Introducing lubricity in pumping of low sulfur marine fuels
I have in an earlier blog post written about the impact of the new regulations for SOx emissions in the maritime industry. In that post I mentioned that the low viscosity of the marine diesel oil (MDO) or marine gas oil (MGO) fuel required in certain ECA (Emission Controlled Area) could adversely impact the operation of fuel pumps. There is another aspect of these low sulfur fuels that shipowners need to consider. It is the fuel’s lubricity.
In general, lubricity of marine fuels has not been discussed in the past because it has not been relevant to marine pumps; however, as low-sulfur MDOs and MGOs are now entering the market, the lubricating properties of fuels are becoming more important.
Low sulfur fuels were first introduced in Sweden & California in the early 90´s for use in trucks in cars. At first the effects on engines and fuel injection equipment was not recognized. After approximately 5000km of operation on the low sulfur diesel, failures of rotary injection pumps started to be reported because the fuels did not provide enough lubrication between the moving parts. . World-wide 65 million pumps were affected. The outcome of that massive problem was the need to measure the Lubricity of fuels using the HFRR (High Frequency Reciprocating Rig) value.
Now fast forward to your ship or your fleet. You need to know that the lubricity of the low sulphur MGO or MDO because it will have an important effect on the life of your engines. The three screw pump or gear pump typically used in fuel forwarding applications aboard ship are supposed to work under “full film” running condition. This means the moving parts (like the rotors turning inside the bore of a three screw pump) are separated from each other by an oil film, carrying the load. To achieve a “full film” condition, the pump needs to run with relatively high speed and the fluid needs to have a relatively high viscosity to carry the radial forces. Furthermore, the radial forces will increase with a higher differential pressure. In order to find out if “full film” condition is fulfilled, a Sommerfeld number can be calculated. A higher Sommerfeld number means a stronger oil film which is good for the long term life of the pump.
However, when a three screw pump or gear pump operates with light fuels, the Sommerfeld number is sometimes not high enough to fulfill the “full film” condition. The pump is said to “operate in the boundary zone”. That means the moving parts are not separated by a film and consequently some level of metallic contact will take place causing wear. When the pumps are operating in this boundary zone, the lubricity of the fuel is important. The lubricity of the fuel is measured as a HFRR (High Frequency Reciprocating Rig) number with the unit "microns", where a higher number means less lubricity.
The revised ISO 8217 standard for these low sulfur fuels that is likely to come in to force on July 1, 2010 will stipulate a max HFRR value of 520. To avoid following the same path as the automotive industry a number of tests have been executed and our studies indicate that there is sufficient lubrication for the pumps to perform. Our three screw pumps (Imo and Allweiler) to operate effectively with the new fuels. If you are not using our pumps aboard your vessels, you may want to check with the pump manufacturer to ensure that your ships will operate safely.
Jon Berggren
Market Manager - Commercial Marine
Anti-Heeling – optimized cargo handling
The Anti Heeling System enables optimized & continuous loading or unloading for container vessels or similar ships in
a much reduced time. Normally, the heeling compensation is automatically achieved by continual measurement of the heeling angle. However, when unloading under tough conditions such as off an offshore supply vessel, the heeling system has to be manually operated. Under those conditions a reliable and fast responding system is of high importance. Today Colfax offers an anti-heeling pump ALLTRIMM® with enhanced capacity as a part of the solution for the application.
This in-line propeller pump contains reversible hydraulics. Its electric motor with enhanced power is integrated into the pump lobe and is designed by standard parts from a German manufacturer. As a result, the pump requires neither a costly valve controller nor a coupling and a transmission.
ALLTRIMM® is available in a single or a twin-stage version with a flow range of 300 to 1200m3/hour and a pump head of 10 meters (single stage) to 20 meters (twin stage; as shown in the picture). Two motor sizes cover the above-mentioned performance range. The sectional drawing depicts the twin-stage version. For more information please click here
Jon Berggren
Market Manager – Commercial Marine
Reliable leakage detection for mechanical seals
To operate properly, every mechanical seal requires a lubricating film between the sliding surfaces. 
This film is formed by the pumping medium itself. Elevated pressure inside the inlet chamber continuously pushes a small amount of lubricant out through the sliding surfaces. Colfax recently introduced a smart leakage detection system for precise monitoring called ALLSEAL.
A coupling bracket captures the standard leakage escaping from the pump. The optoelectronic sensor ALLSEAL with an infrared LED and a light receiver is located in the bracket wall. Light from the LED is directed from inside to the sensor‘s prism tip and is reflected from there to the light receiver. If the standard leakage in the coupling bracket reaches the fixed maximum, it will enclose the prism tip. So light reaches the light receiver not at all or only faintly. ALLSEAL reacts to this change immediately with a switching operation.
Trouble-free cost reduction.
The absence or insufficient formation of the lubricating film leads to defective mechanical seals and thus costly pump failures. The ALLSEAL maintenance indicator will warn you on time about the condition of your pump. Thus, you will have enough time to avoid serious pump failures by using a combined emergency stop controller.
Benefits:
- Very cost effective smart solution for monitoring a mechanical seal
- Unnecessary and unplanned system downtimes can be avoided
- No environmental contamination
- Compliance with safety regulations (e.g. SOLAS)
for more information click here
Jon Berggren
Market Manager – Commercial Marine
SOx emission regulation – impact on fuel supply pumps
Since May 2005, specific environmentally friendly MARPOL regulations stipulate that emissions from main and auxiliary machinery must be kept within specific limits. They require, for instance, reduction of sulphur oxide combinations (SOx), carbon dioxide (CO2) and nitrogen oxide combinations (NOx).
The subsequent EU Marine Fuel Sulfur Directive defines Emissions Control Areas (ECAs) slightly differently. Ships at berth in European ports for more than 2 hours are only allowed to operate on fuels of max 0,1% sulfur content .
In reality this means that the ship will have to switch to low sulphur distillate fuel oil (marine gas oil or MGO) when entering a European port. Switching to MGO means that viscosity will dramatically fall when compared to traditional heavy fuel oils such as number 6 diesel used on most commercial vessels. In some cases, MGO fuels will have a viscosity as low as 1,2 – 2,0 cSt. This low viscosity fuel is not ideal for positive displacement pumps, particularly gear pumps. However, the Colfax positive displacement screw pumps from IMO and Allweiler have been tested and are capable of handling the low sulfur MGO quite well. Shipowners need to consider the impact of this fuel change on their existing fleet and new shipbuilds.
One of the world’s largest tanker operators, which operates and maintains 100 vessels, chose the IMO OptiLine pumps in order to secure his fleet, not only for existing but also for future legislations. Please see case study here!
Jon Berggren
Market Manager – Commercial Marine