US2865566A - Apparatus for the estimation of the distribution of the cargo in a ship - Google Patents

Apparatus for the estimation of the distribution of the cargo in a ship Download PDF

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Publication number
US2865566A
US2865566A US428784A US42878454A US2865566A US 2865566 A US2865566 A US 2865566A US 428784 A US428784 A US 428784A US 42878454 A US42878454 A US 42878454A US 2865566 A US2865566 A US 2865566A
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Prior art keywords
ship
resistances
distribution
load
cargo
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US428784A
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English (en)
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Swenson Kurt Lennart
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Goetaverken AB
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Goetaverken AB
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06G—ANALOGUE COMPUTERS
    • G06G7/00—Devices in which the computing operation is performed by varying electric or magnetic quantities
    • G06G7/48—Analogue computers for specific processes, systems or devices, e.g. simulators
    • G06G7/70—Analogue computers for specific processes, systems or devices, e.g. simulators for vehicles, e.g. to determine permissible loading of ships, centre of gravity, necessary fuel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
    • B63B39/12—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude for indicating draught or load

Definitions

  • trim indicates the distribution of the cargo in the longitudinal direction of the ship and corresponds to the difference between the drafts at the ends of the ship.
  • trim Many important factors are dependent onthe trim, for instance, the propellerefficiency, the speed of the ship, the behavior or performance in-the sea and the general comfort on board.
  • the distribution of the cargo should therefore'bechosen so as to produce a trim which is most advantageous in said respects.
  • the distribution ofthe cargo in the longitudinal direction of the ship determinesv the tensions or stresses in the longitudinal direction of the ship.
  • the deformation of the ship owingto these tensions is not visible to such anextent as the trim 'but in certain types of ships, particularly in tankers, it is possible to, choose the distribution-of the load in so many ways that with an extremely unsuitable distribution of the cargo and under otherwise'unfavorable circumstances theship may be subjected to inadmissiblygreat tensions which may result in the formation of cracks in the material, perhaps-with the risk oftotal'rupture.
  • the theory of calculating the trim of a ship is generally known to the ships officers.
  • the problem in this connection isto obtain the necessary data, for instance, the position of the center of gravity of the different load spaces and hydrostatical data.
  • the procedure in calculating the resulting bending moment and the resulting stresses in the longitudinal ,directionof, the ship is, however, more complicated and is mostly unknown to the ships officers. It is therefore desirable to.have a possibility of controlling or checking the distribution of the load with respect to the resulting trim and the stresses caused thereby. Since said stresses reach their maximum value when the ship occupies a certain position in the waves of the sea, the problem is more complicated owingto the hydrostatical conditions being difficult to define satisfactorily.
  • a certain conception of the magnitude of the resulting stresses may, however, be obtained by the so-called standardized strength calculation.
  • the ship is carried by waves the distance between the wave-crests of which being equal ,to the length of the ship and the depth of which i. e. the verticalv distance between wave-crest and wave-hollow, ,being equalto one twentiethcf the length of the ship.
  • the p t q c th h p ic is thenv ubme s in te a d whichthus actually carries theship including the cargo thereof, canbe indicated graphically'ina diagram.
  • the displacement curve contained in this diagram the appearlevers fore and after said plane.
  • the hogging-pos ition or whether the: stem and the stern are located each on a wave-crest, with a wavehollow beneath the ship atthe center'thereof,""fthe-saggingposition, confines an area, which-is as "large-as but quite different in shape from the area confinedby a curve indicating the weight ofthe ship includingthe cargo thereof as distributed in the longitudinal direction of the ship.
  • the object of the present invention isto providean apparatus by means of which the suitability of a certain load distribution both with the respect to the trim and the stresses in the bulk owing to the length-wise bending moments may be ascertained.
  • the apparatus is constituted by anelectric balancing device including ,a group of series-coupled resistances which are adjustable to valuesproportional to the products of the weights of the loads on one side of an imaginary plane dividing the ship into one'forebody and one after-body, and the distances of saidiloads from said plane, asecond group of series-connected resistances which are adjustable in a similar manner with respect to the loads on the-opposite side of saidplane, a first additional resistance which is M proportional to the moment of the bulk weight and the displacement with respect to said plane and a second additionalresistance which is proportional to the hydrostatic effect of the forebody and the after-body and of the moment of'the bulk weight, a switching means being provided for alternately inserting the resistances in one of two
  • the effect of the last-mentioned forces may besubstituted -by-a single upwardly directed force equal to the magnitude of the displacement and located in its centre of gravity AA, Fig. 1.
  • the trimming moment is then equal to the algebraic sum of the moments of the loads and of the bulk weight with respect to the plane AA, signs being used for If instead of the plane AA another arbitrary plane X-.-X is chosen the same trimming moment may be calculated by adding;to..the algebraic sum of the moments of theloads .andthe bulk weight with respect to,the newplaneX-TX,themQment of the displacement lifting force with respect to jthesame plane while using the same rule for thesigns as men-- tioned above, the force being introduced with a negative sign.
  • the formula for the trimming moment T may generally be written as follows:
  • Lx the length of the lever to the planeX-X for each partial load
  • f'(h) includes, on the one hand, the moment fof the bulk weight and, on the other hand, the moment ofthe displacement with respect to the plane XX and is a constant value at a given displacement condition.
  • the trirnof the ship to be measured is not directly propo rtional to the trimming moment but is also dependent. on. the hydrostatic conditions, particularly the draft.
  • These hydrostatic conditions are represented by the factor f"(h) and its value is equal to thereciprocal value of the trimming moment required at a certain draft to trim the ship one trimming unit, for example 1 inch.
  • the function of f"(h) is contained in the scale of potentiometer unit 21-22 later described and a different scale for that potentiometer is required for each value of mean draft used with the apparatus.
  • the trim t may therefor be written as follows:
  • the ship and its load may at first be assumed to be balanced on a support in the cen Qtr'e of gravity of the displacement.
  • a corresponding simplification as to the hydrostatic forces may be made.' In such case one must consider each part of the ship separately and concentrate the two parts of the displacement to the respective centres of gravity thereof.
  • the ship may be considered to be lying on two supports in the planes BB and CC.
  • the resulting moment is the algebraic sum of the moments of the load and the bulk with respect to the plane BB and .CC respectively, and the total lengthwise bending moment in the plane Y-Y is the sum of the two resulting moments from the fore-body and the after-body of the ship.
  • the resulting moment in each part of the ship may, however, be calculated with respect to an arbitrary plane, while paying due regard to the effect of the moments of the hydrostatic forces with respect to this new plane. It is therefore suitable to calculate the moments with respect to the common plane YY for the two parts of the ship.
  • the plane X-X be identical with the plane YY, which is chosen so as to lie where the lengthwise bending moment has its maximum .value or elsewhere where it is desired to know its magnitude.
  • Fig. 3 shows a circuit diagram of the apparatus and Fig. 4 shows one embodiment of an apparatus according to the invention
  • the electric balancing means includes a current source 9, a switch 10, two known, constant resistances R and a group of series-connected resistances 11, 12, 13, and 14, which are adjusted to values proportional to the products of the weights v -v of the loads on one side of the plane XX (Fig. 1) and their distances L -L from the plane XX.
  • the corresponding load spaces are designated 1-4 in Fig. 1.
  • the balancing means comprises further a second group of series connected resistances 15, 16, 17 and 18 which are adjustable in a similar manner with respect to the loads in the after-body of the ship, the corresponding load spaces being numbered as 5-8.
  • a resistance 19 is adjustable to a value proportional to f'(h) and a resistance 20-corresponds to f(h).
  • the resistance portion of a potentiometer is designated 21, the movable tap of the potentiometer being designated 22.
  • a second potentiometer has a resistance portion 23 and a movable tap 24.
  • the potentiometers may alternately via a galvanometer 25 be connected to a point between the two resistances R
  • the potentiometer 21, 22 is provided with a plurality of scales 26, 27 for different drafts corresponding to the factor f"(h). Switches by means of which two different electric balances may be obtained are designated 0 O and 0 If the switches are in the positions indicated with full lines in Fig.
  • the two resistance groups 11-14 and 15-18 are connected in series to the one side of the potentiometer 23, 24, the other side of which being connected to the resistance 19.
  • the potentiometer 21, 22 and the resistance 20 are then switched out of circuit.
  • the operating parts constitute in this case the one electric balance, the one branch of which being constituted by 2"vLy and the other branch of which being constituted by f"'(l1).
  • the balance consists in the embodiment shown of a Wheatstone bridge which in a manner known per se is operated in such manner that the two branches are balanced by means .of the potentiometer 23, 24, and the current through the galvanometer is zero.
  • the potentiometer scale may advantageously be such that in this case the lengthwise bending moment M or, if desired, the corresponding bending stress is indicated.
  • the scale may be provided with marks indicating the limits of the permissible range of variations of the moment or stress.
  • the zero point on the trim scale can be located at a middle point on the scale.
  • the trim will be either positive or negative (by stem or by stem, respectively) from zero and will be properly indicated dependent upon the direction of movement of the arm 22 required to obtain bridge balance. Should the trim and/or the lengthwise bending moment not lie within the permissible limits a different load distribution must be tried by changing the resistance values of one or both of the resistance groups 11-14 and 15-18 until a load distribution is reached which is acceptable both with respect to the trim and to the lengthwise bending moment.
  • the apparatus according to the invention may for example be built in the manner indicated in Fig. 4, according to which the casing of the apparatus consists of two boxes 30 and 31 the latter being pivotally connected to the box 30 at the lower end thereof so that it can be moved from a vertical to a horizontal position and vice versa.
  • the circuit elements in the boxes are interconnected by means of conductors 32 and 33.
  • the panel of the box 30 is subdivided into different sections or fields.
  • the section 34 indicates the name of the ship and a schematic illustration of the positions of the different load spaces in the ship. It is assumed that the ship comprises 25 load and storage spaces each being represented by a potentiometer r corresponding to the resistances of the two groups of resistances shown in Fig. 3. These resistances are grouped together in a surveyable manner in difierent fields 35, 36, 37, 38 and 39.
  • the box 30 accommodates the resistance 20, the movable part 22 of the first potentiometer cooperating with a plurality of scales, the part 24 of the second potentiometer and the resistance 19.
  • the galvanometer is designated 25 and a handle for actuating the switches shown in Fig. 3 simultaneously is designated 48. It has three different positions, namely two end positions for switching in the two different balances and an intermediate position in which the apparatus is switched off. Lamps 41 and 42 indicate which of the two balances is connected into circuit.
  • a space 43 contains directions for the use of the apparatus, tables showing the hydraulic characteristics of the ship at different degrees of loading, the capacity of the load and storage spaces and suitable corrections for obtaining a better load distribution if the distribution first chosen should prove to be unsuitable.
  • the apparatus is set or adjusted by means of the values obtained upon a standardized calculation of strength.
  • a certain distribution of the load may be chosen, which according to prior experience is likely to be suitable.
  • the liberty of choosing the distribution may be limited in certain respects. So, for instance, the load may consist of oils of different types and quantities in which case it may be necessary to accommodate a certain type of oil in a certain space due to its quantity, while another type of oil cannot be accommodated in a given load space due to the composition of this type of oil.
  • the resistances 11-18 are adjusted to the corresponding values and the resistances 19 and 20 are then adjusted according to the existing hydrostatic conditions at the total load in question.
  • the handle 40 is thereafter turned to the one end position corresponding to the trim and the member 22 is then turned until the pointer of the galvanometer 25 occupies the zero position.
  • the value of the trim may thereafter be read on the scale of the member 22.
  • the member 24 is turned until the galvanometer again shows the zero value, whereafter the sought moment or the corresponding bending stress may be read on the scale of the member 24. If the chosen load distribution should prove to be unsuitable, the procedure has to be repeated after a suitable redistribution of the load as determined by the resistances representing the partial loads, which may be effected with the guidance of a table specially composed for this purpose, so that both the trim and the stresses at least show acceptable values.
  • An apparatus for estimating the influence upon a ship of the distribution of a certain quantity of cargo therein comprising a first group of series-connected resistances, means to adjust said resistances to represent the moments with respect to an imaginary plane dividing the ship into a fore-body and an after-body and caused by parts of said cargo when placed in various holds in the fore-body of the ship, a second group of series-connected resistances, means to adjust said resistances of said second group to represent the moments with respect to said plane and caused by parts of said cargo when placed in various holds in the after-body of the ship, a first additional resistance representing the trimming mo ment of the Weight of the hull and the hydrostatic displacement lifting force with respect to said plane, a second additional resistance representing the lengthwise bending moment of the Weight of the hull and the hydrostatic displacement lifting force, a dual purpose electric balancing device containing a supply of electric current, two reference resistances and a galvanometer, a first potentiometer, a second potentiometer, a switching device for alternatively arranging

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Ocean & Marine Engineering (AREA)
  • Mathematical Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Testing Or Calibration Of Command Recording Devices (AREA)
  • Ship Loading And Unloading (AREA)
  • Vibration Prevention Devices (AREA)
US428784A 1953-05-16 1954-05-10 Apparatus for the estimation of the distribution of the cargo in a ship Expired - Lifetime US2865566A (en)

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DE (1) DE963842C (de)
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3128375A (en) * 1959-04-28 1964-04-07 Sintef Apparatus for calculation of depth, trim, bending moment and shearing stress in a loaded ship
US3329808A (en) * 1963-04-08 1967-07-04 Sperry Rand Corp Cargo loading computer
US3408487A (en) * 1963-03-11 1968-10-29 Wilde Gustavus De Apparatus for calculating the loading effect in a ship
US3441721A (en) * 1964-12-21 1969-04-29 Goetaverken Ab Device for gauging the effect of the cargo distribution on a vessel
US4347574A (en) * 1978-10-11 1982-08-31 Parsons Ward H Method of and apparatus for determining with precision the payload of a water borne vessel
US4858137A (en) * 1985-08-31 1989-08-15 The British Petroleum Company P.L.C. Determination of the stability of floating structures
ITPI20090081A1 (it) * 2009-06-26 2010-12-27 Technological Service S R L Metodo e dispositivo per controllare il carico di un materiale sfuso in una nave
US20130323005A1 (en) * 2012-06-03 2013-12-05 Conveyor Applicant Systems LLC System for conveying drill cuttings
CN113978664A (zh) * 2021-11-19 2022-01-28 华南理工大学 一种半潜运载装备压排载智能测控系统

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1170817B (de) * 1958-08-30 1964-05-21 Kockums Mek Verkst S Aktiebola Vorrichtung zur mechanischen Bestimmung der Beanspruchungsgroessen durch die Ladungs-verteilung eines Schiffes
DE1203633B (de) * 1963-02-16 1965-10-21 Kristoffer Wegger Vorrichtung zum UEberwachen der Lastverteilung in Wasserfahrzeugen
DE1263537B (de) * 1963-07-22 1968-03-14 Inst Schiffbau Einrichtung zur Ermittlung der Anfangsstabilitaet von Schiffen
US10242737B1 (en) * 2018-02-13 2019-03-26 Macronix International Co., Ltd. Device structure for neuromorphic computing system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826762A (en) * 1924-11-20 1931-10-13 Bernard S Franklin Ratio recorder
US2123142A (en) * 1932-09-19 1938-07-05 G M Lab Inc Indicating and calculating system
US2443098A (en) * 1937-10-08 1948-06-08 Rca Corp Apparatus for determining the weight and center of gravity of vehicles
US2520428A (en) * 1946-09-23 1950-08-29 Nilakantan Parameswar Center of gravity calculator

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE921177C (de) * 1951-04-09 1954-12-09 Goetaverken Ab Vorrichtung zur Beurteilung von durch die Lastverteilung in einem Schiff im Rumpf entstehenden Laengsschiff-Biegungsmomenten

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826762A (en) * 1924-11-20 1931-10-13 Bernard S Franklin Ratio recorder
US2123142A (en) * 1932-09-19 1938-07-05 G M Lab Inc Indicating and calculating system
US2443098A (en) * 1937-10-08 1948-06-08 Rca Corp Apparatus for determining the weight and center of gravity of vehicles
US2520428A (en) * 1946-09-23 1950-08-29 Nilakantan Parameswar Center of gravity calculator

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3128375A (en) * 1959-04-28 1964-04-07 Sintef Apparatus for calculation of depth, trim, bending moment and shearing stress in a loaded ship
US3408487A (en) * 1963-03-11 1968-10-29 Wilde Gustavus De Apparatus for calculating the loading effect in a ship
US3329808A (en) * 1963-04-08 1967-07-04 Sperry Rand Corp Cargo loading computer
US3441721A (en) * 1964-12-21 1969-04-29 Goetaverken Ab Device for gauging the effect of the cargo distribution on a vessel
US4347574A (en) * 1978-10-11 1982-08-31 Parsons Ward H Method of and apparatus for determining with precision the payload of a water borne vessel
US4858137A (en) * 1985-08-31 1989-08-15 The British Petroleum Company P.L.C. Determination of the stability of floating structures
ITPI20090081A1 (it) * 2009-06-26 2010-12-27 Technological Service S R L Metodo e dispositivo per controllare il carico di un materiale sfuso in una nave
US20130323005A1 (en) * 2012-06-03 2013-12-05 Conveyor Applicant Systems LLC System for conveying drill cuttings
US9169089B2 (en) * 2012-06-03 2015-10-27 Conveyor Application Systems Llc System for conveying drill cuttings
CN113978664A (zh) * 2021-11-19 2022-01-28 华南理工大学 一种半潜运载装备压排载智能测控系统
CN113978664B (zh) * 2021-11-19 2022-06-17 华南理工大学 一种半潜运载装备压排载智能测控系统

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Publication number Publication date
GB760429A (en) 1956-10-31
NL187586B (nl)
DE963842C (de) 1957-05-16
NL94141C (de)

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