Proof testing and inspection

1 Periodic proof tests shall be conducted using a written procedure (see 16.2.8) to reveal undetected faults that prevent the SIS from operating in accordance with the safety 

2 The entire SIS shall be tested including the sensor(s), the logic solver and the final element (s) (for example, shutdown valves and motors). 

3 The frequency of the proof tests shall be as decided using the PFDgvg calculation. 

NOTE Different parts of the SIS may require different test intervals, for example, the logic solver may require a different test interval than the sensors or final elements. 

4 Any deficiencies found during the proof testing shall be repaired in a safe and timely manner. 

1 The proof test interval should be selected to achieve the average probability of failure on demand as required in the safety requirements specification. 

3 The frequency of proof tests should be consistent with applicable manufacturer s recommendations and good engineering practices, and more frequently, if determined to be necessary by prior operating experience. 

There are a number of strategies being used to select the proof test interval for a SIF. 

Other users may wish to standardize on the basis of a defined test interval and test all systems in a manufacturing plant at the same test interval. For example, they may wish to test each SIF 

Copyright International Sod y of Automation Provided by IHS under license with ISA 

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It is important to document the results of the proof test and inspection for a record of what was found. There are no specific requirements for how long these results should be retained but generally a sufficient number are retained to allow for re-examination of previous results to see if there is a history of component failure. 

The user shall maintain records that certify that proof tests and inspections were completed as required. These records shall include the following information as a minimum ... 

This is very important because proper record keeping could help in future analysis and resolving future maintenance problems. Also traceable data keeping is helpful in dealing with regulatory authorities. As per lEC 61511-1 2003 Clause 16.3.3 The user shall maintain records that certify that proof tests and inspections were completed as required. Minimum data recording shall include but not be limited to ... 

Development of operational and maintenance procedures and plan Proof testing and inspection (see below) ... 

Proof test and Inspection procedure includes Testing identifies failure modes unrevealed by operation in the entire SIS (sensor, logic solver and final element(s)) ... 

Documentation requirements (e.g., frequency of demands placed on SIF/SIS, procedures/methods/techniques, proof tests and inspections, test results, equipment identifiers down to the revision level, responsible persons/departments/organizations)... 

Problem Layer of protection analysis has indicated that a demand would occur every 5 years on average for a particular process hazard. Although most automatic diagnostics execute every minute, the worst-case time period for automatic diagnostics within the equipment is once per week. A proof test interval of one year is proposed for a manual test and inspection. Would this SIF be classified as low demand ... 

All pressure equipment should be tested or inspected periodically. The interval between tests or inspections is determined by the severity of the usage the equipment has received. Corrosive or otherwise hazardous service requires more frequent tests and inspections. Inspection data should be stamped on or attached to the equipment. Pressure vessels may be subjected to nondestructive inspections such as visual inspection, penetrant inspection, acoustic emissions recording, and radiography. However, hydrostatic proof tests are necessary for final acceptance. These tests should be as infrequent as possible. They should be performed before the vessel is placed in initial service, every 10 years thereafter, after a significant repair or modification, and if the vessel experiences ovrapressure or overtemperature. 

However, the formal proof of capability to produce quality of the companies involved and as precise a description as possible of the requirements and conditions of the constmction project is not sufficient to succeed with the constmction project. Those involved must also not only have the formal qualifications but also the capability, i.e. specialist knowledge, experience and availability of specialists, machines and equipment, to meet the project requirements Accreditation procedures and voluntarily certification associations offer the possibility that both testing and inspection bodies, which are involved in the context of qualify assurance, and the companies involved in constmction work can prove their specialist competence. 

Some of the above are internal problems that can not always be detected beforehand. The best prevention is a conscientious program of periodic inspection or proof testing and preventive maintenance. 

The inspection team shall have the right, subject to the agreement of the inspected State Party, to have its inspection equipment installed, if applicable, inter alia, in the temporary holding area, in the chemical weapons disassembly area, in the chemical destruction process area, in the munitions body destruction process area, and in the solid, liquid and gas waste destruction product areas. The inspection team shall have the right to use for their equipment tamper proof seals or, if agreed by the inspected State Party, have its equipment installed in tamper proof boxes. The inspection team shall have the right to test and inspect the equipment under the observation of the inspected State Party. The inspected State Party shall, at the request of the inspection team provide the following ... 

CR-5094 Inspection and surveillance of metallic pressure vessels during proof testing Di. M. Chedaoui CETIM... 

As to the dollar-value of the Arsenal, its facilities are valued at over 500,000,000. The nature of these facilities varies, from the conventional to the nuclear. Conventional ammunition production lines, control laboratories and inspection systems are maintained in stand-by and are occasionally used in experimental or pilot-lot production. Nuclear weapons ammunition, components and devices are developed and produced in the. necessarily special research laboratories, proof-testing facilities and production and pilot assembly lines... 

Inspection and testing requirements are covered in detail. Most vessels are required to be hydrostatic-tested (generally with water) at 1.3 times the maximum allowable working pressure. Some enameled (glass-lined) vessels are permitted to be hydrostatic-tested at lower pressures. Pneumatic tests are permitted and are carried to at least IV4 times the maximum allowable working pressure, and there is provision for proof testing when the strength of the vessel or any of its parts cannot be computed with satisfactory assurance of accuracy. Pneumatic or proof tests are rarely conducted. 

Problem A set of non-redundant (lool) safety equipment is used to perform a safety instrumented function in low demand mode. The equipment is to be inspected and fully restored every five years. Therefore the manual proof test interval is five years and the manual proof test effectiveness can be assumed to be 100%. 

As opposed to testing, which attempts to uncover errors in a product by running the product, analytic techniques try to uncover errors by analyzing arepresentation of the product such as its software code. Program proof techniques fall in this category. A more common approach involves reviews of a work product by peer engineers. Two such techniques are code walk-throughs and inspections. 

An RCM optimization module enabling calculation of effective failure rates for common RCM activity types, i.e., age replacement, functional proof testing, inspection in time-delay models and a gradual failure progression model, see e.g. Vatn (2007) for a description of these models. The RCM module enables maintenance interval optimization taking the entire regularity model into accoimt. 

Inspection of a packaging for heat transfer characteristics, in compliance with para. 501(b), should include a dimensional check and special attention to ventilation apertures, surface emissivity, and absorptivity and continuity of conduction paths. Proof tests, which may normally be necessary only for a prototype package, may be conducted by using electrical heaters in place of a radioactive source. 

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