Kalmar Reachstacker Park Brake Failure Analysis

DEPARTMENT OF MECHANICAL ENGINEERING

KALMAR REACHSTACKER PARK BRAKE FAILURE P2 EXPERIENTIAL TRAINING REPORT

By E W Swartz Contact details:

Lecturer: Subject: Date:

210026480 +264814656032 +26464206881

G. Morris Experiential Training 3 October 2014

I hereby swear that this is the original work of the author. All information obtained from other sources has been fully acknowledged.

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Table of Contents 1

Introduction.......................................................................................................... 2 Background............................................................................................................. 2 Problem Statement.................................................................................................. 3 Objectives............................................................................................................... 3 Planning.................................................................................................................. 3

2.1

Reachstacker – Kalmar Theory..........................................................................0

How the park brake works....................................................................................... 2 Pump Calculations................................................................................................... 0 2.2

Kalmar Practical................................................................................................ 1

Primary assumption................................................................................................. 2 Secondary assumption............................................................................................ 3 Battery not charging problem and solution.............................................................4 3

Conclusion............................................................................................................ 5

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Recommendations................................................................................................ 5

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References........................................................................................................... 7

Table of Figures Figure 1 - Overview of Kalmar Reachstaker...................................................................................2 Figure 2 - Simple park brake system diagram.................................................................................3 Appendix A – RCA diagram for fault finding Appendix B – Hydraulic diagram of the Kalmar reachstaker

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1

Introduction

Background

Figure 1 - Overview of Kalmar Reachstaker

Cummins engine QSM11 –

Diesel 6-cylinder inline 261kW 1830Nm 2400W (alternator)

How the park brake works. The park brake on the Kalmar reachstacker is a hydraulic release spring activated brake. This means that to release the park brake a certain amount of pressure needs to be applied, 19MPa. One pump is responsible for supplying this pressure. The pump has a direct suction line to the tank and has a pressure line, which passes through a filter, to the valve block and then to the brake. The pump is an integral part of the park brake system. A reachstacker is a mechanical lifting machine that operates with a spreader, in this case an ELME spreader, which is attached to its retractable boom. The machine fucntions similarly to a mobile harbour crane in the way it lifts containers. It is a very maneuverable machine in the terminal. It is used to pack the terminal, i.e. load or off load harbour trucks in the container terminal.

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Problem Statement Reachstackers are an important part of terminal operations as they load and offload harbour trucks and pack the container stacks as per request from the yard planners to effectively load trucks in a sequence which accommodates the vessel planner. Only two of these reachstackers are capable of handling containers on and off of the rail cars. One of these machines had been pulled out of operation due to a park brake failure. The park brake would not disengage, not allowing the machine to perform its duties. The student was tasked by the Superintendent of the mobile crane workshop to solve the problem as to why the park brake on the Kalmar reach stacker would not disengage. In addition to this the batteries would constantly drain and the machine would need a jump start, this problem also needed to be solved as it caused delays in production. Objectives Perform a fault finding analysis to determine the fault and its root cause or causes. Develop a solution and repair the machine as soon as possible to keep the ‘mean time to repair’ as low as possible. Planning An RCA diagram taken from the Maintenance Engineering Handbook 7th ed. Section 3, shows how to effectively do fault finding and to not only solve the problem but to also determine the root causes of failures. This diagram is shown in appendix A The student first needed to comprehensively study how the park brake works. This is because without fully understanding the system, it would not be able to develop a proper solution to the problem. After studying the park brake system and how the electronics and electrical system integrates into the hydraulics the student could begin to perform fault finding tests. During the performing of these tests the student rules out different possible causes as to why the park brake does not disengage. When a cause is found and the problem can be solved the student must investigate why something has failed or what caused the part to fail. This will lead to finding the root cause of the failure and then a suitable solution can be found to ensure that the failure does not happen again. In short, the student must:     

Study how the park brake works Perform fault finding Determine why the park brake does not disengage Determine what the root cause of the failure is Find a suitable solution to the failure

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TASK TITLE Week 1

2.1

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Study how the park brake works

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Perform fault finding

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Determine why the park brake does not disengage

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Determine what the root cause of the failure is

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Find a suitable solution to the failure

Reachstacker – Kalmar Theoretical Considerations

Pump Calculations The equations below are considered because of the possibility of pump and motor failure. V m=

T m × 62.83 ∆ P × ηh m .m

Vm = motor displacement Tm = motor torque Δp = pressure difference across motor ports ηhm.m = hydraulic motor/mechanical efficiency (0.9-0.95) Then to calculate motor speed and flow rate: Q m=

V m × nm 1000 ×η vol .m

Qm = flow rate required Vm = motor displacement nm = shaft motor speed

Week 2

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ηvol.m = motor volumetric efficiency Before confirming motor selection, check that the torque is within manufacturer maximum allowed torque. Pump displacement V p=

Qm ×1000 n p ×η vol . p

Vp = pump displacement Qm = flowrate required np = pump shaft speed in rpm ηvol.p = pump volumetric efficiency (0.85-0.97) Drive power P=

p ×(V p × n p ) 600000 ×ηt . p

P = Power in kW p = Pressure in bar Vp = Pump displacement (l/rev) Np = Pump shaft speed in rpm Ηt.p = pump overall efficiency (0.8-0.9) Hydraulic system. The hydraulic system in the Kalmar reachstacker is quite simple when it comes to the brakes. There is one suction line from the tank into the pump and then one pumping line which goes from the pump into the high pressure filter housing and then into the valve block which then allows for pressure regulation and pressure accumulation. After the valve block there is a direct pumping line which goes to the brake. This line to the break is used to release the brake when the solenoid valve is triggered. If the park brake does not disengage, the solution to solving this problem should be simple as well. Follow the path back to the tank from the brake line and determine which parts or components are not working in order to resolve the problem. After the problem is resolved, determine what the cause of the failed part or component was. It is always more prudent to check that all the small components are functioning properly before performing any tests on larger components. Firstly test whether all the electronics are in order. This should be done by disengaging the park brake at the switch to see if the solenoid valve becomes energized. If so, then monitoring the hydraulic pipes, solenoid valves and valve block

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components should be the second thing to be done. When it is clear that there is no fault that can be located at the valve block then you can move on the next component. Further along the line leaves the pressure filter which may be blocked due to dirt in the hydraulic tank and causing the pressure across the line to be lower. If there is no blockages found then a pressure gauge should be applied to the system to determine the pressure on the pumping line. If there is fluctuation in the pressure, there may be a fault on the pump. If the pressure is lower than expected, then the pump may also be the cause of the problem. When investigating the pump, it should be taken into account that there may have been cavitation in the pump, which would cause lower pressures. The pump will however squeal when cavitation has occurred. If this can be ruled out leakage should be taken into account. Either leakage of air into the pump system, internal leakage of the pump or leakage out of the pump system at some point in the system that has not been thoroughly inspected. If all of the above has been tried and no cause can be found it is possible that the cause of the park brake not disengaging could be mechanical and the springs do not release when hydraulically applied.

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Kalmar Practical Considerations

The park brake of this machine would not disengage, preventing normal operation of the machine. Thus the machine could not be used in production. This machine is used to offload the train cars and is one of two reachstackers big enough to be able to perform this job. Only one is used at a time at the rail, then the other does other minor jobs. So there is only one viable spare reachstacker in the sense of loading and off-loading the rail. This is therefore an important machine for port operation. The process of fault finding can be strenuous if there is no planning involved. An RCA diagram taken from the Maintenance Engineering Handbook 7th ed. Section 3 shows how to effectively do fault finding to not only solve the problem but also to determine the root causes. This diagram can be seen in appendix A. The park brake is a spring activated, hydraulic release mechanism which means that there must be a build-up of hydraulic pressure for the park brake to release. So in my opinion there is only two possible causes, either there is a problem with a component related to the solenoid valve or there is no pressure in the system.

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Primary assumption Firstly the student checked the smaller of the two causes, the solenoid valve. I found that the solenoid valve plug was corroded. The student then liaised with the vehicle workshop and electrical workshop to find suitable push-in connector pins (lugs) that could be used to replace the plug to fix the connection. A side cutter was used to cut the wires just before the plug. Then a wire stripper was used to clean up the electrical insulation at the tips of the wires. The student could then attach the push-in lugs to the wires and use the part of the wire stripper which acts as a wire clamp for lugs, which keeps the wire and lug connected. Then the student connected the wires to their respective positions. The machine was started up, letting it idle and revving up the engine to build the necessary pressure, but the park brake would still not disengage. Before the student checked for pressure losses in the system a discussion with one of the artisans was had to ask for some advice as he had extensive training on these types of machines. He recommended that the student check the valve block and the brake oil filter before removing any larger components. The student checked the valve block by starting up the machine, idling, and then switching off before slowly untightening the pressure release valve. After opening the release valve, the hydraulic oil that came out of the orifice was white and foamy. This normally indicates the presence of air within the system. After checking that condition of all the plugs on the valve block and the attachments and they all seemed to be in good condition except the pressure release, which could be blown open quite easily. Yet, it was still a necessary precaution to remove the valve block and replace it with another to check if the problem would be resolved. This was done by closing the ball valve on the hydraulic line to prevent excessive flow of hydraulic oil. Then a 6mm allen key was used to loosen the bolts which held the valve block in place. All of the attachments were then removed as well as all of the solenoid plugs. Then replaced the valve block with the new one. After the new valve block was mounted and tightened the studnet opened the ball valve and started up the machine again. The park brake would still not disengage, even after idling for over 10mins. Secondary assumption The student decided to remove the brake oil filter. A 55mm spanner was needed to loosen the filter housing. After the removal the student cleaned the filter housing with paraffin to remove all the old oil before rinsing it with water and drying it. The filter housing was ready to be fit to the machine and hold a new filter. The old filter had collapsed inward, most probably from the air in the system. Replacing the filter and housing did not fix the problem either. The student also decided to drain the brake oil and refill with clean brake oil, HD30, from Mobil. To have the oil drained, it was allowed to flow out from the drain plug beneath the brake oil tank but to ensure now restriction to the flow the breather cap was also opened up the to allow easy flow of the oil. The breather needed a 36mm spanner to loosen the head. During this process it was found that the breather cap filter was dirty and replaced the breather cap filter as well. I then took this drained oil away with the 4T forklift. Then the student brought a used bin of brake oil by forklift with an air compressor and started filling up the tank again with the use of the compressor which was plugged into mains via 2 electrical leads. The bin got a good 60l of brake oil into the tank but it was not filled yet. The empty oil bin was removed and a new bin was opened to complete

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the filling process. In total the tank took around 80l to reach the middle of the sight glass which is said to be optimum. Now it was decided to get the pressure sensor and test for pressure. It was found that the pressure in the brake system was correct, pressure on the pumping side 19MPa ±1MPa. Below is a diagram showing the brake system. A detailed drawing of the hydraulic system can be viewed in appendix B.

Figure 2 - Simple park brake system diagram

This show how the pump1 pumps the hydraulic brake oil from the brake oil tank and pumps it through the filter2 to the valve block3. The accumulator4 stores pressure. The switch5 sends a signal via CAN-bus to either activate6 or deactivate6 the park brake. The control unit frame front D797-F7 activates the solenoid valve8 to drain the pressure, when activated, to the oil tank. The park brake is then spring activated at 9. Contact breaks at 10 to close the circuit. Applied parking brake: Conn 1: U = 24 V Conn 2: U = 0 V Released parking brake: Conn 1: U = 24 V Conn 2: U = 24 V 11 and 12 are the CAN-bus signal and the activation of the make-contact brake light.

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With the availability of the required pressure, the system should function properly but the park brake does not disengage. The pressures were checked again only to notice that the pressure had drastically dropped. A while later checking the pressure again it had increased by a reasonable amount. This led to the conclusion that it could be possible that the pump was leaking internally. After speaking to the supervisor about taking the pump to a pump specialist, to open and have a look at to ensure that the pump did not have any problems. After being given the go ahead, the student closed the ball valve to the system and and removed outlet pipe going to the filter using two 22mm spanners and then removed the inlet pipe using the same 22mm spanners. There are two bolts with nyloc nuts on diagonally opposite ends of the pump holding it in place. Due to the positioning of the bolts it prohibited the use standard spanners, the student had to use one standard 19mm spanner as well as a 19mm C-spanner. After the bolts were loosened, the pump slid out of position. It was noticed that one of the o-ring seals had failed and that there was only one seal instead of two, one on each end of the spacer. Since this was the first time this pump had been removed, there was no-one to give advice on having two seals between the pump and the motor and there was a coupling spacer with o-ring edges on both sides. The parts list only indicated that a seal be there but did not indicate if it need be sealed at both ends. Instead of having the pump checked by the 3-rd party company, it was first decided to get 2 high pressure and high heat o-rings and then test the system again. After the fitment of the o-rings and then assembling the pump again, the student started up the machine to test the park brake. The park brake light indicator switched off immediately after deactivating it at the switch. Thus the problem was caused by a leak between the pump and motor because of the failure of the o-ring seals. Battery not charging problem and solution With this problem solved there was another issue that had come up. The batteries were almost constantly flat, needing to be jumpstarted or charged at every point where I wanted to test the machines park brake. Discussing this with the artisan, he recommended changing the alternator, but it is possible that it is only the voltage regulator that has failed. So to solve this problem I began removing the alternator. I firstly used a 13mm spanner and 8mm spanners to remove the wires that were connected to the alternator. Those were the power wire, ignition and the ground. I removed the tension from the belt and removed the belt. Then I removed the fixed nut and bolt by 19mm spanner and lastly the tensioner bolt. The alternator now slid out of position. I took the alternator to 3-rd party auto-electricians to have a look at it. They tested it immediately on their test bench. They showed that the alternator is not faulty but the voltage regulator. They then replaced the voltage regulator and I went back to the workshop to replace the alternator. After replacing the alternator, we started up the machine and checked the battery voltage. The voltage was checked by multi-meter, the voltage showed 26.5V which is optimal for 2 12V batteries. The problem was solved. 1

Conclusion The park brake failed due to a leakage of the pump. The fault finding did consume a great deal of time but was well worth it and unnecessary finances were not given out to replace parts because of an assumption. It is always better to be sure of the root cause before attempting a solution. Checking all the valve block fittings led to no feasible results. After ruling out the vavle block as

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the cause of the problem a blockage became the next target point. With only 3 pipes before the valve block it became easier to find the problem. Pressure tests after the filter showed a slight decrease in pressure. This pressure drop was assumed to be because of the filter which was then changed. After this a pressure drop was still found and the suction side pipe was then targered. To check the suction pipe the pump needed to be removed. In the process of removing the pump the problem was found. The pump seals had gone. New seals were ordered and the problem was solved. Replacing the seal solves the problem but the root cause is that there was only one seal and if there had been two the problem may never have arose. The project describes how to develop a plan before jumping into the fault finding process. This is to prevent unnecessary time wasted by trying to go through components which are not directly related to the problem. It also describes that even when the problem is solved, it should be taken into consideration that something made the component fail and that something should be changed to prevent another such failure. This can be used as a guideline to other fault finding processes as well, it is not restricted to hydraulic brakes. The student learnt that it is better to start off with a good plan than to jump into something unprepared. When preparing for a job, it can be more easily seen what should be done and what is important. Also, the student learnt how to effectively make use of a pressure gauge to test pressures on a closed system and to know how to check for air in a hydraulic system. Most of all it was important in finding out how to determine how the pump and motor correlate to ensure the correct operation.

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Recommendations

When doing fault finding on a hydraulic system it is important to determine what pressures are needed and where in the system they act. When you have found out where the pressures should be, make use of a pressure sensor and test for those pressures. This will rule out certain aspects even before fault finding has begun. This will reduce the time spent on the job as well as the machine downtime. It is always good practice to keep the work area clean to ensure leaks can easily be spotted and dealt with. When performing any fault finding and there is uncertainty, refer to the manual for clarification and discuss the issue with a colleague to gain a better understanding. Check pump seals at certain service intervals to prevent such breakdowns. Also, make sure that the engine bay is always clean so that inspections and breakdown maintenance can be done more easily.

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References

Courses Mathematics 1 Drawings 1 Manufacturing 1 Maintenance Management skills Thermodynamics 2 Strength of materials 3 Communication 1 Computer skills 1 Electrotechnology 2 Fluid mechanics 3 Production engineering

Mathematics 2 CAD Manufacturing 2 Manufacturing 3 Mechanical design 2 Strength of materials 2 Applied strength of materials 3 Communication 2 Electrotechnology 1 Fluid mechanics 2 Hydraulic machines Mechanics of machines 2

Manuals Kalmar Workshop Manual DRF400-450, Kalmar Industries AB Short PDF Basic Electrical Systems, Unknown Hydraulic Valve Symbols, Unknown Books Maintenance Engineering Handbook 7th ed, McGraw-Hill, R. Keith Mobley, Lindley R. Higgins, Darrin J. Wikoff

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Appendix A

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Appendix B

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