PPS Lab 2 - Purifier Optimization

License help for Canadian engineers

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Propulsion Plant Simulator, Level One
British Columbia Institute of Technology
Pacific Marine Training Campus
Version 1 by: Martin Leduc, July 1998
Version 2 by: Myles OBrien, Sept 2002

Persons wanting to obtain the Canadian marine engineering license, or chief endorsement, need to complete the PPS L1 and L2 courses, in which they will have to carry out five labs. These are results for one lab for your comparison. Findings are based on observation carried out and graphs not all presented here.

 

Purifier Optimization
Lab 2 - Version 1

Introduction

This lab was performed to study of the relationship between lube oil temperature, gravity ring, and pump flow. These factor can be altered to optimize the purifier’s efficiency.

Method of investigation

Procedure . The procedure set forth in the PPS Level 1 Course booklet were followed, they consisted of these steps: Cycling through each parameter to record the optimum setting for them.

Results

Equipment Used. The equipment used for this experiment was the Nor Control PPT2000-M22MAK workstation. The simulated ship is Ro/Ro Passenger Vessel. Two medium speed MAK engines drive Controllable Pitch Propeller. A shaft generator is driven by the port main engine. The ship has two service generators they serve a common bus.

Data. The parameters were recorded by the program’s ‘pen recorder’. The accompanying graphs, Appendix 01, 02, & 03, illustrates the lube oil purifier behavior while undergoing change of; Gravity ring: Appendix 01, Temperature: Appendix 02, and Pump flow: Appendix 03.

Analysis of Results

From the results on the individual graphs (not supplied here), we observe that when :

  1. Flow rate is set at 45% and the temperature is set at 86C, the optimum setting for the gravity ring is about 25%.Furthermore we can observe the continued increase of the gravity ring results in high amount of ‘good oil’ being discarded. The dirt index diminished, meaning the dirt expelled from the oil was less.

  2. When the temperature is gradually increased from 75C to 90C. The pump flow remains constant at 45%, and the gravity ring is being set 25% The optimum setting seems to be about 85C, where dirt is still being expelled, yet ‘good oil’ waste is being kept to minimum.

  3. With flow rate variation. The ideal flow rate setting of this particular setup, gravity ring at 38% and temperature at 86C, is about halfway through it’s cycle , or 50%.

Conclusion

The ideal setting for any purifier depends on many variables. For lube oil purification, as a rough guide, a setting of 50% for flow rate, 25% gravity ring, and a temperature of 85C would provide a good base for initial operation. Further adjustment should be made as required.

Purifier Optimization
Lab 2 - Version 2

 

Objective of Lab: To investigate the factors affecting the operation and efficiency of lubricating oil purification.

The Lube Oil Purification System is printed on print out #3.  For diagram purposes the sensors tracked on the pen recorder have been numbered as follows;

Description

Line color

Reference #

Relationship

L/O Purifier Suction Line Flow

Red

#1

Feed pump setting

L/O Purifier Heater Outlet Temp

Dark Yellow

#2

 

L/O Purifier Gravity Ring (100 max. dia.)

Green

#3

 

L/O Purifier Waste Flow

Magenta

#4

 

L/O Purifier Sludge Flow Oil Index

Blue

#5

% of oil lost in #4

L/O Purifier Outlet Flow Dirty Index

Black

#6

% of dirty oil in #1

Objective of Exercise #1: To examine the affects of varying the gravity ring of an operational purifier.

Set up for Exercise #1: The Lube Oil Purifier is set up with a feed pump flow rate of 45% and lube oil heater set at 860C . The Gravity ring is initially set at 25% and slowly increased to 100% or when the purifier losses a seal.

Observations for Exercise #1: Refer to Pen Recorder print out #1 for exercise #1.

  1. As Gravity Ring value increased (Green Line), Outlet Flow Dirty Index (black line) decreased due to cylindrical water/oil interface moving away from the center of the bowl. The diagram below shows the initial condition, at the beginning of exercise #1, with a small gravity ring setting resulting in dirty oil flow on the outlet side of the purifier.

  1. As the Gravity Ring continues to increase and pass through 54%, the Sludge Flow Oil Index (blue line) began to increase dramatically. This is also due to the cylindrical water/oil interface moving away from the center of the bowl. The diagram below shows this condition, with a large gravity ring setting, resulting in oil flow being lost to the waste side of the purifier.

  1. As the Gravity Ring continues to increase and pass through 56%, the Total Waste Flow (magenta line) begins to escalate.

  2. Finally, the purifier losses the water seal at about 59%. At this point Total Waste Flow, Sludge Flow Oil Index and Outlet Flow Dirty Index skyrocket due to the lost water seal. Now there is no purifier effect and at best the bowl is clarifying the Lube Oil as shown below.

Conclusions for Exercise #1: The largest diameter gravity ring with out breaking a seal should be used. As well, we want to keep Outlet Flow Dirty Index and Sludge Flow Oil Index to a minimum (preferably under 0.50%). According to the Pen Recorder print out we begin to see a rise in Sludge Flow Oil Index at about 54% (indicated by cross hairs) and the water seal was lost at 59%. Due to the sharp increase in Sludge Flow Oil Index in relation to the Gravity Ring setting it would not be advisable to use a gravity ring setting more than 54%. Therefore the optimal gravity ring setting would be 53.5%.

 

Objective of Exercise #2: To examine the affects of varying the flow rate of an operational purifier.

Set up for Exercise #2: The Lube Oil Purifier is set up with a gravity ring setting of 53.5% (exercise #1) and the feed pump flow rate initially set at 20%. The feed pump flow rate is slowly increased to 70%. Lube oil heater set at 860C

Observations for Exercise #2: Refer to Pen Recorder print out #2 for exercise #2.

1.  As feed pump flow rate increased, so did Outlet Flow Dirty Index. This is due to the increased volume of oil passing through the purifier. The higher the volume (through-put), the less time available for particles to move to the edges of the bowl and separate from the oil. Also, since the oil is flowing towards the center of the bowl, the particles must overcome the forces exerted by the flow of oil. The result is a higher percentage of dirty oil on the outlet side of the purifier. This is evidenced on the pen recorder print out by the black line increasing steadily across the chart.

2.  As feed pump flow rate increased, so did Total Waste Flow. This is also due to the increased volume of oil passing through the bowl yet not as evident until very high flow rates were achieved. With increased flow rate, come increased particles, which partially accounts for this affect. As well, observation #3 also accounts for this increase. This is evidenced on the pen recorder print out by the magenta line increasing in the last 1/3 of the chart.

3.  As well, with the increased Flow rate and increased Total Waste Flow, an increased Sludge Flow Index was observed way across the chart. A larger percentage of oil is lost through the outlet side due to flow rate and density. Because of the high volume, there is less time available for particles to move to the edges of the bowl. Also, since the oil is flowing towards the center of the bowl, the particles must overcome the forces exerted by the flow of oil. Time in the bowl is a factor of separating foreign objects and liquids with different densities. The less time in the bowl, exposed to centrifugal force, the less separation that takes place.  The result is oil lost through the waste side of the purifier.

4.  The Lube Oil purifier in this particular plant employed in a continuous by-pass system. The continuous by-pass system is usually used for engines with a forced lubricating oil system (MaK plant) where large quantities of oil are circulating very quickly. With this, oil deteriorates continually and the amount of time oil spends in the bowl is an important factor as shown in the diagram on the next page; 

A.  Too low of a flow rate will produce good quality oil in the centrifuge outlet. But the generated contaminants will cause impurities to build up in the system due to a longer period of time between cycling the oil through the purifier.

B.  Too high of a flow will produce a poor quality oil in the centrifuge outlet. As well, impurities will build up in the sump.

C.  Too low of a flow rate will produce good quality oil in the cThere is an optimum balance of flow to impurities that can only be found by trial and error. Make an adjustment and test the oil for impurities.

Conclusions for Exercise #2: If a purifier is employed in a DFO system or HFO system, the demand for flow rate can be determined by the consumption of fuel oil. As long as the flow rate of the purifier is above the consumption rate of the system, the likelihood of consuming poor quality fuel is minimized. For a purifier employed in a Lube Oil system there is little or no consumption. Therefore, to determine the demand rate the following formula is used;

When this formula is put to work for the MaK plant 2000 liters is used for engine sump. The result is 375kg/h. On the pen recorder print out this can be seen plotted at about 42% (linear scale for all monitoring points). As well, at this point in time the Outlet Flow Dirty Index, Sludge Flow Oil Index and Total Waste Flow are at minimum levels. Therefore, in order to maintain an oil cycle of 2.5 times per engine sump, 375kg/h would be the correct flow rate setting to use.

 
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