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                                                                                              Problems/Questions  223
                                             4. Employers should ensure that fall protection equipment is appropriate and main-
                                                tained in good condition. Employees should inspect fall protection equipment
                                                before each use to ensure that all components are in operational order.
                                             5. Employers should ensure that material hoists are not used for raising or lowering
                                                employees to or from the worksite.
                                             6. Employers should ensure that electrical safety practices are followed when welding.
                                             7. Owners of water towers and similar structures should design and install a permanent
                                                static safety line system on the tower to facilitate the use of fall protection devices.


                    PROBLEMS/QUESTIONS
                    6.1  An elevated water reservoir (water level at 210 m) is to
                                                                                 Pipe   d (mm)  L (m)
                    supply a lower groundwater reservoir (water level at 138 m).
                    The reservoirs are connected by 800 m of 400-mm ductile
                                                                                 AB      200     800
                    cast pipe (C   100) and 1,200 m of 300-mm ductile cast pipe
                                                                                 BC      200     200
                    (C   100) in series.
                                                                                 AD      200     200
                        (a) What will be the discharge delivered from the upper  DC      300     800
                           reservoir to the lower one?
                        (b) If the water demand increases by 50% in the future,  The elevation of point A is 600 m and of point B is 590 m. The
                           determine the required size of pipe that has to be in-  C value for all pipes is 100. Find the following:
                           stalled in parallel with the existing piping.
                                                                        (a) The length of a single 400-mm pipe that can replace
                    6.2  The following data are given for the water supply network  the water network from A to C.
                    shown in Fig. 6.20:
                                                                        (b) The residual pressure at point C, given that the flow
                                                                           through the network is 250 L/s and the pressure at A
                                 Pipe   d (in.)  L (ft)                    is 300 kPa.

                                 AB       8     2,500               6.4  For the water supply network shown in Fig. 6.21, the fol-
                                 BC       8      500                lowing data are given:
                                 AD       8      500
                                 DC      12     2,500                           Pipe   d (mm)   L (m)
                                                                                AB      300      1,200
                    The elevation of point A is 100 ft and of point B is 90 ft. The C
                                                                                BD      300       300
                    value for all pipes is 100. Find the following:
                                                                                AC      200       300
                        (a) The length of a single 18-in. pipe that can replace the  CD  200     1,200
                           water network from A to C.                           SA       d SA   10,000
                        (b) The residual pressure at point C, given that the flow
                           through the network is 4,000 gpm and the pressure at
                                                                    Elevation   655 m
                           point A is 40 psi.
                    In   A                                B
                                                                              S



                                                                                     A                   B


                         D                                C
                                                               Out
                    Figure 6.20 Water Network for Problems 6.2 and 6.3               C                  D
                                                                                                            60 L/s
                    6.3  The following data are given for the water supply network
                    shown in Fig. 6.20:                             Figure 6.21 Water Network for Problem 6.4
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