Centrifugal Pump
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Centrifugal Pumps Schlumberger Private
The term “centrifugal pump” has been used to describe a wide variety of pumping applications and designs throughout the years.
Centrifugal Pump
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The REDA centrifugal pump is a multistage pump, containing a selected number (application dependent) of impellers equipped with vanes, inside a closely fitted diffuser, located in series an axial shaft, driven by the electrical motor.
Centrifugal Pump A centrifugal pump creates pressure by the rotation of a series of vanes in an impeller. Schlumberger Private
The impeller’s job is to transfer energy by rotation to the liquid passing through it, thus raising the kinetic energy.
Centrifugal Pump
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The diffuser section then converts this energy to potential energy, raising the discharge pressure.
Centrifugal Pump
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From there, the rotation of the high-speed impeller throws the liquid into the diffuser.
Centrifugal Pumps
Upthrust Washer Impeller Down Thrust Washer Diffuser
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Each "stage" consists of an impeller and a diffuser. The impeller takes the fluid and imparts kinetic energy to it. The diffuser converts this kinetic energy into potential energy (head or pressure).
HEAD Head: The height to which the pump will "lift" the fluid
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• Curves for centrifugal pumps are normally shown as flow versus head in feet, meters, or some other consistent unit.
Propane
Water
Oil
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• A centrifugal pump produces "constant head". – This means that, regardless of the fluid being pumped, it will be lifted to the same height as any other fluid for the same flow rate.
Maximum Head-Capacity 4.5" Casing 5.5" Casing 7" Casing
15000
10000
5000
0 0
10000
20000
Flow Rate - BPD (60 Hz)
30000
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Total Dynamic Head -Feet
20000
SN2600 60 HZ / 3500 RPM
REDA Rev. B
Optimum Operating Range1600 - 3200 Nominal Housing Diameter 5.38 Shaft Diameter 0.875 Shaft Cross Sectional Area 0.601 Minimum Casing Size 7.000
Pump Performance Curve 538 Series - 1 Stage(s) - Sp. Gr. 1.00 bpd inches inches in2 inches
Shaft Brake Horsepower Limit:Standard High Strength Housing Burst Pressure Limit:Standard Buttress Welded
Feet
256 410 N/A 6000 6000
B.E.P. Q = 2581 H = 46.75 P = 1.31 E = 68.09
60
Hp Hp psi psi psi
Hp Eff 3.00 60%
2.50 50%
40
2.00 40%
30
1.50 30%
20
1.00 20%
10
0.50 10%
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
Capacity - Barrels per Day
• From this curve we can determine the head produced, brake horsepower required and hydraulic efficiency at any flow rate.
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50
Pump Descriptions and Names The series designations are defined as: Type
P
338 400 540 538 562 675 738 862 950 950 1125
DN 1300
Outside Diameter 3.38” 4.00” 5.13” 5.38” 5.63” 6.75” 7.25” 8.63” 9.5” 10.00” 11.25”
Minimum Casing Size 4 ½” 5 ½” 6 5/8” 7” 7” 8 5/8” 9 5/8” 10 ¾” 11 ¾” 11 ¾” 13 3/8”
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A D G S H J L M N
Series
Pump Descriptions and Names:
• H (Extrude Honed) • E (Epoxy Coated Stages) SN3600E • C (As Cast) • Other letters may be used from time to time, but these should be considered as experimental and not used in pump selections.
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• Other Letters (Suffix only) used in PAD to describe special pumps
Pump Nomenclature: Frequently Used Terms Definition Abrasion Resistant: Zirconia bushings and sleeves Abrasion Resistant: Silicon Carbide sleeves Abrasion Resistant: Silicon Carbide bushing and sleeves Abrasion Resistant: Tungsten-Carbide sleeves Abrasion Resistant: Tungsten-Carbide bushings and sleeves Abrasion Resistant: Zirconia bushing bushings and Silicon sleeves Abrasion Resistant: Zirconia bushing bushings and Tungsten sleeves Compression Center Tandem Compression-Center Tandem Compression-Lower Tandem Compression Ring Compression Ring-Center Tandem Compression Ring-Lower Tandem Enhanced Stability Floater Floater-Center Tandem Floater-Lower Tandem Floater-Single section Hydraulic Balance Housing Single Stainless Steel Stainless Steel Head and Base Carbon Steel Monel Trim Redaloy Self Lubricating bearings (Graphalloy) High Strength Shaft
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Abbreviation ARZ ARZ-S ARZ-SS ARZ-T ARZ-TT ARZ-ZS ARZ-ZT C CT C-CT C-LT CR CR-CT CR-LT ES FL FL-CT FL-LT FL-S HB HSG S SS SS H and B CS M-Trim Rloy SLB HSS
Pump naming conventions A DN1400 indicates: = 400 series, therefore, 4.0” in diameter
1400
= the best efficiency flow rate (60 Hz : 3500 RPM) in barrels per day.
N
= the material of the stage, in this case ni-resist.
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D
Pump naming conventions A D950 indicates: = 400 series, or 4.0” diameter
950
= 950 bpd flow rate
“N” is missing from the description so the impellers are Ryton (thermo plastic)
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D
Centrifugal Pumps There are two types of impellers that determine the amount flow available for the specific design. Schlumberger Private
Centrifugal Pumps
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The difference between these two types of designs is described by the pump impeller vane angles and the size and shape of the internal flow passages.
Centrifugal Pumps Schlumberger Private
A mixed flow impeller has vane angels at close to 45 degree, and therefore, are usually found in pump ranges for higher flow rates.
Centrifugal Pumps
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A radial flow (pancake) impeller has vane angels at close to 90 degree, and therefore, are usually found in pump ranges for lower flow rates.
Pump Construction
Floater - Type Compression - Type
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There are two types of pump stage construction for ESP oil field applications:
2 Types of Stage Construction Impeller Thrust
Floater
Protector Thrust Bearing Motor Thrust Bearing
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Compression
Pump Down Thrust Carried here
"Compression" Pumps In a compression pump, all the impellers are rigidly fixed to the shaft so that if an impeller wants to move up or down, it will take the shaft with it. Schlumberger Private
The impeller is normally sitting down on its lower diffuser during assembly due to gravity. Because of this, the pump shaft is "raised" with shims in the coupling so that the impeller is not allowed to touch the diffuser after final assembly. This allows all thrust developed in the pump shaft to be transferred to the protector shaft directly.
Pump Shimming
There is a small amount of free play in the coupling such that the pump shaft can fall down to where the impellers ride directly on the lower diffusers or on the downthrust washers if available.
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Impeller is in full down position
Pump Shimming
When shimming 675 Series pumps down thrust washers), Impeller is lifted slightly off diffuser.
Shims placed in coupling to raise the shaft
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and larger (which do not have
Pump Shimming
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If we are shimming 562 Series pumps and smaller (which have downthrust washers) we match the shafts flush.
Shims placed in coupling to match the shafts
Why use Compression Pumps? •
• •
•
the stage. Some fluids (e.g. liquid propane) do not have enough lubricity to properly lubricate a thrust washer. If abrasives or corrosives are present, it may be beneficial to handle the thrust in an area lubricated by motor oil rather than well fluid. Occasionally in very gassy wells, the flow volume changes so drastically within the pump that parts of a floater pump could be in very severe thrust while others are not so a compression pump could be one alternative. Since all the thrust is handled in the protector, as long as the protector has a great enough capacity, the pump operating range can be extended over a much wider area without any increased wear or reduced life.
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•
Some stages generate too much thrust to be handled by a thrust washer in
"Floater" Pumps Why use a floater pump? Schlumberger Private
Let's look at a floating impeller in detail.
Floating Impellers: Since a floating impeller is free to move up and down the shaft, the only thing to stop it is either the upper or lower diffuser. "Thrust washers" are provided at all mating surfaces between the impeller and diffuser to absorb any thrust generated. Schlumberger Private
Thrust Washers
Floating Impellers: The blue area shows the "upthrust" washer between the impeller and upper diffuser. Schlumberger Private
Upthrust is absorbed here
Force
Floating Impellers: The blue area shows the "downthrust" washers between the impeller and lower diffuser.
Downthrust is absorbed here
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Force
Floating Impellers:
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Seal here prevents abrasives from getting into washer
We lose efficiency in the upthrust position because of the fluid's ability to recirculate from the high pressure to low pressure eye area. In addition to loss in efficiency, this can promote erosion in the diffuser in abrasive fluids. Schlumberger Private
Why use floater pumps? • Since each stage handles its own thrust, a very large Schlumberger Private
number of stages can be put in a pump without having to worry about protector bearing capacity. • Floaters are also very good with mild abrasives since they prevent material from getting into the radial bearing area. • Floaters are much more forgiving in manufacturing since tolerance stack-up is not a concern. • Easier field assembly - no shimming required.
