Prior use assessment

The primary function of Prior Use assessment is to obtain a level of comfort regarding systematic (design) faults. One must develop confidence that a product does not have inherent design flaws. Sometimes the data gathered in a Prior Use assessment is used to calculate failure rates but this must be approached with caution whenever it is suspected that all failures are not reported. 

Prior use assessment is the responsibility of an end user. However some manufacturers are working to help their customers in prior use evaluations by providing hiformation. Some manufacturers have had a third party assessment of the field failure records that exist for a device. Failures attributable to both hardware and software are considered. As part of this process an assessment must also be made of the field return data gathering procedures and the product modification process. 

SIL-Safety Instructions SM/265/7/9/S1L-EN Rev. 03 Pressure-Transmitter 2600T.SIL2 lEC 61508 ABB Exida management summary FMEDA and prior use assessment. 

There is no mention that a prior hazard assessment will be acceptable. It is only common sense that OSHA would not expect employers with a previously documented hazard assessment program that meets the new requirements to perform another assessment. Yet there is no way of knowing if this will be acceptable. Employers should use good judgment on what is an effective hazard assessment. Bear in mind, hazard assessment should incorporate any applicable American National Standards... 

A number of substances have been identified that have either a specific virucidal effect on HIV or prevent infection of cells in vitro. The virucidal activity of potential topical agents can be assessed against cell-free and cell-associated virus using these assay systems. They allow the measurement of precise contact times between the HIV and virucides, enable the protective effect of preparations to be examined, and allow removal of the virucide from the system prior to assessment of cell viability. 

Recently, much attention has been devoted to prior learning assessment (PEA) as a method to award academic credit or advanced level placement for competencies acquired through previous work experience. As is discussed in more detail later in this article, PEA is a useful methodology for decreasing coursework and time requirements. However, it is not a simple process and requires considerable effort by both students and faculty. 

A complete lEC 61508 assessment includes a FMEDA, a study of Prior Use and adds an assessment of all fault avoidance and fault control measures during hardware and software development as well as detail study of the testing, modification, user documentation and manufacturing processes. The objective of all this effort is to provide a high level of assurance that an instrument has sufficient quality and integrity for a safety instrumented system application. This is clearly more important for products containing software as many end users have the strong opinion that software is "bad... 

Assessment Criteria FMEDA only Prior Use IEC 61508 Certification... 

If the equipment is classified as a SIS, then the next task is equipment justification. This must be done by either a "prior use" justification or equipment must be assessed per lEC 61508 (Ref. 2). Most choose the lEC 61508 certification route, especially for the logic solver, since the documentation burden is high and data gathering can be painful and fruitless when good systems are not in place. This is discussed in detail in Chapter 7. 

Indicator Time used to review and reflect on prior incidents. Time lag between plaimed actions and actual actions related to prior incidents. Assessment of safety culture based on Hearts and mind methodology to identify the degree of learning organization . 

Always combine prior use with quantification techniques in assessing the adequacy of the power sources and/or power supplies. 

NOTE - 2 A device does not have an SIL, since SIL is a quantitative measure of the performance of the overall SIF. lEC 61508 expands the use of the SIL terminology to device design requirements documented in lEC 61508-2 and lEC 61508-3. Therefore, a SIL 3 device means that the device has either completed an evaluation that the device design meets the requirements of lEC 61508-2 and lEC 61508-3 to the SIL 3 requirements and/or has been analyzed to these same requirements through prior use or lEC 61508 Compliance assessments. Since a SIL claim limit can be achieved through different methods and may have many restrictions for use, always ask the manufecturer of a device how the claim limit was achieved and any restrictions for use that may apply. 

ANSI/ISA-84.00.01-2004-1 allows prior-use justification of non-PE devices and PE devices, using FPL (e.g. a SMART Transmitter), when the SIL claim limit is less than 4 (i.e., SIL 4 claim limit per ANSI/ISA-84.00.01-2004-1 is not allowed). If an SIL 3 claim limit is required, formal assessment should be performed as part of the prior use evaluation, and a safety manual should be prepared based on the results of the assessment. ANSI/ISA-84.00.01-2004-1, Clause 11.5.4, provides the requirements for... 

The manufacturer s analysis is then balanced with field history in similar applications to obtain a better understanding of potential device performance. Prior use is established for each selected device (e.g.. Brand X pressure transmitter) in its operating profile, which includes examination of process, environmental, and field installation conditions that may affect the device s operation. Prior use requires review of the manufacturer s design and development processes to ensure the required level of quality control. Further, any data used to justify prior use should be carefully assessed to ensure it adequately represents the device in the operating profile. 

The term prior use is used in ANSI/ISA-84.00.01-2004-1. This term is applied when the owner/operator is justifying the implementation of a device in an SIF application based on prior use of the device in a similar operating profile. The standard provides specific requirements for assessing prior use for devices based on the device type, safety integrity level, and, in the case of PE logic solvers, the safe failure... 

As the pressure transmitter XXX is supposed to be a proven in use device an assessment of hardware with additional prior use demonstration for the device and its software was carried out. The prior use investigation was based on field return data collected and analyzed by. .. manufacturer. This data cannot cover process connection. Prior-use justification for the process connection still needs to be done by end user (to make a note by reader)... 

According to die requirements o/IEC 6151 LI first edition 2003-01 Section 11.4-4 and the assessment described in Section 5.1 the Type B pressure transmitter XXX with a hardware fault tolerance of 0 and SFF 60 to <90% is considered suitable for use in SIL2 safety function. The decision on the usage of prior-use device, however, is always with the end user (to make a note by reader). 

In order to assess the novelty of an invention, officials at the Patent Office will search the world-wide Uterature in that field, and even publication years before, e.g. in an obscure journal available only in one library, will destroy novelty. But the irrformation must be available to the public, hence, if it is known somewhere, but kept secret, this will not destroy its novelty. If the Patent Office searches discover prior use or disclosure, the patent will not be granted. But all is not safe even after the patent is granted, becairse competitors can use lack of novelty at the time of filing to challenge the patent. Competitors therefore frequently employ researchers to search the Uterature in the hope of finding something which they can use to attack the patentee s monopoly. If the invention is not new, no-one can patent it, and a patent already granted will be revoked. 

TABLES FOR ASSESSING, FROM PRIOR USE, A STANDARD PLC (LVL PROGRAMMABLE DEVICE) UP TO SIL2... 

One particular common piece of legislation worth noting is the requirement for an Environmental Impact Assessment (EIA) to be performed prior to any appraisal or development activity. An EIA is used to determine what impact an activity would have on the natural environment (flora, fauna, local population), and will be used to modify the activity plan until no negative impact is foreseen. More details of the EIA are given in Section 4.0. 

Selection of an in-house group or consulting firm to do a market or marketing research study does not foUow any set pattern. In some cases, an outside consulting group is retained to do an independent study of an area already researched by an in-house group. Most often the consultancy is unaware of the prior in-house study, and its report is used as a check study or an assurance to management that its report made a proper assessment. 

Erythrocyte Entrapment of Enzymes. Erythrocytes have been used as carriers for therapeutic enzymes in the treatment of inborn errors (249). Exogenous enzymes encapsulated in erythrocytes may be useful both for dehvery of a given enzyme to the site of its intended function and for the degradation of pathologically elevated, diffusible substances in the plasma. In the use of this approach, it is important to determine that the enzyme is completely internalized without adsorption to the erythrocyte membrane. Since exposed protein on the erythrocyte surface may ehcit an immune response following repeated sensitization with enzyme loaded erythrocytes, an immunologic assessment of each potential system in animal models is required prior to human trials (250). 

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