Page 24 - CPVC Fire Sprinkler Products Installation Instructions & Technical Handbook
P. 24

of tamped earth or sand beneath the pipe as a cushion and to protect the pipe from damage. Sufficient cover must be maintained to keep external stress levels below maximum design stress. Reliability and safety of service is of major importance in determining minimum cover. Local, state and national codes may also govern.
• Maintenance - Maintenance of TYCO CPVC Pipe and Fittings for underground water service shall be in accordance with the Standard for Inspection, Testing and Maintenance of Water Based Extinguishing Systems as defined by NFPA 25.
• Snaking of Pipe - After TYCO CPVC pipe has been solvent cemented, it is advisable to snake the pipe according to the following recommendations beside the trench during its required drying time. BE ESPECIALLY CAREFUL NOT TO APPLY ANY STRESS THAT WILL DISTURB THE UNDRIED JOINT. Snaking is necessary to allow for any anticipated thermal contraction that will take place in the newly joined pipe line. Snaking is particularly necessary on the lengths of pipe that have been solvent cemented during the afternoon hours of a hot summer day because the drying time will extend through the cool of the night when thermal contraction of the pipe could stress the joints to the point of pull out. This snaking is also especially necessary with pipe that is laid in its trench (necessitating wider trenches than recommended) and is back-filled with cool earth before the joints are thoroughly dry. Tables C1 and C2 show the Pipe Snaking and the Loop Offset dimensions to compensate for contraction.
• Back-Filling - Ideally, back-filling should only be done early in the morning during hot weather when the line is fully contracted so that there is no chance of insufficiently dried joints being subject to contraction stresses.
The pipe should be uniformly and continuously supported over its entire length with firm, stable material. Blocking should not be used to change pipe grade or to intermittently support pipe across excavated sections. Pipe is installed in a wide range of sub soils. These soils should not only be stable, but applied in such a manner so as to physically shield the pipe from damage. Attention should be given to local pipe laying experience that may indicate particular bedding problems.
Back-filled material free of rocks with a size of 1/2 in. (12,7 mm) or less should be used to surround the pipe with 6 in. to 8 in. (152,4 mm to 203,2 mm) of cover. The back-filled material should be placed in layers. Each soil layer should be sufficiently compacted uniformly to develop laterally passive soil forces during the back-fill operation. It may be advisable to have the pipe under water pressure, 15-25 psi (1,0-1,7 bar) during the back-filling.
Vibratory methods are preferred when compacting sand or gravel. Best results are obtained when the soils are in a nearly saturated condition. Where water flooding is used, the initial back-fill should be sufficient to ensure complete coverage of the pipe. Additional material should not be added until the water flooded back-fill is firm enough to walk on. Care should be taken to avoid floating the pipe.
Sand and gravel containing a significant portion of fine-grained material such as silt and clay should be compacted by hand or preferably by a mechanical tamper. The remainder of the back-fill should be placed and

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