the center with the bearing's outer diameter, and machine the outer and inner diameters.

3) The stern bearing must be machined with a water groove (rudder bearings do not require this). For water (or oil) grooves, this is typically done with a forming cutter head, which is typically used to make multiple grooves. Each cut should be made with a small amount of feed, as this will cause cracking.

4) After the water groove is machined, cut the bearing to length.

5.Measure the inner and outer diameters of the bearing based on the actual machining temperature. This will ensure that the bearing conforms to the drawing requirements. Due to clamping and other factors, the bearing may become oval after being removed from the lathe, exceeding the tolerance range. However, after being pressed into the housing, it will conform to the housing's shape and return to a rounded shape.

6. The material is non-metallic and cannot be machined to the same tight tolerances as metal. However, due to its properties, it can achieve ideal operating results with a lower surface finish than metal.

Requirements Ofassembling Bearing

Bearing materials have a high coefficient of thermal expansion and contraction. Shrinkage is the easiest installation method.

1. Using dry ice as a refrigerant ensures effective shrinkage. Liquid ammonia is not recommended. If shrinkage is used with liquid nitrogen, specialized procedures must be followed.

2. Place the product in a well-insulated circular container. To conserve dry ice, place an empty bucket (such as a paint bucket) in the center of the product. Ensure there is sufficient space inside and outside the product (50mm per side). Pour dry ice into the container and tamp it down with a wooden stick. Cover the top with dry ice. The outside of the container must be insulated.

3. Freezing generally takes about two to three hours. Before installation, check and measure the bearing's outer diameter to ensure it has shrunk properly (generally, it should be 0.5-1mm smaller than the bearing housing bore). If not, continue freezing.

4. Before installation, clean the inner wall of the bearing housing. Check for burrs or protrusions. No lubrication is required.

5. During installation, align the bearing with the bearing housing and carefully push it in without pausing. Allow a certain amount of clearance at both ends to prevent the bearing from absorbing water and stretching, potentially pressing against the baffle and causing it to bulge.

6. The stern bearing can be installed in multiple sections, but water must flow freely in the water tank to cool and lubricate the bearing.

7. After the bearing is installed, do not perform any cutting or welding near the bearing, as these operations could cause deformation, burning, or cracking.

DY-ⅢA  Ship Bearings Operation Instructions

DY-ⅢA marine bearings use water as both a cooling and lubricating medium. Therefore, ensuring smooth water flow is crucial for proper bearing operation.

1. The bearing cooling water system must be connected in parallel with the main engine cooling system. Main engine cooling water must not be used as a bearing cooling medium.

2. To ensure safe and unobstructed cooling water flow, it is recommended to add a cooling water pipe connected from the main engine cooling water pressure cabinet to the bearing water inlet.

3. The cooling pressure should generally be no less than 2 kg. This overcomes pipe resistance and the resistance caused by the ship's draft, while maintaining a certain outlet pressure to ensure smooth water flow.

4. Cooling water flow rate: Q > 16D liters/minute, where Q is the flow rate and D is the stern shaft diameter (decimeters).

5. Before starting the main engine, turn on the cooling water supply and check the water pressure and flow to ensure they are normal.

6. For airbag seals, the inflation valve must be closed and leak-proof to prevent the airbag from seizing the shaft and blocking the flow of cooling water.

7. For ships installing stuffing box seals, check the position of the distributor within the packing seal to ensure that some cooling water is leaking out.

8. For ships installing stern shaft flat seals (including rubber ring, spring leaf, and column spring types), ensure that the dynamic and static rings of the flat seal are lubricated during stern shaft operation, and allow for a certain amount of leakage.

9. During navigation, regularly monitor cooling water flow and pressure. When the bearing temperature exceeds 60°C, shut down the ship for inspection and troubleshooting, then restart the ship.

10. For ships operating offshore and along rivers, clear silt from cooling water lines and bearing water tanks before and after voyage to prevent blockage. Where possible, install cooling water filters and propeller anti-fishing nets.

These operating instructions are essential for ship management personnel and crew members to familiarize themselves with and apply. They are also valuable references for shipbuilding and repair engineers.