White Paper
Dairy Producer Experiences Production Improvement with Process And Controls Upgrades to Their Evaporation System
Background
A major provider and producer of dairy products and ingredients wanted to improve the quality, consistency, yield and throughput for 30+ year old pasteurization, separator and evaporator systems at one of their plants. Our client knew it needed a supplier who could provide design and implementation expertise in pasteurization meeting legal requirements, separator and evaporator processes, instrumentation, controls, and production reporting. Malisko was requested to provide the client with such a comprehensive list of deliverables to help the client improve their production systems.
System Background
- Evaporator was installed in 1987
- Control and operation of the process was primarily “manual”,relying heavily on operator intervention and their process knowledge:
- Pumps started manually (PBs)
- Temperature, level, flow, and pressure control were all individual PID Controllers
- Control of the process by the operators was primarily “reactive” – observe a condition then make a change to control parameters then wait to see the results
- Process Valve positioning was manual (switches)
- Manual adjustment of regulating valves – many of these valves had to be adjusted in the field by the operator during production
- Some obsolete stand-alone operator stations displaying Separator status and some silo level status
- Numerous standalone PID single-loop controllers
- Complex wiring system
- Over 450 individual electrical components including:
- General purpose relays
- Interposing Relays
- Push Buttons
- Switches
- PID Controllers
- Timing relays
- Trip Amplifiers
- RTD to 4-20 transmitters
- Numerous circuit breakers
- Indicating lights
- Allen-Bradley PLC-5 and SLC-500 control platforms with the PLC-5 being obsolete and no longer supportable by the OEM
- Most motors were powered through full-voltage motor starters – Very few VFDs
- Separator and Milk Silos each had standalone control systems
- Field wiring and conduit had become degraded (insulation failures) over the years and required replacing
- MCCs required replacement
- The complex electrical system was becoming increasingly burdensome to maintain and was becoming ever-more fragile – for example, physically walking near some of the electrical components would cause the system to, literally, shut down production
System Background
- Evaporator was installed in 1987
- Control and operation of the process was primarily “manual”,relying heavily on operator intervention and their process knowledge:
- Pumps started manually (PBs)
- Temperature, level, flow, and pressure control were all individual PID Controllers
- Control of the process by the operators was primarily “reactive” – observe a condition then make a change to control parameters then wait to see the results
- Process Valve positioning was manual (switches)
- Manual adjustment of regulating valves – many of these valves had to be adjusted in the field by the operator during production
- Some obsolete stand-alone operator stations displaying Separator status and some silo level status
- Numerous standalone PID single-loop controllers
- Complex wiring system
- Over 450 individual electrical components including:
- General purpose relays
- Interposing Relays
- Push Buttons
- Switches
- PID Controllers
- Timing relays
- Trip Amplifiers
- RTD to 4-20 transmitters
- Numerous circuit breakers
- Indicating lights
- Allen-Bradley PLC-5 and SLC-500 control platforms with the PLC-5 being obsolete and no longer supportable by the OEM
- Most motors were powered through full-voltage motor starters – Very few VFDs
- Separator and Milk Silos each had standalone control systems
- Field wiring and conduit had become degraded (insulation failures) over the years and required replacing
- MCCs required replacement
- The complex electrical system was becoming increasingly burdensome to maintain and was becoming ever-more fragile – for example, physically walking near some of the electrical components would cause the system to, literally, shut down production
PROJECT SCOPE
Front-End Engineering and Design (FEED) Phase
- Replacement of the obsolete PLC-5 and SLC-500 control systems
- Replacement of the numerous “manual” control devices and single loop controllers with a more efficient and contemporary platform
- Consolidation of the stand-alone legacy control systems into one fully integrated system
- New pasteurization controls for cream and skim meeting USDA compliance and legal certification
- Create Bills of Material for the needed hardware and software licenses
- Analyze control system code to see if a conversion or complete re-write was required
- Create a detailed plan for the demolition of the existing field wiring, conduit, motor leads, MCCs, and complex electrical system
- Specify and document the physical installation requirements of new MCCs and electrical/control system components and assemblies
- Create an electrical contractor and automation bid package including deliverables and schedule
Process Controls Upgrade
- The evaporator control code would require a total re-write
- Malisko, utilizing their evaporator process knowledge, wrote a functional specification on how the new system should operate
- The customer chose the process improvement options giving Malisko the ability to further automate the system and incorporate these improvements into the functional specification
- The goal was to have an almost complete hands-off system with limited operator intervention
- Automated the 21 loops that use to be standalone PID Controllers
- Set points automatically adjust based on the batch phase:
- Startup, Continuous Processing, Flush Out, Shutdown, CIP
- Added over 26 VFDs to system for increased control of material flowrates and pressures
- Automated Startup, Flush Out and Shutdown sequence to where it is now 95% hands off
ELECTRICAL
- Minimum down time. This meant we had to install the drives and motor leads prior to the shutdown
- The existing MCC had to remain in place until shutdown. This meant we had limited space to install new motor drives. A new MCC would not fit in any available space
- Saved the client money by going with an MCE vs a traditional MCC
- With the MCE we could install and run motor leads to existing motors while the plant was running
- Used Allen-Bradley PowerFlex 525 VFDs with ethernet communications to the new Controller
PNEUMATIC SOLENOID PANELS
- SMC Ethernet Solenoid Banks
- Ethernet banks reduced the number of digital outputs needed from the new PLC
- Designed two Pasteurization Panels with Anderson AV9900 Chart Recorder, DART, and Differential Pressure Switch in each
- Located in Control Room so that operators could monitor “Cut-In” and “Cut-Out” events of the pasteurizers
MAIN CONTROL PANEL
- Simplified control panel with 1756 I/O and IFM Modules
- The need for physical digital I/O modules was greatly reduced by leveraging ethernet drives, solenoid banks, and elimination of alarm relays, trip amplifiers, and indicating lights
- Contained the pasteurizer USDA sealed legal panels
- Utilized CompactLogix for Legal HTST controls
USDA CERTIFICATION
- Demolition
- Plasma cut out the old manual control panel with the 450 components
- Removed all the field wiring in the process area
- Removed all conduit in the process area
- Removed MCCs and all their components
- Removed all motor leads in the from the MCCs to the physical motors in the process area
- Removed old field instrumentation (transmitters and valves)
ELECTRICAL
- Minimum down time. This meant we had to install the drives and motor leads prior to the shutdown
- The existing MCC had to remain in place until shutdown. This meant we had limited space to install new motor drives. A new MCC would not fit in any available space
- Saved the client money by going with an MCE vs a traditional MCC
- With the MCE we could install and run motor leads to existing motors while the plant was running
- Used Allen-Bradley PowerFlex 525 VFDs with ethernet communications to the new Controller
PNEUMATIC SOLENOID PANELS
- SMC Ethernet Solenoid Banks
- Ethernet banks reduced the number of digital outputs needed from the new PLC
- Designed two Pasteurization Panels with Anderson AV9900 Chart Recorder, DART, and Differential Pressure Switch in each
- Located in Control Room so that operators could monitor “Cut-In” and “Cut-Out” events of the pasteurizers
MAIN CONTROL PANEL
- Simplified control panel with 1756 I/O and IFM Modules
- The need for physical digital I/O modules was greatly reduced by leveraging ethernet drives, solenoid banks, and elimination of alarm relays, trip amplifiers, and indicating lights
- Contained the pasteurizer USDA sealed legal panels
- Utilized CompactLogix for Legal HTST controls
USDA CERTIFICATION
- Demolition
- Plasma cut out the old manual control panel with the 450 components
- Removed all the field wiring in the process area
- Removed all conduit in the process area
- Removed MCCs and all their components
- Removed all motor leads in the from the MCCs to the physical motors in the process area
- Removed old field instrumentation (transmitters and valves)
Shut Down Period – Demolition / Installation / Commissioning
- Provided electrical contractor oversight during the demolition and installation activities
- Added the new automation system to the plant’s existing servers, network and domain
- Performed full operational checkout of all discrete and analog devices connected to the new system
- Identified and help troubleshoot existing process devices, such as valves, that were not 100% operational
- Facilitated the certification by the USDA local authority of the HTST controls and data recorders
- Assisted plant operations with water tests of the new systems
- Assisted plant operations with running initial production
- Trained the operators and technical support group
- Provided both on-site and remote support for plant operations during the first several weeks after resuming full production
- Analyzed empirical data from the new instrumentation to adjust control sequences, algorithms and setpoints to achieve quicker ramp-up from water to milk as well as improve efficiency of cleaning during CIP
- Also adjusted setpoints, sequences and algorithms to achieve consistent and repeatable total solids and butter fat content
Both the client and Malisko achieved the project objectives of upgrading the controls of the milk process to achieve…
PROCESS IMPROVEMENTS DURING THE PROJECT
New Instrumentation Specified and Supplied on the Project by Malisko
Scope of NEW Monitoring and Control for Each Process Parameter Automated on the Project
Level Monitoring and Control on Evaporator Passes:
- Implemented level monitoring on PASS 1 THROUGH 4 and LEVEL CONTROL ON PASS 5
- Utilized VFDs eliminating the need for operators to manually adjust butterfly valves
Level Control on Skim and W/M Balance Tank (existing but replaced Level Transmitters):
- During a water-to-product shift, the tanks now drain the water prior to milk being introduced:
- Benefits are more consistent cream at the beginning of a production run
- Faster time to build total solids on the evaporator
- Once product is introduced the tanks maintain a consistent level of W/M and Skim
Level control on Cream balance tank:
- Previously the tank would either overfill or get “sucked dry” when running production
- Benefit now is a steady level control. Timing pump (Tank’s Outlet Pump) is now driven by a VFD which allows the pump to speed up or slow down as needed to maintain a controlled level in the balance tank
Pressure control on cream and skim outlets from the separator + Mass Flow Meter – Butterfat Control:
- Existing pressure regulating valves were Alfa Laval CPM valves. Operators had to manually adjust air pressure to reach desired pressures
- Malisko implemented Pressure Transmitters in place of Pressure Indicators. Replaced the CPM Valves with FlowServe regulating valves
- Added Mass flow meter to monitor – cream temperature, flow, and density
- Benefits:
- Totalize cream production
- Monitor the density of cream for an indication of cream Butterfat Content
- Automated control of pressures for skim and cream
- – Collected cream samples for Butterfat and worked with E&H in developing the correct coefficients to put into the Mass Flow Meter. The plant is now able to read Butterfat Concentrations in real time.
Flow meter on cream pasteurizer:
- Existing controls had the timing pump speed locked at the maximum hertz – no variation
- Flow previously controlled via an embedded PID controller in the existing ABB chart recorder
- Benefits:
- Pasteurizer is now a flow meter-based timing system
- Totalize actual cream flow
- Can control flow within a tight setpoint for maintaining cream balance tank level (will make incremental flow changes so to not upset the system balance)
- Warning indication of eminent cream plugging at the heat exchanger’s cooling plates
Mass flow meter on outlet of the evaporator:
- Before the operator would take samples every hour to see where their solids were located
- Benefits:
- Taking inputs (temperature and density) from the mass flow meter to constantly calculate total solids instead of relying on periodic (hourly) tests
- Now the operators see their total solids value constantly and in real time
- Totalize condensed skim flow
- In steady state operation, the speed of the compressor fan is governed by the total solids setpoint for automated control of total solids
Flow Meter on Whole Milk Tank:
- Previously, operators calculated flow to the separator based off of hourly level readings in the source silo. Whole Milk flow was then controlled by manually adjusting a regulating valve
- Benefits:
- Flow setpoint automates Whole Milk flow to the separator by controlling the VFD on the motor/pump
- Totalize whole milk flow
Conductivity transmitter on the evaporator outlet:
- Previously, the CIP chemical charge and rinsing was based purely on timing. Issues occur when CIP’ing is based only on “time” because the soil load varies between runs due to the amount of milk solids fouling and water in the system which can directly affect chemical concentrations and rinsing times
- Benefits:
- Now CIP chemical charge and rinsing based on conductivity for more consistent CIP
Conductivity transmitters on CIP Caustic Tanks:
- Previously, operators charged the system but would not be able to measure the chemical concentration until the system was fully charged
- Benefits:
- Conductivity meters now giving real time indication of caustic concentration in the CIP tanks prior to chemical addition into the evaporator’s CIP cleaning circuit
Vacuum Pressure Transmitter:
- Previously, operators manually viewed a vacuum gauge on an old control panel
- Vacuum pumps ran 100% of the time at full speed
- Benefits:
- Now vacuum transmitter is tied into control system and vacuum pumps are on VFDs
- Vacuum pumps can now go into energy saving mode when vacuum setpoint is reach
Mass Balance:
- Totalize Whole Milk (W/M), Skim, and Cream flow to calculate any shrinkage – W/M = Skim + Cream
- Totalizing Skim and Condensed Skim flow to calculate evaporation rate. Skim – Condensed Skim = Evaporation Rate (Condensate/Cow Water)
Additional Photos of the Completed Project
NOTE
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