KONGSBERG SR/SV Steering Servo Maintenance Comprehensive Guide

KONGSBERG SR/SV Steering Servo Maintenance Comprehensive Guide

The SR and SV steering servos of Kongsberg Maritime are the core components of ship handling systems, known for their compact design, efficient hydraulic transmission, and excellent reliability. It is crucial to follow a systematic and specialized maintenance strategy to ensure optimal performance of the servo throughout its entire lifecycle and prevent unexpected shutdowns. This guide is based on the official maintenance manual of Kongsberg, integrating all key information from daily inspections to annual major repairs, aiming to provide a detailed operational reference for marine engineers and maintenance engineers.

Chapter 1: Safety First - The Foundation of Maintenance Work

Safety is an unbreakable red line before performing any maintenance tasks. Kongsberg emphasized that maintenance work is directly related to personnel safety, equipment integrity, and environmental health.

General safety statement: Any maintenance operation may pose on-site risks. Executors must identify and take appropriate control and preventive measures in accordance with relevant laws, regulations, and industry standards. Users (i.e. ship owners or operators) have a responsibility to ensure that these measures are implemented to protect the safety of operators and prevent damage to Kongsberg servos and their components.

Interpretation of safety labels: Standardized safety labels are used in the manual.

Warning: Indicates the presence of potential hazards or unsafe practices. If the instructions are not followed, it may result in serious or even fatal personal injury, or significant equipment and property damage.

Attention: Used to remind technicians to pay attention to information that may not be obvious and has technical importance, or to point out important matters in the subsequent operation steps.

Chapter 2: Maintenance Overview and Strategic Cooperation

At the beginning of the design of the Kongsberg servo, the focus was on achieving safe operation with minimal maintenance. However, preventive maintenance is the key to avoiding unexpected failures.

Maintenance philosophy: It is recommended that users perform maintenance at fixed intervals. For regular inspections and routine maintenance required by classification societies, it is strongly recommended to have service engineers from Kongsberg perform them. This not only minimizes maintenance time, but also ensures the continuous safety of operation.

The influencing factors of maintenance cycle: After years of equipment operation, replacing internal and external wear parts is the basis for ensuring its predictable and safe lifecycle. The maintenance interval depends on various dynamic factors, including the alignment of the rudder stock and servo, radial forces from the rudder blades, the operating mode of the servo (such as power positioning DP operation), oil temperature, pressure, oil condition, and duty cycle.

Fault reporting mechanism: The manual emphasizes that any equipment malfunction or maintenance work, regardless of size, should be reported to Kongsberg. This will help establish accurate equipment history records, and through data analysis and comparison, Kongsberg can provide better service, faster spare parts delivery, and more precise preventive maintenance guidance.

Chapter 3: Time based Strategic Maintenance - Docking Cycle Planning

The best time for deep maintenance is to cooperate with ship docking and classification society inspection. Kongsberg provides a maintenance plan based on equipment lifespan (with five-year intervals):

5 years: Based on current device performance and the status reported through the Kongsberg mobile application (such as self-assessment reports, leakage and steering time tests), provide recommendations.

10 years: Implement according to the recommendations in the table above (see below) and historical maintenance records.

15 years, 25 years: It is recommended to base on previous maintenance records, current performance, submitted self-assessment reports, leak testing, and servo PMS log files from the past 12 months.

20 years: Refer to the maintenance table and historical records for a 10-year cycle.

Key 10-year maintenance tasks (recommended to be carried out by Kongsberg engineers at dry docks/ports):

Replace the actuator seals and bearings

Replace hydraulic oil

Maintenance distribution valve

Replace the elastic coupling of hydraulic pumps (No. 1 and No. 2)

Replace the shock absorber (if applicable)

Replace the hydraulic pump

Replace the frequency converter

Replace the cooler (if applicable)

Replace the rubber hose

Replace or overhaul the motor

Chapter 4: Crew led Daily and Regular Maintenance

To ensure that the servo is always in a healthy state, the crew needs to perform a series of daily and regular preventive maintenance tasks. The following table summarizes the key tasks and their frequencies:

Daily: Check for leaks around the actuator, abnormal surface temperature of the equipment, and any abnormal vibrations or noise.

Weekly: Check the oil level of the expansion tank (supplement if necessary), start/stop the standby pump, and check for error messages on the frequency converter display screen.

Monthly: Clean the servo compartment and surrounding environment, test all control consoles (including emergency and normal steering), check steering time according to SOLAS, check the blockage indicator of the dual filter, check the coupling between the pump and motor, and ensure that the control panel indicates normally.

Quarterly: Conduct alarm system function testing according to the manual.

Every six months: Conduct internal leak testing, collect hydraulic oil samples from actuators, and replace filters.

Every year: Check the alarm logs of the frequency converter, test the communication system between the servo and the cab, conduct insulation tests on the motor (Megger test), and inspect the electrical components and grounding connections.

Chapter 5: Core components - Steering actuator

The core of SR/SV type servos lies in their unique actuator design. It adopts a cylindrical rudder, with blades/pistons working inside a spherical rotor centered on the rudder. This design allows the blades to adapt to rotor spherical deflection caused by installation deviations or rudder deflection. Synthetic bearing gaskets can maintain 100% surface contact, absorb and suppress vibration and shock pulses, and are continuously lubricated by hydraulic oil.

Important notice: To access the lower seal and bearing gasket, it is necessary to lift the rotor. Prior to this, it is necessary to securely lock the rudder blades and prepare the lifting equipment. Kongsberg is not responsible for fixing the rudder blades, which is entrusted to the shipyard or a suitable third party by the shipowner.

Chapter 6: Power Unit - Motor, Pump, and Valve Block

SR/SV servos can be configured with two main hydraulic power systems:

Variable frequency pump system (FCP):

Design feature: Two reversible pump units controlled by frequency converters are used. The motor only starts when receiving the rudder command and stops when it reaches the command position.

Working principle: Under normal circumstances, when a single pump is running and both pumps are running simultaneously, the steering speed doubles. The pump unit consists of a reversible pump, a motor, and a bell shaped housing with an elastic coupling.

Valve block integration: The integrated valve block has fewer and simpler valve components due to the use of reversible pumps. Including one-way valve, load control valve, electromagnetic isolation valve, safety valve, and return oil filter, etc.

Conventional pump system:

Design features: Equipped with an independent pump unit, the pump operates continuously, and the oil is controlled by the steering valve. The pump unit includes an oil tank with a base, a steering valve, a return oil filter, and a vane pump (or gear pump) with an elastic coupling. The motor is connected to the top plate through a flange.

Pipeline connection: The pump unit needs to be connected through three pipelines: two to the distribution valve of the actuator and one to the oil tank.

Chapter 7: Detailed Explanation of Core Maintenance Programs

This chapter is the practical core of maintenance work, covering the most critical technical operations.

7.1 Inverter Error Log

Check that the cooling air duct of the frequency converter is unobstructed and free from dust cover.

Ensure that the cover plate is properly secured.

View through the alarm log button on the local control panel, navigate using the directional keys, and all events are timestamp based on running hours.

7.2 Hydraulic oil recommendation - crucial

Warning: Using fluids not specified by Kongsberg may result in vessel maneuvering malfunctions, causing personal injury and equipment damage.

Attention: Hydraulic oil is the main component and should not be mixed with other oil products. The performance of the servo is highly dependent on the viscosity of the oil, and the selection must take into account the ambient temperature.

Standard: It shall meet DIN 51524 standard, pour point shall be lower than -30 ° C, and it must have anti-wear, water resistance and foam resistance characteristics.

Recommended brands: The manual provides a detailed list of models from multiple manufacturers, such as Shell Tellus S2 VX 32、Mobil DTE 10 Excel 32、BP Bartran HV 32、Statoil Hydraway HVXA 32 Etc., as well as biodegradable types.

Oil change indicator: When laboratory testing shows an increase in neutralization value, low residue of extreme pressure additives, an increase in insoluble particles, and oil cleanliness below ISO 4406 standard 17/14 or NAS 1638 standard level 8, it must be replaced.

7.3 System oil quantity

The manual lists the approximate oil quantities of different models (SR562 to SR743, SV430 to SV850) under variable frequency pump and conventional pump configurations. For example, the SR722 variable frequency pump system requires approximately 125 liters, while the SR722 with PU50 pump system requires approximately 450 liters.

7.4-7.6 Oil level inspection and oil sampling

Oil level: If the liquid level gauge on the expansion tank shows oil, it indicates that the oil level is normal. Long term unchanged oil level indicates no leakage.

Sampling: It is necessary to use chemically pure oil bottles and perform highly clean operations. The sampling point is usually located on the upper housing, rear of the valve block, or on the filter housing. Rinse the sampling tube during operation, mark and compare the new oil immediately after sampling.

7.7 Internal Leakage Test - Variable Frequency Pump

Purpose: To evaluate the internal sealing of pumps and valve assemblies.

Prerequisite: When the vessel is stationary in sheltered waters, it shall be executed by the chief engineer. Pump 1 and pump 2 need to be tested separately.

Steps:

Close the valve from the leaking oil pipe to the expansion tank.

Remove the leaking oil pipe from the top of the actuator and connect the drainage pipe to the measuring bucket.

In the motor control cabinet, select "local control" for the pump to be tested and "stop" for the other pump.

Use the emergency steering button to operate the servo from 30 ° on one side to 30 ° on the other side, record the time, collected oil volume, pressure, and oil temperature.

Test completed, restore the pipeline and open the valve.

Result: Record in the feedback form. If any abnormalities are found, send them to Kongsberg.

7.8 Steering Time Test - Variable Frequency Pump

Purpose: To confirm the health condition of the internal seal of the servo motor.

Steps:

Ensure that all valves in the expansion tank are open.

Set the pump to local control and stop the other pump.

The operation of the servo starts at approximately 33 ° on one side, and the timing starts when the rudder blades pass 30 °. The timing stops when they reach 30 ° on the other side.

Test two directions and two pumps separately.

Result: Record the time of tests # 1 and # 2.

7.9 Feedback Form

The manual provides a standardized feedback form for recording the results of leak testing and steering time testing, including oil level, time, pressure, temperature, etc., and requires them to be sent to a designated email address.

7.10-7.11 Testing of Conventional Pump Systems

For conventional pump systems, the testing logic is similar but the operational details are different.

Leakage test: Close the ball valve of the return oil pipe and introduce the return oil into the measuring bucket. By using solenoid valve emergency control, operate the servo from one side limit to the other side limit, and stop at the limit to measure the oil collection amount within 1 minute.

Steering time test: measure the time required to travel from 30 ° on one side to 35 ° on the other side.

7.12 Visual inspection

Limit switch: Check if the fastening screw on the cam is tightened, manually turn the switch to confirm the function of the spring and contacts.

Electromagnetic valve coil: Check whether the connecting plug has water or moisture to prevent grounding or short circuit.

Feedback potentiometer: Check if the fastening screw that fixes the potentiometer shaft is secure and if the circuit is loose.

7.13 Emergency steering test

Before operation, be sure to notify the driver's console and maintain wireless communication. Turn the selection switches of the two motor controllers to "local control" and operate them using the emergency steering button on the cabinet. After the test is completed, reset the switch to "remote control".

7.14 Alarm System Function Test

The manual provides a detailed list of simulation testing methods for various types of alarms (note that there is a 5-second delay for alarms, and one alarm needs to be cleared before testing the next):

Overload alarm: FCP system disconnects overload contact; Press the overload relay test button on the PU system. The standby pump should be started.

Phase loss alarm: Remove one fuse. The standby pump should be started.

Power/frequency failure: Turn off the main switch. The standby pump should be started.

Power control failure: Turn the selection switch to local or stop. The standby pump should be started.

Low oil level alarm: Disconnect the connector plug on the expansion tank. The standby pump should be started.

Hydraulic lock alarm: FCP system disconnects X1-2 in the junction box; The PU system manually activates the solenoid valve for more than 5 seconds. The standby pump should be started.

Isolation valve fault alarm (FCP only): Disconnect the solenoid valve plug of the corresponding pump, the pump should stop, and the backup pump should start automatically.

Auxiliary alarm: Disconnect the feedback line of U10 module in the control system, and the alarm should be triggered after 5 seconds (DP2 level and above ships will also trigger "rudder freeze").

7.15 Grounding Inspection

Power on inspection: Use a voltmeter to measure the voltage between the grounding terminal of the component and the hull. A reading above 0V may indicate the presence of abnormal voltage or induced current, posing a risk of electric shock and requiring investigation by an electrician.

Power off inspection: Measure the grounding resistance with an ohmmeter.

7.16 System temperature check

It is recommended to use an infrared thermometer to check the temperature of the pump, valve block, housing, and expansion cabinet to ensure no sudden changes. The maximum ambient temperature is 45 ° C, and it is recommended that the short-term peak value of the system should not exceed 70-80 ° C. If the system remains below 10-20 ° C for a long time, the ambient temperature should be increased or low viscosity oil should be replaced.

7.17 Filter replacement

Filter blockage will trigger an alarm or local indicator. Replacement steps:

Stop the corresponding pump.

Close the oil circuit plug from the expansion tank to the pump.

Put the bucket under the filter cup and unscrew the bottom drain plug (if any).

Remove the filter cup and replace the filter element.

Reinstall the filter cup, open the oil circuit plug, exhaust through the top of the distribution valve, and finally restore the pump to remote control mode.

7.18 Cleaning of Air/Oil Coolers

A complete process from simple backwashing to disassembly and cleaning is provided for B10/M10-30 type coolers. For stubborn dirt, a 5% phosphoric acid or oxalic acid solution can be used for rinsing, followed by rinsing with plenty of water. When disassembling and cleaning, attention should be paid to marking the order of the plates. After reassembly, the nominal width of the plate package should be controlled at 88.4mm to prevent damage.

7.19 Log file submission

The SG PMS system records operational data on the microSD card of the amplifier card. The file naming convention is RRYYMMDD.LOG. When submitting, if the vessel has two sets of left and right servos, separate emails should be sent and the servo identification number (left or right) should be indicated in the title. Before removing the SD card, press the remote SD card button and wait for the "SD card removal OK" LED light to turn off before safely removing it.

Chapter 8: Self assessment and Maintenance Inspection

Kongsberg provides a digital self-assessment checklist, and crew members can conduct self-assessment through the Kongsberg Mobile Forms app on iOS devices. It is recommended to complete the inspection in advance before entering the dock, so that there is enough time to handle spare parts and repair suggestions. Alternatively, maintenance inspections can be carried out by engineers from Kongsberg.

Chapter 9: Spare Parts Suggestions

To ensure rapid response, the manual recommends keeping the minimum number of spare parts on board, including:

Mechanical/hydraulic components: 4 filter elements, 2 load sensing valves, 2 proximity switches, 2 electromagnetic coils.

Control components: 1 phase loss relay, 2 relays, 2 selection cards, 1 pump control card, 1 power supply, 1 feedback potentiometer, and a 2-year consumable electrical spare parts package.

When ordering spare parts, detailed information such as ship name, servo model, IMO number, installation number, drawing number, and required quantity must be provided.