3　Prevention of Static Accumulation and Discharge

3.0.1　Petrochemical particulate solids silos，equipment，piping，pipe fittings and metal accesories shall be bonded and reliably earthed，and earthing conductor shall be multi-strand metal wire or metal body with sufficient mechanical strength and corrosion resistance，and shall be difficult to break.Volume resistivity of petrochemical particulate solids may be selected from Appendix A of this Code.

3.0.2　Non-metallic piping and equipment should not be used in material handling system or for silo design.Non-metallic parts in contact with flammable particulate solids or dust should be made of anti-static material，and shall be earthed.

3.0.3　For particles with size ranging from 1 mm to 10 mm，measures shall be taken to reduce or prevent particles from breaking，forming into streamers and peeling-off in handling process.Purification and homogenization design for petrochemical particulate solids silo shall not result in particulate solids boiling and collision.

3.0.4　Metal components and metal protrusions insulated from earth must not be provided inside the petrochemical particulate solids silo.

3.0.5　Earthing measures to eliminate static electricity on human body and spare earth terminal shall be included in the earthing design for petrochemical particulate solids silo.

3.0.6　Non-metallic coating covered upon inner wall of silo should be no thicker than 2 mm.Antistatic materials with volume resistivity no greater than 109Ω·m shall be used for coating thicker than 2 mm.

3.0.7　Silo should be equipped with ionizing static electricity eliminator near the inlet.The ionizing static electricity eliminator shall be designed to meet the explosion-proof requirements in explosion hazardous areas，and should be provided with powder electrostatic online detecting and eliminating-adjusting function.

3.0.8　When the silo is provided with emergency or packaging discharge port（s），and the material in silo has high volatile content，the following measures shall be taken to prevent the static combusting and blasting when discharging or packaging:

1　Ionizing static electricity eliminator（s）should be equipped near the discharging or packaging port（s）；

2　Dedicated earth terminal or jumper cable shall be equipped near the discharging or packaging port（s）；

3　Explosion-proof human body static eliminator shall be equipped near the discharging pipe.

3.0.9　When no combustible gas exsists in the silo or the volume concentration of combustible gases less than 20% of its lower explosive limit（LEL），the provisions specified in Articles 3.0.2，3.0.4，3.0.6 of this Code shall be adopted to prevent high energy discharge，such as propagating brush discharge，spark discharge of insulated conductor，and spark discharge from metal protrusions above the particulate solids heap.3.0.10　When the volume concentration of combustible gas is greater than or equal to 20% of the gas lower explosive limit（LEL）in the silo or the minimum ignition energy（MIE）is less than or equal to 10mJ，ionizing static electricity eliminator shall be used to prevent conical discharge above the particulate solids heap，lightning-like discharge between space dust cloud and metal protrusions.