MARITIME APPLICATION Martechnic GmbH of Hamburg is a specialist company focused on delivering solutions for fuels, lubes and hydraulic oils in the marine industry. Ships and other maritime assets operate in the most hostile environment on the planet with challenging logistics, remote circumstances and unforgiving economics. The management of these fluids presents critical challenges for operators and Martechnic is constantly seeking better methods of delivering security and efficiency in these applications. Its participation in DYNAMITE reflects this commitment. 5.1 Introduction The significance aspects of lubrication systems aboard a ship are that they operate under the most extreme conditions while required to deliver a performance standard far beyond that of equivalent systems ashore. By definition a ship is a remote transportation asset operating in extremes of temperature, motion akin to that of an earthquake and many other factors that expose its vulnerability. Onboard there are a number of critical lubrication systems upon which the vessel is dependent. Any interruption of service of these systems could leave a ship dead in the water and at the mercy of the elements. The survival of a ship s crew and the security of an asset and its cargo worth possibly hundreds of millions of euros can be dependent upon lubrication systems that are minimally supervised and exposed to a high contamination potential. Because of the asset value any interruption of service is an expensive event. There can be a number of critical lube/hydraulic oil systems aboard a ship: The main propulsion engine(s) and power generating engine(s) The Common Fuel Rail hydraulic system Stern tube/tail end shaft lubricant system. Steering Engine (Rudder) hydraulic system The one chosen for this exercise is the stern tube/tail end shaft lubrication system on an 8000TEU Container Ship. Lube oil circulates around the revolving propeller shaft reducing friction and maintaining in serviceable condition the shaft metal and bearing surfaces and returning to a sump that holds up to 10,000 litres of lube oil. Typically for a large Container Ship, the power of a 12 cylinder, 70,000kW engine is transmitted through a shaft turning a 120 ton, 10 meter diameter propeller at 102 rev/min. The massive forces that surround a ship of 150,000 metric deadweight tons, particularly in heavy seas, creates stress and vibration at the tail-end shaft. The extreme forces acting upon this system can result in sea water ingress and lube oil leakage into the sea which is a major concern. Corrosion and wear of the shaft can cause deterioration and the system is regularly subjected to mandatory removal and inspection surveys - a process that requires drydocking the ship at considerable cost and interruption to service! Monitoring the quality of lube oil can provide early warning of deteriorating conditions triggering intervention by the crew. Remedial action can involve changing or cleaning the lube oil itself in an expensive commodity. In addition, continuous monitoring of the lube oil condition can provide an authoritive record of lube oil conditions over an extended period that classification bodies and other regulatory organizations will accept as evidence. If the condition can be shown to be water free and of optimal standard, in such circumstances mandatory surveys may be waived with considerable economic and operational benefit to operator.
This picture shows a propeller comparable with one used in the application under consideration. Circumstances resulting in failures whereby the tail end shaft breaks or the propeller falls off while un-common still occur. This picture is of a typical Stern tube bearing.
This simple schematic below portrays the application. Basically, there are just two components, the stern tube and the tail end propeller shaft in consideration. Lubrication between these two components is subjected to a high Seawater contamination potential and there is also considerable risk of lube oil pollution of the sea. Consequently this critical system becomes a prime candidate for a sensor application or condition based monitoring. The lube oil sump and headed tank are shown in yellow with the Martechnic AHHOI sensor system connected to the LO circulation system. 5.2 Objectives of Testing and Demonstration For logistic and legal reasons it was not possible to conduct a demonstration on board an operating vessel therefore a close-to-reality simulation was arranged on a specially designed test rig. The objectives were as follows: 1. to demonstrate the operation of the sensor 2. to demonstrate the communication of results locally 3. to demonstration the communication of results via DynaWeb assets to the Mimosa database. The objectives of installing such a system aboard a ship are: 1. to protect critical systems in order to avoid an interruption of service that could endanger lives, property and environment. 2. to extend the life of shipboard machinery for economic benefit by avoiding repairs, unscheduled downtime, and off hire circumstance. 3. to provide input for condition-based monitoring to enable the extension of service time between remove/inspection surveys. 5.2.1 Description of Test Platform The test rig was constructed to replicate the conditions of a lubrication oil circulation system of a stern tube/tail end shaft lubrication system. The means of adjusting lube oil flow velocity, pressure and temperature (plus viscosity) were provided to create conditions likely to prevail in a typical stern tube/tail end shaft lubrication system operation. The overall dimensions of approx. one square meter x 1.8 metre high provided a convenient working arrangement and the oil capacity of 10 litres enabled sufficient volume for accurate measurement while facilitating instant adjustment and oil changes that were both affordable and manageable. The circulation system was mounted on a horizontal framework and the oil circulated by an adjustable gear pump to determine flow velocity. A thermostatically controlled heater provided the desired operating temperature, while the pressure was controlled by partially opening or closing the pressure regulating valve. Suitable instrumentation displayed these parameters.
A Manifold with a range of fittings allowed access in various ways for connecting sensors to the circulating oil and to draw samples from the flowing stream. At the lowest point in the circulation system a valve allows the oil to be drained into a sump to facilitate oil changes. At two points in the system a facility was provided for venting air from the system. The above describes the Primary Circuit replicating the stern tube/tail end shaft lubrication system. 5.2.2 The Sampling System A secondary system designed to simulate the arrangement for monitoring the quality of oil using a bleed from a bypass through the sensors was set up using 3mm plastic tubing. The pressure from the primary circuit provided a constant flow into open sampling bypass circuits. Separate sampling lines feed the four sensors with solenoid valves to open and close the flow. The sensors had either integral operating software or were served by software loaded on a computer/pc/laptop that determined the sequencing. The IR sensor was set-up for batch processing and the visible sensor operating continuously. After passing through the sensors the samples are returned to the system via the sump. 5.2.3 Testing Method The test rig was custom designed to provide the appropriate sample flow equally to each sensor. Clean flushing oil was charged to the system and circulated for two days to ensure that any debris and fouling would be removed and to test the integrity of the plumbing and accuracy of the system components (temperature, pressure, filters, etc.). The system was then charged with clean new lubricating oil of the specification used in the stern tube/tail end shaft application. With all of the sensors fitted and connected to the various electronic and recording systems the oil was circulated and brought to its operating temperature and pressure. These changes were noted on the monitors as the system progressively settled in to a stable operating condition. The testing period commenced with the instruments recording zero water and zero particular contamination. The testing period although not preset lasted for nine days. At regular intervals small known quantities of water where injected into the primary oil flow. The changes in waterin-oil content were realized by the sensors and recorded. Manual samples are taken as a reference check against the measurements. This process was continued until a series of measurements were achieved to demonstrate the system. Following this a similar process followed for the particular matter with similar results. All of the sensors identified the changes producing data that could be observed on the various monitors. The objective of the demonstration was not to assess the accuracy or reproductability of the sensors but to show that the data generated in an operational situation could be managed and communicated. This was achieved.
5.2.4 Technical Specification Dimensions: 100 x 100 x 180 centimetres Weight (empty): 35 kilograms Oil capacity: 10 Litres Operating temperature range: 20 70 C Operating pressure range: 0 3 bar The test rig connected with 3mm plastic tubing for sample delivery to the four sensors with PCs or Laptop and a PDA to provide the interface to the MIMOSA database. 1 Martechnic AHHOI Water-in-oil Sensor 2 Tekniker Particle Sensor 3 Martechnic AuLUmo Dielectric Sensor 4 VTT Fibre Optical Particle Scatter Sensor 5 Test Rig Primary Oil Circuit 6 Monitor for Tekniker Particle Sensor 7 Monitor for the AHHOI & AuLUmo Sensors 8 Laptop with VTT Particle Scatter Sensor Software 9 PCs for Monitors