SIS-TECH announces its new Tank Protection System (TPS) – an independent, cyber-proof system that uses the Diamond-SIS® to monitor and report asset threatening conditions in terminals, tank farms and process vessels. The Diamond-SIS^® is a state-based controller rated for hazardous locations, allowing local installation, minimizing installation and wiring costs. The Diamond-SIS^® is specifically designed for low I/O applications and its installed cost is 10% of conventional safety controllers. The Diamond-SIS^® has over a decade of continuous industrial service with zero reported failures and is certified for use in SIL 3 applications.

 

The TPS is flexible and customizable for any application. A popular configuration provides dual alarms for each condition of concern, a local operator interface for safe operation and shutdown, and an automatic overfill prevention system (AOPS). The low power consumption of the Diamond-SIS^® is ideally suited for solar power where utilities don’t exist. Options are available for communicating tank fill status to remote monitoring stations.

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Hui Jin was recently promoted to Senior Risk Analyst with SIS-TECH Solutions in Houston, TX. Hui Jin has a PhD in reliability engineering from NTNU in Norway, where he developed a keen interest in the numerical assessment of safety instrumented systems in process industrial applications. At SIS-TECH, he leads the software design team for SIL Solver NG, a tool for calculating the probability of failure and nuisance trip potential of safety critical systems. Hui Jin is bilingual with fluency in Chinese and English.

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SIS-TECH Solutions strongly supports The Center by sending gift boxes of their delicious gingersnaps to our best clients every holiday season since the early 2000s. The Center is a private not-for-profit United Way agency, which has for more than 60 years served children and adults through educational, residential and work training programs. The holiday gingersnaps are shipped in gold tins that are decorated with gilded handmade paper ornaments. All proceeds from cookie sales (see www.gingersnapsetc.org) are used to enrich the lives of the 600 adults at The Center located in Houston, TX.  For more information on The Center please visit www.thecenterhouston.org.

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Automated systems, whether in manual or automatic mode, are complex systems where many different devices must work successfully to achieve the desired functionality. Sustaining automated system performance requires many different skill sets and planned activities to assure that the systems work as desired when required. In general, inherently safer practices can create safeguards that have less potential for dangerous failure, whether the failure occurs due to safeguard design, to a support system disruption or to human error. Some inherently safer practices bring a higher potential for spurious, or unnecessary, activation of the safety systems. If spurious operation causes intolerable losses, the functional specification should state a target spurious trip rate.

Inherently safer practices can significantly influence the automation equipment selection, fault tolerance, response to detected equipment failure, and response to detected support system failure, such as loss of communications or utilities. It is not possible to create a complete list of the automation features that could be considered inherently safer than alternative choices.  Instead, each inherently safer strategy is defined below as it applies to automation. Then, a short list of examples is provided to illustrate the strategy.

Minimize applied to automation – reducing the use of automation features that tend to increase the failure mechanisms that result in system failure.

• Select devices that do not require additional instrumentation in order to make them function properly in the given process; for example, using a remote sealed level in plugging services instead of using a device that requires process connection purging, or using a mass flow meter instead of using pressure, temperature, and density to compensate a volumetric flow reading
• Minimize blind spots in measurement by using devices that are applicable over the full range of process operating modes
• Where possible, eliminate inherently weak components, such as sight glasses, hoses, rotameters, bellows, and plastic components

Substitute applied to automation– replacing an automation feature with an alternative that reduces or eliminates the frequency of dangerous failure.

• Use materials of construction with lower corrosion or erosion rates
• Use a device that provides a direct measurement of the process parameter being controlled rather than using an indirect measurement
• Select devices that fail to the safe state on loss of any utility, such as power or instrument air, instead of devices which require energy to take action

Moderate applied to automation– using automation features to facilitate operating the facility under less hazardous conditions; using automation features which minimize or limit the impact of dangerous failure of the automation system on the process operation.

• Provide operator with redundant indication of safety variables using simple graphical displays that build trust in the automation system
• Consider minimum flow stops to prevent loss of flow in sensitive services
• Use confirmation of change prior to taking action on operator commands
• Provide first out indication and sufficient additional information to allow the operator to quickly diagnose and respond to the causes of process deviation

Simplify applied to automation– specifying automation features in a manner that eliminates unnecessary complexity and makes operating and maintenance errors less likely, and which is forgiving of errors.

• Configure systems such that loss of communication or loss of signal results in the safe state
• Make the navigation of the operator HMI and safety HMI intuitive and user-friendly
• Use distinctive labeling in plant documentation, the operator HMI, and on the components in the field for safety devices: use logical numbering for device groupings
• Use valve designs that offer a visual indication of actual position

These inherently safer practices should be implemented as part of the design, operation, maintenance, and testing of the process control and safety systems, where practicable. The sustainability and resiliency of these automation systems can be significantly enhanced through the application of the inherently safer strategies during the automation lifecycle. Contact SIS-TECH for more information on how to design and manage inherently safer automation.

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Houston, Texas – SIS-TECH Solutions 2017 Training Course Calendar is now available. Courses cover process hazards analysis, risk assessment, alarm management and the design of instrumentation and controls systems for safety applications.  Whether you simply need to know more about a subject or wish to obtain your certification in functional safety, SIS-TECH has a course for you.

SIS-TECH offers approximately 2 courses per month through-out the year. Course duration varies from 1 day to 4 days depending on course topic. All courses are taught by SIS-TECH employees with extensive knowledge and experience in process safety management and control system design.

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SIS-TECH Solutions LP has hired Monica Hochleitner as a Senior SCAI consultant. Along with her over 25-year experience in the process industry, Monica is a certified functional safety expert since 2008 and holds a FS Eng (TÜV Rheinland) certificate. She specializes in hazards analysis, alarm management, safety instrumented system design, and auditing.  Monica conducts training for instrumentation and controls professionals in English and Portuguese.

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SIS-TECH’s Diamond-SIS has recently completed the rigorous testing in the FM Approvals test lab to demonstrate the new design still meets the requirements for Class 1, Div 2 Groups A, B, C, D. With the addition of the isolated 4-20mA repeated output, configuring the Diamond-SIS in an existing marshaling cabinet in the field becomes much less arduous and does it with less space. Z-Purge no longer has to be considered and finding that extra 3 inches of din rail space to mount it on is not so rare anymore. SIS-TECH has recently increased orders to electrical supply houses that report “due to its versatility, compactness (size), and the fact that it can be mounted virtually anywhere on site” offering protection from the weather, “becomes the independent layer of protection of choice”.

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Safety Instrumentation and Control Reliability

Angela E. Summers, PhD, PE, President

A site’s risk analysis assumes that a particular level of risk reduction can be provided by the installed safeguards. The fundamental basis for this assumption is that the equipment is designed and managed according to recognized and generally accepted good engineering practices. Safe operation in the field is the goal, so site operation and maintenance records must ultimately demonstrate that the equipment as installed achieves the required risk reduction and is fit for purpose.

The achieved reliability of the process control scheme impacts the safety and profitability of the process unit operation. Higher process control reliability reduces the number of process upsets, shutdowns and restarts. Essentially, the more reliable the process control scheme, the safer the process unit is.

The key process safety objective is to identify failures, gaps or conditions and to correct them before they contribute to a major process safety incident [1].

The contribution of the process control scheme to abnormal operation can be tracked by automatically saving process safety event data whenever a safeguard is challenged. A process safety event reporter can be configured to flag events and to display important data for root cause analysis. Safety equipment are normally dormant and take specific action only when abnormal operation occurs, so it is a critical site responsibility to assure that safety equipment are not run to failure. An failure discovered during abnormal operation is not only undesirable but potentially dangerous.

Process safety regulations require a proactive maintenance program combined with quality assurance metrics to be applied to safety equipment. Many owner/operators establish a classification scheme to identify and prioritize the equipment that they will more highly manage. A process industry classification scheme can be found in ANSI/ISA 84.91.01 [2], “Mechanical Integrity of Safety Controls, Alarms, and Interlocks (SCAI).”  Safety controls, safety alarms, safety interlocks, and safety instrumented systems (SIS) are frequently implemented as safeguards to address abnormal process operation that potentially leads to loss of containment.

Procedures are needed for gathering information about failures and developing useful metrics regarding failures. The owner/operator must take corrective action to maintain safety if the failure rates exceed those assumed during design. Competent people are necessary to evaluate and analyze the data and then develop and implement plans to improve the instrument reliability. ISA TR84.00.04 Annex R [3] and ISA TR84.00.03 [4] provide guidance on selecting metrics for SIS, which can be applied equally as well to SCAI.

A database is needed to log service time and other information defined by the chosen failure data taxonomy. This database can be as simple as a spreadsheet or as complex as a computerized maintenance management system. Also needed is a collection method that is easy to follow, technicians motivated to correctly document the information, and people assigned responsibility for improving instrumentation reliability. Once sufficient information has been collected, the good and bad actors can be identified, and plans can be formulated and implemented to eliminate the bad actors and improve reliability.

Good actors are reliable technologies that have been proven through a volume of operating experience that they are fit for purpose.  Understanding what makes a device a good actor can help improve the site practices needed across the lifecycle and potentially reduce the overall cost of ownership through better design, specification, construction, installation, operation, and maintenance.

Bad actors are instruments that have repeated failures at a frequency inconsistent with design assumptions or operational needs. They are not only a reliability problem; they also increase operating costs, consume maintenance resources, and impact productivity. Identifying bad actors and resolving underlying problems shifts the instrument maintenance program from one that is reacting to work orders to one that is proactively taking care of problem devices before they affect safe operation.

An instrument reliability program with quality assurance metics provides many benefits to the owner/operator:

• Ensures that maintenance procedures are performed effectively throughout the safety equipment life
• Provides feedback to validate riskanalysis and functional specification assumptions
• Identifies sources of human errors and common cause failures so that the safety equipment can be designed to reduce the impact of these sources
• Demonstrates through prior useevidence (historical performance) that installed safety equipment is fit for purpose and acceptable for continued use
• Ensures that poorly performing safety equipment is identified and that actions are taken to correct deficiencies

References

• 2010. Guidelines for Process Safety Metrics. New York: AIChE.
• ANSI/ISA 84.91.01. 2012. “Mechanical Integrity of Safety Controls, Alarms, and Interlocks (SCAI)
• 2015. Guidelines for the Implementation of ANSI/ISA 84.00.01- Part 1, TR84.00.04-2015. Research Triangle Park: ISA.
• 2012. Mechanical Integrity of Safety Instrumented Systems (SIS), TR84.00.03-2012. Research Triangle Park: ISA.

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