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ASME A112.18.3-2002 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 EVALUATION OF BACKFLOW PREVENTION DEVICES 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 3 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. 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 indepen- dently 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 preventer is operating properly. The test shall be in accordance with para. 12. 8.1.3 The manufacturer shall specify the type and locationofthebackflowprotectionsysteminthe product literature or in the installation instructions.
11 FUNCTIONAL TEST OF BACKFLOW PREVENTION DEVICES When the backflow prevention devices are check valves, testing shall be conducted in accordance with para. 11.1. When the backflow prevention devices are vacuum breakers or automatic diverters and vents, test- ing shall be conducted in accordance with para. 11.2. Install the devices in their normal position in a test rig in accordance with the manufacturer’s instructions. Where the device is intended to be installed in a housing or test fixture supplied by the manufacturer, the dimen- sional requirements, including tolerances, shall be accounted for in the installation. 11.1 Check Valves (New and After Durability Tests) Check valves shall be watertight over the range of back pressures from 0.5 in. to 80 in. H 2 O (0.12 kPa gage to 19.9 kPa gage) and at vacuums from 0 in. Hg to 25 in. Hg (0 kPa gage to 84 kPa gage). Connect the inlet of the devices to a water supply capable of delivering water through each device at a flow of 1.0 gpm to 2.0 gpm (0.063 L/s to 0.126 L/s), to a vacuum system capable ofmaintaining a vacuum from 0 in. Hg to 25 in. Hg (0 kPa gage to 84 kPa gage) and to atmosphere. Flush the devices to purge air from the system. For basic test setup, see Fig. 3. Connect a 0.25 in. (6.35 mm) minimum nominal inside diameter transparent sight tube in a leakproof manner to the devices or test rig outlet such that the tube is vertical upward. Apply 0.5 in. H 2 O (0.12 kPa gage) back pressure and observe for leaks during a 5 min interval. Increase the back pressure up to 80 in. H 2 O (19.9 kPa gage) and inspect for leakage during a 5 min interval. Reduce the back pressure to 1 in. H 2 O (0.25 kPa gage) by opening the drain valve. Apply a vacuum of 5 in. Hg (17 kPa gage), increase up to 25 in. Hg (84 kPa gage), and inspect for leakage by observing the water in the sight glass.

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