US2860781A - Cathodic protection of metal structures - Google Patents

Description

Nov. 18, 1958 J. H. P. RANDALL cmuonxc PROTECTION OF METAL STRUCTURES F-iled March 15, 1957 3 Sheets-Sheet 1 MIVE/VT Q y p N m N 2 K m A P M M M M a m J Nov. 18, 1958 .1. H. P. RANDALL CATHODIC PROTECTION OF METAL STRUCTURES 3 Sheets-Sheet 2 Filed March 15, 1957 Fig.3.

Nov. 18, 1958 J. H. P. RANDALL 2,860,781

CATHODIC PROTECTION OF METAL STRUCTURES Filed March 15, 1957 a Sheets-Sheet 3 Fig.5.

Arrow/i) United States CATHODIC PROTECTION OF METAL STRUCTURES Application March 15, 1957, Serial No. 646,448 Claims priority, application Great Britain March 21, 1956 6 Claims. (Cl. 204-196) This invention relates to the protection of large metal tanks, for example the tanks (including cargo compartments) of ships against corrosion by the provision in electrical communication therewith of consumable anodes of a metal or alloy anodic to the metal of the tank, or of anodes used with applied electric current.

Hitherto such anode systems have been attached from the inside of the tank or compartment and this has necessitated the provision of temporary scaffolding or like means within the tank for their erection and replacement. Moreover, because of this and the difiiculties associated with the mechanical means of attachment employed, such work is usually carried out while vessels are in port.

The object of the present invention is to enable anode systems, incorporating anodes fixed below the underside of the tank top or in other normally inaccessible positions, to be installed and removed or replaced without the use of scaffolding or like means, and also to permit the work to be carried out more easily, not only while the vessels are in port but also while they are at sea, thus saving installation cost and docking time.

According to the present invention, a method of mounting anodes in a ships tank comprises providing in the tank top a small bolt hole separate from the normal hatchway; lowering through the hatchway an anode having a supporting member attached thereto, lowering a cable through the small hole and joiningv it by a connecting device to said supporting member; pulling the cable up until the supporting member extends above the top of the tank, fixing the supporting member to the tank by fixing means located above the top and disconnecting the cable.

The invention also includes means for mounting the anode comprising a bolt adapted to pass through a bolt hole in the top of the tank, means on the lower end of the bolt for attaching an anode to it, means on the upper end of the bolt for fixing it to the top of the tank, means on the upper end of the bolt for fixing it attachably to a lifting cable, and means for making the connection gastight.

The invention may be used for suspending anodes singly near the top of the tank or for suspending a collapsible anode assembly such as is described in the specification of our British patent application No. 765,085 which describes an anode assembly which is readily removable and replaceable by being carried on a flexible supporting structure which, together with the anodes, can be rolled or folded for storage.

Provision is made for ensuring electrical continuity between the anodes. For this purpose the complete apparatus in itself may be made in such a way that the parts thereof themselves provide the electrical path, or, alternatively, special means of ensuring this electrical conductivity may be provided by utilising separate electric cables independently connected to the anodes and to the top of the tank, and also where the anode supporting structure is secured in the base of the tank. Where such additional means are included, the whole of atent ice the work necessary for electrical communication may be carried out before the complete anode assembly is erected into its final position. x 4,

The invention will now be further described by way of example with reference to the accompanying drawings wherein:

Figure l is an elevational view of an anode mounting means made in accordance with the invention; 3

Figure 2 is a sectional view on the line 2-2 on Figure 1; and p Figures 3, 4 and 5 are vertical sectional views showing three modified forms of the said mounting means.-

The top of a ships tank which may also form the deck of the ship is shown in section at 10. A small hole, e. g. one and three quarter inches diameter, is drilled in the deck at 11 and a collar 12 is welded on to the deck around the hole 11. A bolt or bar 13 is connected at its lower end 14 into the upper end of a metal tube 15. Welded at 17 to this tube are the lower ends of four arms 18 (three being shown in the drawing) which extend upwardly and diverge to provide a support for a horizontal steel plate 20 which is welded to the arms and carries tour ribs 21 which seat on the top 10, being drawn up tightly against it by a. nut 22 on the upper end of the bolt 13. A locking washer 23 is provided on the bolt 13. A gas tight cover 25 covers over the upper end of the bolt and nut and is clamped against the collar 12 by nuts 26 with the interposition of a packing 27. i i

The lower end of the tube 15 is connected by welding 2% or other means to an anode 29 such as a block of magnesium alloy. i i i The upper end of the bolt is of fiat shape asshown in Figure 2 and engages in a similarly shaped opening in the washer 23. The cover 25 has fiat interior walls 30, 31 parallel to each other which engage: flats on the nut 22 and washer 23 and thereby prevent anyrotation of the bolt or. nut.

In operation, the anode with the tube 15 and bolt 13 is connected by the latter to a cable and lowered through the normal tank hatchway to the bottom of the tank. The cable is detached, hauled up, the nut 22 is threaded on to the cable and the cable is then lowered through the hole 11 to the bottom of the tank and again fixed to the bolt 13. The cable is hauled up until the bolt 13 projects through the hole and the nut 22 is then screwed down. The cable is removed and a locking washer 23 placed in position. Finally the cover 25 is applied and fixed by the nuts 26. 3

In the arrangement shown in Figure 3 a somewhat similar bolt 13 is shown but this has a fiange'33 to engage the tank top 10 and has a tapped hole 34 at its upper end to attach the hoisting cable and to receive a screw 35 which holds a gas tight cover or cap 25 with an extension 37 thereof down on to a soft metal packing disc 40 that rests on the tank top or deck 10. Two nuts 22 are provided, the lower of which seats on a copper packing ring 41. The bolt has a tapped hole 36 for engagement by a threaded pin which carries the anode.

Figure 4 shows a modification in which the bolt 13 has its upper end slotted at 4-4 to receive an eyebolt on the cable and apertured at to receive a pin to hold the eyebolt. In this case the packing ring 40 seats on the extension 37 which is made radially thicker for this purpose. The extension 37 which is welded to the tank top Ill carries a bar 46 which engages in a slot 47 in the collar 33 to prevent rotation of the bolt. The cover 25 may have a small collar 56) thereon for engagement by a tommy bar. in the arrangement shown in Figure 5 the bolt 13 has a transverse hole 52 to receive a bar 53 for holding the bolt suspended while the cable is detached and a plate 54 and thimble 56 are attached to the bolt.

For locking purposes the threads of these parts may be of opposite hand or different pitch. The bar is then withdrawn and the parts '54, 56 screwed down. Packing rings 57.,- 58 p'rovide gastight'nes's.

1he"'ope'ration is asfollow'sz-Theanode-assembly is lowered into the tank through the normal hatchway'with or without' the thimble -56 already-secured, as desired.

Fhe hoisting ropes are lowered through the hole 11 in the deck to the bottom of the tank and attached to the said connecting means, a cap for covering the bolt hole, bolt and nut, and means for connecting said cap to the tank top.

2. Means for suspending an anode from the top of a ships tank comprising a tube'carr'yingan anode at its lower end portion, upwardly extending diverging arms attached at their lower ends to said tube, aplateufixed horizontally on the top of said arms for engagement with thirnble 56 and the complete assembly hoisted to deck 10 the underside of the top of the tank, a; bolt rigidly atlevel andpulled'through the hole'sufiiciently to disclose tached to theupper end of the tube and having its "the -hole 52 "above the welded ring to allow the bar 53 threadedupper portion passingupthrough a bolt hole to be inserted. At this stage, therefore, the whole assemin the tank top, connectionmeans on said bolt for debly is held'suspended by the bar on the welded collar 12. tachable engagement with a lifting cable whereby said The hoistizig rope and thimble can then be removed, and bolt may be drawn up through theholein the tank top, the plate or flange'54 assembled on the bolt 13, having a nut threaded on the bolt for drawing the tube upwardjeviou' sly placed'th'e packing'ring 53 in position. The ly whereby the tank top is clamped between the plate fiah'ge' '54 can--then be 'tightly screwed on the bar, the and the nut, said connection means being of a size to 1aae,r being prevented from turning during this operation permit the nut to pass freely over-the cable andsaid 'jby engagement of the bar 53 against the screws 26. T he 20. connecting means, a cap for covering the bolt hole,-bolt hoisting r'ope and thimble 56 can then be re-attached to and nut, and means for connecting said cap to the tank the-bolt 13"totake theweight ofthe assembly and the top.

-*b'ar"53 removed. This will permit the assembly to be 3. Means as claimed in clam 2 wherein theconnec- {lowered in" position-on to the facing of the welded collar tion means comprises internalthreads on the upper end "12,' and"tobe secured to this by the nuts 60, a gas tight of the bolt. p

joint being efiected. -The thimble can then be freed from 4. Means as claimed in claim 2 wherein means are 'fthe rhoisting rope and tightened on to the bolt 13 thus yprovided for preventing rotation of the bolt, comprising ""l'ocking'the'bolt 13 and the flange 54 together. If necesa part fixed to the top of the tank and engaging a part sary, a'pa'cking ring 57rnay be provided between the fixed to the bolt.

"thimble'and the flange'at the time of final assembly to 5. Means as claimed in claim 2 wherein a collar is provide an additional security for gas tightness. This, welded on the upper surface of the tank around the however, is optional, since it is usual practice to rely *upon threads for gas tightness.

"To'remove'the assembly, the operation described is carried out in reverse.

"When-the anodes are carried by a ladder-like device *as" described in our said prior patent specification, the

bolt which collar carries upstanding threaded studs, and

an apertured ring threaded on to the bolt and fixed by nuts to said studs.

6. Means as claimed in claim 2 wherein the cap has internal non-circular shaped partsto engage non-circular parts of the bolt to prevent rotation of the bolt.

upper ends of the ladder are secured to one or more bolts 13.

What is claimed is:

1. Means for suspending an anode from the top of References Cited in the file of this patent UNITED STATES PATENTS Towne July 27,1915

" a ships tank comprising upwardly extending diverging 1,147,989

arms attached together at their lower ends, a plate fixed 1,440,024 Meyer et al. Deep-'26, 1922 horizontally on the top of said arms for engagement with 1,816,694 Pope July 28, 1931 theunderside of the top of the tank, said plate being 2,063,819 Mattson "Dec.= 8, 1936 fixed to said arms, a bolt rigidly attached to the plate 2,444,174 Tarr etal. June 29,. 1948 and having its threaded upper portion passing up through 2,556,089 James et a]. 5. June 5,-1951 abolt hole'in the tank top, connection means on said 2,603,596 Vangsne July 15, .1952 fbolt for detachable engagement'with a lifting cable 2,805,987 Thorn et al. Sept.10,-1957 w'her'eb'y said bolt may be drawn up through the hole in the tanktop, a nut threaded on the bolt for drawing the PATENTS plate upwardly whereby the tank top is clamped between 2,254 Great Brltain June 28, 1873 the plate" and the nut,"said connection means being of a

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