5.4　Reinforced Concrete Silos

5.4.1　The layout of the silo shall be determined according to the process，topographic，geological and construction conditions and after technical and economical comparison.Grouped silos can adopt single-row or double-row arrangement.

5.4.2　The planar shape of the silo should be round.Small-sized cylinder silos，if grouped，should adopt tangential connection at excircle of silo wall.Silos with diameter equal to or larger than 18.00m should be arranged separately.

5.4.3　No vibrating equipment should be installed on the top of the cylinder silos with diameter larger than 10.00m.

5.4.4　The width and height of any opening on the wall of the silo should not be larger than 1.00m.

5.4.5　For silo feeding，top belt conveyor should be adopted.Fixed belt conveyor equipped with electric plough tripper discharger should be adopted.Deironing unit shall be provided for warehouse-in transportation equipment.Grating shall be provided for the inlet on the top of the silo.The minimum side size of the grating holes shall be 1.2 times larger than the maximum particle size of the material transported into the silo.

5.4.6　The isoparametrics of type，quantity，size，funnel wall dip angle and height-diameter ratio of the silo outlet shall be determined according to the granular composition，flowability and design flow pattern of the material，as well as the foundation and process conditions.Silo bottom discharge shall be smooth.

5.4.7　For silos with diameter of 15.00m or above，slot type funnel should be provided at the bottom.For silos with diameter larger than 18.00m，annular funnel and corresponding discharging equipment may be adopted.For silos with diameter smaller than 15.00m and provided with 2 to 4 conical funnels at the bottom，the funnel part shall be smooth，abrasion resistant，and ready to receive flow aid unit，or have space reserved for future flow aid unit.

5.4.8　When any flammable or explosive material is stored in the silo，protective measures shall be taken against fire and explosion.A combustible gas concentration alarm shall be provided inside the silo.On the surface of the silo，ventilators shall be provided.Gas vent holes shall be arranged on the top of the silo along the wall of the silo.Explosion venting measures shall be taken for the silo top structure.When spontaneously combustible，heat emitting，moisture emitting and harmful gas emitting bulk materials are stored in the silo，ventilating and air vent nozzles shall be arranged on the upper part of the silo.

5.4.9　The silo shall be equipped with safety protection and monitoring devices.The indication and control unit of such monitoring instrument and fire/explosion protection shall be installed collectively in the central control room of the transportation system or of the silo.The central control room of the silo shall be arranged outside the silo.

5.4.10　The silo shall be equipped with material level signal，material level indication and lightning protective facilities.

5.4.11　The silo shall be provided with facilities for protection against dust and spontaneous combustion and venting facilities according to the characteristics of the stored material.The top and outlet of the silo storing material liable to generating dust shall be provided with appropriate sealing and dust collection device.

5.4.12　The silo shall be provided with an emergency outlet at the bottom.Appropriate measures shall be taken to send the material discharged back into the system.

5.4.13　When the stored material is not allowed to be broken，an intermediate spiral chute should be installed inside the silo（deep one），or a shallow silo shall be used.

5.4.14　Besides the belt conveyor passage leading to the top of the silo，an additional access shall be provided for the building on the top of the silo.

5.4.15　Anti-freezing measures shall be taken for silos built in cold areas.

5.4.16　The bottom of the cylinder silo may be flat or conical.The angle between the inner wall of the cone and horizontal level shall be determined according to the static repose angle of the material stored.

5.4.17　The shape of the conic section of the silo shall be determined according to the process requirements and after technical and economic comparison.Double-row slit type or conical four-outlet type shall be adopted.For small-sized silos，hyperbolic single-outlet type may be adopted.

5.4.18　A rain shed shall be installed on the top of the silo.A walkway at least 0.80m wide shall be provided around the inlet on the top of the silo.

5.4.19　When the silo adopts bottom discharging and truck loading，the headroom clearance under the bottom of the silo shall be at least 0.30m above the maximum height of the loaded truck.

5.4.20　When discharging from the bottom of the silo for loading of railroad car，the size of the soil shall meet relevant requirements specified in the current national standard GBJ 12 Code for Design of Standard Track Gauge Railway in Industrial Enterprises.

5.4.21　The silo for storage of abrasive materials shall be provided with a wearing layer at the bottom conical section.

5.4.22　Silos shall be designed in accordance with the following requirements:

1　Lifting equipment shall be provided in the building on the top of the silo，the boom of which shall be extended beyond the body of the silo.

2　For large-sized silos with total volume exceeding 25000t，passenger-and-freight elevator may be provided.

3　For silos adopting impeller feeder for discharging，area shall be reserved at both ends of the rotary part of the impeller feeder for maintenance.In addition，lifting equipment shall be provided.

4　The outlet shall be equipped with a gate to cut off the material stream when the bottom of the silo is a conical funnel.

5　Maintenance manhole shall be provided on the top of the silo and covered.The size of such manhole shall be no less than 0.60m×0.70m.