ASME A112.18.3:2002 pdf free download

ASME A112.18.3:2002 pdf free download.PERFORMANCE REQUIREMENTSFOR BACKFLOW PROTECTIONDEVICES AND SYSTEMS INPLUMBING FIKXTURE FITTINGS.
Two sampic sets, each coisstmg of a minimum of seven specimens, shall be evaluated for durability by tests defined in para. 15. At the start of the evaluation, beth sets samples shall 1w tested for functional performance (para. II). Thereafter, one sample set shall be tested for mechanical wear and mineral deposition (para 15.2), and the second sample set shall be tested for aging and orrosion (pisra. 151). When retested, there shall be a maximum of three incremental increases.
7.3 Conformance
Any physical damage to internal devices known to preclude functional performance shall be cause for rqection. The allowable failures shall not exceed the values shown in Table 1.
8 FIXTURE FiTTiNGS WITH INTERNAL DEViCES COMPLYING WITh PARAS. 6 AND 7
The purpose of this paragraph is to define the requirenwnts and test procedures for the evaluation of finished products incorporating certified backflow protection devices whbch have been demonstrated to be in compliance with paras. 6 and 7 of this Standard.
8.1 Health and Safety
8.1.1 There shall be at least two backfiow prevention devices, in series proven by tests as in compliance with para. 7 of this Standard. They shall operate independently as integral parts of the fixture fitting. At least one device shall be a check valve, called the primary check in this Standard.
Among the protection devices arc
(a) check valves
(b) vents to air
(c) vacuum breakers
(d) automatic diverters
8.1.2 Contaminants shall not enter the potable water system through hackflow nor shall contaminants be allowed to enter the fitting beyond the first barrier when the backflow preventer is operating properly. The test shall be in accordance with para. 12.
8.1.3 The manufacturer shall specify the type and location of the backflow protection system in the product literature or in the installation instructions.
8.2 Performance Tests
8.2.1 SelectIon of Test Specimens. To comply with this Standard, two specimens will be selected at random from a lot of five production fittings. Before mounting the fixture fittings in the test rig, correct installation of
The upper confidence limits are based on measured failure rates for devices subjected to the durability tests defined in ASME A 112.18.3-2002.
The upper confidence limits, for a P,, of 97.5% unilateral, being usual for technical products of the type under examination, are given in Table Al for selected sample sizes and failure rates.
If. for example, 2 out of n = 10 specimens (= 20%) fail to meet the requirements in the life test, the upper confidence limit for all of these products in the field is 55.6%. This means the maximum probable failure rate may account for 55.6%.
For devices of the type under examination, it is proposed not to permit an upper confidence limit, i.e., the maximum probable failure rate in the field, in excess of 56%.
It shall also be mathematically possible to add the results of several tests performed to the same specification on differing numbers of specimens. This technique is referred to as a multiple sampling scheme and is widely recognized in quality control work.
Therefore, adding a second test result from 5 test specimens with I failure to the above described result produces an upper confidence limit for the final test result of <48.1% and means, with respect to the above assumed limit of 56%, that the product tested in this way has passed the test. It is proposed that the tested device, or the entire product in the case of integrated solutions, be certified. The described method of computing the reliability of safety systems is mathematically exact, noninterpretable, extremely simple for test engineers and manufacturers to use, and extremely flexible in application. The latter two criteria are of particular significance to pragmatic approval testing. The failure rate confidence limit, Table Al, is computed from the binomial distribution according to Clopper-Pearson (see Reference 131) for the upper limit as.