Patent Description:
This disclosure relates to a blender and method for preparing an oil to be supplied to the cylinders of a two-stroke crosshead engine, in particular to a method for preparing such an oil on board of a marine vessel where the two-stroke crosshead engine is installed or on site at a power plant where the engine is used as a prime mover and to a blender for preparing an oil to be supplied to the cylinders of a two-stroke crosshead engine.

Of the oils that are used in the lubrication of a large two-stroke compression ignited internal combustion engine two stand out and are quite different in chemical composition and physical properties from one another. The oil used in the crankcase lubrication system is referred to as system oil, and lubricates and cools the main, bottom end and crosshead bearings, the crosshead guide plates, camshaft, bearings and followers, and the chain or gear drive. On modern engines the oil is also used to cool the piston undersides. The system oil is in general never fully replaced, but topped up over time to maintain its condition.

The oil used to lubricate the running surface of the cylinder liners and the piston rings as they reciprocate in the cylinder liner and to neutralise the acids formed in the combustion chamber by the combustion of sulphur in the fuel is referred to as cylinder oil. However, herein this oil is also denoted as the oil to be supplied to the cylinders.

Acid neutralisation is a critical property to protect the inner surface of the cylinder liner from the acids generated during combustion. The cylinder lubrication oil is a total-loss oil since it is consumed through combustion and scraped down in the lubrication process. The cylinder oil is depleted with each revolution of the main engine and replaced by fresh cylinder oil through intermittent injections.

The oil that is supplied to the cylinders usually has an SAE (society of automotive engineering) viscosity equivalent grade of <NUM> and can have any total base number (TBN) between <NUM> and <NUM> for the neutralization of acid products generated during the combustion process. The TBN reflects the oil's reserve alkalinity, i.e. its ability to neutralize acidic materials. The TBN of an oil can e.g. be determined in accordance with the ASTM D2896 standard, which is a standard test method for base number of petroleum products by potentiometric perchloric acid titration. Typically system oil has an SAE viscosity grade of <NUM> with a relatively low TBN that is typically below <NUM>. These values are though merely by way of example, and may vary depending on the actual application-specific design of the systems that the oils are used in.

In recent years, there has been a trend towards blending the oil for delivering to the cylinders of the main engine on board the marine vessel where the main engine is installed. Hereto, used system oil is withdrawn from the crankcase lubrication system and blended with a TBN agent, such as a TBN additive, a TBN additive package or a fresh cylinder oil with a high TBN to create a cylinder oil with the appropriate lubrication characteristics, as known from <CIT> (it is noted that there is no clear technical difference between a TBN agent that comprises one or more alkaline additives in oil and a fresh cylinder oil).

In recent years two-stroke crosshead engines have been operated for a large portion of their operation time at an engine load that is significantly below their maximum continuous rating. This is due to the fact that many freight ship companies choose to sail slower (slow steaming) than before, which results in the main engines being operated well below the maximum continuous rating, since these marine vessels were originally constructed to sail at significantly higher speed.

The viscosity of the cylinder oil specified (by the original engine manufacturer - OEM) for a particular engine is generally selected such that the actual viscosity (dynamic (shear) viscosity) at the temperature of the cylinder liner where the cylinder oil is applied is optimal for the cylinder liner temperature at maximum engine load (<NUM>% maximum continuous rating), i.e. sufficiently high for providing a proper lubrication of the piston rings against the inner surface of the cylinder liner at maximum engine load. The viscosity of a cylinder oil in operation is affected by a number of factors. As temperature increases, the viscosity of a fluid decreases, and vice-versa. During the operation of a two-stroke crosshead engine the temperature varies according to engine load and RPM (revolutions per minute). As engine load and RPM increase, the temperature also increases and hence the viscosity of the lubricating oil decreases.

For a typical two-stroke crosshead engine the oil delivered to the cylinders should have a viscosity between approximately <NUM> and <NUM> cSt at the (running) temperature of the cylinder liner. The cylinder liner temperature at the maximum continuous rating of the engine (maximum load) will typically be well above <NUM>, e.g. approximately <NUM> to <NUM>, whilst the cylinder liner temperature at lower loads, such as <NUM>% of the maximum continuous rating, will typically be well below <NUM>, e.g. approximately <NUM>- <NUM>.

Present dosage regimes for cylinder oil are based on fuel sulphur content, i.e. a cylinder oil with a high TBN used when the engine runs on fuel with a high sulphur content and a cylinder oil with a lower TBN is used when the engine is running on fuel with less sulphur. The feed rate of electronically controlled cylinder lubrication devices is typically proportional to the load, e.g. some engine manufacturers/developers recommend <NUM>-<NUM>/kWh, others <NUM>/kWh.

In known engines where the blending of the oil for delivering to the cylinders of the main engine is done locally by e.g. blending used oil with a TBN agent or with a cylinder oil with a high TBN to create a cylinder oil with the appropriate lubrication characteristics the same principles are applied, i.e. the feed rate is proportional to the engine load and the TBN is selected in relation to sulphur content of the (heavy) fuel oil. For engines that use locally blended cylinder oil it is possible to react quicker to changes in the fuel sulphur content of the fuel since the TBN of the oil supplied to the cylinders can be readily adjusted in accordance with need.

The costs associated with cylinder oil form a significant part of the operating cost of an engine in e.g. a marine vessel or in a power plant.

Thus, there is a need for a reliable and simple capacity to effectively blend a base oil, such as used system oil or fresh cylinder oil with a TBN agent and possibly also with other agents or additives on board of a marine vessel or in situ in a power plant.

There is also a need for a capacity to accurately blend a base oil, such as used system oil or fresh cylinder oil with a TBN agent and possibly also with other agents or additives on board of a marine vessel or in situ in a power plant. Especially, on board of a marine vessel the conditions are not always optimal for precise measurements, due to e.g. the motion of the marine vessel, such as the linear motions heaving, swaying and surging and the rotation motions pitch, roll and yaw, that may affect measurements.

There is also a need for a capacity to accurately and effectively blend a base oil, such as used system oil or fresh cylinder oil with a TBN agent and possibly also with other agents or additives on board of a marine vessel or in situ in a power plant. Especially, on board of a marine vessel the conditions are not always optimal for precise measurements, due to e.g. the motion of the marine vessel, such as the linear motions heaving, swaying and surging and the rotation motions pitch, roll and yaw, that may affect measurements.

There is also a need for safe and reliable a capacity to blend a base oil, such as used system oil or fresh cylinder oil with a TBN agent and possibly also with other agents or additives on board of a marine vessel or in situ in a power plant. Especially, on board of a marine vessel the safety requirements are particularly high, and therefore there is a need to provide a blender that fulfils these high safety requirements.

It is an object of the invention to provide a blender that at least partially accommodates one or more of the above needs.

According to a first aspect, there is provided a blender in accordance with claim <NUM>.

By providing a blender that bases its measurements on weight and by providing control that is capable of calibrating the weight under difficult circumstances, such as a moving ship, inaccurate and relatively simple and inexpensive blender is provided that can be used on board of a marine vessel.

In a first possible implementation form of the fist aspect the tank is provided with a minimum level sensor with an output that indicates that a liquid level in the tank is above a given minimum level or not, and wherein the controller is configured to perform the calibration process only when the new level sensor indicates that the liquid level in the tank is above the given minimum level.

In a second possible implementation form of the first aspect the controller is configured to initiate supply of oil from the first port to the tank if the minimum level sensor indicates that the liquid level in the tank is below the given minimum level.

In a third possible implementation form of the first aspect the controller is configured to control sequential supply of the oil and the composition for filling the tank in order to blend the oil and the composition, and wherein the controller is configured to perform the calibration process before supplying the oil and the composition.

According to a second aspect there is provided a method in accordance with claim <NUM>.

In a first possible implementation form of the second aspect c) is performed before a).

In a second possible implementation form of the second aspect the method further comprises d) ensuring that a liquid level in the tank is above a given minimum level before step c).

In a third possible implementation form of the second aspect the method further comprises d) blending the oil and the composition in the tank to obtain a blended composition in the tank.

In a fourth possible implementation form of the second aspect the method further comprises e) discharging the blended composition from the tank. These and other aspects of the invention will be apparent from the embodiment(s) described below.

In the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to the example embodiments shown in the drawings, in which:.

In the following detailed description, a blender for preparing cylinder oil from two or more different compositions for use in a two-stroke crosshead engine will be described by the example embodiments. A method of operating the blender will also be described by the example embodiments.

<FIG> diagrammatically shows a large low speed turbocharged compression ignited two-stroke crosshead engine <NUM> with a crankshaft <NUM> and crossheads <NUM> in sectional view. Two-stroke crosshead engines typically have between four and sixteen cylinders in line, carried by an engine frame <NUM>. The engine <NUM> may e.g. be used as the main engine in an ocean going vessel, or as prime mover in a stationary power plant. At the maximum continuous rating of the engine the total output of the engine may, for example, range from <NUM>,<NUM> to <NUM>,<NUM> kW.

The engine is a diesel (compression ignited internal combustion) engine of the two-stroke uniflow type with scavenge ports <NUM> at the lower region of the cylinders <NUM> and an exhaust valve <NUM> at the top of the cylinders <NUM>. The engine can be operated on various types of fuel, such as e.g. marine diesel, heavy fuel, or gas. The scavenge air is passed from the scavenge air receiver <NUM> to the scavenge ports <NUM> of the individual cylinders <NUM>. A piston <NUM> in the cylinder liner <NUM> compresses the scavenge air, fuel is injected and combustion follows and exhaust gas is generated. When an exhaust valve <NUM> is opened, the exhaust gas flows through an exhaust duct associated with the cylinder concerned into the exhaust gas receiver <NUM> and onwards through a first exhaust conduit to a turbocharger (not shown), from which the exhaust gas flows away from the atmosphere. The turbocharger (not shown) delivers pressurized scavenge air to a scavenge air conduit leading to the scavenge air receiver <NUM>.

A piston rod <NUM> extends from the bottom of the piston to the crosshead <NUM>. A connecting rod <NUM> connects the crosshead <NUM> to one of the throws of the crankshaft <NUM>. The crankshaft <NUM> is rotation suspended in the engine frame and bedplate by the main bearings <NUM>. A thrust bearing (not shown) is provided at the aft of the engine to accommodate the thrust created by a propeller (not shown) driven by the engine <NUM>. The thrust bearing is supplied with lubrication oil by the same conduit that supplies the main bearings <NUM>. In the main bearings <NUM> an oil film between the bearing surface and the journal surface carries the journal and prevents substantially any direct contact between the journal surface and the inside surface of the shells and provides lubrication. A flow of lubrication oil is supplied to the bearing surface. The lubrication oil film assists in cooling the main bearing.

Two-stroke crosshead engines include an array of components that are for lubrication and/or cooling purposes supplied with lubrication oil. All these components are provided with lubrication oil via the crankcase lubrication system except for the cylinders and piston rings which receive another type of oil from the cylinder oil system.

The crankcase lubrication system is essentially a closed loop lubrication system in which the system oil is circulated. The crankcase lubrication system provides lubrication and cooling for a range of components of the engine. For example, the crankshaft <NUM> is placed in an oil sump <NUM> that is provided in the lower part of the engine <NUM> and supplied with lubrication oil under pressure that is circulated through the oil sump <NUM>. Other lubrication positions, such as bearings, etc. are separately provided with lubrication oil, as will be described in greater detail further below. The surplus leakage oil is collected in the oil sump <NUM>. A lubrication oil supply loop is provided for supplying lubrication oil to all lubrication oil consumers. The lubrication oil supply loop includes a supply conduit <NUM> that starts at the oil sump <NUM>. The supply conduit <NUM> includes two low-pressure pumps <NUM> arranged in parallel with respective electric drive motors for arranging the oil transport (although it is understood that there could be any other number of supply pumps). The supply conduit <NUM> also includes a cooler <NUM> for cooling the lubrication oil and a filter <NUM> for filtering out contamination. This can in one embodiment be a BσK 50µ filter.

The supply conduit <NUM> splits downstream of filter <NUM> into an oil sump supply conduit <NUM> and a bearing supply conduit <NUM>. The oil sump supply conduit <NUM> delivers filtered and cooled lubrication oil to the oil sump <NUM>. The bearing supply conduit <NUM> branches into a main bearing supply conduit <NUM> and a crosshead bearing supply conduit <NUM>. The main bearing supply conduit <NUM> also provides the thrust bearing the aft of the engine <NUM> with lubrication oil.

The main bearing supply conduit <NUM> includes an electronically controlled valve <NUM> for controlling the flow. The main bearing supply conduit <NUM> also includes a feed pump <NUM>. In the present embodiment a pair of parallel feed pumps is shown, but it is understood that any number of pumps could be used, although a plurality of pumps is preferred for redundancy reasons. The feed pump <NUM> is driven by one or more electric drive motors. The main bearing supply conduit <NUM> delivers a substantially constant flow of lubrication oil to the main bearings <NUM> during engine operation.

The crosshead bearing supply conduit <NUM> includes an electronically controlled valve <NUM> for controlling the flow. The crosshead bearing supply conduit <NUM> also includes a feed pump <NUM>. In the present embodiment a pair of parallel feed pumps are shown, but it is understood that any number of pumps could be used, although a plurality of pumps is preferred for redundancy reasons. The feed pump <NUM> is driven by one or more electric drive motors. The crosshead bearing supply conduit <NUM> delivers a substantially constant flow of lubrication oil to the crosshead bearings during engine operation.

A portion of the system oil is withdrawn from the crankcase lubrication system. Hereto, a feed pump transports an amount of system oil from the oil pan <NUM> to a used system oil tank <NUM>. The used system oil tank <NUM> may also receive used oil from other engines or other devices, such as e.g. from auxiliary engines (generator sets) on board of a marine vessel together with the large two-stroke crosshead engine <NUM>.

A cylinder oil system supply conduit <NUM> connects to the used system oil tank <NUM>. The cylinder oil system supply conduit <NUM> provides the cylinder oil system with used system oil that has been withdrawn from the crankcase lubrication system. The cylinder oil system supply conduit eighteen is also connected via a valve to a base oil tank <NUM>, in case it is desired to use another base oil instead of used system oil. For example, fresh oil could be used, such as for example a commercially available cylinder oil with a relatively low TBN, i.e. a cylinder oil that has the required properties to be directly used in the cylinder but with a low TBN so that it can be blended with a higher TBN composition, such as a TBN agent or TBN additive or another cylinder oil with a high TBN to achieve a desired TBN for the blended product.

In order to maintain a substantially constant amount of system oil in the crankcase lubrication system, an approximately equal amount of fresh system oil as withdrawn therefrom is added to the crankcase lubrication system from a fresh oil system tank <NUM> using a feed pump that connects to the oil sump supply conduit <NUM>. Thus, the system oil is continually replenished with fresh system oil, thereby rendering it practically unnecessary to completely replace the system oil in the crankcase lubrication system with fresh system oil.

The cylinder oil system includes a blender <NUM> that receives base oil, such as e.g. used system oil from the used system oil tank <NUM>. The first or base oil can be a used or fresh oil. In the embodiment of <FIG> the feeding of the base oil is controlled by an electronic control unit <NUM>. The electronic control unit <NUM> can be part of the blender <NUM> or part of a central electronic control unit <NUM> that controls many aspects of the engine <NUM>.

The electronic control unit <NUM> controls the blender <NUM> so that the system oil is supplied to the blender <NUM> intermittently for batch wise preparation of oil to be delivered to the cylinders <NUM>; this is explained here below in more detail with reference to <FIG>.

In the blender <NUM> the withdrawn system oil (first or base oil) is mixed or blended with a TBN agent (e.g. TBN additive, TBN additive package, high TBN oil or high TBN cylinder oil) and optionally with a viscosity agent to prepare the oil to be supplied to the cylinders. The details of the blending process are described in detail further below. From the blender <NUM> the prepared oil, "blended cylinder oil" is transported by a feed pump <NUM> via a feed conduit <NUM> to a blended cylinder oil day tank <NUM>. An additional cylinder oil storage tank <NUM> is provided and connected to the feed conduit <NUM>. The additional cylinder oil storage tank <NUM> can be used as an additional storage tank for cylinder oil that is blended by the blender <NUM> or for storing "fresh" cylinder oil for if it is desired to provide the cylinders with a fresh cylinder oil instead of a blended product from the blender <NUM>.

The blended cylinder oil day tank <NUM> is connected to a blended cylinder oil dosage pump <NUM>. The dosage pump <NUM> ensures precise and correctly timed dosage of the cylinder oil to the individual cylinders <NUM>. In an embodiment the electronic control unit <NUM> is operatively connected to the cylinder oil dosage pump <NUM> and configured to control the feed rate of cylinder oil delivered by dosage pump <NUM> to be proportional to the engine load. The oil to be supplied to the cylinders is delivered to the liner surface of the cylinder liner <NUM> to a plurality of cylinder lubrication holes through the wall of the cylinder liner. The cylinder lubrication holes are distributed around the circumference of the cylinder liner <NUM> at substantially equal height. The lubrication holes are connected to one another by a lubrication line <NUM> that typically has a zigzag shape. The supply of the blended cylinder lubrication oil through lubrication holes and the lubrication line <NUM> is precisely timed to occur when the piston <NUM> passes the lubrication line <NUM>. Thereafter, the piston rings distribute the oil over the running surface of the cylinder liner <NUM>.

The blender <NUM> receives a TBN agent from a source of TBN agent <NUM> via a supply conduit. The TBN agent is a composition with a high TBN that can be used to increase the TBN of a base oil with a first TBN that is lower than the second TBN of the TBN agent. After blending the base oil with the TBN agent a blended product, e.g. a blended cylinder oil with a third TBN is achieved. The TBN of the blended product is selected by the operator and depends on the operating conditions of the engine, such as for example the sulfur content in the fuel.

The source of TBN agent can be a tank with a dedicated TBN agent with a TBN for example between approximately <NUM> and approximately <NUM>, or a tank with an oil with a high TBN such as a fresh commercially available "cylinder oil" with a high TBN such as e.g. a TBN equal to or above <NUM> or equal to or above <NUM>.

In an embodiment the blender <NUM> also receives a viscosity agent from a source of viscosity agent <NUM> via a supply conduit. The source of viscosity agent can be a tank with a dedicated viscosity agent or a tank with an oil with a high viscosity, such as an oil with a viscosity equal to or above SAE <NUM> or equal to or above SAE <NUM>. The oil used as viscosity agent is preferably single grade SAE. Alternatively, the viscosity agent may have a low viscosity in order to reduce the viscosity of the blended oil, for example equal to or below SAE <NUM>.

The system oil for the crankcase lubrication system is normally a high quality paraffinic base oil containing a number of performance additives. The alkalinity of the system oil (defined by its TBN number) must be sufficient to neutralize any strong acids formed from combustion of the fuel which may find their way into the crankcase.

The characteristics of an example of system oil for use in the crankcase lubrication system of a two-stroke crosshead engine are as follows:.

The total base number is an indication of the alkalinity of an oil in the milligrams of acid, expressed in equivalent milligrams of potassium hydroxide (KOH), required to neutralize all basic constituents.

The oil delivered to the cylinders <NUM> by the cylinder oil system must be thermally stable. The oil needs to be able to retain an oil film at the high surface temperatures of e.g. the piston rings and the cylinder liner <NUM>. The oil delivered to the cylinders must have anti wear characteristics and detergents to minimize deposits on the pistons <NUM> and in the ring grooves.

The oil delivered to the cylinders typically has a high TBN between <NUM> and <NUM> to neutralize the acids formed by the combustion of sulphur in the fuel. The required TBN value is dependent on e.g. the sulphur content in the fuel (which may vary) and is set at a value anywhere between e.g. <NUM> and <NUM>, or controlled by the electronic control unit <NUM>. Alkaline additives can make up a significant portion of the oil delivered to the cylinders.

The viscosity of fresh cylinder oil delivered to the cylinders is normally relatively high (e.g. <NUM> cSt (<NUM><NUM>/s) at <NUM> for an SAE <NUM> oil) in order to lubricate effectively at the higher temperatures (e.g. <NUM>) of the cylinder liner <NUM> resulting in a viscosity of approximately <NUM>,<NUM> cSt (<NUM>,<NUM><NUM>/s) where the oil is applied. However, when a blended cylinder oil is supplied to the cylinders, the viscosity of the blended product has typically been much lower without any perceivable drawbacks.

The oil delivered to the cylinders is a "use once consumable". The oil is injected into the cylinder at a feed rate to give optimum protection against acid corrosion and microseizures (scuffing).

The characteristics of an example of blended cylinder oil for supplying to the cylinders of a two-stroke crosshead engine are as follows:.

A non-exhaustive list of viscosity agents includes but is not limited to: Used and fresh finished lubricants such as hydraulic oils, turbine oils, monograde and multigrade engine oils, gear oils, base oils including naphthenic and paraffinic mineral oils (of Group I, II and III), synthetic polyalphaolefins (PAO), polymeric entities such as polymethylmethacrylate (PMMA) and olefin copolymers (OCP) and mixtures thereof.

The source of viscosity agent may comprise a source of high viscosity agents for increasing the resulting viscosity and a source of low viscosity agents for decreasing the resulting viscosity.

Adjusting the TBN preferably comprises adjusting at least one additive level or adding one or more additives, where the additives comprise at least one base comprising basic salts of alkaline or earth alkaline elements, and/or detergents and/or dispersants. Alternatively, adjusting the TBN comprises blending with a high TBN oil, such as a commercial cylinder oil with a high TBN value, e.g. with a TBN above <NUM>.

The alkaline/earth alkaline elements may be e.g. K, Na, Ca, Ba, Mg or the like. The basic salts may belong to the inorganic chemical families of e.g. oxides, hydroxides, carbonates, sulphates or the like. The detergents may belong to the organic chemical families of e.g. sulfonates, salicylates, phenates, sulphophenates, Mannich-bases and the like. The dispersants may belong to the organic chemical families of succinimides or the like.

An electronic control unit <NUM> receives signals that contain information about the engine, such as specific temperatures and pressures, and operating conditions, such as the engine load and speed. The electronic control unit <NUM> is also connected, e.g. via signal cables to the feed pumps <NUM> for the main bearings, the control valve <NUM> in the main bearing supply conduit <NUM>, the feed pumps <NUM> for the crosshead banks, control valve <NUM> in the crosshead bearing supply conduit <NUM> and to the control valve <NUM> in the crosshead bearing supply conduit <NUM>.

The electronic control unit <NUM> is also connected, e.g. via signal cables to the blender <NUM> and to the cylinder oil dosage pump <NUM>. Alternatively, the blender <NUM> may be provided with its own electronic control unit (not shown), that carries out the functions that are described below that relates to the blender <NUM>.

The electronic control unit <NUM> is configured to determine the amount (flow rate) of lubrication oil that needs to be delivered to the main bearings <NUM>. The electronic control unit <NUM> is also configured to determine the amount (flow rate) of lubrication oil that needs to be delivered to the crosshead bearings.

The electronic control unit <NUM> can also be configured to determine the required TBN for the oil that is delivered to the cylinders <NUM>. Hereto, the electronic control unit <NUM> is in receipt of information on the fuel quality, i.e. sulphur content, and determines the required TBN e.g. from lookup tables stored in the electronic control unit <NUM> or by using an algorithm or equation stored in the electronic control unit <NUM>, taking into account the sulfur content of the fuel.

In an embodiment the electronic control unit <NUM> is in receipt of a signal representative of the engine load. The engine load is a parameter that is indicative of the cylinder liner temperature. Alternatively, the electronic control unit is in receipt of a signal from the temperature sensor (not shown) that measures the jacket cooling water temperature. The jacket cooling water temperature is also indicative of the temperature of the cylinder liner and can be used as an alternative parameter by the electronic control unit <NUM>. Alternatively, the electronic control unit is in receipt of a signal from a temperature sensor <NUM> in the cylinder liner. Based on the temperature of the cylinder liners, or on a parameter representative thereof the electronic control unit <NUM> is configured to determine the optimal viscosity for the oil that is delivered to the cylinders.

Alternatively, the electronic control unit <NUM> determines directly from the parameter that is indicative of the cylinder liner temperature the required proportions of withdrawn system oil, TBN agent and viscosity agent.

The electronic control unit <NUM> is configured to determine the required viscosity for the oil that is delivered to the cylinders <NUM>. Hereto, the electronic control unit <NUM> is provided with an algorithm that determines the required proportions of withdrawn system oil, viscosity agent and TBN agent that results in a prepared oil in the blender <NUM> that has the determined optimal TBN value and the determined optimal viscosity. The electronic control unit <NUM> is configured to control the blender <NUM> and optionally the feed pumps that deliver the withdrawn system oil, the viscosity agent and the TBN agent respectively to deliver the appropriate amounts of respective fluid to the blender <NUM> and to blend or mix the appropriate amount of the respective fluids in the blender <NUM>.

The electronic control unit <NUM> is configured to recalculate the required proportions of system oil, viscosity agent and TBN agent when the temperature of the cylinder liner changes and/or when the sulfur content of the fuel changes and to control the blender <NUM> and the feed pumps of the withdrawn system oil, of the TBN agent and of the viscosity agent accordingly.

<FIG> illustrate a blender <NUM> according to an example embodiment. The blender <NUM> according to this embodiment is configured to blend a base oil with a TBN agent, i.e. this blender <NUM> is not configured to blend a viscosity modifier into the oil to be delivered to the cylinders <NUM>.

The blender <NUM> according to the embodiment of <FIG> is provided with two intake ports and one discharge port. The blender <NUM> is further provided with two intake conduits that connect to the respective intake port. The first intake conduit <NUM> is used to taking TBN agent, e.g. from conduit <NUM> that connects to the source <NUM> of TBN agent. A first electronically controlled valve <NUM> that is controlled by the electronic control unit <NUM> is placed in the first intake conduit <NUM>. In this example the first electronic control valve <NUM> is a pneumatically actuated electronic control valve, but any other electronically controlled valve could be used instead. The first intake conduit <NUM> connects to the aspiration conduit <NUM> of a pump <NUM>. Depending on the position of the first control valve <NUM> the intake of the pump <NUM> is connected to the source of TBN agent or not. The second intake conduit <NUM> is used to taking base oil from e.g. the used system oil conduit <NUM> that connects to the used system oil tank <NUM>. A second electronically controlled valve <NUM> that is controlled by the electronic control unit <NUM> is placed in the second intake conduit <NUM>. In this example the second electronic control valve <NUM> is a pneumatically actuated electronic control valve, but any other type of electronically controlled valve could be used instead. The second intake conduit <NUM> connects to the aspiration conduit <NUM> of the pump <NUM>. Depending on the position of the second control valve <NUM> the intake of the pump <NUM> is connected to the source of base oil or not.

The pump <NUM> is provided with a pressure sensor <NUM> at its intake side and a pressure sensor <NUM> at its outlet side. The pump <NUM> is driven by an electric drive motor <NUM> under control of the electronic control unit <NUM>. Preferably, the pump <NUM> is a fixed displacement pump driven by a variable speed drive motor. According to another embodiment, the pump <NUM> is a variable displacement pump. The outlet of the pump <NUM> is connected to an outlet conduit <NUM>. The outlet conduit <NUM> connects the outlet of the pump <NUM> to a third electronically controlled valve <NUM> that is under command of the electronic control unit <NUM>. The third electronic control valve <NUM> connects also to a discharge conduit <NUM> and to a first flexible conduit <NUM>. The discharge conduit <NUM> is intended to be connected to the feed conduit <NUM> via the discharge port for transporting the blended product (blended cylinder oil) from the blender <NUM> to the blended cylinder oil day tank <NUM>.

The blender <NUM> comprises a tank <NUM> that is provided with an outlet, an inlet and a vent <NUM>. The vent <NUM> opens to the ambient air around the tank <NUM>. The outlet of the tank <NUM> is connected to the aspiration conduit <NUM> via a second flexible conduit <NUM> and a restriction <NUM>. The restriction <NUM> is preferably a variable restriction. The inlet of the tank <NUM> is connected to the third electronically controlled valve <NUM> via the first flexible conduit <NUM>. The tank is provided with a low level sensor <NUM>, a high level sensor <NUM> and an overfill sensor <NUM>. The low level sensor <NUM> and the high level sensor <NUM> are connected to the electronic control unit <NUM>. The overfill sensor <NUM> is hardwired to cut off all electric power to the blender <NUM> upon activation.

The signal high level switch <NUM> will cause the electronic control unit <NUM> to shut down the pump <NUM> and all valves will go back to "OFF Mode" (no electrical signal to open any valves). The signal from the low level switch <NUM> will position the third electronic control valve <NUM> to connect the outlet conduit <NUM> to the first flexible conduit <NUM> (so some oil always will remain in the bottom of the tank <NUM> to prime the pump <NUM>).

The tank <NUM> is suspended from a frame <NUM> or other support by a weighing device. In an embodiment the weighing device comprises at least one load cell <NUM>. In the shown embodiment the weighing device comprises <NUM> load cells <NUM> that are supported by the frame <NUM> via a support structure <NUM>. The <NUM> load cell <NUM> are distributed under the tank <NUM> as indicated by the "+" signs in <FIG>, so that weight of the tank <NUM> is substantially equally distributed over the three load cells <NUM>. However, it is understood that a single load cell <NUM> can be sufficient, e.g. a single load cell placed centrally under the tank <NUM>. The load cell or load cell <NUM> having output that is representative of the weight on the load cell and the electronic control unit <NUM> is in receipt of the output of the load cells <NUM>, e.g. via signal cables. The tank <NUM> is not supported by any other elements except for the load cells <NUM>. In order to achieve this the conduits <NUM>,<NUM> that connect to the tank are flexible conduits that exert practically no force on the tank when it moves relative to the frame <NUM>.

The frame <NUM> has a cuboid outline and supports both the electronic control unit <NUM> and the tank <NUM> as well as the pump <NUM> piping and electronic first, second and third control valves <NUM>,<NUM>,<NUM> and the conduits (piping). The blender <NUM> with frame <NUM> forms a skid that can easily be transported and installed. The electronic control unit <NUM> is provided with a display screen <NUM>, and input means, such as a keypad or a touch function of the display screen <NUM>. The mass (weight) of the content of the tank <NUM> is measured by the weighing device, for example a weighing device including load cells.

<FIG> is a flowchart that illustrates an example embodiment of the operation of the blender <NUM>. The blender can be operated in several modes. One load is a manual mode and the other one is an automatic operation mode.

Before initiating a batch sequence in auto operation mode, the following blending parameters are to be entered in the electronic control unit <NUM> using e.g. the touch display:.

The program in the electronical control unit <NUM> will run the following sequences in automatic mode:.

The blender will run the exact same sequence as described above several times when a plurality of batches have been requested. When the requested amount of batches has been blended, the system will stop and wait for a new input by the operator.

The controller <NUM> is configured to use of the equation below for calculating the required blending proportion or ratio: <MAT> where.

The method of blending the cylinder oil for use in the cylinders of a large two-stroke compression ignited crosshead engine will be described with reference to the flowchart in <FIG>.

At the start of the procedure (block I), there is a content (e.g. from a previous blending operation) in the blending tank <NUM> that causes the liquid level in the blending tank <NUM> to be above the level of the low level liquid sensor <NUM>. If the controller <NUM> detects that the liquid level is below the low liquid sensor <NUM>, the controller will instruct electronic control valve <NUM> to open so that the first intake conduit <NUM> gets in fluid communication with the cylinder oil system conduit <NUM> to take in base oil from the used system oil tank <NUM> until the controller <NUM> receives a signal from the low liquid sensor that the liquid level is above the low level liquid sensor <NUM>.

The pump <NUM> is running at a constant speed throughout the intake, blending and discharge process. A first pressure sensor <NUM> at the pump inlet and a second pressure sensor <NUM> at the pump outlet provide the controller <NUM> with a signal corresponding to the inlet pressure and the outlet pressure of the pump, respectively.

At the start of the procedure the pump <NUM> takes in content from the blending tank <NUM> via the flexible tubing <NUM> and the restriction <NUM> and pumps the taken in content back to the blending tank <NUM> via the output conduit <NUM>, the third electronic control valve <NUM> and the flexible conduit <NUM>. Commercially available flexible hydraulic hoses or pipes are suitable to be used as a flexible conduit.

The controller <NUM> is configured to perform a calibration process wherein the controller records the output of the weight sensor <NUM> multiple times at intervals for a predetermined period of time, thereafter determines the average of the recorded outputs of the weight sensor, and (block III) thereafter stores the determined average as an initial weight of the tank <NUM> including its present content. This is done for calculating the start weight of the tank <NUM> including the present content in the tank in order to calibrate the weight (block II). Marine vessels unavoidably have various types of motion, such as the linear motions heaving, swaying and surging and the rotation motions pitch, roll and yaw, that may affect a momentary output of the weight sensor. The calibration is performed in order to avoid that motion of the marine vessel in which the blender could be installed affects the recorded initial weight of the tank <NUM> inadvertently. This can be achieved by performing multiple measurements of the output of the weight sensor over a given period of time that is sufficiently long to include a plurality of motions of the marine vessel and by averaging out the recorded output. The motion of a large marine vessel is relatively slow and therefore the given period of time needs to be relatively substantial, i.e. at least one minute and preferably several minutes. Preferably, the weight measurements are recorded at regularly spaced intervals, preferably several times per second.

When the initial weight of the blending tank <NUM> in its initial content have been calibrated or "zeroed", the controller <NUM> initiates the intake of base oil (block IV) by commanding the second electronic control valve <NUM> to move to its open position. When taking in base oil the first electronic control valve <NUM> is closed, so that only base oil is taken in.

The controller <NUM> calculates the amount (weight) of base oil that needs to be taken in in order to produce a requested amount (as e.g. selected by an operator) of blended product. The controller <NUM> instructs the second control valve <NUM> to move to its open position to initiate the intake of base oil. This will allow the pump <NUM> to aspirate the base oil via the aspiration conduit <NUM> that is now connected to the second intake conduit <NUM>. During the intake of the base oil the controller <NUM> monitors the weight of the blending tank <NUM>, and when the weight increase of the blending tank <NUM> has reached <NUM>% (or another selected major portion of the weight to be taken in) of the amount (weight) that was calculated to be taken in, the controller <NUM> terminates the intake of base oil by instructing the second electronic control valve <NUM> to move to its closed position (block V). A major portion of the calculated amount of base oil is taken in instead of the full amount in order to avoid that too much base oil is taken in due to measuring errors which cannot be completely avoided when the blender <NUM> is installed on a marine vessel due to the marine vessel's motion, and in view of the fact that it is easier to add more base oil or additive when an insufficient amount of either component has been added whilst it is impossible to add more product to the blending tank <NUM> than it can hold.

Next (optionally), the controller <NUM> verifies the weight increase of the blending tank <NUM> during intake of the base oil to thereby accurately determine the weight of the base oil that has been added to the blending tank <NUM>. On the basis of the amount (weight) of base oil that has been taken in the controller <NUM> calculates the amount (weight) of component (TBN agent) that needs to be taken in in order to arrive at the determined or calculated weight ratio (blending ratio) (block VI).

Thereafter, the controller initiates the intake of the composition with the second TBN, such as a TBN agent, from the source of TBN agent, such as the tank <NUM> by instructing the first electronic control valve <NUM> to move to its open position to thereby allow the pump <NUM> to aspirate the composition from the source of composition via the first intake conduit <NUM> and conduit <NUM> (block VII). The controller <NUM> monitors the weight increase of the blending tank <NUM> during the intake of the component. When the weight increase of the blending tank <NUM> corresponds to <NUM>% (or another selected major portion of the calculated amount) of the calculated amount (weight) of the component to be taken in, the controller terminates the intake of the component by instructing the first electronic control valve <NUM> to move to its closed position.

In the next step (block VII) the controller <NUM> optionally verifies the weight of the component that has been taken in. The controller <NUM> has monitored the process of taking in the base oil and taking in the component and associated all actions with a timestamp. Based on these timestamps the controller <NUM> determines the length of time that was used to take in the component, and based on the weight of the component that has been taken in the controller determines the average flow rate during intake of the component (block IX). Further, the controller <NUM> determines the difference between the actually taken in amount of component and calculates the to be taken in amount of component. If the intake process of the component was measured and controlled <NUM>% accurately the remaining amount of composition to be added should be <NUM>% if it was planned to take in <NUM>% from the start. However, if for any reason more or less component was taken in during the intake process, the controller can in this step compensate for such an error. Based on this difference in amount (weight) the controller determines the length of the intake time (pump running time with the inlet of the pump connected to the source of component) in order to taking the calculated amount of component to be taken in. Next, (block X) the controller <NUM> instructs the first control valve <NUM> to move to its open position for length of time corresponding to the determined length of time so that the remaining portion of the amount of component that was calculated to be taken in is added to the blending tank <NUM>.

During the next phase of the process (block XI) the first electronic control valve <NUM> and the second electronic control valve <NUM> are in their closed position and the third electronic control valve <NUM> is in its position where it connects the outlet conduit <NUM> to the first flexible conduit (pipe) <NUM>. Thus, the pump <NUM> will aspirate content of the blending tank <NUM> via the second flexible conduit (pipe) <NUM>, via the restriction <NUM> and pump the aspirated tank content back to the tank via the outlet conduit <NUM>, the third electronic control valve <NUM> and the first flexible conduit <NUM>. Thus, content from the blending tank <NUM> is circulated and thereby blended. The inlet of the tank <NUM> that is connected to the first flexible conduit <NUM> is provided with a hold that creates a liquid jet into the blending tank <NUM> to further enhance blending of the conduit of the tank. In a preferred embodiment the inlet of the blending tank <NUM> is connected to a pipe <NUM> that extends into the blending tank <NUM> and this pipe <NUM> is provided with a plurality of holes that are arranged to create a plurality of differently directed liquid jets into the blending tank <NUM> to further enhance the blending process.

The controller <NUM> determines the length of time in which the content of the blending tank <NUM> is circulated. This length of time can be based on an algorithm or on a lookup table and depend on the characteristics of the oil and composition to be blended, as well as on temperature of the content of the blending tank <NUM>. Optionally, the controller <NUM> performs a final verification of the weight of the blend product on the basis of the signal from the weight sensor.

When the content of the blending tank <NUM> has been circulated and blended for a sufficiently long time, the controller <NUM> instructs the third control valve <NUM> to move to the position where the outlet conduit <NUM> connects to the discharge conduit <NUM>, to thereby discharge the content of the blending tank <NUM> via the discharge conduit <NUM> (block XIII). The discharge conduit <NUM> can be connected to the feed conduit <NUM> so that the content of the tank is discharged to the cylinder oil day tank <NUM>. This ends the blending process. It is of course understood that the controller <NUM> can be programmed to run several batches sequentially, as e.g. instructed by an operator.

The high level switch <NUM> is operably connected to the controller <NUM> and the high level switch is configured to issue a high-level signal when the liquid level in the tank <NUM> exceeds a first level limit. The high level limit my e.g. be <NUM>% of the total volume that can be held in the tank before it flows over via the vent <NUM> and an overfill limit can e.g. be <NUM>% of the total volume. The controller <NUM> is configured to prevent intake of content to the blending tank <NUM> when the controller <NUM> receives a high level signal from the first high level switch. The overfill switch <NUM> is configured to detect that the liquid level in the tank exceeds a second level limit that is higher than the first level limit. The overfill <NUM> switch is hardwired to cut power to the blender <NUM> when the overfill switch <NUM> detects that the liquid level in the blending tank <NUM> is above the second level limit. The controller <NUM> is configured to terminate operation of the blender <NUM> when the high level switch <NUM> has detected that the liquid level in the blending tank <NUM> is above the first level limit threshold.

The blender <NUM> comprises a safety circuit (not shown) that is independent from the controller <NUM>, the safety circuit including the hardwiring to cut electrical power to the blender <NUM> when the overfill switch <NUM> has detected that the liquid level in the blending tank <NUM> is above the second level limit.

In an embodiment the controller <NUM> is configured to take in an amount by weight of the oil before taking in an amount by weight of the composition, and the controller <NUM> is further being configured to obtain or determine a weight blending ratio for the oil and the composition. The controller (<NUM>) is configured to determine the weight of the oil in the tank <NUM> after taking in the oil, and the controller <NUM> is configured to determine the amount by weight of the composition that needs to be added to the amount by weight of oil determined to be in the tank <NUM>, and the controller <NUM> is configured to determine if the total amount of content in the tank <NUM> by weight or volume will cause the liquid level to exceed the first level limit when the determined amount of composition is added to the oil in the tank. The controller <NUM> is configured to take in the determined amount of composition only when the determined total amount does not exceed the first level limit.

In an embodiment the controller <NUM> is configured to terminate operation of the blender <NUM> when a weight change measured with the weight sensor <NUM> does not correspond to an expected weight change. For example, when the weight of the tank <NUM> and its content does not increase during intake of oil or during intake of the component or during discharge of the content of the tank <NUM>, the controller will issue an alarm and stop the blending procedure and/or shut down the blender.

In an embodiment the controller <NUM> is configured to verify that the overfill switch <NUM> is tested at regularly spaced intervals, e.g. monthly. The controller <NUM> is configured to prevent initiation of operation of the blender <NUM> if the overfill switch is not tested at the end of an interval.

The low level switch <NUM> is configured to detect that the liquid level in the tank is above a third level limit that is lower than the first level limit. The third level limit can e.g. be at a level that corresponds to <NUM>% of the maximum volume that can be held inside the tank, and the controller <NUM> is configured to allow operation of the blender <NUM> after a high level switch activation and/or an overfill switch activation only after receiving a signal from the low level detector that the liquid level in the tank has fallen below the third level limit. The overfill sensor <NUM> can be provided at an upper region of the tank (<NUM>) or at the vent <NUM>.

<FIG> is a diagram showing a blender according to another example embodiment, that is essentially the same as the embodiment described with reference to <FIG>, except that in this embodiment there is a third intake conduit <NUM> for the intake of a third composition into the blending tank <NUM>. Hereto, the third intake conduit <NUM> is connected with one end to a third inlet port and with its other end to the aspiration conduit <NUM>. The third inlet port can be connected to e.g. a source of viscosity agent, such as the tank <NUM> with a viscosity agent. A fourth electronic control valve <NUM> under command of the controller <NUM> is placed in the third intake conduit <NUM>. The controller <NUM> is configured to take in the viscosity agent either before or after taking in the TBN agent. The amount of viscosity agent taken in is controlled by the controller <NUM> monitoring the weight increase of the blending tank <NUM> whilst the forth electronic control valve <NUM> is in its open position. The controller <NUM> determines the amount of viscosity agent to be taken in as indicated here above. The controller <NUM> is also configured to ensure blending of the compositions that are taken into the blending tank <NUM> after all of the components have been taken in by allowing the content of the blending tank <NUM> to circulate through the circulation circuit established between the inlet and the outlet of the blending tank <NUM>, via the first and second flexible conduit, the restriction <NUM>, the pump <NUM> and the third electronic control valve <NUM>. The controller determines the length of the time for circulating the basis of an algorithm that takes account of the amount of components taken in, in particular the total amount of all the components that have been taken in. The controller <NUM> can also be configured to provide for a first blending phase after two compositions have been taken in and a second blending phase after all three components have been taken in. After the blending process has been completed, the controller <NUM> will verify the total amount of blended product and the range discharge of the blended product via the discharge conduit <NUM> by changing the position of the third electronic control valve <NUM>.

According to another embodiment (not shown) the blender has only a single intake conduit with an electronic control valve and the selection of the appropriate composition to be taken in is done upstream of the inlet port at the start of the intake conduit. The construction of the blender according to this embodiment is essentially identical to the embodiment shown in <FIG>, except for the absence of the second intake conduit <NUM> and its electronic control valve and the of course adapted configuration of the controller. In this embodiment, an operator or an external signal will indicate to the controller <NUM> whether a <NUM>st, <NUM>nd and <NUM>rd or other composition is being supplied from the exterior of the blender to the inlet port of the <NUM>st intake conduit <NUM>.

In manual mode the steps described above can be controlled directly by an operator, but otherwise the process is essentially identical to the automatic mode.

In an embodiment the blender for batch blending an oil having a first TBN with a composition having a second TBN that is higher than the first TBN to produce a blended composition with a desired third TBN for use as a cylinder oil in a two-stroke compression ignited crosshead combustion engine, the blending apparatus comprises:.

The invention has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. A single processor, controller, control unit or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claim 1:
A blender (<NUM>) for batch blending an oil having a first total base number -TBN-with a composition having a second TBN that is higher than the first TBN to produce a blended composition with a desired third TBN for use as a cylinder oil in a two-stroke compression ignited crosshead combustion engine (<NUM>), the blender comprising:
- a tank (<NUM>) for containing at least one of the oil having the first TBN and the composition having the second TBN,
- a weight sensor (<NUM>) operably coupled to the tank (<NUM>) and configured to produce an output indicative of the weight of the tank (<NUM>) and a content of the tank (<NUM>), and
- a controller (<NUM>) configured to receive the output from the weight sensor (<NUM>),
- the controller (<NUM>) being configured to perform a calibration process wherein the controller (<NUM>) is configured to record the output of the weight sensor (<NUM>) multiple times at intervals for a predetermined period of time, to determine an average of the recorded outputs of the weight sensor (<NUM>), and to store the determined average as an initial weight of the tank (<NUM>).