Case Study

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.

• 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

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)