Morrell C-model - Revision history

Alex Doll: /* Model Outputs */

2025-09-15T13:47:59Z

Model Outputs

← Older revision		Revision as of 13:47, 15 September 2025
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	==Model Outputs==		==Model Outputs==
	The published version of this model provides power measured at the '''motor input''' of an induction motor driving a gearbox on a geared mill. This motor input is immediately converted to '''mill shell power''' for use in circuit model equations by multiplying the model result by 0.97 mechanical efficiency factor and by 0.96 typical induction motor efficiency factor.		The published version of this model provides '''electrical''' power measured at the '''motor input''' of an induction motor driving a gearbox on a geared mill. This motor input is immediately converted by the software to '''mill shell mechanical power''' for use in circuit model equations by multiplying the model result by 0.97 mechanical efficiency factor and by 0.96 typical induction motor efficiency factor. Steve Morrell was known to use a lot of African and Australian mills in his model calibration, and these mills are overwhelmingly induction drives with gearboxes, which are assumed to average efficiency values of 0.97 and 0.96 for mechanical and electrical power, respectively.

	The displayed Morrell C-model result in sagmilling.com is always corrected to '''mill shell power'''.		The displayed Morrell C-model result in sagmilling.com is always corrected to '''mill shell power'''.

Alex Doll: /* Model calibration */

2025-09-15T13:45:11Z

Model calibration

← Older revision		Revision as of 13:45, 15 September 2025
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	==Model calibration==		==Model calibration==
	Alex Doll did a model calibration check of several SAG mill power draw models (including the C-model for SAG milling) in Procemin 2013 and IMPC 2016. The model deviation from measurements has a standard deviation of 9% and average/median of 1.1%/1.5% (meaning there is a ~~minor~~ bias ~~high~~).		Alex Doll did a model calibration check of several SAG mill power draw models (including the C-model for SAG milling) in Procemin 2013 and IMPC 2016. The model deviation from measurements has a standard deviation of 8% and average/median of 0.3%/-0.4% (meaning there is no meaningful bias).

	These works are available from:		These works are available from:

Alex Doll: /* Model Outputs */

2025-09-15T13:41:12Z

Model Outputs

← Older revision		Revision as of 13:41, 15 September 2025
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	The displayed Morrell C-model result in sagmilling.com is always corrected to '''mill shell power'''.		The displayed Morrell C-model result in sagmilling.com is always corrected to '''mill shell power'''.

			==Model calibration==
			Alex Doll did a model calibration check of several SAG mill power draw models (including the C-model for SAG milling) in Procemin 2013 and IMPC 2016. The model deviation from measurements has a standard deviation of 9% and average/median of 1.1%/1.5% (meaning there is a minor bias high).

			These works are available from:
			<li>[https://www.sagmilling.com/articles/20/view/Procemin2013-AlexDoll-SAGPowerModels.pdf?s=1 Technical paper for Procemin 2013]
			<li>[https://www.sagmilling.com/articles/29/view/IMPC2016-AlexDoll-SAG%20data%20set.pdf?s=1 Technical paper for IMPC 2016] (supersedes the Procemin 2013 paper)
			<li>[https://www.sagmilling.com/articles/25/view/SurveyTabulation-IMPC2016-v6.ods?s=1 Data set for IMPC 2016]

Alex Doll at 13:32, 15 September 2025

2025-09-15T13:32:04Z

← Older revision		Revision as of 13:32, 15 September 2025
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	This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.		This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.

	The simplest explanation of the model is that it is a friction balance between concentric layers within a moving mill charge which is used to calculate the torque experienced by the mill due to the charge geometry. The model contains several sub-equations that govern the charge geometry and is too complicated to explain here. People seeking more information should buy the book ''Mineral Comminution Circuits, Their Operation and Optimisation'' from JK Tech: ~~http~~://~~www~~.~~jktech~~.~~com~~.au/~~mineral-comminution-circuits~~ .		The simplest explanation of the model is that it is a friction balance between concentric layers within a moving mill charge which is used to calculate the torque experienced by the mill due to the charge geometry. The model contains several sub-equations that govern the charge geometry and is too complicated to explain here. People seeking more information should buy the book ''Mineral Comminution Circuits, Their Operation and Optimisation'' from JK Tech: https://smi.uq.edu.au/jkmrc/monographs?p=3#3 .

	==Model Inputs==		==Model Inputs==

Alex Doll: /* Model Inputs */

2016-06-17T23:01:11Z

Model Inputs

← Older revision		Revision as of 23:01, 17 June 2016
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	* pulp percent solids		* pulp percent solids
	* mill speed		* mill speed
	* sphere packing geometric factor J<sub>void</sub>
	* liner effective thickness		* liner effective thickness
	* cone end angle		* cone end angle
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	* Motor efficiency and any other efficiency factors to the DCS measurement position in the network.		* Motor efficiency and any other efficiency factors to the DCS measurement position in the network.
	* Motor rated speed, in units of mill RPM (not motor RPM, must multiply by gear ratios).		* Motor rated speed, in units of mill RPM (not motor RPM, must multiply by gear ratios).
			* Quantity of pinions (and motors)

	==Model Outputs==		==Model Outputs==

Alex Doll: /* Model Inputs */

2016-06-17T22:56:36Z

Model Inputs

@@ Line 10: / Line 10: @@
 The same underlying model is used for SAG and ball milling, with minor differences for the way the charge density is calculated and whether the mill is a grate discharge (most of the SAG mills) or overflow discharge (typically a ball mill).
-Within the classification, there are also two versions of the Morrell C-model, the "simplified" model where only the major inputs are requested from the user and the "full" model where all possible inputs are available.
+Within the classification, there are also two versions of the Morrell C-model:
 * mill effective grinding length
 * ball load
 * pulp percent solids
 * mill speed
 * sphere packing geometric factor J<sub>void</sub>
 * k-factor, empirical conversion of "net power to gross power" (1.26)
 ==Model Outputs==

Alex Doll: /* Model Inputs */

2015-05-14T17:05:54Z

Model Inputs

← Older revision		Revision as of 17:05, 14 May 2015
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	* cone end angle (only full model, simplified: 30° for SAG and 15° used for ball mill)		* cone end angle (only full model, simplified: 30° for SAG and 15° used for ball mill)
	* trunnion diameter (only full model, fraction of mill diameter used for simplified)		* trunnion diameter (only full model, fraction of mill diameter used for simplified)
	* k-factor, conversion of "net power to gross power" (1.26)		* k-factor, empirical conversion of "net power to gross power" (1.26)

	==Model Outputs==		==Model Outputs==

Alex Doll at 16:37, 1 May 2014

2014-05-01T16:37:16Z

← Older revision		Revision as of 16:37, 1 May 2014
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	[[category:Models]]		[[category:Models]]
	[[category:Mill power draw models]]		[[category:Mill power draw models]]
			Applies to both SAG and ball mills, with variants for grate-discharge and overflow mills.

	This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.		This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.

Alex Doll: /* Model Outputs */

2014-05-01T16:29:01Z

Model Outputs

← Older revision		Revision as of 16:29, 1 May 2014
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	==Model Outputs==		==Model Outputs==
	~~Power~~ measured at the motor input of an induction motor driving a gearbox on a geared mill. This motor input is immediately converted to mill shell power for use in equations by multiplying the model result by 0.97 mechanical efficiency factor and by 0.96 typical induction motor efficiency factor.		The published version of this model provides power measured at the '''motor input''' of an induction motor driving a gearbox on a geared mill. This motor input is immediately converted to '''mill shell power''' for use in circuit model equations by multiplying the model result by 0.97 mechanical efficiency factor and by 0.96 typical induction motor efficiency factor.

			The displayed Morrell C-model result in sagmilling.com is always corrected to '''mill shell power'''.

Alex Doll at 04:59, 7 February 2014

2014-02-07T04:59:28Z

← Older revision		Revision as of 04:59, 7 February 2014
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			[[category:Models]]
			[[category:Mill power draw models]]
	This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.		This model was developed as part of the PhD thesis of Stephen Morrell at the University of Queensland and is the model used in the JK SimMet software for determining mill power draw. It is described as the "C-model" and should not be confused with the more empirical "D-model" that has a form similar to the Loveday equation.