Finish Grinding Ball Mill Interlocks-v0.0

FINISH GRINDING BALL MILL - CONTROL LOOPS V0.0 Controlled Parameter

Actuator

Target

Mill Fresh Feed

Optimisation of the production and specific power reduction

Operator to set the setpoint for the elevator power. Fresh feed to mill can be optimized based on Elevator power. To avoid over filling of mill, fresh feed is reduced based on Mill sound level and mill power indications

Mill Fresh Feed

Optimisation of the production and specific power reduction

Operator to set the set point for Total Mill Feed (Fresh Feed + Rejects). Fresh feed to mill can be optimized based on Separator Rejects. To avoid over filling of mill, fresh feed is reduced based on Mill sound level and mill power indications. Separator Rejects measurement is required. NOTE:- Either Total Mill Feed Loop or Mill Outlet Bucket Elevator kW Loop could be used.

Separator fan Variable Speed Drive or adjustable Damper

Ensure a constant quality of classification (for a constant feeding of classifier)

Constant air flow through the separator is maintained by keeping the power of separator fan at predetermined level by varying the fan speed or adjustable damper.

Separator Inlet Pressure (for plants having recirculation duct)

Adjustable Damper in Recirculation Duct

Allow complementary flow from recirculation

To maintatin constant separator inlet pressure by varying the adjustable damper in the recirculation duct.

Separator Outlet Temperature

Fresh Air Adjustable Damper

To reduce cement temperature

To avoid dehydration of gypsum in silo and maintatin cement temperature of 70°.

Separator Variable Speed Drive

Constant product fineness

Mill Outlet Bucket Elevator kW

Total mill feed (Fresh feed + separator rejects)

Separator Air Flow

Final Product Fineness

Comments

Separator motor speed is set to optimum value by operator to maintain required product fineness or could be a control loop for mills having online lazer particle size analyzer.

Water spraying is a worst case cenario if other means of temperature control are not sufficient! First priority is control of mill ventilation, which is usually a set point for the pressure after the mill controlled by Drying and to avoid excessive gypsum dehydration the variable speed of the mill filter fan or position of fan damper. Could by also a set point for temperature but pressure is much quicker and accurate.

Gas Temperature at mill outlet

Water spraying device

Gas Temperature at mill inlet (if hot gas is used)

Mill Inlet Fresh Air Damper

To control the cement temperature and also to avoid risks of clogging due to water spray when run in manual

Mill Feed Composition

Weigh Feeders Proportions

To maintain set proportion of feed components

Regardless of any change in fresh feed set point the proportion in terms of percentage for each raw material is kept constant for the fresh feed

DATA TO BE FILLED BY PLANTS Control Loop Available in PCS (Y/N)

Control Loop in Auto/Manual

Reason for run in Manual Mode

Comments [if any]

FINISH GRINDING BALL MILL - ESSENTIAL PROCESS INTERLOCKS V0.0 Process Group

Hoppers Feeding

Source of condition

Start Condition

Stop Condition

Delay for stop [seconds]*


> HH > HH > HH

3 3 3

Avoid overfilling Avoid overfilling Avoid overfilling

Not activated

Activated

3

Avoid overfilling

Not activated

Activated

3

Avoid overfilling

Not activated

Activated

3

Avoid overfilling

< LL

3


>HH

3

L

>HH
3 3 3

Avoid overfilling of the mill. Stop Fresh Feed. Cement transport sequence is stopped Stop Fresh Feed/Reduce Fresh Feed

Deviation

5*60

>HH

30 min

OFF

5*60

Avoid empty running of mill and damage to liners

>HH >HH Activated

3 3 5*60

Mill Filter DP

>HH

3

Avoid overfilling of mill 1st chamber Avoid overfilling of mill 1st chamber Trip Mill Filter Fan. Trip Mill Filter Fan. To protect bag filter from underpressure.

Mill filter outlet pressure

>HH

3

Trip Mill Filter Fan to protect bag filter from under pressure

Clinker Feed Bin Level Gypsum Feed Bin Level Additives Feed Bin Level Clinker Feed Bin digital Level Sensor Gypsum Feed Bin digital Level Sensor Additives Feed Bin digital Level Sensor Mill Sound Level

Silo Level Mill feeding (including weigh feeder) Roller Press Bin Level Hopper Level Mill Power Weigh Feeder's Deviation

Mill

Mill Outlet Temp Weigh Feeders Mill feed bins level Mill Outlet Elevator Boot Level Mill Outlet Elevator power Mill Filter Hopper Level Sensor


>L
Mill Filter & Fan

Separator Filter DP Separator Filter & Fan

Separator Filter Hopper level sensor

Not activated

Mill filter outlet pressure

Mill Water Spray

Cement Transport/Others

*Delay for stop:-

Avoid overfilling of the mill. 5% Deviation in weigh feeders. To avoid quality deviations and empty run of mill. Need to to be set in weigh feeder controller Avoid quality deviations. Adjust ventilation or start Water Injection System on Mill Outlet Temperature High.

>HH

3

Trip Separator Fan

Activated

5*60

Trip Separator Fan

>HH

3

Mill feed

ON

OFF

Mill Outlet Temperature

>L


Pneumatic Transport Line Pressure(if applicable) Silo Selection for Product Silo Level

Comments

>HH

3

ON >HH

3 seconds is proposed in order to avoid stoppage due to signal perturbation (can be increased/reduced according to site conditions) In general, delays can be adjusted according to site conditions/circuit configuration/OEM recommendation.

Trip Mill Filter Fan to protect bag filter from under pressure Enabled Temperature Deadband to be fixed by plant. When started, the injection should be included in control loop or set point given by operator Trip pneumatic pump Ensure correct silo is selected Avoid overfilling

Note:-

Some limit values mentioned in comments are for ultimate safety. Operational limits needs to be set based on supplier/OEM recommendation or circuit configuration.

DATA TO BE FILLED BY PLANT Interlock Available in PCS (Y/N)

Value of Start Condition

Value of Stop Condition

Values of Alarm Limits

Sensor Operating Range Min Value

Sensor Operating Range Max Value

Existing Delay for Stop [Seconds]

Interlock Active /Bypass

Reason for Bypass

Comments [if any]