Case Study: Creating a Better User Experience using PlantPAx

Case Study: Creating a Better User Experience using PlantPAx

At times, we work with partner engineering firms to help them with projects that may be outside of their normal scope of offerings. Here’s how Matrix Technologies successfully helped a small engineering firm move a manual process to a fully-automated process using PlantPAx.

The Problem

When a latex carpet company needed help moving their manual chemical mixing process to a fully-automated process control system, they approached another Midwest engineering firm (an original equipment manufacturer) for help. While this OEM was able to help the company with some of their needs, creating a chemical mixing process using PlantPAx (a Rockwell ControlLogix Platform requested by the customer) was a task slightly outside of their normal scope of operations. So, the OEM engaged Matrix Technologies for our PLC/HMI and automation expertise.

Because Matrix was not dealing directly with the chemical company, our team faced many challenges, including:

• A condensed schedule (about 50-75% of the time we would normally need to complete the project)

• A poorly defined process with no existing PLC program or HMI application

• Disorganized IO (input/output) from the customer

To get started, the engineering firm sent our team the electrical drawings, device lists, and piping and instrumentation diagrams they had put together. They also gave our team a basic description of the different sequences that would need to be run in the system. However, because they had put together each document at a different part in their process, some of the information was not updated properly. In order to continue on to the programming stage, our team had to first create consistency among these documents, which required a lot of back-and-forth conversations (not only with the client but also between our Maumee, Indianapolis, and Minneapolis locations) to update all the drawings. This process, of course, further complicated our short timeline.

Once we had completed and updated all of the drawings, lists, and diagrams, the customer asked our team to program all the devices and add specific automated sequences into the program. With no existing PLC program or HMI application, this meant creating a new program from scratch, which can be quite time-consuming. Plus, when writing entirely original code, it is possible to create a process that is disjointed with variable inputs, which can be confusing for the end user.

Fortunately, we have the expertise to save time creating the program, do it well, and make the entire program easy for the end user to understand and execute. In this case, our expertise in PlantPAx was an incredibly valuable asset for this job.

The Solution: PlantPAx

Creating the program using PlantPAx provided us the best results in the shortest amount of time. PlantPAx is a library of control objects developed by Rockwell Automation that is most commonly used to integrate process-based control systems. With the pre-made, segmented code provided by the PlantPAx Process Library, our team could start programming PlantPAx templates for each device and link up inputs and outputs to this code.

Using these PlantPAx templates, we created code to control each device. Once the control code for each device was in place, we created automated sequence code to run the process automatically. Our next step was to write simulation code that would make the HMI screens imitate what the end user would view during normal process operation. We conducted some quick testing in the office and ran a FAT (factory acceptance task) at the OEM office with the end user customer to ensure everything was working properly and acceptably. The customers (end users) at the chemical company loved the look and feel of the screen interactions as well as the functionality PlantPAx provided.

Why PlantPAx?

As is demonstrated in this chemical company case, PlantPAx can help process-based clients standardize their controls system. The advantage for the programmer is that PlantPAx standardizes the code, reduces troubleshooting, and minimizes the time to create control code. For the client, the advantage is that the standardized system makes it easier to understand and control all parts of the system and reduces maintenance and troubleshooting time. The end product is a system with high functionality and smooth interactions that leave the customer satisfied and confident that their systems are under control.

Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about what our process engineers can do for you, contact Tom Hudson, Project Engineer.

© Matrix Technologies, Inc.
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Understanding and Preventing Fault Masking

Understanding and Preventing Fault Masking

It’s critical that industrial machinery stops safely when a system fault occurs.  However, older safety systems and complex systems with multiple safety switches may be prone to fault masking.

Fault masking is a dangerous condition in safety circuits.  It results from daisy chaining multiple safety devices in a safety circuit, which raises the possibility of hiding safety device faults during troubleshooting.

What causes fault masking and how to prevent it

This dangerous situation commonly occurs in older safety systems with electromechanical switches.  For example, the image below shows a typical Category 3 circuit for three doors on a machine.

Each door is monitored by its own dual-input safety limit switch, which is daisy chained and fed into a monitoring safety relay.  If a door is opened, both sets of contacts on that door’s safety limit switch are opened.  This breaks the circuit and triggers the safety relay to safely shut down the hazardous area of the machine.

Safety Switch

Some possible failures that could occur is a contact weld on the second set of contacts of the door limit switch, or from damage to the wiring to those contacts.  Both situations could cause a short circuit in the bottom circuit, shown in red below.

Safety Switch

Assume that an operator has to open the second door to clear a jam.  The safety limit switch on that door is now open, triggering the monitoring safety relay to safely shut down that part of the machine.  However, the safety relay will also fault because it would see a disparity between the top circuit (open) and the bottom circuit (closed).

When the second door is closed, the safety relay would not reset because of the fault.  Typically to clear the fault from a safety relay requires all power to be removed from the safety circuit and then restarted.  To troubleshoot the problem and reset the fault either the operator or maintenance personnel would start testing the door safety limit switches by opening each door to see if it clears the fault.

Opening and closing the second door would not clear the fault due to the short circuit.  However opening either the first door or the third door would open that door’s safety limit switch, removing power from the monitoring safety relay.  Closing that door would then clear the fault on the safety relay, making it seem like that door’s limit switch was the problem—and hide the fault on the second limit switch.

In this scenario, the troubleshooting process would attribute the malfunction to the wrong limit switch and it would probably be replaced.  Every time door number 2 is opened and the real safety problem is not discovered, the plant may experience additional costs, and the original problem would still exist in the safety system.

If the other contact in the second limit switch were to weld or otherwise short circuit, it would be unable to detect if a person opened the machine door—resulting in a dangerous situation during machine operation.

How Matrix can help

Understanding the issues created by fault masking is a critical step in designing safety systems.  During the engineering design process, safety inputs should not only be used to monitor hazardous parts of a machine, but also be designed to reduce the probability of fault masking as much as possible.

The proper number of safety limit switches that can be daisy chained without fault masking depends on the faults that can be anticipated and the number of safety input devices involved.

Using safety limit switches with powered OSSD outputs (Output Signal Switching Device) can be an effective way to eliminate certain faults such as contact welds and shorts to power.  Another method to reduce the risk of fault masking is to use a monitoring safety relay with individual safety inputs, especially if there are only a few safety inputs to be monitored. Also, maintenance staff should be trained in ways to troubleshoot that can uncover fault masking.

Matrix Technologies is one of the largest independent process design, industrial automation, engineering, and manufacturing operations management companies in North America.  To learn more about our risk assessment and industrial safety services, contact Carl Bohman, PE, FS Project Engineer (TUV Rheinland).

© Matrix Technologies, Inc.
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Food Packaging Case Study – Part 3: Carton & Case Count Reductions

Food Packaging Case Study: Carton & Case Count Reductions

Imagine you’ve been tasked with leading a high-profile capital project that will impact multiple lines at every site in your manufacturing network. Marketing is driving R&D to change package formats to meet the demands of key retail customers, Planning is projecting growth, and it’s up to you to figure out how to meet both the format and volume requirements within the financial constraints of the project.

This is an exciting opportunity, but it’s a major challenge. You start by considering your existing assets. Can they be retrofitted? Do you have OEM support? What is the current utilization of assets and how will that be impacted by this new format?

You may need to consider new equipment alternatives. Where does the plant have whitespace? Can existing lines be replaced? How much space will new equipment need in old plants where equipment, people, and materials are already stacked on top of each other?

Before you get started, Planning revises growth projections down and you lose 10% of your budget. Then someone mentions that central palletizing is at full capacity. You take a deep breath, realizing this is going to be a long project – and the perfect time to consider a preliminary engineering assessment.

Our three-part series on preliminary engineering methodology explains how preliminary engineering assessments help food manufacturers investigate alternative packaging specifications and project scopes before spending time and money on plans that will never achieve an acceptable internal rate of return (IRR).

Part 1 introduced the project risks associated with minor packaging changes and how a preliminary engineering assessment can be leveraged to mitigate risks and save capital budget.

Part 2 detailed the benefits of preliminary engineering and the steps of an assessment.

Part 3, below, is a case study of how a preliminary engineering assessment by Matrix Technologies helped a large food manufacturer deal with the complex challenge described above while reducing the preliminary capital cost estimates by 50%.

The Client’s Challenge

A large food and beverage manufacturing company in the snack food market needed to update its successful but outdated Point of Sale (POS) packaging. Marketing required the current double face cartons be reduced to a single face, with pack counts and pallet heights also to be reduced by half.

Point of Sale shelf space with single and double face cartons.

The products impacted by the packaging change were run on several legacy packaging legs at two different sites. There was a strong desire to replace the aging, unsupported equipment with the latest state-of-the-art equipment. Also, since the case size was being cut in half, there were significant concerns about how central case sorting and palletizing would react to a doubling of the case traffic.

When the cost of the new equipment, combined with the required major infrastructure changes, resulted in capital cost estimates more than double the budget for project feasibility, the manufacturer knew a more detailed analysis would be required. 

Understand the Existing Production Process

The food and beverage engineering team at Matrix began by gathering available production data for the existing equipment. Automated data gathering was only happening in the central palletizing area, but no production information could be reported for the individual packaging legs.

To put hard numbers to the capabilities of each line, Matrix conducted time studies coordinated with the production schedule to observe the widest possible range of package formats. In addition to the individual packaging legs, constraints in product delivery and central case sorting and palletizing were studied. These time studies were important to the development of current state equipment utilization models.

Matrix then developed future state utilization models to understand the impact of the packaging change across the manufacturing network.

How to Approach Modeling a Production System

Deciding how to model a food and beverage manufacturing production system is a critical step that requires many important decisions, including model type, timescale, input data type, as well as the number and diversity of options under consideration. Perhaps the most important decision is the output data format required to facilitate decision-making.

Static spreadsheet models and discrete event simulations (DES) are two common types of models:

  • Static spreadsheets, developed per application, are appropriate for high level “mass-balance” applications and for long timescales typically measured in shifts, weeks, or periods.
  • DES, which utilizes specialized software, is appropriate when discrete products have highly complex interactions between each other and multiple systems, and typically have timescales measured in seconds or minutes. DES is particularly useful for analyzing buffer capacities and bottlenecks influenced by the downtime interactions of multiple systems.

How to Validate a Production Model Against Historical Data

Another important step when developing a production model is validating the model against historical data. Historical data often is more granular than Planning’s projections for the future. For instance, historical data might include tonnes per shift, while Operations planning can only provide a rough projection of tonnes per period.

By rolling the actual historical data up into tonnes per period and inputting it into the model, you can compare the average utilization output from the model to the actual utilization found in the historical production data. Not only is this critical to assuring the model is working as intended, but it’s crucial to gaining buy-in from project stakeholders. There will always be assumptions and the model output will never be perfect. The challenge is to identify the simplest model that will yield results accurate enough to make a decision and take action.

Modeling the Future State

Modeling must begin with the end in mind: Make a decision and take action. But what does that decision-making process look like for a capital project?

This manufacturer had a clear idea of where they wanted to invest in new equipment and where they wanted to only invest in retrofits. With project cost estimating happening in parallel, process modeling was intended to confirm Operations’ requirement that the plan would not exceed 80% equipment utilization during seasonal peaks. However, as they  quickly discovered, the project was challenged on both cost and equipment utilization.

The models included two sites with over 100 SKUs and were validated against historical production, seasonal peak demand, and projected future growth data. Using these models, strategies were developed to shift production volumes between sites, update existing equipment, purchase new equipment, and expand plant facilities.

Chart showing projected equipment utilization by period for the original packaging specifications. Three new legs are required and utilization targets are still exceeded.

Fortunately, the manufacturer had the foresight to hold off on ordering long lead time equipment until the initial scope assumptions were validated. The assessment showed that the equipment strategy would not meet Operations’ utilization limits and the true magnitude of investment required throughout the entire downstream process would have never achieved a favorable IRR.

An Iterative Process

A preliminary engineering assessment creates a communication loop that diagnoses challenges, generates and evaluates solutions, and delivers a well-honed scope, schedule, and budget.

Project scope vetted through Preliminary Engineering Assessment.

In this project, the manufacturer’s Packaging Design and Marketing teams used the initial preliminary engineering results to collaborate on a revised carton design, incorporating recommendations for slightly larger carton and case counts that could better utilize the existing equipment infrastructure.

Engineering Results

Matrix engineers updated the process model to reflect the new packaging specifications and analyzed 20 new scenarios reflecting varying levels of equipment investment and demand load balancing across the sites in the network.

In conjunction with slight adjustments to the timing of inventory builds to meet peak demands, the new carton allowed existing equipment to be retrofitted with only modest investment in new equipment, while avoiding major investment in downstream systems.

Chart showing projected equipment utilization across the network for the revised packaging specs. Only one new leg is required and utilization limits are not exceeded.

The assessment provided bottom-line results: The project was re-chartered with alternative packaging specifications, reducing capital project costs from initial projections of $15-$20MM to below $8MM, while still satisfying Planning’s volume projections and Operations’ utilization limits.

Realizing Value with Preliminary Engineering Assessments

Packaging changes are often viewed as low risk, particularly when the package size is reduced but stays within the size capability of the equipment, and when production volumes remain constant.

However, the details of production rates and the complete process design associated with making “just a minor format change…” can create serious challenges for the project team. A preliminary engineering assessment by food and beverage engineering experts can remove these obstacles and create a path to success.

Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To discuss a project, or learn more about our Packaging Services, contact Brandon Grodi, PE.

© Matrix Technologies, Inc.
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Design Considerations for Equipment and Piping Layout: Locating Valves and Special Equipment

Design Considerations for Equipment and Piping Layout: Locating Valves and Special Equipment

This is the last article in a four-part series on equipment and piping layout.  This article reviews guidelines for locating various types of valves, and also considers the equipment needs of heat exchangers, fired equipment, and instrumentation.

The first article provided guidelines for vessels, cooling towers, and compressors. The second article discussed equipment layout considerations for pumps.  Piping and pipe rack guidelines were covered in the third article of the series.

Properly Locate Each Valve Based on Its Application

Valves come in all shapes and sizes. Based on the application and the fluid in the piping, the valve required for the job could be a gate, ball, butterfly, globe, check, safety/relief valve, or control valve.  Some valves are operated manually, by turning the handwheel or pulling on an overhead chain.  Others open and close using motors and solenoids.

Piping engineers have a lot to consider when locating valves for the equipment and piping layouts discussed in the previous articles.  They often work closely with the process engineers to select the correct valve for each application.  Some general location guidelines that apply to most valves are listed below:

  • Review the valve manufacturer’s installation recommendations to determine if the valve should be mounted vertically or horizontally. Also review the owner/client requirements. Take care to never install the valve upside down or backwards.
  • Frequently operated valves should be easily accessible from grade, platforms, or permanent ladders. If the bottom of the handwheel of a horizontal valve is more than 6 feet above grade, such as for a seldom-used valve, use valve extensions, chain operators, or a platform for access.
  • Focus on personnel safety for anyone walking near valves or operating them. Make sure handwheels and chains do not present a safety hazard. Keep valve handwheels out of operating aisles wherever possible. Avoid tripping hazards and head bangers. Valves that handle steam, acids, and caustics should be located below eye level to prevent eye and facial injuries.
  • Provide enough clearance for servicing and replacing valves. Also provide at least 4 or 5 inches clearance around a valve handwheel for easier use by an operator.
  • Use lug type valves unless directed otherwise by the client.

Pressure safety valves protect equipment from over-pressurization. Generally, they are installed so they drain freely into the flare header.

  • If the safety valve can’t be serviced during operation, it’s necessary to install block and bypass valves, with the block valves being locked or car sealed open.
  • Also, the block valve handwheels should be installed in the horizontal not vertical position. This will prevent a mechanical failure of the valve from blocking the line.

Valves often have specific piping layout needs, such as a minimum number of diameters of straight pipe before and after the valve.  Complying with the “rules of thumb” and the laws of physics can prevent “water hammer” conditions that lead to valve failure.

Heat Exchangers Run Hot and Cold—Relatively Speaking

A heat exchanger is a piece of equipment with two fluids flowing in opposite directions in order to exchange heat through a solid boundary or surface. Common types of exchangers include shell and tube, double pipe or fin tube, plate and frame, and air coolers.

The basic rule for flow through an exchanger is that the fluid being heated must flow up, while the fluid being cooled flows down. That means that hot fluids enter at the top of the exchanger, while cold fluids enter at the bottom.

  • Exchanger elevations are typically determined by piping layout or system hydraulic requirements.       Ensure proper clearance between the drain on the lower piping and grade.
  • The channel nozzles in a bank of exchangers should line up whenever possible.
  • Bundle pulling must be from the end of the exchanger opposite the pipe rack.
  • Exchangers with removable tube bundles should have a clearance for maintenance equal to the bundle length plus 20 feet from the tube sheet.
  • Air-cooled exchangers are normally located on the top of pipe racks, with platforms provided for tube sheet access. Air coolers with multiple bays require the inlet piping to be symmetrical to equalize the flow to each bay.
  • Design the piping so that the channel end of the exchanger can be removed without removing the isolation valves.
  • Provide a bypass line between the cooling water supply and return lines to prevent freezing when the exchanger is out of service.

Be Careful with Fired Equipment

Fired equipment includes heaters, incinerators, and boilers. Fired equipment should be located, if practical, so that gases from process areas and hydrocarbon areas cannot be blown into the open flames.

  • Review the owner/client specifications to properly set the height of heater stacks relative to other equipment and platforms. Maintain at least 7 feet of clearance from the bottom of the heater to the high point of the grade.
  • Provide sufficient clearance and access for the easy removal of tubes, burners, fans, and other related equipment.
  • Locate fired heaters around the outside of a unit plot, and adjacent to an unrestricted road.
  • Provide access for firefighting on all sides.

Instruments

Many instruments, such as flow meters, have piping design requirements so they can operate correctly and accurately. Industry standards, vendor literature, and owner specifications all provide guidance.

  • Control valves with actuators should be installed with the centerline 2 feet above grade. Provide a minimum of 12 inches of distance (or the manufacturer’s recommended distance) above the actuator.
  • Provide a minimum of 2 feet of clearance from the connection taps on an orifice flange to adjacent piping, equipment, or steel.

This fourth article in the series concludes our overview of the process involved in equipment and piping layout. We hope this information will guide you in designing your next industrial project.

Matrix Technologies is one of the largest independent process design, power systems engineering, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about our manufacturing operations management capabilities and manufacturing process control solutions, contact Jeremy Runk, Department Manager of the Process & Electrical Design Department.

© Matrix Technologies, Inc.
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