[0001] This invention relates to fluidic pump-off control devices, particularly for use
in oil wells.
[0002] Means of closing down the oil pump is required if oil stops flowing into the well
in order to avoid unnecessary wear of the parts of the pump and also to avoid the
cost of running the pump when no oil is flowing.
[0003] A typical pumping assembly includes a reciprocable piston member in the well head
which is in communication with the discharge line. The reciprocable piston member
is raised and lowered by a cable attached to a cable head on a pivotable beam, which
is rockable via a connecting rod, by cranking means. The cranking means is operable
through reducing gearing and drivable by a prime mover e.g. a motor. As the pump is
raised and lowered, oil is sucked out of the well and discharged through the discharge
line.
[0004] There are conventional control systems located in the discharge line which employ
movable floats or valves which move to an-extreme or closed position when minimal
or no oil is being pumped and in this extreme position cause a switch to disconnect
power from the pump so that the pump is closed down until oil begins to flow again
in the well e.g. USP 3963374, on which this invention is an improvement.
[0005] A movable member is prone to mechanical wear and failure, and thus unreliability,
and it also suffers from the possibility of contamination by sand and/or paraffin
which retard the movement of the member.
[0006] It is an object of this invention to obtain an improved fluidic pump-off control
device in which the above disadvantages are obviated.
[0007] According to this invention, I propose a fluidic pump-off control device which is
for location in the discharge line of a fluid pump and which comprises a housing,
which is in communication with the pump discharge line via an inlet passage and which
encloses a chamber having an outlet passage spaced apart from the inlet passage, the
chamber further housing air sampling means associated with pressure sensing means
for actuating the disconnection of power to the pump upon a predetermined pressure
level being reached corresponding to a predetermined liquid level in the chamber,
and timing means for turning the pump on and/or off after a predetermined time in
cooperation with the pressure sensing means.
[0008] Preferably, the pressure sensing means comprises a Reed Switch or a pressure monitoring
means, operating on pressure difference or measurement, which may be computerised.
[0009] I also propose a fluidic pump-off control device for location in a fluid pump discharge
line, comprising a housing, which is in communication with the pump discharge line
via an inlet passage and which encloses a chamber having an outlet passage spaced
apart from the inlet passage, the chamber further housing means for detecting or measuring
the rate of fluid flow in the chamber whereby upon a predetermined minimum amount
of liquid flowing the pump is shut-off, a portion of the bottom of the chamber having
means to induce a vortex flow in liquid draining away into the relief line.
[0010] Other improvements are as follows. The upper end of the inner passage in the chamber
may be divided to produce a laminar flow of the fluid into the chamber. This may be
achieved with regularly spaced dividing means. Turbulence of the fluid in the chamber
is minimised in this way.
[0011] A relief line may be employed in the bottom of the housing so that liquid remaining
in the chamber after the pump has stopped may be drained away. The bottom of the housing
proximate and around the orifice of the relief line may be in the form of a trough,
which is preferably conical, to produce a vortex flow in the draining liquid so as
to prevent particulates, such as sand, from passing into and clogging up the relief
line. Dividing means may be disposed in the bottom of the chamber or in the orifice
for regulating the outlet flow through the relief line.
[0012] The mouth of the air sampling means e.g. in the form of a tube may be slanted, which
will minimise the effect of turbulence in the chamber on sampled air or gas in the
sampling means.
[0013] The proposed means for reducing turbulence removes the need for means for shielding
the sampling means within the chamber.
[0014] An embodiment of the invention is described by way of example only with reference
to the drawing, in which:
Figure 1 is a diagrammatic side view of a fluidic pump-off control device according
to this invention; and
Figure 2 is a section taken through line A-A on Figure 1.
[0015] A fluidic pump-off control device 1 is secured in a fluid delivery line and has a
housing 2 with an inlet 3 and an outlet 4. Typically the device would be about 20"
high and about 10" in diameter.
[0016] The housing has a generally cylindrical vessel 5 and a top cover 6 is secured to
the vessel via an "0-ring" to provide a seal. A measurement chamber 7 is defined within
the housing. The inlet and outlet lines are generally L-shaped passages, typically
22" in diameter and have a vertical portion extending upwardly in the housing 2 with
the horizontal portion of the inlet line in communication with the delivery line from
the pump and the horizonta1.portion of the outlet line oriented away from and at right
angles to the housing 2.
[0017] The upper end of the inlet passage in the chamber is divided, for instance so as
to provide a step-wise exit from the passage into the chamber. This has the effect
of producing a laminar flow of fluid into the chamber, so reducing possible turbulence
in the fluid in the chamber.
[0018] A tube 8 is disposed in the chamber between the inlet and outlet passages. The tube
may be %" in diameter and it may have an opening 9 sloping at e.g. 45°. Liquid may
rise up or down the tube and the resulting air or gas pressure in the tube is detected
by any suitable means, for example by a Reed switch carried on the cover or pressure
measurement means which are both employed to disconnect the pump. As the level of
liquid decreases in the chamber 7 the pressure within the tube is decreased and similarly
for an increased liquid level. Monitoring means may be employed to the pressure measured
in the tube 8 in order to determine the liquid level within the chamber 7.
[0019] The monitoring means is connected with a switching device for turning off the pump.
[0020] A relief drain line 10 of typical diameter 8" is connected between the bottom of
the housing 2 and the outlet passage. The relief line is for removing fluid from the
chamber 7 when the pump is out of action. The drain line 10 may be connected to a
conical trough 11 in the bottom wall of the housing 2. The trough 11 has walls inclined
e.g. at 45
0, to the relief outlet 12.
[0021] When excess fluid is draining out through the relief line, a vortex flow is produced
which allows the fluid to pass unobstructed through the relief line and foreign matter
such as solid particulates, e.g. sand, and paraffin included in raw oil are prevented
from passing into the relief line and from clogging up the line. A needle valve may
be optionally employed in the relief line to open or close it.
[0022] Alternatively, the relief line may be.made with a sufficiently large diameter to
allow the foreign matter in the fluid to pass straight through the relief line.
[0023] Furthermore, the relief line need not include a right-angle bend in Figure 1 between
the bottom of the housing and the discharge line. The relief line may be a straight
pipe inclined with its outlet lower than its inlet therebetween or a pipe with a gradually
curved bend.
[0024] When the pump is not pumping liquid into the inlet passage, the liquid level in the
chamber 7 of the contrd device is at a lower, non-existent level. In this condition
the pressure in the chamber and the tube 9 is lowered relatively to when liquid is
being pumped and the pressure detector and optionally monitoring means causes the
pump to shut down.
[0025] A timing mechanism is associated with the pump so that pumping is restored after
a predetermined time. For instance once no fluid is being pumped, the pump may be
turned off after a predetermined period of time e.g. 10.minutes and if liquid becomes
available for pumping, then the pump will remain in operation until liquid is not
available. When no more liquid becomes available within the predetermined time interval
during which the pump is kept running, the pump is shut down for a predetermined time.
[0026] Any desired timing control may be incorporated with the control device according
to this invention.
[0027] When fluid is available it is sucked upwards and flows into the discharge line and
then the inlet passage. As pumping continues, the fluid level in the chamber rises
until fluid is able to pass out of the outlet passage. A syphon effect is set up and
fluid is delivered usually for storage.
[0028] If gas is being pumped instead of liquid, the gas will pass into the chamber of the
control device and rise to the top of the chamber. Any liquid in the chamber will
be depressed and flow out of the relief line. As a result, the sampled air pressure
in the tube is reduced and if the predetermined low value is reached, pumping is stopped
in the usual manner.
[0029] The features of the fluidic pump-off control device herein proposed are useful for
the pumping of all liquids, particularly oil.
1. A fluidic pump-off control device for location in a fluid pump discharge line,
comprising a housing, which is in communication with the pump discharge line via an
inlet passage and which encloses a chanber having an outlet passage spaced apart from
the inlet passage, the chamber further housing air sampling means associated with
pressure sensing means for actuating the disconnection of power to the pump upon a
predetermined pressure level being reached corresponding to a predetermined liquid
level in the chamber, and timing means for turning the pump on and/or off after a
predetermined time in co-operation with the pressure sensing means.
2. A device as claimed in claim 1, wherein the pressure sensing means comprises a
Reed Switch.
3. A device as claimed in claim l, wherein the pressure sensing means is in the form
of computerised pressure monitoring means.
4. A device as claimed in claim 1, 2 or 3, wherein the upper end of the inlet passage
to the chamber is divided to produce a laminar flow of the fluid into the chamber
and minimise turbulence of the fluid in the chamber.
5. A device as claimed in any preceding claim, having a relief line in the bottom
of the housing whereby fluid in the bottom of the chamber may be drained away.
6. A device as claimed in claim 5, wherein the bottom of the housing proximate and
around the orifice of the relief line is in the form of a trough to produce a vortex
flow in the draining fluid.
7. A device as claimed in claim 5 or 6, having dividing means in the bottom of the
chamber or in the orifice, for regulating the outlet flow through the relief line.
8. A device as claimed in any preceding claim,. wherein the air sampling means is
in the form of a tube.
9. A device as claimed in any preceding claim; whereby a predetermined minimum liquid
level in the chamber is detected or measured.
10. A fluidic pump-off control device for location in a fluid pump discharge line,
comprising a housing, which is in communication with the pump discharge line via an
inlet passage and which encloses a chamber having an outlet passage spaced apart from
the inlet passage, the chamber further housing means for detecting or measuring the
rate of fluid flow in the chamber whereby upon a predetermined minimum amount of liquid
flowing the pump is shut-off, a portion of the bottom of the chamber having means
to induce a vortex flow in liquid draining away into the relief line.
11. A device as claimed in claim 10, wherein the inducing means comprises a conical
trough formed in the bottom of the chamber and communcating with the relief line.
12. A device as claimed in claim 10 or 11, having dividing means in the bottom of
the chamber or in an orifice leading into the relief line from the chamber, for regulating
the outlet flow through the relief line.
13. A device as claimed in any of claims 10 to 12, wherein the flow detecting or measuring
means comprises air sampling means associated with pressure sensing means for actuating
the disconnection of power to the pump upon a predetermined pressure level being reached
corresponding to a predetermined fluid level and flow rate in the chamber in conjunction
with timing means for turning the pump on and/or off after a predetermined time.
14. A device as claimed in any of claims 10 to 13, wherein the air sampling means
is in the form of a tube.
15. A device as claimed in any of claims 10 to 14, wherein a predetermined minimum
liquid level in the chamber is detected or measured.