ASME A112.18.3 pdf download

ASME A112.18.3 pdf download.PERFORMANCE REQUIREMENTSFOR BACKFLOW PROTECTIONDEVICES AND SYSTEMS INPLUMBING FIXTURE FITTINGS.
the second sample set shall be tested for aging and corrosion (para. 15.1). 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 reection. 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 requirements and test procedures for the evaluation of finished products incorporating certified backflow protection devices which 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 backflow 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 are
(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 backflow nor shall contaminants be allowed to enter the fitting beyond the first barrier when the backflow pre’enter 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 hackflow protection system in the product literature or in the installation uistructions.
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
If, for example, 2 out of ii = 10 specimens (= 2O%) 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 A.l, is computed from the binomial distribution according to Clopper-Pearson.