1 edition of Grounding resistance of unidirectionally stiffened double hulls found in the catalog.
Grounding resistance of unidirectionally stiffened double hulls
Timothy Lee McKenney
by Available from the National Technical Information Service in Springfield, Va
Written in English
|The Physical Object|
|Number of Pages||47|
High Resistance Grounding (HRG) systems limit the fault current when one phase of the system shorts or arcs to ground, but at lower levels than low resistance systems. In the event that a ground fault condition exists, the HRG typically limits the current to A, though most resistor manufacturers label any resistor that limits the current to. Measuring Ground Resistance with the 62% Method. Baseline Support: 2 8. Position. electrode Z out approximately 10x the depth of the grounding point. Example for a grounding rod: If you are testing an 8ft ground rod, the location for electrode Z is 80ft from the ground rod. Example for a ground plateFile Size: KB.
Before measurements of ground resistance are conducted with a ground rod, soil or ground resistivity testing is usually conducted with a series of four evenly-spaced stakes. A current is applied across the outermost pair of stakes and the voltage drop across the inner pair is measured with a ground resistance meter. The meter is calibrated to automatically convert the voltage reading to resistance. Collision and Grounding of Ships and Offshore Structures contributes significantly to increasing the safety and reliability of seaborne transport and operations, and will be useful to academics and engineers involved in marine technology-related research and the marine industry.
Ideally, a ground should be zero ohms of resistance, but. Unfortunately, there is not one standard ground resistance threshold recognized by all certifying agencies. The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC texts All Books All Texts latest This Just In Smithsonian Libraries FEDLINK (US) Genealogy Lincoln Collection. National Emergency Library. Top American Libraries Canadian Libraries Universal Library Community Texts Project Gutenberg Biodiversity Heritage Library Children's Library. Open Library.
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USDHvsConventional(MixedFrame)DoubleHull A USDH structure has some common advantages,regardless of payload, over a conventionaldouble hull in theareas of preliminarydesign,fabrication, andmaintenance. Unidirectionally Stiffened Double Hull (USDH) ships a general grounding scenario must be defined.
The following scenario is assumed for this analysis. A ship of mass M (displacement full load) runs into a narrow rigid reef. The ship is moving with a forward speed V. The reef contacts the forward end of the ship where the bottom is nearly.
Grounding resistance of unidirectionally stiffened double hulls. By Timothy Lee McKenney Download PDF (3 MB)Author: Timothy Lee McKenney. A study of the wedge cutting force through longitudinally stiffened plates: an application to grounding resistance of single and double hull ships.
[Mark Douglas. The U.S. Navy has undertaken a study of a unidirectionally stiffened double-hull design (advanced double-hull concept) with emphasis on fatigue life and producibility as well as resilience to collision, grounding, and attack (Melton et al., ; Sikora et al., ).
Book Description. Collision and Grounding of Ships and Offshore Structures contains the latest research results and innovations presented at the 6th International Conference on Collision and Grounding of Ships and Offshore Structures (Trondheim, Norway, June ).The book comprises contributions made in the field of numerical and analytical analysis of collision and grounding.
Abstract: It is the purpose of this Guide to describe and discuss the present state of the technique of measuring ground resistance and impedance, earth resistivity, and potential gradients resulting from currents in the earth and the prediction of the magnitudes of ground resistance and potential gradients from scale model tests.1 Factors governing the choice of instruments and the techniques.
Reply to grounding thru-hulls Scott, We are often confused by what we read or are told and what we see on our boats. The following is a quote from the USPS Marine Electronics course regarding bonding systems. I apologize in advance for the length of the reply; however, it answers your question about bonding thru-hulls.
Grounding: The Grounds for EMC Design 15 • Work done against an electric force in carrying a charge along a path from point a to b • Electric Potential between with the points a and b: b b b a a a W F dl qE dl q E dl=− • =− • =− •∫ ∫ ∫ work,or Δelectric-energy charge moved b Ea b a W V E dlFile Size: 3MB.
A.R. Prabowo et al. / Structural Analysis of the Double Bottom Structure During Ship Grounding by Finite Element Approach Latin American Journal of Solids and Structures 14 () During experiment, the indenter will penetrate the stiffened plate approximately until m while the stiffened plate is supported by hollow by: 5.
The ship was an idealized double hull oil/chemical tanker with dimensions as given in Table 5. Figure 1 presents the double bottom part of the ship’s three-dimensional (3D) geometry.
The numerical model of the bottom structure defined in ANSYS LS-DYNA [ 26 ] with reference to Author: Aditya Rio Prabowo, Teguh Putranto, Jung Min Sohn. Transient response of grounding resistance is simply represented by circuits shown in Fig. High grounding resistance of more than Ω often shows a capacitive type and a low resistance of less than 10 Ω the inductive type.
Thus, the grounding resistance should be treated as impedance. Introduction. The objective of this paper is to study structural failure mechanisms in ships subjected to stranding.
The resistance to penetration of the hull plating is of special interest. This is because onset of fracture in the outer hull and in cargo tanks is directly linked to oil spill and compartment by: Measurement of Grounding Abstract: This chapter introduces the methods and instruments for grounding resistance measurement, the factors Influencing the result of fall‐of‐potential method, including the influence of overhead ground wires, the measurement method of potential distribution, and corrosion diagnosis method for grounding by: 2.
to the grounding resistance of single hull and double hull ships. Two types of ship hull designs were used as prototypes for the development of small scale models: a conventional longitudinally stiffened Single Hull (SH) and the Unidirectionally Stiffened Double Hull (USDH) design.
To model the cutting : Mark Douglas. Bracco. Crushing resistance of web girders in ship collision and grounding Article in Marine Structures 21(4) October with 64 Reads How we measure 'reads'. Request PDF | On the resistance to penetration of stiffened plates, Part I-Experiments | a b s t r a c t The paper deals with hull damage in ships which are subjected to grounding actions.
A ship. (Green Book) , the resistance of the soil outward from a ground rod is equal to the sum of the series resis-tances of the earth shells. The shell nearest the rod has the highest resistance and each successive shell has progressively larger areas and progressively lower resis-tances.
Don’t be concerned if you don’t understand this. The following are the disadvantages of resistance grounding: 1. Since the system neutral is displaced during earth faults, the equipment has to be insulated for higher voltages.
This system is costlier than the solidly grounded system. A large amount of energy is produced in the earthing resistance during earth faults. for low resistance grounding of generators than solid grounding, to give the system better reliability against overvoltage and harmonics.
Resistance grounded systems are best suited for voltages below Volts. High Resistance Grounding. Similar to low resistance grounding but differs in the value of resistance. Here the value of File Size: KB. Grounding 1. 1 INTRODUCTION According to Zhang () the grounding rate for Ro-Ro and merchant navy ship types with lengths over m, is per ship year.
That means that every second ship is expected to experience grounding in her .Grounding System Theory and Practice. Introduction. measure ground resistance in order to maintain the grounding system.
The definition of grounding is commonly used for both, system grounding and equipment - Resistance grounded: A system grounded throu gh a resistance, the value of which can.Where R1 and R2 are resistance of all ground rods and grid conductors respectively and R12 is the mutual resistance between the group of grid conductors and group of ground rods Fig.2 gives charts of grounding system contains rods with 50mX50m grid earthing system placed in uniform soil with 3 parallel grid conductors at each direction.