ASME PTC 1:2015 pdf download

ASME PTC 1:2015 pdf download General Instructions Performance Test Codes
1-5 APPLICATIONS OF PTCs
Code tests are suitable for use whenever performancemust be determined with minimum uncertainty.Theyare meant specifically for equipment operating in anindustrial setting.Typical uses include
(a) determining if the equipment meets design orexpected performance criteria.
b) incorporating by reference into contracts to serveas a means to determine fulfillment of guarantees.(c) evaluating performance following modification,change in operating conditions,or any suspected changein performance for which such investigation is required.(d) conducting studies to help determine the value ofpossible upgrades or modifications to equipment.
(e) benchmarking performance, sometimes to helpdetermine the necessity for specific preventive mainte-nance, or possible upgrade or modification.
(f)trending performance in time by scheduling per-formance tests at regular intervals.Such trends are alsoused to help determine necessity for specific preventivemaintenance, or possible upgrade or modification.(g ) validating results from online or continuousperformance-monitoring systems, which are usually lessaccurate than results of tests conducted in accordancewith PTCs.
PTCs can be used to quantify the magnitude of per-formance anomalies of equipment that is suspected tobe performing poorly or to confirm the need for mainte-nance, if simpler means are not adequate.PTCs are excel-lent sources or references for simpler routine or specialequipment test procedures.
Conducting periodic performance tests on equipmentcan uncover the need for further investigation, whichcan lead to preventive maintenance or modification.
1-6TEST UNCERTAINTY
1-6.1 Definition
Test uncertainty is an estimate of the limit of error ofa test result. It is the interval about a test result thatcontains the true value with a given probability or levelof confidence.lt is based on calculations utilizing statis-tics,instrumentation information, calculation proce-dure, and actual test data. ASME PTC 19.1 is the PTCSupplement that covers general procedures for calcula-tion of test uncertainty.PTCs maintain a 95%level ofconfidence for which uncertainty is calculated as theirstandard. This confidence level therefore represents a 95%chance that the uncertainty interval contains thetrue value.
1-6.2 Applications of Test Uncertainty Analysis –
General
Analysis of test uncertainty is useful because it
(a) identifies dominant sources of error, their effectson a test result, and estimates of their limits
b) validates quality of test results
(c) facilitates communication regarding results
(d) facilitates the choice of appropriate andcost-effective measurement devices and procedures
(e) reduces the risk of making erroneous decisions(f) demonstrates compliance with test requirements(g) facilitates interpretation of test results
1-6.2.1 Pretest Uncertainty Analysis.PTCs requirea pretest uncertainty analysis in order to effectively planthe test.A pretest uncertainty analysis allows correctiveaction to be taken prior to the test, either to decreasethe uncertainty to a level consistent with the overallobjective of the test or to reduce the cost of the test whilestill attaining the objective.
1-6.2.2 Post-Test Uncertainty Analysis.PTCsrequire a post-test uncertainty analysis to determine theuncertainty intervals for the actual test. This analysisshould confirm the pretest systematic and randomuncertainty estimates. It serves to either validate thequality of the test results or to expose problems.
1-6.3 ASME PTC Treatment and Uses of Test
Uncertainty
Code-writing committees shall state the magnitude ofthe uncertainties expected in individual measurementsand instruct the user in calculation of uncertainty of thefinal test results.A sample post-test uncertainty analysisbased on PTC 19.1 shall be included. This shall includetypical random uncertainties based on the experienceof the committee.
Application of test uncertainty analysis can vary basedon the experience of each committee and on the manydifferent types of equipment for which codes are written.There are several acceptable ways to utilize test uncer-tainty analysis in ASME PTCs (see paras. 1-6.3.1 and1-6.3.2).
1-6.3.1 Permissible Uses of Test Uncertainty. Thefollowing uses of test uncertainty to prepare for and tovalidate the acceptability of a test are permissible.Oneor more shall be used in a single code.
a)Specify the maximum test result uncertainty abovewhich the test result is not acceptable for each type orconfiguration of equipment. The maximum test resultuncertainty is a limit and not a target in designing a test.