Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention rel~tes ~o ~n irnproved yoli~h rod centralizer whlch guides
the polish rod or pump rod ln a well head mlnimizin~ wear on the pump rod and
wear in a conventional oil well stuffing box.
In oil retrieval from deep wells, it i~ normal to pump the oil from the
~round by utilizing a reciprocating pump which i~ driven by n mechanlsm on the
surface throu~h a pump rod which extends from the operatinK mechanism down
into the well through a well caslng. The oil i6 lifted up through the casing
by the reciprocating pump to be pumped to a gtorage facllity before bein~
further processed. A stuffing box or packing ~land is normally used between
the upper end of the casing snd the pump rod to prevent the escape of oil.
Durin~ operation of the pump, there i8 a glightly transverge movemsnt of the
pump rod during its reciprocation, which under normal clrcum~tances very
quickly wears the packlng in the stuffin~ box. Furthermore, ~n pumpin~ from
inclined well casings or crooked well casin~s, there i~ llabl~ to be uneven
wear of the pump rod and the stuf~ing box during operation due to the pump rod
lying on the lower side of the stuffing box. As leakage of oil throu~h the
stuffing box cannot be tolerated, there is therefore, during normal pumpin~
operations, a requirement to replace the packing in the 5tuffin8 box st
frequent intervals. This problem has been overcome by utilizing a roller
guide as disclosed in the assignee~s Canadian patent number 1,154,307 which
issued on September 27, 1983. In this patent there i8 discl~sed a gulde
consisting of a housing which includes two sets of parallel rollers mounted
upon axes which are at right anglefi to each other, each roller of a palr being
spaced apart such that the pump rod can be guided between the rollers without
any transverse movement of the pump rod occuring through the guid~. The ~uide
is positioned in B normal well head apparatus between the well head tee and
the normal stuffin~ box.
In order to reduce the number of components which are utillzed upon a well
head, which are required when using the roller guide of Can~dian patent
1,154,307, it is now proposed to combine certain of the components and improve
the known roller guide so that it becomes part of a pump rod centralizer which
also includeg at least one stuffing box, an oiler, and preferably a flap valve
for preventing oil leakage which could occur lf a pump rod breaks in the
region of the centralizer. Provision is also made in the centralizer for
monitoring the prer~ure within the unit so that operation of the pump can be
PAT 1454-1
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stopped if l~aka~e occurs from the well through the lower stuffin~ box.
The centralizer ha~ algo been made with a Rmooth flowlng cylindrical outsr
surface. The upper and lower threaded enda both utilize thread~d connections
with preferably knurled cnd surfaces for gripping ~urlne ~nst~llation, ~n~
there are no extending flanges or bolts. The unlt there~ors pres~nt~ a
relatively ~mooth outer ~urface which cannot catch a workman'~ clothe~ or
cause injury.
The centralizer of this invention therefore con~lst~ in its most basic
form of a housing having two sets of parallel rollers mounted on axes which
are at riBht angles to each other, each roller of a pair being spaced apart
such that a pump rod can be guided between the roller~ without any transverse
movement of the pump rod. The hou~ing also has a lower stuf~ing box wlth a
lower thresded bushin~ which screws into the well head tes and, in one
embodiment, has an upper stuffing box which has a stuffin~ box cap thereover.
The housin~ preferably hag a lubricator so that the pump ro~ can be lubricatea
to prevent scorchlng or burnlng of the packin~ within the stuffing box.
The invention will now be described with reference to the accompanying
drawings in which:
Flgure 1 is a sectional view of one embodiment of the centralizer of this
invention ta~en along its longitudinal axis,
Figure 2 is a sectionsl vlew of a second embodiment of the centralizer
taken along its lon~ltudinal axis, and
Pigure 3 is a sectional view of a third embodiment of the centrali7er
taken along its longitudinal axis.
Referring to the drawin~s and specieically to the embodiment shown in
Fi~ure 1, the centralizer consists of a hollow cylindrical body 1 havine a cap
3 which is held to the body throu~h a scre~ threadsd joint 5. The lower ena
of the body 1 has an outer screw threaded extension 7 and the upper end of the
cap 3 has an outer screw threaded extension 9. Within the body 1 there is a
cylindrical roller cage 11 having rollers 13 spaced vertically apart ln pairs,
the upper pair beinB aligned lB0- from the lower pair. The roller cage and
roller assembly is fully described in Canadian Patent 1,154,307.
A screw threaded aperture 15 is provided through the wall of the body 1 50
that lubricant, which is normally kerosene, can be fed in~ide the housin~ to
provide lubrication for the pump rod 2 passlng throu~h the centralizer.
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An upper stuf~ing box 17 is provided within the cap 3 and during operation
includes a cylindrical spacer 19, a set o~ packing ring~ 21 and a further
spacer 23. The packing is squeezed to~eth~r and s~ainst the pump rod 2 by a
stuffing box cap 25 which is screwed onto threaded extension 9,
A lower stuffing box 27 is provided within the extension 7 and during
operation includes a spacer 29, a set of packing rings 31 and another ~pacer
33. A coupling is utilized to both compress the packin~ 31 and provlde a
screw threaded extension for connection to the well head tee, the coupling
consisting of a cylindrical packing retaining part 35 having a spigot 37, a
collar 39 between the cylindrical part 35 and ~he gpigot 37, ana 8 screw
threaded extension bl. SpiBot 37 slides within the inner bore of ~crew
threaded extension 7 and has a set of 0 ring~ 43 to prov~de a ~eal between the
spi~ot and the inner bore of 8crew threaded exten~ion 7. The coupling i~ hald
in place by a cylindrical sleeve 45 which has a lip 47 which pU115 against the
collar 39 to pull the spigot 37 into the bore within the screw threaded
extension 7 so squeezing the packing 31 into contact with tha pump rod 2 and
the inner bore of the stuffing box.
Referrin~ specifically to Figure 2, like ite~s to those shown in Pigure 1
have been identified by the same reference numerals. ~his ambodiment is th~
same as Fi~ure 1 except that the body 1 of the centralizer i9 of longer
dimensions and includes therein a flap valve havin~ a flap 49 preferably m~da
from a plastic material such as nylon or the like, the flsp baing pivoted by a
pivot 51 secured to a cylindrical ca~e 53. A seat portlon 55 is formed on a
short exte~sion from cap 3 so that if the pump rod falls into the well after
breakin~ within the centralizer, the flap valve will pivot upwardly due to oil
pressure and close off the well. The flap v~lve is detailed ln Cana~ian
Patent 1,154,307.
Furthermore, an extra tapped hole 57 i8 formed through the bo~y 1 near its
top end, this hole 57 being advanta~eously connected ~o a pressure operated
electrical switch so that if oil leaks up from the well and through ths lower
stuffin~ box, the rise in pressure within the centralizer will shut off the
pumping mechanism and sound an alarm so that the fault in the lower stuffing
box can be corrected before it reaches the proportions which woul~ cause
leaXage of oil from the well head.
Referrin~ to Figure 3 there is shown a thir~ embodiment of the
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centrslizer, and agaln llke item9 to those shown in Figures 1 ana 2 havs the
same reference numerals.
This embodiment o~ centrali~er has been de~i~ned as a short unit wherein a
short well head apparatus is raquired. Thi~ unit is al80 espsclally usaful
for wells using steam in~ectlon as there is provision for adequate
lubrication, and also wells which are missligned as there i~ no gtuffing box
at the upper end o~ the unit so that ~light transver8e movement of a pump rod
is permitted to occur.
Referring first to the iower end of the unit, ~here i8 an inner screw
threaded bore 59 which accommodates a cylindrical part 61 which ha~ an
enlarged bore 63, part ~ay throu~h, within which i8 accommodated an upper
spacer 65, packing rin~s 67 and a lower spacer 69. An upper ~crew threaded
end 71 screws into the threaded bore 59 and a lowar screw thre~de~ extension
73 screws into a well head tee.
The upper end of the centralizer has an upper cup 75 of hollow cyllndrical
form within which is an oiler media such as wadding 77, a ~asket 79 and a
compression plate 81. Thc top o~ th~ cup 75 hag 8 cover 83 whlch pa~ses
thereover and i~ held in place by hold down tap bolts 85. The lubricating
liquid, such as kerogene, is therefore poured into the top of th~ CUp, tha
cover 83 is then secured in place and this reservolr of oil ensures that thera
is adequate lubrication on the pump rod 2 80 that burning of tha packing
within the stuffin~ box does not occur even when the well i~ uslng a ~taam
injection process. The lack of an uppsr stuffing box also permit~ ~reater
flexibility of the pump rod through the csntralizer.
A plu~ 87 is shown within threaded bore 15 and, in this embodiment, this
bore 15 can be used for instance for flushing out wax etc. from the inside of
body 1 at intervals to ensure that an excessive build up floe~ not occur ~ithin
the cantrallzer.
The materials from which the centralizer can be made are of co~rse
numerous, however, preferAbly the housin~, stuffing boxes, roller an~ flap
cages, to~ether with roller pins, are ~ads from a suitable corrosion resistant
steel and the rollers and the flap valve are preferably made from eithsr
nylon, ~E~RON , or TeFLO~ .
It is beliaved that a novel compact centralizer has been disclosed, this
centralizer includlng stu~in~ boxes snd oilers ar well as ~uide rollers and
* Trade Mark
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preferentially an anti-leakagc flap, and hencc u~e of thl~ centrallzer wlll
reduce the nu~ber of units utili~ed on a well h~ad. The centrali~er i~ al~o
resistant to wear and needs little maintenance,
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