Although parts inspection is a complex business driven by the ever-increasing complexity of manufactured goods, it has stuck pretty close to its roots, relying on decades-old Coordinate Measuring Machines (CMMs) as the go-to technology to get the job done.

Yet increasingly, traditional metrology methods like CMMs do more to slow down the process without adequately delivering accuracy, especially as products sport tighter tolerances, and demand precision manufacturing. CMM’s use of an articulating robotic arm to direct a touch probe to test individual points along the surface contour of an object doesn’t support the speed at which companies need to conduct business given time-to-market pressures and the quest for a competitive advantage. In addition, CMMs’ output–typically a table of coordinate numbers—often results in miscommunication of geometry details with studies showing the report details being misinterpreted as much as 20 percent of the time.

Level 3 Inspection (L3I), with a history seeped in reverse engineering and production in the aerospace industry, recognized early on that there was an opportunity to vastly improve the traditional CMM inspection process. During its work reverse engineering turbine engine parts, L3I found it wasn’t collecting nearly enough information from its use of CMMs on such complex parts as blades and vanes. As a result, it began the hunt for technology to simplify this engineering task and ultimately bring better quality inspection and reverse engineering processes to the marketplace.

White Light Scanning + CAI = Process Transformation

The search led L3I to a decade-long practice of evolving the use of white light scanning (WLS) and computer-aided inspection (CAI) technologies to change up the traditional CMM-driven parts inspection process. By applying a set of new technology, the goal was to turn the traditional inspection paradigm on its head, substantially reducing the number of physical prototypes and product iterations while speeding up development cycles, often at reduced costs.

At a base level, core technology differences give WLS/CAI an edge. Because a CMM probe is physically moved from point to point to capture surface data, the process is slow and it requires a highly-trained specialist to manually place the calipers and interpret the readings, opening the door to human error when gathering results. Moreover, CMM analysis is limited by its ability to capture a clear and coherent image of the surface geometry. While WLS can yield watertight scans comprising hundreds of millions of points, a complex CMM program, in comparison, might yield a few hundred or at best, a few thousand touch-data points depending on the part size, its complexity, and the requirements. Finally, studies have shown that the digitized surface of the point cloud data, which is the output of WLS, can be accurate up to +/- 0.00004 inches (~1 micron), providing a much more accurate and vastly more comprehensive picture of the entire geometry.

Beyond the physical data capture efficiencies, the WLS/CAI combination also has advantages for data analysis and visualization, the more time-consuming part of the inspection process. Traditional CMMs output tables of numbers are difficult to interpret, even for highly-trained experts, and they do not provide any visibility into the actual geometry of a part. Not so with CAI-driven parts inspection, which generates color-coded plots that can be overlaid with a CAD model for comparison, allowing inspection engineers to easily identify non-conforming part features in a small fraction of the time.

With a technology duo deemed superior to traditional metrology methods, L3I embarked on the journey of transforming the parts inspection workflow. Typically, with a CMM-driven workflow, a prototype or sample part is produced and then compared to specified set of dimensions and geometric dimensioning & tolerance callouts from the inspection blueprint.

In comparison, L3I began to leverage WLS/CAI to study the part’s geometry first, focusing on the resolution of geometric conformance and deviation, as well as anomalies first, evaluating the form first. The result yielded a number of positive outcomes. For one thing, geometric anomalies that might have gone unnoticed with the traditional workflow are detected earlier, reducing the risk of launching a non-conforming product into the marketplace. In addition, the comprehensiveness of the inspection provides greater insights into the manufacturing process with accelerated optimization and the streamlined workflow, cutting iterations and scrap to cut time to market costs.

The Smart Inspection Station combines a 3D scanner and Geomagic’s Qualify inspection software, automating the process of scanning and analyzing parts against CAD models and blueprints.

Consider the new inspection process applied to the development of a shoulder dome implant. The original CMM inspection process, which gathered data from 200 CMM points, indicated that the part was dimensionally acceptable. That same process turned over to the WLS/CAI technology revealed a completely different story. A scan of that same part, comprising 200,000 data points (1,000-times more data), was analyzed, revealing that the part was out of tolerance. While the CMM points overlaid on the 3D structured light scan correlated perfectly to 5 or 6 decimal places, the CMM completely missed a ring-shaped anomaly in the part, detected by the scanner because of the expansiveness of its data collection. In another example, L3I was able to help a jet engine foundry client transform a two-week inspection process that consumed the time of two highly-paid engineers by 95%, whittling it down to a half-day process and saving thousands of dollars per part number.

This is a cross section of jet engine air foil showing the difference between the CAD design and the actual part. The CAI approach makes it readily visible to see where the part conforms, depicted in green, where it is too small, shown in blue, and where it is too big, displayed in orange and yellow. SOURCE: Level 3 Inspection

Based on those successes, L3I has pushed the promise of WLS and CAI a step further, creating a turnkey, integrated system that automates the complete inspection process. The Smart Inspection Station, which combines a 3D scanner and Geomagic’s Qualify inspection software, automatically makes precise 3D scans of parts, analyzes the parts against CAD models and blueprints, determines the part disposition, and creates comprehensive inspection reports, all with a non-technical operator in just a few minutes, on the shop floor. Vastly superior production inspection results in very short time.

Visualization capabilities allow engineers and workers to focus on the areas that need attention, as opposed to wading through tables of numbers for areas that are well within conformance. SOURCE: Level 3 Inspection

The FUD Factor

While the benefits of WLS and CAI seem clear and the technology is fairly mature, it remains a challenge to get manufacturers on board with production parts inspection processes.

Inertia and resistance to change are perhaps the biggest barriers to adoption, keeping the CAI industry focused on early-adopters and professional services despite its 13-year application history. Many companies are so entrenched in their CMM heritage, they think what they have is good enough and that newer WLS/CAI technology is risky, and still perceived as “too new”. There are also plenty of long-time CMM specialists who are leery of new inspection technology because of their fears it could have negative career ramifications. Fear of change is still alive and well.

Clearing these hurdles requires a dogged commitment to on-going education and repeated exercises proving out the value of the new 21^st century inspection processes. Companies also need to understand that CAI is a process, not just an exercise in buying scanner equipment and analysis software. Only by thinking process optimization and by having a clear financial understanding of the time it takes to get a product to market will companies open themselves up to transforming parts inspection and in the process, make better precision products much faster, at lower costs, and with far greater confidence.

Background

I have been fascinated by the process of commissioning chemical and processing plants ever since my introduction to the discipline. At that time I had worked at ICI (Imperial Chemical Industry) for four years and then as a process plant operator. While operating and assisting in the commissioning of a new plant, I was intrigued by the activities that had to be compiled and organized—the checking out, the testing, and the rechecking of many plant items—to allow the asset to be started up in an efficient and effective way. As I became engrossed by the experience and moved from the first commissioning project to the second, I was amazed that the whole process had to be rethought, almost reinvented, and that there was so much scrambling by the commissioning engineers on the new project to piece together the paperwork, procedural format, and general documentation from past commissioning campaigns to allow the new plant to begin to be organized so that its delivery could be completed. By that time I had subconsciously chosen commissioning as my future career and made a personal commitment to document the whole process in the best way I could. The result was my book Chemical and Process Plant Commissioning Handbook.

Process plant commissioning in the chemical industry and related industries has an interesting dynamic, as there are few or no formal qualifications for commissioning a new plant. Process engineering has elements that address the subject, but the lack of published works on the topic has created the potential for commissioning to be a discipline that can be susceptible to serious problems during the key stage in a project’s delivery. There is a three-step methodology that works well and has formed the basis of my career in process plant commissioning, which has now spanned more than 30 years.

The Three-Phase Methodology

The commissioning of a process plant should be considered and implemented in three distinct phases.

Prepare

This phase covers activities undertaken to set up the commissioning, gather information, select the commissioning team, develop the schedule, and create documentation. These all are typically home office tasks.

Implement

This phase, which traditionally has been perceived as commissioning, involves examining the facets that address the installation, checking out, precommissioning, wet and dry commissioning, and start-up of the new equipment at the job site.

Closeout

This is the final stage of the commissioning process and the one most often neglected. It entails ensuring that all paperwork systems and trials are complete and updated to “as commissioned” status and that the plant and equipment have met the performance and acceptance criteria, allowing the plant to be handed to the ongoing operations group.

For optimum success in a commissioning exercise, the members of a project team responsible for the commissioning phase should be involved at an early stage of the project to ensure that all considerations related to the start-up of the plant are considered.

Much emphasis is placed on the design and construction phases of a project, yet what is arguably the most important phase—the start-up and delivery of the asset—is an activity that may be neglected. Commissioning teams can turn up toward the end of construction and hurriedly compose the documents normally created during the preparation phase, but I believe that what you get out of an endeavor is directly proportional to the effort you put in; if your preparation for the commissioning of a new asset is sloppy, late, without research, ill prepared, and unplanned, the start-up will be pretty much the same. Projects that are driven with a successful start-up as the aim and that have duly considered and implemented the commissioning tend to be the most successful.

The main activities associated with and conducted in each of the three commissioning phases are shown in Table 1.

Table 1 Main Activities and Phases

Commissioning Logic

The logical steps required to complete the three-phase commissioning process can be shown to flow in accordance with a simple logic, although it is accepted that some activities may run in parallel when actually delivered (see Figure 1).

Figure 1 Logic of the Three-Phase Commissioning Project

Prepare

The major preparatory activities before the work actually commences in the field can include the following main elements. Some of the tasks more relevant to milestone events are not explained here.

Appoint the Commissioning Manager

The commissioning manager is an important part of the project team, and by its nature, the role requires a close working relationship with both the construction manager and the operations manager to ensure that the delivery of the new asset as a fully functional operation plant is completed in the most cost-effective and schedule-efficient manner. A good commissioning manager must have the ability to understand chemical processes; have knowledge of instrument, electrical, and control systems; be familiar with structured work methodologies; and be experienced in commissioning plant and equipment.

Define the Commissioning Scope

The area that can cause the most confusion if it is poorly prepared and drafted in a contract for commissioning services is scope definition. The exact role of the commissioning organization, the full scope of its activities, and definitions of when those activities are deemed complete should be documented clearly. It is important to specify clearly who will draft operating procedures and prepare and deliver training packages. In any scope document mention should be made of the practical factors such as who will operate valves, how control of energy introduction will be managed, and who has management control of all the various commissioning stages.

Prioritized Asset Systemization

Once the commissioning scope of the project has been defined and the initial key project documents (P&IDs, layout drawings, plot plans, and mechanical handling drawings) have been drafted and issued, commissioning systems can be identified in priority order. This is the first and one of the most important activities the commissioning team will undertake as it provides the structure for all the other organizational tasks the team will perform, sets the priority for document and checkout progress management, and assists in the efficient initial plant commissioning and start-up in the most effective and timely way.

Input to Design

As was indicated above, commissioning engineers are typically experienced individuals in their initial disciplines and invariably have commissioning-specific and operational experience. This type of expertise is invaluable at engineering design reviews, and the engineers’ attendance should be encouraged. Their experience adds value to the appreciation of P&IDs, 3-D models, and control philosophy reviews.

Create the Commissioning Philosophy

The aim of this document is to identify the key commissioning project aims, objectives, activities, and general philosophy; this should be compiled at an early stage in the commissioning team’s life, after the team scope definition. The initial commissioning plan most often is utilized when a contracting commissioning organization is appointed to a project, and it may be the first indication to the client project management and operations and engineering teams of how the commissioning will be planned and the activities managed.

Compile the Commissioning Estimate and/or Budget

Many factors should be considered for inclusion in the commissioning team budget, including labor power costs, initial chemical fill costs, travel, and accommodation at the job site. Typically calculated on a simple spreadsheet, each cost should be accompanied with adequate descriptions of the expense in question. Many projects have a percentage commissioning cost scheme in place; in general, these costs range from 2 to 3% of the overall capital spent on simple projects up to 25% of the capital cost for complicated nuclear facility commissioning, where much simulant testing must be developed and performed.

Devise Handover Procedure

It is absolutely crucial to clarify, agree on, and document the various handover steps among the range of engineering disciplines in a project. The focus here is on handovers between the construction group and the commissioning team and then between the commissioning team and the operations team. It is important to clarify what will be handed over and how and what the acceptance criteria are.

Compile Initial Commissioning Schedules (Levels 2 and 3)

The level 2 commissioning schedule, which is compiled at an early stage in the commissioning team’s formation, entails drafting acurate estimates of all the team’s activities. These activities include tasks in all three phases of a project. However, other than showing the duration of an activity (e.g., compilation of commissioning documents), the actual commissioning system in question is not specified.

The level 3 schedule will provide a very acurate timeline for all the in-depth commissioning activities, typically from the mechanical completion phase. The schedule is compiled on a task-by-task basis and written on a system-by-system basis and is very detailed.

Create Commissioning Documents and the System File

In the commissioning of a processing plant, the creation of the specific documents and the accompanying filing system is of some significance. The suite of commissioning documents produced provides a demonstration and shows that everything necessary has been done by the commissioning team to check and countercheck the constructed plant. This allows the delivery of the project to design specifications in the most safe, effective, and timely manner, to the highest possible standard, backed up by correct, prudent, and accurately composed documentation that is completed and signed off on in full. Anything undertaken in a commissioning campaign must be documented and stored in the system file to which it belongs; hence, the complete picture of all that has been done to commission the plant safely and efficiently can be demonstrated.

Implement

The field execution activities will change the plant from a build project to an operating asset.

Attendance at Factory Acceptance Tests

Much of the work to start the checkout of equipment can be completed at the factory before delivery to the site, and the completion of this work should be encoraged as it has the potential to save costs and time if vendor equipment does not perform initially. Activities performed at the factory acceptance test can include leak tests, intial operational runs, control system checkout, cleanliness checks, and test fitting of internals.

Check Construction and Quality of Build

The commissioning team plays a key role in the checkout of the systems in conjunction with the main plant construction. Schedule time and costs can be reduced by means of prompt identification and correction of faults; these faults can range from equipment installed incorrectly to valve handles protruding into walkways, causing safety hazards.

Cleaning Procedures and Drying

Before pipes and equipment are put in service, it is important that good cleaning procedures be conducted to help ensure a successful and trouble-free start-up. Unfortunately, it is not uncommon for an initial plant commissioning period to be marred by foreign materials that have been left inside pipe work and then find their way to pumps and other equipment, causing significant damage and schedule delay as a result of rectification work. The following methods of cleaning are common to fulfill this task: cleaning by blowing (air or nitrogen), steam blowing, cleaning via flushing (water), chemical cleaning, use of a “pig,” and mechanical cleaning and visual inspection.

Vessel Check Sheets

Conducting the checkout of the plant and equipment being installed requires documentary evidence that each item has been installed in accordance with the design and is fit for ongoing commissioning and operations. No plant item should be closed until an internal inspection has taken place. This documents that an inspection with authority to close equipment has been made.

Commissioning Punch Listing

This is one of the major activities the commissioning team will conduct. The setting of high standards, principles, and methodology for effective punch listing, snagging, or checkout of the system that has
been constructed is vitally important to the smooth ongoing commissioning of the asset and is the standard and key indicator by which a commissioning team will be measured.

Precommissioning Hazard and Operability Studies or Pre-Start-Up

Before the introduction of hazardous chemicals into a commissioning system or systems, a detailed check must be made to ensure that the plant is ready and fit for ongoing operation.

Commissioning Leak Testing

During the construction phase, hydrostatic tests will have been conducted to prove pipe integrity; however, many potential leak path points will still exist in an untested state. The object of a full system leak test is to test all leak potential suitably and practically before the introduction of process and hazardous chemicals.

Commissioning and initial Start-Up-Plus Procedures

This activity could be described as the flagship activity among the many the team will undertake during a project. Here, where possible, “safe” chemicals are introduced—water, steam, and air—to simulate closely the unit in actual operation and to provide an indication of how the plant will perform when the process chemicals are introduced and the main commissioning and start-up event takes place. During commissioning execution, all safety-related systems are checked rigorously, including confirmation of alarm activation points by means of manipulation of the actual process variables; confirmation of the operation of all control system software trip logic by various means, including variability of the process conditions both manually and via the control system; confirmation of all hardwired emergency shutdown systems by various documented operational means; and confirmation of the operation and control of all DCS sequences, including full testing of all failure monitoring. All aspects of future operation are tested, including starting up, scheduled and emergency shutdowns, and the actions required after a loss of site services, including power and instrument air.

Closeout

The activities in the final phase are all associated with the successful and efficient closeout of the commissioning team’s actions.

Conclusion

Monitoring and helping to mold the transformation of a plant from initial design intent, through the building and construction site phase, to successful commissioning and operation is an occupation that requires much organization and disciplined delivery. However, when it is based on and assisted by a methodology such as the one described here, it can lead to commissioning being a career that provides job satisfaction and pride.

Enjoy safe and happy commissioning.

Introduction

Stage fire protection measures, details differing from one region to another, have been established, codified and enforced throughout the world and have changed little over the past 100 years. Technological advancements in both stagecraft and fire protection systems have led to a need in the theater community to study the current state of theater fire protection requirements.

The objective of this study was to assess the level of protection afforded by stage active fire protection measures, as prescribed by the International Building Code (IBC), NFPA 80 Standard for Fire Doors and Other Opening Protectives, and as implemented in current design practice in the event of a fire in the stagehouse of a proscenium theatre. This study identifies (1) the magnitude of fire necessary to activate the automatic fire protection systems including rate-of-rise heat detectors, sprinklers, fire curtain, and roof vents; (2) the activation order of the fire protection systems; (3) whether or not tenable conditions are maintained for occupants evacuating an auditorium for a sufficient period of time; (4) whether the prescriptive criterion for sizing the natural vents (i.e., vent size equal to 5 percent of a stage area) is appropriate; (5) whether the suppression system and the roof ventilation system provide an additive level of safety or counteract one another; and (6) which fire safety measures have the greatest overall impact on the life/fire safety in a theatre.

Computational fluid dynamics (CFD) has been utilized to examine fire conditions and to assess the effectiveness of the fire protection systems provided within a stage. The input data including representative theater dimensions, fuel loads, and fire scenarios have been determined by a survey of theatre design professionals.

The Fire Research Division at the National Institute of Standards and Technology (NIST) studies fire science and fire safety engineering, and develops products and data that supports innovation and safety in the built and natural environment. The Fire Research Division has been developing what is called the Fire Dynamic Simulator (FDS) CFD model that has been optimized for use in simulating the effects of fire. FDS solves numerically a form of the Navier-Stokes equations for low speed, thermally driven flows such as occur during, and as a result of, fires. The program is available free from NIST and is used world-wide, essentially becoming the standard for fire CFD in the built environment. The model has been updated regularly since its public release in 2000. In the Arup Theatre Fire study FDS V5.2.4 was utilized.

The Data

The Arup team needed the input data to build the computer models. It was decided early on that the models would need to be representative of theatres being built today, with currently mandated code requirements since the goal was to look at the performance of modern, current fire protection systems. For quality and relevant data, the assistance was provided from both American Society of Theatre Consultants (ESTA) members and the theatre consulting community through an online survey that gathered dimensional criteria for three theatre models—small, medium and large—which is summarized in the table below. Thirty five responses were returned, the results compiled and averaged, and the data turned into plans, sections and finally a three dimensional notional models to be dropped into the fire models.

The survey asked respondents to rank the most likely location for the fire and materials involved in the conflagration, based on each individual’s experience or knowledge. Several Technical Directors around the country offered material lists from recent shows in their proscenium theaters. Rationalizing the responses, three locations for the fire were proposed: (1) center stage at floor level, (2) center stage approximately 25′ above the stage involving flown scenery, and (3) in the stage wings at stage level. Based on the survey results, it was determined that of the common materials on stage including muslin, wood, plywood, vinyl, medium-density-fiberboard (MDF), masonite, (cardboard) sonotubes, velour and wool draperies, etc. A mix of 75 percent to 25 percent of natural and synthetic materials respectively was appropriate and representative of sensible “scenery stuff” and the team utilized this information to define the combustion properties.

Figure 1 – Rendering illustrating the dimensions and general layout of the medium theater models

The code-mandated requirements were looked into in order to incorporate then into the fire models. Today in the United States, most jurisdictions are adopting the International Building Code (IBC) so this model code served as the basis for the fire protection systems in our theatre model. The primary life safety features required for proscenium type theaters with stages greater than 1,000 ft² in plan, and more than 50 feet high include:

• • Proscenium wall opening protection by a fire curtain or water curtain activated by rate-of-rise heat detectors and by manual operation.
• • Sprinklers at the roof and under the gridiron, as well as under catwalks and galleries if they are more than 4 feet in width.
• • Stage smoke ventilation by natural means with vents sized at no less than 5% of the stage area, or mechanical smoke evacuation designed to maintain the smoke layer above the highest level of the seating or the top of the proscenium opening.
• • Stages with a roof height less than 50 feet are not required to employ a fire safety curtain, although the rest of the requirements (sprinklers, ventilation, etc.) are.

At this point it is worth recalling that: (1) the study is focused on the proscenium stage, (2) all ignition sources in the model are on the stage (center or in the wings) or in the flytower, and (3) all the fire protection systems are in the stagehouse. Although the study would examine each of the principal life safety measures listed above and the way in which they interact, the objective of the study was the broad determination of whether the code requirements make sense in the theatres in which we create, work, perform and are entertained.

The Fire Modeling

Prior to modeling, a calibration study was done to determine the optimal cell size and approximate calculation accuracy. A series of models were set up to recreate the results from the set of fire tests that were conducted previously by Underwriters Laboratories on the interaction of sprinklers, smoke vents and draft curtains.

The first step, the results of which will be touched on below, was to study the placement of devices, including sprinklers, heat detectors, and fusible links and determine what conditions were necessary for each of them to activate and in what order they would likely activate. A series of “sensors” were placed in each model to represent sprinklers, heat detectors and fusible links that are commonly found on stages. Activation times for these various detectors were calculated in the model and/or during post processing. Temperature rating and the Response Time Index (RTI) were specified for each sensor.

The RTI is a relative measure of how long it takes for a fusible element, such as a sprinkler, to activate. The RTI is affected by the mass, surface area and geometry of the element. A lightweight thin element would have a lower RTI than a thicker, heavier element. RTI’s range from 70 to 450 ft^½s^½ for most sprinklers, with quick response sprinklers at the lower end of 70 to 90 ft^½s^½ and standard response typically in the range of 150 to 250 ft^½s^½. Sprinklers were located at grid level and ceiling level with an activation temperature of 165°F. Rate of rise detectors were located on the wall above the proscenium opening, 6 inches below the ceiling and on the ceiling just upstage of the proscenium opening. “Fusible links” were located every 10 feet along the safety curtain release line at a slightly higher resolution than that required by NFPA 80 (one every 15 feet) and at the hatches for roof venting.

Figure 2 – Rendering of the medium theater model highlighting the placement of “sensors” (yellow, blue, and red spheres) throughout the stagehouse

The second step in the study was to determine which fire safety measures have the greatest overall impact on the life/fire safety in a theatre. This has been semi-quantitatively evaluated by determining the effects of system failures or omissions. Initially a baseline level of performance is established through the modeling of the effects of the stage-based fire safety measures operating as intended or designed in response to a series of assumed design fires. Once the baseline is established, each of the systems is modeled to fail to activate properly or is omitted from the design altogether. This approach allows the positive contributions of each fire safety measure to be qualified, if not quantified, in order to provide a means for ranking the contribution of each of the measures to achieving fire and life safety objectives.

The Results

First Step of Study

The results from the first step of the study were analyzed to determine when it may be expected that life safety devices are activated and what this event would correspond to in relation to fire growth and fire size. The results of the modeling have been summarized in the graph below—although a graph has been developed for each size theater and for each fire scenario examined, the single example below will be used for illustration in this article. The graph illustrates the relationships between the time when items are expected to operate relative to each other and their respective RTI’s. Most importantly, the red dash-dot line represents the time when smoke would be expected to spill from under the proscenium if the fire safety curtain or roof venting has not yet activated. This was taken as a critical event in assessing the effectiveness of the fire safety curtain or stage emergency ventilation in preventing smoke spread and accumulation in the auditorium.

Figure 3 – Exemplar graph of device activation results from the medium theater model for a center stage fire

Several observations can be made from the graph. The results indicate that a rate-of-rise heat detector with an RTI less than approximately 70 would be required to either deploy the curtain or open the roof vents prior to smoke spilling. Reliance on fusible links alone would result in significant delays and hence increased life safety issues for the audience.

The data can also be interpreted to determine a critical RTI to assure that protection measures such as the fire safety curtain or flytower roof vents are deployed or activated prior to sprinkler activation—this, too, would be a critical event, as the cooling effects of sprinkler spray would be expected to delay subsequent activation of either smoke management system relying on either heat detectors or fusible links.

Not obvious in this chart, but expected, is the tendency of the ceiling sprinklers to activate prior to the under-grid sprinklers. This chart shows that the first under-grid sprinkler activates prior to the first ceiling sprinkler; however, this was true only for the under-grid sprinkler fully immersed in the fire plume (the fire is directly beneath the sprinkler). In general, the ceiling level sprinklers activated more rapidly than those under the gridiron.

There are also several general observations to be made regarding each of the theater types and fire scenarios:

• • A fire located on the stage resulted in a deep, but cool, smoke layer in the fly tower. This results in slower or delayed activation of the protection devices (such as rate of rise detectors and fusible links) relative to other fire scenarios and may result in the auditorium being exposed to high radiant heat levels unless the life safety systems are activated manually
• • A fire in the rigging, conversely, resulted in higher temperatures closer to the safety devices resulting in earlier activation of life safety systems via automatic means
• • In order to get the fire safety curtain and smoke hatches to activate prior to smoke spillage, a rate of rise heat detector with an Ultra Fast RTI would be required and the preliminary results indicate that ceiling mounted detectors provide quicker response than those on the walls
• • The fusible links in the fire curtain safety line are unlikely to activate in any of the fire scenarios

The full report for the first step of the study can be found at the NFPA website.

Second Step of Study

While the device activations were not modeled in the first step of the study, they were modeled to activate in the next step of the study. The key results of the first step in the modeling process are provided below.

• • The visibility contours from the vent failure model and the sprinkler failure model are compared in Figure 4. This shows the operation of the roof vents is most critical in providing a safe environment in the auditorium for egress of the theatre occupants/patrons.
• • Figure 4 shows that a fire safety curtain alone is inadequate to stop smoke from spreading to the auditorium completely, although the fire curtain restricts air movement reducing the rate of smoke spread to the auditorium.
• • The fire safety curtain and roof vents are fire and life safety systems that are intended to work in tandem. Alternate strategies that employ only ventilation or stage exhaust in lieu of a fire safety curtain require a thorough analysis to be completed to establish acceptable fuel loads and fire sizes. Such an approach would also likely call for a detailed fuel management program that might, in turn, reduce the flexibility in theatrical use of the space. As scenic elements/arrangements are changed, such spaces should require special analysis for each production as to whether the modified arrangement would produce smoke/fire exceeding the capacity of a smoke control system provided.
• • The results show that the late activation of the roof vents may result in unsafe conditions for egress in the auditorium. This indicates that the roof vents need to be activated as early as possible by the rate-of-rise heat detectors and/or by a means of manual activation.
• • As can be seen in Figure 4, delayed activation of sprinklers and even failure of sprinklers to operate can be tolerated in terms of a life safety provided the fire safety curtain and/or roof vents are designed properly and actuated rapidly to preclude smoke spread to the auditorium.
• • Activation of the roof vents and the fire curtain by rate-of-rise heat detectors provides the most rapid means for system deployment (notwithstanding manual operation) thereby increasing the likelihood of maintaining a tenable environment within the auditorium regardless of the presence or successful operation of sprinklers.
• • Opening of the stage roof vents by means of rate-of-rise heat detectors will likely precede the activation of sprinklers; open roof vents will tend to delay in actuation of sprinklers.
• • While the activation of sprinklers is not essential to the effective operation of the roof vents and fire safety curtain or the maintenance of a tenable environment within the auditorium, sprinklers are key to limiting the ultimate magnitude of the fire, protecting the integrity of the structure, and limiting property damage and losses.
• • No automatic means of fire protection systems were activated when the fire occurred in the center of a stage in the large-sized theatre, indicating human intervention and manual activation of stage fire safety systems become increasingly important as the size of the theatre increases. Theatres falling into the “large” classification require special consideration because of the potential delays in system activation owing to the height of the stage.

Figure 4 – Comparison of visibility contour between the case of the roof vent failure and the case of the sprinkler failure (Plan view taken 6 feet above the highest walking surface in the auditorium at 600 seconds [Center Stage Fire - Medium Theatre])

As a hospitalized patient is waiting for the real-time radiology results for his or her knee, the orthopedic surgeons are trying to determine which ligaments on the knee have been sprained or torn. To evaluate the trauma, the surgeons have to rely on clear and discernible color images produced by the flat panel displays. The “human factors”¹ of the display are vital here. The different shades of color help the doctors determine which ligaments have been strained or torn.

The medical industry is a good example, along with the aerospace industry, of a field in which the human factor of the displays is vital to discern images and colors so that the user, surgeon, or pilot can evaluate them and respond appropriately. With so many different technologies being introduced in visual displays and touch screens, their human factor performance can be affected adversely. Integrating the two technologies can introduce challenges for system designers and integrators. This article will discuss some of the challenges in integrating the two technologies and discuss an anomaly known as chromaticity shift. First it is necessary to frame the issue by briefly discussing the two key subsystems: the displays² and touch screens.

Displays

Visual displays have been in use for a long time, and the list of types keeps growing: cathode ray tubes (CRTs), plasma, liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs), E-Ink, liquid crystal on silicon (L-COS),³ and translucent, among others. All of these types have proprietary unique designs and processes in which the wavelengths of the light propagated can be distinct. For the output light from the visual displays to be processed, the light has to penetrate through unique materials such as the liquid crystal, phosphor, polarizing⁴ lenses, thin films, ink, and light-emitting diode (LED) lenses, depending on the type of display technology. These unique differences in color performance can be measured and quantified, as will be discussed below.

Touch Screens

A touch screen is a surface that can be used to detect and sense a presence on a certain location by the touch of a finger or other types of object. The surfaces that can be used for a touch screen are glass- and polymer-based materials. The types of touch screens a designer can encounter are resistive, capacitive sensors,⁵ optical, and sound as in surface acoustic wave (SAW) and optical projection, among others. All of these types of touch screens have unique coatings and thin films to operate and process light or wavelengths for a certain behavior. With so many unique materials and thin films to process the wavelengths of light, optical issues can occur. Furthermore, with the key proprietary thin films that are derived from the manufacturers for the operation of the touch screens, additional degradation can be seen. The human factor of the display and the touch screen system can be affected dramatically (see Figure 1).

Figure 1 Touch Screen and Display

Compatibility Issues and Chromaticity Shift

When system designers or integrators combine the display and touch screen technologies, optical losses occur immediately. The types of optical losses and degradations that can appear are luminance and contrast loss, hue and chroma degradation, sparkling phenomenon, and chromaticity⁶ changes or shifts.

Color or chromaticity shifts can occur when the output light wavelengths of the display are interfered with by the reflection of the front and back edges within the thin films of the touch screen. As a result, the output color from the combined system has changed or shifted from the original color in the display.

In some industries chromaticity shift may not be critical; however, in other industries, as was mentioned above, the ability of the brain to interpret the colors correctly can be vital. It can be a matter of life or death, especially in cockpit displays,⁷ for flight engineers, and for air traffic controllers. The display of reds and greens has to be as precise and true as possible as specified in aircraft industry standards. Those standards specify where chromaticity values have to exhibit for the combined system of a display and touch screen.

Causes of Chromaticity Shift

As with many type of touch screens, a vast number of types of materials are used for antireflective, antiscratch, and antiglare coatings, along with directional thin films to enhance the visual effects of a display image. Undesirable phenomena can occur with these coatings and films. An example is thin film interference, both constructive⁸ and destructive, by which a new wave can be created from the reflection of the edges of the coatings. These new waves could introduce changes in wavelength and in chromaticity values from the original wavelengths emanating from the displays. Examples of abnormalities of colors from displays with touch screens include pink for reds and yellowish for greens and even a slight purple for blues. The color changes can be calculated analytically or measured by utilizing a color analyzer or a spectrophotometer. Color metrology is the preferred method for measuring these chromaticity changes.

Color Metrology for Chromaticity Shift

Some knowledge of optical physics, quantum mechanics, and chromatography is needed to measure the color performance of a display and touch screen system. A couple of methods can be used to measure chromaticity shift in these systems. We will assume the color analyzer method and utilize the CIE 19319 chromaticity diagram using x, y, Lv (Figure 2).

Figure 2 CIE 1931 x, y Chromaticity Diagram

Measuring chromaticity shift is simple, but mitigating its effects can be challenging. The preferred method for measuring this phenomenon is as follows:

1. Utilizing the color analyzer, measure the display’s chromaticity values (x, y, Lv) at red, green, blue (RGB¹⁰) and the white color balance at different color temperatures. Compare the values measured to the C.I.E. diagram.
2. Attach the touch screen to the display and remeasure all of the chromaticity values. Note any differences.

The noted difference in chromaticity values between the display and the combined display and touch screen system for a particular color measurement is referred to as chromaticity shift. Statistical methods can be used to attain better accuracy on how much color shift there is in a system.

How to Resolve and Mitigate Chromaticity Shift

This is not a straightforward issue to resolve as the system engineer or integrator needs to examine the different layers of the thin films within the touch screen. He or she needs to determine and define the layers and complete an interference analysis of the thickness of the films and coatings. System engineers more than likely will have to work with the touch screen supplier to eliminate or lessen the thickness of certain thin films or coatings such as the antiglare or antireflective coatings¹¹ to determine which will look best with minimal chromaticity shift.

If the system engineer cannot resolve it and has time, the technology of the touch screen can be changed as certain types are more impervious to the chromaticity shift phenomena. Optical or surface acoustic wave touch screens are less prone to optical degradation because of their lack of indium tin oxide (ITO) or conductive plating films. One must be aware that different touch screen technologies have much different behavior in terms of their touch capabilities and features. Any technology changes require a thorough reevaluation of the entire display and touch screen system, including the touch screen controller hardware and software for the intended platform.

A worst case scenario and a last resort solution when all else fails would be to replace the display. This potential solution is very cumbersome and may take time to implement. Again, this major change would require a thorough reevaluation of the entire display and touch screen system, including the video/display controller hardware and software for the intended platform.

Recommendations and General Tips for Integrating Touch Screens

1. Know the system and platform requirements along with the industry standards (aerospace, medical, commercial).
2. Define the features that the touch screen system needs to support.
3. Determine the physical size and thickness of the touch screen.
4. Determine the technology of the touch screen system (resistive, capacitive, etc.).
5. Specify a touch sensor controller. Touch suppliers usually have them as they are combined with their touch screens.
6. Specify enhancement films and coatings and determine their thicknesses along with a layer specification for the touch screen.
7. Create a detailed drawing and specification of the touch screen system. Include wiring, schematics, and performance parameters for the system.
8. Determine a mounting method for the touch screen. Note active, visible, and nontouch areas of the touch screen and ensure that they are compatible with the display.
9. Complete operational and optical evaluation of the display and touch screen system, including any optical losses and degradation, including chromaticity shift.
10. Complete any off-angle chromaticity shift for wide view angle clarity.
11. Use your own eyes for any visible anomalies. Inspect the system.
12. Work closely with the supplier to resolve issues and ensure that designs are manufactured for the intended applications.

In summary, optical degradation of chromaticity can be apparent in display and touch screen systems in which many layers of thin film coatings have been applied to the glass or plastic. This particular anomaly, depending on the type of platform, can be critical. By using the color metrology method described above, a system engineer or integrator can quantify it and mitigate its effects by eliminating or adjusting the thickness of certain thin films to exhibit a desired effect.

As technologies change and improve for upcoming types of displays, these types of anomalies will occur more often, and a system designer needs to be equipped to resolve them if and when this happens.

1. Salvendy, Gavriel. Handbook of Human Factors and Ergonomics, 3rd ed. Hoboken, NJ: John Wiley & Sons, 2006, section 57.5.4.1. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=2488&VerticalID=0.

2. Lee, Jiun-Haw, Liu, David N., and Wu, Shin-Tson. Introduction to Flat Panel Displays. Chichester, UK: John Wiley & Sons, 2008, section 1.41. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=4504&VerticalID=0.

3. Lueder, Ernst. Liquid Crystal Displays: Addressing Schemes and Electro-Optical Effects, 2nd ed. Chichester, NY: John Wiley & Sons, 2010, section 16.3. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=4508&VerticalID=0.

4. Bass, Michael, DeCusatis, Casimer, Enoch, J., et al. Handbook of Optics. Volume I: Geometrical and Physical Optics, Polarized Light, Components and Instruments, 3rd ed. New York: McGraw-Hill, 2010, section 28.4.5. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=2839&VerticalID=0.

5. Wilson, Jon S. Sensor Technology Handbook. Burlington, MA: Elsevier, 2005, section 8.2. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=1659&VerticalID=0.

6. Kaplan, Steven M. Wiley Electrical and Electronics Engineering Dictionary. Hoboken, NJ: Wiley–IEEE Press, 2004. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=3663&VerticalID=0.

7. Moir, Ian, and Seabridge, Allan. Military Avionics Systems. Hoboken, NJ: John Wiley & Sons, 2006, section 9.5.5. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=1428&VerticalID=0.

8. Hariharan, P. Optical Interferometry, 2nd ed. Amsterdam and Boston: Academic Press, 2003, section 2.10. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=3534&VerticalID=0.

9. Lee, Liu, and Wu, 2006, section 2.3.2.

10. Lee, Liu, and Wu, 2006, section 2.3.2.

11. SVC-54^th Annual Technical Conference Proceedings. Society of Vacuum Coaters. Chicago: April 16–21, 2011, section 44. Online version available at
http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=4536&VerticalID=0.

Law enforcement officers carry handguns in their day-to-day activities, and those handguns are selected on the basis of manufacturers’ performance data and personal shooting experience. Additionally, the weapons must be proved adequate for offensive and defensive use in almost any situation involving armed criminals.

Choosing an effective weapon often requires examining a wide variety of what appear to be the outstanding capabilities of the weapon of choice. Thus, that weapon must have reliability, accuracy, a rapid firing capability, a large magazine capacity, and excellent penetration capability and stopping power. Many of these data are available from the manufacturers, but experience and observation of performance on the range also play an important role. The choices made are usually revolvers or semiautomatic handguns that fire that have a single propellant charge, a single bullet, and a magazine of variable capacity.

However, a revolver has become available that has a magazine capacity of six .410-bore shotgun shells, each with a single propellant charge and four 0.361-inch-diameter spherical in-line lead projectiles. This type of handgun has a much greater probability of hitting its target than does a conventional handgun firing conventional single-bullet ammunition because of the multiple rather than single projectiles discharged from the muzzle each time it is fired. The velocity of the multiplicity of shot discharged from the .410 handgun is 1200 feet per second (FPS), which may be somewhat greater than the velocity of the shots from most but not all handguns that fire conventional single-bullet ammunition. As a result, the combination of higher velocity and lower weight of the individual projectiles of the .410 ammunition compensates for the heavier weight and lower velocity of the heavier-weight bullets used in conventional handguns. Therefore, the penetration capabilities of the .410 are about the same as those of conventional handguns that fire single-bullet ammunition. This characteristic is particularly important in situations in which the target is shielded by glass or metal enclosures or when other obstacles have to be penetrated before the target can be reached.

However, other characteristics of importance also must be considered. Among these,
accuracy may be the most important. Although the number of hits made with each firing of the .410 may be greater when the targets are close to the shooter, this may not be the case with more remote targets, which can be hit with greater accuracy with conventional handguns and ammunition. The .410 shotgun shell revolver is at a disadvantage in these situations.

Target Shot Distribution Data

Shot distribution data for various shooter-to-target distances for the.410-bore shotgun shell revolver are given in Table 1.

Table 1: .410 Bore Shotgun Shell Revolver Shot Distribution Data

Calculated Shot Grouping Data

A measure for weapon accuracy and the proficiency of a shooter is twofold. First, the shots fired must be close to the aiming point, and second, the placement of multiple shots must lie within a circle, centered at the aiming point, that has as small a diameter as possible, preferably no more than 3 inches. This is possible for the .410 shot shell revolver even if the shooter is an inexperienced one, but only when the target is reasonably close to the shooter – say, about 15 feet – but is entirely possible at much greater ranges – say, about 75 feet – for an experienced shooter using a conventional .45 semiautomatic handgun that fires conventional ammunition.

Although Figure 1 provides the observed shot grouping diameter for only a single .410 round, it was of interest that the shot grouping for this round corresponded reasonably well with the calculated shot groupings at various shooter-to-target distances, as indicated by the curve in that figure, which was generated from Equations 1 through 5. The pertinent variables needed to estimate the shot groupings are as shown in the definitions of terms for Equations 1 through 5. The muzzle velocity is dependent on propellant weight, projectile weight, barrel length, barrel diameter, and muzzle velocity. The variables indicated and the relationships between variables are discussed at length elsewhere.¹ However, the muzzle velocity of the shot shells is already known from data obtainable from the manufacturer, so that the calculations referred to are unnecessary at this time and shot grouping diameters can be calculated from Equations 1 through 5:

Figure 1 and 2: (top) Shot grouping diameter for a .410 round. (bottom) Four-shot cluster for a shot shell cartridge

It has been assumed in Equations 1 through 5 that despite the fact that the shots in the shot shell cartridge are arranged in a row of four, the shots leave the muzzle as a four-shot cluster, as shown in Figure 2. As a result, the surrounding air passes horizontally and vertically through the cluster as shown, causing the shot to be displaced vertically and horizontally as a result of the passage of air through the spaces between the shots in the cluster at a velocity equal to the velocity of the shot:

• (Re) = Reynolds number, unitless
• (Dshot) = shot diameter, feet
• (Vair) = air velocity in spaces in .410 shot cluster, feet/second
• (Dens. air) = air density, pounds/cubic foot
• (Visc. air) = viscosity of air, pounds/foot second
• (Shot drag) = air drag on shot, pounds
• (Cd) = drag coefficient², unitless
• (Acc.shot) = shot acceleration caused by air drag, feet/second²
• (D) shot grouping = diameter enclosing shots on target, feet
• (L target) = distance of target from shooter, feet
• (t) = travel time from shooter to target, seconds

Steel Plate Penetration Calculations

Equations 6 through 8indicate the steel plate penetration capability of the individual 70-grain shot pellets fired from the .410 shotgun shell revolver so that they can be compared with that of the single 230-grain bullet fired from a conventional .45 semiautomatic handgun. The penetration data do not account for the effects of bullet or shot deformation, although the latter could reduce the calculated penetrations significantly.

Where:

• (Fshot) = impact force on steel plate, pounds
• (Wshot) = shot weight, pounds
• (Acc.)shot = shot deacceleration resulting from impact force (F), feet/second²
• (g) = acceleration of gravity = feet/second²
• (Vshot) = shot velocity at impact = feet/second
• (Lplate) = thickness of steel plate, feet
• (Dprojectile) = projectile diameter before impact, inches
• (Sshear) = shear stress³ for annealed steel plate with 0.2 % carbon

Performance Data and Conclusions

Comparative performance data for a shot shell revolver and a conventional .45 semiautomatic handgun are given in Table 2, and targets for both are shown in Figures 3 and 4.

Table 2: Comparative Handgun Data

Figure 3: Target cluster for a .410 shot shell revolver

Figure 4: Target cluster for a .45 semiautomatic

Conclusions

Although the shot shell revolver provides a means of assuring the infliction of serious multiple damage to a target at close range – say, 10 to 20 feet – when used by an inexperienced shooter, the severity of the damage would be minimal compared with that attainable by an experienced shooter firing a weapon such as a .45 semiautomatic even at much greater ranges of 75 feet or more. Therefore, the .45 or a comparable weapon would be the carry weapon of choice for an experienced shooter and the .410 shotgun shell revolver would be the carry weapon of choice for an inexperienced shooter.

Notes

1. Cross, Alan. Removal of Fouling Deposits on Heat Transfer Surfaces in Coal Fired Process Heaters and Boilers. Chemical Engineering, vol. 116, no. 7, p. 44, 2009.
2. Binder, R. C. Fluid Mechanics, 2nd ed. Englewood Cliffs, NJ: Prentice-Hall, 1956, p. 173.
3. Marks’ Standard Handbook for Mechanical Engineers, 10th ed. New York: McGraw-Hill, 1978, pp. 13–15.