ASME A112.18.3 pdf download

ASME A112.18.3 pdf download

6 GENERAL REQUIREMENTS FOR BACKFLOW PREVENTION DEVICES 6.1 Functional Backflow prevention devices shall be designed to pre- vent pollution and contamination of the potable water system.
6.2 Materials Materials in contact with potable water shall comply with the requirements of ASME A112.18.1M.
6.3 Environment
6.3.1 WorkingPressure. Backflow prevention devices shall be designed to functionat water working pressures up to 125 psig (861 kPa gage).
6.3.2 Working Temperature. Backflow prevention devices shall be designed to function at water supply temperatures ranging from 40°F to 160°F (4.4°C to 71°C).
6.4 Reliability Backflow prevention devices shall be resistant to mechanical wear, deposition ofminerals, aging, and cor- rosion of the materials as determined by the test proce- dure of para. 7. The manufacturer shall establish the reliability of the individual backflow prevention device, and it shall be confirmed by durability tests in accor- dance with para. 7.
7.1 Sample Size The minimuminitial sample size per setshall be seven specimens. The incremental increases and cumulative sample sizes shall be as shown in Table 1.
7.2 Test Methodology
7.2.1 Facilities. The backflow prevention devices shall be tested individually in fittings or test fixtures representing the dimensions and tolerances specified by the device manufacturer.
7.2.2 Protocol. The functional performance of the device shall be determined before and after the durabil- ity testsequence. The functional performance ofa device shall be determined in accordance with para. 11. The durability test sequence for a device shall be conducted in accordance with para. 15. The process for evaluation of backflow prevention devices is illustrated in Fig. 1.
Two sample sets, each consisting of a minimum of seven specimens, shall be evaluated for durability by tests defined in para. 15. At the start of the evaluation, both sets samples shall be tested for functional perform- ance (para. 11). 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 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 rejec- tion. 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 ofthis paragraph is to define the require- ments and test procedures for the evaluation of finished products incorporating certified backflow protection devices which have been demonstrated to be in compli- ance with paras. 6 and 7 of this Standard.

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