MARINE SHAFT BRAKING SYSTEMS

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2 MARINE SHAFT BRAKING SYSTEMS Technical Review, Applications Engineering May 2017 Rev 3

3 AGENDA Overview Opportunities Sizing a Brake - Process Sizing a Brake - Examples SLIDE 3

4 Overview - Shaft Brakes Shaft Brakes are not as common as they once were, but there remains a big opportunity here Ferries, ATB s, Various River Boats and inner harbor boats (running in tight quarters) as well as the sailboat market A small sailboat may only require a 5019 whereas a larger ferry or ATB would require a much larger system (often in excess of USD$100) SLIDE 4

5 Overview Recent Projects DRBA Bouchard Towing SLIDE 5

6 Overview - Shaft Brakes This is a new introduction from Dellner Altra has followed SLIDE 6

7 Overview - Shaft Brakes Kobelt took a different design approach We can customize solutions for a specific project or customer requirement SLIDE 7

8 Overview - Shaft Brakes There remains a strong market for shaft brakes and it is one more system that can be added to the Kobelt scope of supply Strategic channels to opportunity pipeline: Companies that are supplying the drive line Shipyards Naval Architects Don t forget to inquire if a project needs Shaft Brakes SLIDE 8

9 Overview Various Arrangements Single Screw Twin Screw SLIDE 9

10 Twin Screw Shaft Brakes High Level Requirement What is the purpose of a shaft brake: 1. To stop or slow down propeller to allow transmission to shift quickly into reverse Need enough torque to stop inertia of propeller while vessel is drifting Enough dynamic capacity to grab a spinning rotor 2. Locking of one shaft while powering the other Need enough static torque to lock shaft when vessel at speed Propeller acts like a hydroelectric generator SLIDE 10

11 Twin Screw Shaft Brakes System Components SLIDE 11

12 Twin Screw Shaft Brakes System Components Air applied disc brakes Preferably (2) brakes per disc to balance reaction force on shaft bearings Ventilated disc is fitted to the coupling, after the reducer Brake controls SLIDE 12

13 System Components Pneumatic Controls 6503 controller Brake control solenoid valve Regulator Filter Drive interlock pressure switch Kobelt 3905 quick release valve SLIDE 13

14 Twin Screw Shaft Brakes Sizing Methodology Step 1. Determine shaft torque - obtain motor power - obtain shaft speed Step 2. Apply safety factor - 75% of shaft driving torque Step 3. Select brake model & brake disc - reference data sheets - series of disc needs to match the brake Step 4. Check dynamic braking intensity - determine braking power per pad area Step 5. Check heat sinking capability of the disc SLIDE 14

15 Twin Screw Shaft Brakes Sizing Calculations Step 1. Determine shaft torque: T s = 5252 P m ft-lbf N s where; P m = motor power - per shaft - in horsepower N s = shaft speed - in rpm = motor speed reduction ratio Note: for KW and Nm substitute 9.55 for the 5252 constant SLIDE 15

16 Twin Screw Shaft Brakes Sizing Calculations Step 2. Apply safety factor: T b = T s x.75 ft-lbf where; T b = required brake torque - per shaft Why 75%? propellers typically have an efficiency of 75% to 80% That means 75-80% of the energy gets transmitted to the water Therefore 75-80% of the energy when drifting gets back driven into the drive shaft 77% x 77% = 60% x 1.25 safety factor = 75% SLIDE 16

17 Twin Screw Shaft Brakes Sizing Calculations Step 3. Select brake model & brake disc: The objective is to find a brake & disc combination to produce the torque determined in step 2 Refer to the torque chart in the brake datasheets Select an available disc size for the brake It s an Iterative process SLIDE 17

18 Twin Screw Shaft Brakes Sizing Calculations Step 4. Check dynamic braking intensity: Divide the braking power by the total pad area Braking intensity should not exceed 5 hp/in 2 It s an Iterative process Choose a larger brake / smaller disc combination May have to regulate the air supply to pressures less than 100 psi to meet the braking intensity requirement. Estimate pad area from dimensioned drawing in the data sheets Height of shoe x face width x 2 x number of brakes SLIDE 18

19 Twin Screw Shaft Brakes Sizing Calculations Step 5. Check heat sinking capability of the disc: 5a. Calculate braking energy E b = P b x 20 2 hp-secs where; E b = braking energy P b = braking power - per shaft - in horsepower Note: this estimate assumes a 20 second braking time SLIDE 19

20 Twin Screw Shaft Brakes Sizing Calculations Step 5. continued 5b. Obtain heat sinking capacity of the disc refer to the table in the brake disc data sheet. 5c. Calculate the temperature rise from one stop: T d = E b E s o F where; E b = braking energy E s = heat sinking capacity of disc - per shaft - in hp-sec/ o F 5d. Disc temperature after one stop must not exceed 600 o F SLIDE 20

21 Twin Screw Shaft Brakes Sizing Example Application: Bouchard Towing M/V Donna Bouchard Vessel Data: Twin Screw, 147 rpm Size 150' x 50' x 29' Horsepower 5,000 per shaft SLIDE 21

22 Sizing a Brake Donna Consider operational requirements of vessel SLIDE 22

23 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 1. Determine shaft torque: T s = hp 147 rpm = 178,640 ft-lbf Step 2. Apply safety factor: T b = 178,640 x.75 = 133,980 ft-lbf Step 3. Select brake model & brake disc: due to space constraints the largest disc that could fit in the space was a due to time & space constraints the largest brake that could fit into the space was two 5030-A caliper brakes SLIDE 23

24 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 3. Select brake model & brake disc: Two brakes will produce ~ 98,000 ft-lbs! SLIDE 24

25 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 4. Check dynamic braking intensity: Total pad area A p = 2 x 2 x 25 x in 2 SLIDE 25

26 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 4. continued. braking intensity; p b = T b x N s 5252 x A p hp/in 2 p b p b = 98,000 x x 700 hp/in2 = 3.9 hp/in2 SLIDE 26

27 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 5. Check heat sinking capability of the disc: 5a. Calculate braking energy E b = P b x 20 E b = hp-secs 2 98,000 x 147 x E b = 27,430 hp-secs SLIDE 27

28 M/V Donna Bouchard Sizing Example - Twin Screw Shaft Brakes Step 5. continued Heat sinking capacity of a disc is 99 hp-sec/ o F Estimated temperature rise from one stop: T d = o F T d o F T d 377 o F SLIDE 28

29 Single Screw Shaft Brakes High Level Requirements SLIDE 29

30 Single Screw Shaft Brakes High Level Requirements What is the purpose of a shaft brake? 1. Locking of the shaft while under sail or against a current Need enough static torque to lock shaft when vessel at speed Propeller acts like a hydroelectric generator SLIDE 30

31 Single Screw Shaft Brakes System Components Spring applied disc brakes Use air actuator because of relatively low hydraulic pressure from transmission Do not use air applied brakes Preferably two brakes per disc to balance reaction force on shaft bearings Ventilated disc is fitted to the coupling, after the reducer Brake controls SLIDE 31

32 System Components Brake Controls Solenoid valve Pressure reducing valve Pressure gage Brakes receive pressure from transmission clutch supply Typically psi range. Must reduce to 150 psi maximum SLIDE 32

33 Single Screw Shaft Brakes Sizing Methodology Basically identical to twin screw vessels except for Only a static braking application do not need to worry about braking intensity or heat sinking capabilities Sailing speed or river current may be less than motoring speed. In these cases the torque determined from following earlier methodology may be reduced according to; T b2 = T b1 x V 2 V 1 2 SLIDE 33

34 Thank You! Dave Bockhold Heiko Epkins