PBS_Powder & Bulk Solids

Powder & Bulk Solids, May 2014

Issue link: http://dc.cn.ubm-us.com/i/301026

Contents of this Issue

Navigation

Page 13 of 87

Powder & Bulk Solids 14 TechnicalExclusive M a y 2 0 1 4 Types of FIBCs and Selection Criterion There are currently four types of FIBCs: Type A, B, C, and D. Important Notes • If left electrically ungrounded, type C FIBCs (groundable bags) can give rise to a higher explosion risk than type A and B (insulat- ing) FIBCs. • It is not possible to make gen- eral recommendations for the safe use of type D FIBCs under all op- erating conditions. In particular: - The existing type D FIBCs that incorporate antistatic yarns and an antistatic coating can still create a localized electrostatic field around the FIBC. Ungrounded conductive objects that may be present in the close proximity of such charged FIBC could become polarized and become charged by the process of induction. Such charged objects could give rise to subsequent spark discharges which could be a poten- tial ignition source. Hence it is rec- ommended that conductive objects in close proximity of type D FIBC need to be electrically grounded. - Incendive sparks may occur during filling and emptying of type D FIBCs if the surface of the FIBC is partially covered by an electrically conductive substance (e.g. a wet patch). • Irrespective of the type of FIBC used, and depending on the electro- static properties of the powder and the powder handling equipment (for example, whether the plant is con- ductive or insulating, grounded or ungrounded) other electrostatic igni- tion sources may still exist. • Conductive powders (having volume resistivity < 10 6 Ohm.m) could accumulate electrostatic charges in type A, B, or even D FIBCs (in the absence of direct ground connection), it is recom- mended to use only type C FIBC with conductive powders to avoid spark discharges from the powder material itself. Use of Inside Liners in FIBCs The use of liners in any type of FIBC can increase the risk of an electrostatically initiated flash fire or explosion. There are three types of liners that are permitted to be used in a particular type of FIBC depending on the elec- trostatic properties of the liner material. Depending on the liner type, the following physical and electrostatic properties may need to be determined to ensure the suitable type of liners: • Surface Resistivity • Breakdown Voltage • Liner Thickness • Resistance to Groundable Point These tests results provide valuable information that will be utilized to determine the safe use of a particular type of liner with a specific type of FIBC. Qualification Criterion for Liners inside the FIBCs Type L1 Liner A type L1 Liner should meet the following criterion: • Made from materials with Surface Resistivity on at least one surface ≤ 1.0x10 7 ohm per square • If the material is multi-lay- ered, or if the material has outer surface with Surface Resistivity >1.0x10 12 ohm per square, Breakdown Voltage through the material shall be < 4KV • If the material is multi-layered, or if the material has inner surface with Surface Resistivity >1.0x10 12 ohm per square, Breakdown Voltage through the material shall be < 4KV and thickness shall be <700 micrometer Type L2 Liner A type L2 Liner should meet the following criterion: FIBC Inner Liner Type L1 TypeL2 TypeL3 Type B Not Permissible Permissible Permissible Type C Permissible (a) Permissible Not Permissible Type D Not Permissible Permissible (b) Not Permissible a. To ensure inner liner is properly earthed, resistance from at least one side of the inner liner to the ground- able points on the FIBC shall be <1.0X10 7 ohm b. Combination of FIBC and liner shall meet the testing requirements • Type A FIBC shall not be used in hazardous explosive atmospheres irrespective of the type of liner used • Liners shall not be removed from emptied FIBC in hazardous explosive atmospheres Tel: 800-601-5949 or 630-365-9403 ▼ www.monitortech.com ▼ www.flexar.info E-mail: monitor@monitor tech.com ▼ Blog: monitor tech.typepad.com D o i n g O u r D o i n g O u r L e v e l L e v e l B e s t B e s t Flexar Flexar ® Guided wave radar real- time level SafePoint ® "Truly" fail-safe rotary paddle SiloPatrol ® "Smart" plumb bob To Maximize Your Safety & Convenience Who wants to climb silos? It costs time and presents safety issues. Monitor Technologies, LLC offers a large variety of solutions for Point Level Indication, Continuous Level Sensing and Inventory Management. Some examples include: TrueCap ® MK-2 RF Capacitance with push-button calibration SiloTrack TM inventory management software Visit us at the Powder Show booth #2407 ES425454_PB1405_014.pgs 04.18.2014 03:54 UBM black yellow magenta cyan

Articles in this issue

Links on this page

Archives of this issue

view archives of PBS_Powder & Bulk Solids - Powder & Bulk Solids, May 2014