Health & Safety inc Dust Control
Vacuum Trucks: API 2219 provides guidance on the protection of vacuum trucks when they are used to suck up flammable or combustible products. Examples include waste collection during storage tank cleaning operations and the suction of combustible powders from dust collection chambers. Of the many recommendations outlined in API 2219, the most relevant instruction is to fully ground the truck by connecting it to “a designated, proven ground source”, before commencing with transfer operations.
The “ground source” describes an object with a low resistance connection to ground (ground). The standard also states the importance of confirming that the connection resistance between the truck and the designated grounding point is less than 10 ohms and that this resistance should be verified with the use of an ohmmeter (or some other type of measurement device).
Portable containers: When portable metal containers like IBCs and drums are being filled or dispensed from the advice in all standards is to ground and bond all of the filling system and the receiving vessels. NFPA 77 (8.13.3.2) states that: “Bonding should be done with a clamp that has hardened steel points that will penetrate paint, corrosion products, and accumulated material using either screw force or a strong spring.” There is some guidance in the standards regarding the use of plastic lined containers. NFPA 77 states that a metal container, with a plastic of lining of 2mm, or less, can be treated as a metal drum. CLC TR: 50404 contains a table with the maximum recommended lining thicknesses and emphasises the importance of ensuring that their interaction with conductive objects does not promote high energy propagating brush discharges. In general, filling insulating plastic containers is not recommended, particularly if the liquid or powder is highly resistive. If a conductive liquid is being processed it may be possible to dissipate charges using a conductive dip tube, however, the use of dip tubes carry extra precautionary measures.
People: As highlighted earlier, people, through regular movement, can generate large potential differences on their bodies and the accumulation of static charges should be minimised so that operators do not discharge sparks in the presence of ignitable atmospheres. The advice in the standards is to ensure hazardous area floors are conductive and that operator’s working in these areas should be wearing static dissipative shoes to prevent charge accumulation on their body. CLC TR: 50404 (8.1.3.3) states the shoes should be tested prior to entry into the zoned (classified) area: “All personnel should be grounded by means of conducting floors and footwear (see 9.2 and 9.3). A personnel resistance monitor should be installed at every entrance to any area where such footwear
is required.” LEFT: Sole-Mate footwear tester.
www.solidsandbulk.co.uk August 2010 • Solids & Bulk Handling 45
FIBCs: CLC TR: 50404 provides the clearest guidance in respect of resistance values that should be maintained when filling or discharging from FIBC Type C bags. NFPA 77 states that the bag should be grounded but does not specify a maximum resistance value. CLC TR: 50404 (7.2.6.8.3) states: “The conductive fabric and the conductive threads or filaments shall have a resistance
of the grounding point on the FIBC of less than (1 x) 108 Ω.” Type D bags are designed to dissipate charges from bags through “low energy” corona discharges. The potential drawback, however, is that the bag could induce charges on surrounding conductive objects.
Summary: Identifying electrostatic hazards can be a daunting prospect for those of us responsible for ensuring our colleagues, employees, equipment and property are fully protected from electrostatic ignition hazards. There are many factors that can contribute to the presence of a static hazard but if the examples of grounding and bonding protection outlined above can be followed, the majority of processes at risk of static discharge will be controlled and accounted for.
When an audit of a process or procedure has identified an electrostatic ignition hazard, it is important to specify grounding and bonding systems that can demonstrate compliance with the standards. Where possible, static grounding instruments that can demonstrate resistance levels recommended by the standards will ensure companies are protected from this ever-present and hazardous source of ignition. For more information visit:
www.newson-gale.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68