API RP 545:2009 pdf download

API RP 545:2009 pdf download.Recommended Practice for Lightning Protection of Aboveground Storage Tanks for Flammable or Combustible Liquids.
4.2.1.1.4 Durability
The shunts and lemimation connections shaM be of sufficient flexibility, cross-sectional area, and corrosion resistance to have a mwumum service life of 30 years.
4.2.1.2 Bypass Conductors
4.2.1.2.1 General
Bypass conductors are used for conduction of the intermediate and long duration component of lightning-stroke current.
4.2.1.22 Number, Length and Electrical Resistance
The tank floating roof shall be bonded to the tank shell by direct electrical connection through an appropnate number of bypass conductors. Each conductor, induding connections, shall have a maximum end-to-end electrical resistance of 0.03 i. The bypass conductors shall be of the minimum length necessary to permit full movement of the floating roof. Bypass conductors should be evenly spaced not more than every 30 m (100 It) around the tank circumference with a minimum of two.
4.2.1.2.3 Durability
The bypass conductors and termination connections shall be positioned and of sufficient flexibility, cross-sectional
area, and corrosion resistance to have a minimum service life of 30 years.
4.2.2 Parallel Conducting Paths (Seal Assembly from the Floating-roof Tank)
Any non-fully submerged conductive seal assembly components including springs, scissor assemblies, seal membranes. etc. shall be electrically insulated from the tank roof. The insulation level shall be rated 1 kV or greater.
NOTE This aows any bghtning discharge current from the floating roof to the tank shell to take the preferential path through the shunts and bypass conductors.
4.2.3 Insulation of Gauge or Guide Poles
My gauge or guide pole components or assemblies that penetrate the tank floating roof shall be electrically insulated from the tank floatbng roof. The insulation level shall be rated 1 kV or greater.
NOTE This alows any lightning discharge current from the floating roof to the tank shell to take the preferential path through the shunts and bypass conductors.
5 Metal Thickness
Minimum metal thicknesses for tanks are provided In API 650 and API 653.
Mditional information is presented in El/API 545-A. Verification of lightning protection requirements for above ground hydrocathon storage tanks.
6 Inspection and Maintenance Requirements
AJI bonding and grounding appurtenances shall be maintained and inspected in accordance with API 653. Below- deck inspections shall coincide wth API 653 out-of-servIce inspections.
A.1 Phenomenon of Lightning and Secondary Effects on Tanks
A.1.1 Introduction
This section summarizes the present knowledge on the lightning flash process and attachment mechanism.
&1.2 Lightning Principles
Under fr weather conditions, there is normally a steady but weak vertical electric field at the earth’s surface with virtualy no ground currents and a small distributed charge on the ground. Horizontal flat surfaces will have a very uniform charge distribution, (i.e. a similar surface charge density everywhere). The highest surface charge occurs on thin pointed obØcls such as church spies, tops of aerials, tips of lightning rods. etc. Where the surface charge is highest, the local electnc field is the highest. Sharp-pointed, upward-faong Items will tend to discharge a small current into the air, such as aerials and lightning air terminals This will often be a silent, invisible discharge wi the order ot a micro amp.