US3319574A - Pumping arrangement for cargo ships arranged to carry liquid bulk cargo - Google Patents

Description

M y 6, 1967 c. H. CARSLAW 3,319,574

PUMPING ARRANGEMENT FOR CARGO SHIPS ARRANGED TO CARRY LIQUID BULK CARGO Filed May 24, 1965 HA no 4. l2 T 3 13 J United States Patent Ofiice 3,319,574 Patented May 16, 1967 3,319,574 PUMPING ARRANGEMENT FOR CARGO SHIPS ARRANGED TO CARRY LIQUID BULK CARGO Charles Henderson Carslaw, Yoker, Glasgow, Scotland, assignor to Drysdale & Company Limited, Yolrer, Scotland, a corporation of the United Kingdom of Great Britain and Northern Ireland Filed May 24, 1965, Ser. No. 458,037 Claims priority, application Great Britain, May 23, 1964, 21,400/64 1 Claim. (Cl. 103113) The subject of this invention is an improved pumping installation for a ship constructed to carry liquid bulk cargo.

A pumping installation as at present constructed for such a ship incorporates at least one trunk closed at the top and extending from deck level downwardly into the storage tanks, a pump being located at the bottom of the trunk and being connected by a driving shaft to driving mechanism at deck level. The trunk may incorporate openings at various levels into different tanks. In operation there is a partial vacuum in the trunk when liquid is being drawn from a low level in the tanks and frequently air and liquid vapour are drawn into the pump along with the liquid. To prevent air locks from forming in the impeller of the pump such air and vapour must be vented and as the air and vapour are at sub-atmospheric pressure they cannot be vented until their pressure is raised to super-atmospheric pressure. The present method of doing this is by refluxing which requires that the liquid level in the trunk is periodically drawn down so that the air and vapour may enter the main pump and pass through at least the first stage of the impeller so that its pressure may be raised to above atmospheric. This operation must be performed fairly frequently so that suflicient air and vapour to air lock the impellers of the main pump is not allowed to accumulate. It is an object of the present invention to provide a construction which obviates the need to permit any air and vapour to pass through any part of the pump.

A pumping installation according to the present invention incorporates evacuating mean connected to the top of the trunk.

The evacuating means may include a floatgear and a vacuum pump.

A practical embodiment of the invention is illustrated in the accompanying diagrammatic drawing in which 1 denotes a ships deck, 2 denotes storage tanks, 3 denotes a trunk closed at the top and extending from the deck 1 to the lowermost level of the storage tanks 2 and containing a pump 4 having a suction inlet 5 and a discharge main 6 passing upwardly through the trunk 3 to a discharge opening 7, the discharge main 6 containing a driving shaft 8 for the pump 4 connected to a driving motor 9. 10 denotes a vacuum pump at deck level, the suction connection 11 of the vacuum pump 10 being connected by way of a float valve 11A into the top of the trunk 3. 12 denotes suction pipes from the trunk 3 terminating in suction openings 13 in the tanks 2.

In practice, since it is refluxing operations the liquid in the trunk 3 is never disturbed so that the rate of movement of the liquid in the not necessary to perform any trunk 3 down towards the pump is steady and low. The trunk thus becomes in the construction according to the invention a large and eflicient separator for air and vapour entrained in the liquid and such air and vapour can escape up through the column of liquid at a rate faster than the liquid is moving downwardly. Air and vapour separated from the liquid accumulates at the top end of the trunk 3 while liquid free of air and vapour enters the suction inlet 5 of the pump 4 and is discharged up through the discharge main 6 to the discharge outlet 7. The vacuum pump 10 draws off the air and vapour continuously as it accumulates at the top of the trunk 3. As liquid is drawn from the trunk 3 liquid from the tank 2 enters the trunk 3 through the suction openings 13 and the suction pipes 12. Air and vapour are thus continuously separated from the liquid which had been stored in the tank 2 as this liquid makes its way to the pump 4.

In the arrangement according to the invention the pump 4 can deliver liquid continuously at its maximum pumping rate or at least as fast as the liquid can flow from the tank 2 to the pump 4. The continual supervision and intermittent discharge required in the use of hand-operated or even automatic reflux flow arrangements are thus avoided.

What is claimed is:

A pumping installation for a ship constructed to carry liquid bulk cargo in storage tanks, comprising at least one trunk closed at the top and extending from the level of the ships deck downwardly as far as the bottom of the storage tanks, which latter are in communication with the interior of the trunk at points above the trunk bottom, a pump located at the bottom of the trunk and having a suction port open to the trunk, driving means for the pump located at deck level, a driving shaft connecting said driving means and said pump, and evacuating means comprising a vacuum pump and float gear connected to the top of the trunk for drawing off air and vapor continuously as it accumulates at the top of the trunk, causing the trunk to function as a large separator for air and vapor entrained in the liquid and permitting such air and vapor to escape upwardly through the column of liquid in the trunk at a rate faster than the liquid is moving downwardly.

References Cited by the Examiner UNITED STATES PATENTS 1,337,180 4/1920 Carden 1035 1,547,197 7/1925 Arbon 103-4 1,573,931 2/1926 Gayne 103113 2,765,742 10/1956 King 1036 2,800,085 7/1957 Hansen 103203 2,833,222 5/1958 Hansen 103203 3,048,122 8/1962 Hansen 103203 3,094,167 6/ 1963 Hine 1034 FOREIGN PATENTS 102, 827 1/ 193 8 Australia. 616,514 7/1935 Germany.

DONLEY J. STOCKING, Primary Examiner. HENRY F. RADUAZO, Examiner.

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