US2392033A - Sucker rod coupling with zinc inserts - Google Patents

Description

Jan. 1, 1946. Y J, F, EATON y2,392,033

SUGKER- ROD GOUPLING WITH ZINC INsERTs Filed NOV. l, 1941 Patented Jan. 1,1946

SUCKER ROD COUPLING WITH ZINC l A l t INSERTS John F. Eaton, Tulsa, Okla., assignor to Bethlehem Steel Company, a corporation of Pennsyl vania Application November 1, 1941, Serial No. 417,422

(Cl. 21M-197) 4 Claims.

This invention relates to an improvement in sucker rod joints, and more particularly to a protective coupling guide for use under electrolytlc conditions in oil wells.

Four methods of producing oil from wells are today in use: natural iiow, artificial flow induced b foil or gas lift, swabbing and pumping. But p ping is certainly the method most widely utllized, and the pumps are usually actuated by a string of sucker rods. The success of deep oil well pumping, in particular, is largely dependent upon the length of service received from sucker rods, for rod 4breaks arey costly in labor, down time, and replacements.

Standard sucker rods, made according to American Petroleum Institute specifications, are highgrade steel rods from 5A; inch to 1V; inch in nominal diameter and 25 to 30 feet in length overall, including the coupling if any. Pony rods are similar, but shorter. Bothsucker and pony rods are characterized 'by an'enlarged or upset portion at each end, which at one end at least terminates in an externally threaded pin.

The box and pin type of sucker rod has an interiorly threaded end or box at the opposite end from the pin, which dispenses with the use of couplings to make connections, but the double pin type, exteriorly threaded at .both ends', employs couplings and subcouplings to make up a string of sucker rods. These last are short internally hereto'f ore been used in such wells, but' these steels are not only rather high-priced, even in normal times, but are now practically unobtainable due to shortages. Since iron and zinc form a galvanc couple, zinc dissolving, and iron remaining unaffected, galvanizing is a good protectant against electrolysis, but galvanized rods and couplings are fairly expensive also, and inA dynamic tests the soft zinc coating has been found to resist abrasive wearvery poorly and to facilitate the formation of surface nicks or notches which concentrate operating stresses and produce proy gressive cracks and breaks ending in costly lishthreaded members screwed onto the pins, being called couplings i-f both ends are threaded alike and subcouplingsif the ends are threaded differently, as in joining rods of different sizes for the tapered strings of deep wells.

The advantage of using the double pin type of rodis that all abrasion against the side of the tubing is taken on the coupling, so that the coupling rather than the much more expensive sucker rod receives the wear. Couplings can thus be removed and are usually renewed several times during the life of the rods, for the failure of a I coupling' would obviously entail the same considerable expense as the breakage .of a sucker rod.

Electrolysis is provably the main cause of sucker rod and coupling failure in some fields, as in certain West Texas wells where about '75 per cent of the rod breaks are due to electrolytic action. Brlnes impregnated with hydrogen sulphide gas, shown by the familiar test for discoloration or v.blackening of lead acetate paper and found in many oil bearing horizons, have a highly destructive electrolytic pitting effect upon sucker rods or the like of ordinary steels.

Special corrosion resistant alloy steels have ing jobs. Moreover, detached flakes of the zinc coating which have dropped to the bottom of the well will tend to hang between the ball and seat ofthe traveling or standing 4valves of thepump, thereby breaking the fluid seal, if adequate provision is not made for prevention. And for long life of the couplings and well tubing, the couplings should be extremely hard and highly polished on their outer surface, which is impossible with galvanizing.

To utilize this principle'of the selective corros ion of zinc in contact with iron, withoutpermitting undue abrasive weakening of the couplings or rods, is one object of my invention.

Another object is a sucker rod coupling of high resistance to attack by electrolysis.

A further object is a guide or coupling which will protectv the adjacent sucker rods from electrolytic action.

Still another object is a coupling which is provided with inexpensive, self-cleaning and readily renewable zinc inserts.

Other objects, advantages and purposes of my linvention will hereinafter appear in the following pages of the specification and claims.

Having thus given a general description of the advantages of my invention, I shall now in order to make the same more clear refer to the annexed sheet of drawings forming a. part of this specification and in which like characters of reference indicate like parts.

Figure 1 is a side elevation of the coupling shown connecting two sucker rods within the well tubing;

Fig. 2 is a longitudinal section of the coupling which more clearly shows the zinc inserts and sucker rod pins;

Fig. 3 is a, transverse sectional view taken substantially on the line 3-3 of Fig. 1, showing the wrench flats on the coupling and the top sucker rod pin;

Fig. 4 is a transverse sectional view taken cates the well tubing, 2 identical sucker rods,

and 3 the coupling joining said sucker rods. Each sucker rod 2 is provided with a slender rod or bar portion 4, a head 5, a wrench engaging square 6, pin shoulder "I, and externally threaded pin 8. At both ends of coupl'ng 3 is an internally threaded box portion 9 adapted to engage the externally threaded pink8. Milled flats` I supply means for wrench engagement and the enlarged middle body portion I I is provided with a longitudinally bored central chamber I2, connecting said box portions 9, and with vertically fluted elongated slots I3. Within said chamber I2 are vertically arranged several spool-shaped zinc inserts I4 each provided with a circumferential groove I5.

The zinc inserts I4 are placed within `the chamber I2 at the time of making up the sucker rod string, sufficient open space being left in the chamber I2 above zinc inserts I4 to permit a limited amount of free vertical movementfto said inserts. For illustration the coupling has been shown as equipped with five (5) zinc inserts, but it will be readily understood that this number is not critical and `may be varied as. de-

sired to accord with the size of coupling used and other operating conditions. The number loosen and knock off the corrosion products as .soon as they form, maintaining thu: the prior as a joint for pony rods, equally as well.

In other respects also, although I have shown and described my invention in considerable detail, Iv do not wishto be limited strictly to the exact and specificv details shown and described.

' but may use such substitutions, modifications or equivalents thereof as are embraced within the scope of the invention or as are pointed out in the claims. Having thus described my invention, what I claim Vas new and desire to secure by Letters Patent is:

`1 ,A couplingfor sucker rods pumping corrosive well fluid comprising end box portions and of zinc inserted 'couplings required willvary also with the concentration of electrolyte in the particular well, but one to every 50 or 60 feet of ex posed rod, i. e., at every other joint. will usually be found ample to protect both the rods and the other couplings.

Besides guarding the zinc inserts I4 froml abrasion against the tubing I, the enlarged'body portion II serves to hold the rods in the center of the tubing during the pumping stroke Iand lessens the chance of buckling.

If the zinc inserts I4 were permittedto become coated with corrosion products theywould lose a great part 'of their effectiveness in comhating corrosion within a short time. But in operation most of the well fluid flowing past the moving coupling passes -through the fluid passage slots I3 and is directed against the surface of the zinc inserts I4. Thegrooves I5 in said inserts increase the surface -friction of the fluid passing the inserts, with the effect of lifting and agitating the inserts; and the fact of a plurality of small inserts instead of one large one further adds to the agitation and movement of the inserts in the coupling. The resultof the continuous vibration and impact shocks is to a vertically slotted central'chambercontaining a plurality of loosely movable spool-shaped zinc inserts having fluid-engagingv grooves so placed that the fluid strikes them 'while moving In the direction oftheir long axes.v

2. A coupling for sucker rods comprising end box portions, an. enlarged hollow longitudinally pierced portion perforated to permit the passage of fluid vertically, and within said hollow pierced portion a plurality of vertically disposed superposed movable cylindrical zinc inserts each having in the middle `a circumferential groove to frictionally engage said fluid.A

3. A coupling for sucker rods for ,use in corrosive well fluids,comprising a hollow steel shell `internally threaded at both ends to `engage vmovable'coupling section located intermediate adjacent lengths of sucker rods and consisting ofY an enlarged perforated outer steel shelll with `exterior diameter slightly less than the interior diameter of the tubing. and a plurality of movable selectively corrodible metallic spools therein.

. JOHN F. EATON.

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