This standard is for types, nomenclature, and definitions of vertical turbine, mixed flow, axial flow vertical diffuser, submersible motor deepwell and short-set pumps, types VS0, VS1, VS2, VS3, VS6, VS7, and VS8 (Figure 2.1.3) that are driven by vertical electric motors or horizontal engines with right-angle gears.
Excluded from the scope of this document are vertical in-line volute pumps; horizontal centrifugal pumps mounted vertically, such as sewage pumps; and vertical overhung impeller types VS4 and VS5 (Figure 2.1.3).
2.1.2 Definition of rotodynamic (vertical) pumps
Rotodynamic pumps are kinetic machines in which energy is continuously imparted to the pumped fluid by means of a rotating impeller, propeller, or rotor. The most common types of rotodynamic pumps are centrifugal (radial flow), modified radial flow (turbine pumps), mixed flow, and axial flow (propeller pumps). (Refer to Sections 220.127.116.11 to 18.104.22.168.)
These pumps, particularly the radial flow and modified radial flow types, are usually designed for multistaging, by bolting or threading individual bowls together.
The pumping element (bowl assembly) is usually suspended by a column pipe, which also carries the liquid from the bowl (assembly) to the discharge opening.
Rotodynamic (vertical) pumps are normally classified as deep well, short set, or submersible motor-driven. The driver for these pump configurations is mounted either on the discharge head (lineshaft pumps); directly to the bowl assembly, either above or below (i.e., pumps with submersible motors); or in a horizontal configuration, such as an electrical motor or engine, driving through a right-angle gear.
2.1.3 Types of vertical pumps
See Figures 2.1.3 to 22.214.171.124.
126.96.36.199 Deep well (lineshaft)
This type of vertical pump is commonly installed in a drilled and cased well. Its function is to move liquid (usually water) from the liquid level in the well to the surface and provide a specified discharge pressure at the surface (see Figure 188.8.131.52). The pumping element consists of a single or multistage bowl assembly. The first-stage impeller is located below the lowest liquid level. The bowl bearings are usually lubricated by the pumped liquid. The open lineshaft pump is often referred to as a product-lubricated or water-lubricated pump. The lubrication for an enclosed lineshaft pump may be oil, grease, filtered pump discharge water, or clean water from an external source. The column pipe and lineshaft assembly is either an open-type, product-lubricated assembly or enclosed-type oil or external liquid-lubricated assembly. The column pipe is supported at the surface by a discharge head. The discharge head directs the water from vertical to horizontal flow and also supports a driver or right-angle gear. A shaft sealing arrangement is contained within the discharge head. This type of pump is self-priming. Typically the vertical electric motor or vertical right-angle gear drive is of the “hollow shaft” design.
184.108.40.206 Wet pit, short set (lineshaft) – single and double suction
This type of vertical pump usually is suspended in a wet pit. (See Figures 220.127.116.11a, b, c, and d.) The pumping element can be fitted with a bowl assembly of any desired specific speed. Normally the bowl assembly bearings are product-lubricated; however, they can be force-lubricated by grease, water, or other lubricants. The column pipe assembly supports the bowl assembly and houses a lineshaft. The lineshaft bearings are usually open-type, product-lubricated. However, enclosed-type lineshaft, force-feed lubrication with oil, grease, or water may also be supplied. A shaft sealing arrangement is contained within the discharge head on product-lubricated pumps. This type of pump is self-priming.
18.104.22.168 Barrel or can (lineshaft)
This type of pump is mounted in an enclosed container (barrel or can) and typically is used in booster applications where inadequate suction pressure conditions exist, or where the upstream flow under pressure or vacuum must be conveyed to the pumping unit. The can pump contains the same pumping elements and column pipe as the wet pit type pumps (see Figures 22.214.171.124a and b). The lineshaft bearing assembly is usually product-lubricated. The discharge head performs the same functions as the wet pit head except the base is sealed to atmosphere. Liquids other than water are commonly pumped by this type of pump. This type of pump is very effective where inadequate system net positive suction head (NPSH) is available. Additional NPSH is created by extending the pump can length and lowering the bowl assembly by lengthening the column assembly to create additional submergence (suction head). In applications with limited floor space, and where high developed pressure is required, the vertical, multistage volute arrangement shown in Figure 126.96.36.199c may be used.
188.8.131.52 Radial multistage in-line pump
In this type pump (see Figure 184.108.40.206) the fluid enters one nozzle of the in-line casing and is directed to the inlet of an internal multistage diffuser pump. After traveling through multiple stages, the liquid exits at the top stage of the pump where the flow is redirected via the outer sleeve to the opposing nozzle of the in-line casing. Note that this pump is sometimes mounted horizontally for special installation requirements, yet the fluid flows through the pump in the same manner described. Axial thrust loads are transmitted to the thrust bearing, which is usually located in the driver or optional housing supplied as an integral part of the pump assembly. This pump is typically floor mounted but contains a vertically suspended rotor element.
220.127.116.11 Submersible – turbine bowl
This type of pump consists of an electric drive motor coupled directly to the bowl assembly. See Figure 18.104.22.168. The driving “submersible-type” motor and bowl assembly are designed to be submerged in the liquid pumped. The pumping element usually is of the turbine bowl design; however, mixed flow and propeller types are also available.
This type of unit is normally used in wells and occasionally for wet pit or canned booster service. With this style pump the motor is fully submerged in the pumped liquid. A minimum velocity flow is required to cool the motor during operation. Where liquid temperatures exceed specified values, the motors must be derated according to manufacturers’ recommendations.
2.1.4 Classification by configuration
Listed below are the general configurations that describe vertically suspended pumps.
22.214.171.124 Discharge, above and below floor discharge
Vertical pump bowls discharge the pumped liquid into a column, which takes it to the discharge.
There are two basic types of pump discharge configurations. Pumps with above floor discharge (see Figure 126.96.36.199b) and pumps with below floor discharge (see Figure 188.8.131.52d). The driver is mounted above the floor in both.
184.108.40.206.1 Solid shaft driver
The solid shaft driver (see Figures 220.127.116.11a, 18.104.22.168b, 22.214.171.124c, 126.96.36.199a, 188.8.131.52b, 184.108.40.206c, and 220.127.116.11) is coupled to the lineshaft by an axially adjustable rigid coupling. The coupling is installed below the driver on the extended driver shaft.
18.104.22.168.2 Hollow shaft driver
The hollow shaft driver has a tubular shaft extending through the rotor of the driver. The pump head shaft extends through the tubular driver shaft (See Figures 22.214.171.124 and 126.96.36.199d). A lineshaft coupling located in the pump discharge head is not necessarily required.
188.8.131.52 Open/enclosed lineshaft
With open lineshaft pumps (see Figures 184.108.40.206-i, 220.127.116.11a, 18.104.22.168b, 22.214.171.124c, 126.96.36.199a, and 188.8.131.52b), the pump shafting is exposed to the pumped liquid, which also cools and lubricates the lineshaft bearings.
Enclosed lineshaft pumps (see Figure 184.108.40.206-ii and 220.127.116.11d) have the lineshaft protected from the pumped liquid by the shaft enclosing tube. The lineshaft bearings may be lubricated by freshwater, oil, or some other liquid injected into the enclosing tube at the ground or floor level.
18.104.22.168 Impeller types
A typical semi-open impeller (see Figure 22.214.171.124-i and ii) has a back shroud, with integral impeller vanes, but the vanes are open to the front (no front shroud). The leakage control is adjustable between the impeller vanes and bowl or bowl liner. This is achieved by positioning the impeller shaft axially for close impeller vane-to-bowl clearance.
The enclosed impeller, single and double suction (see Figure 126.96.36.199-iii, iv, and v), have both a back shroud and a front shroud. Leakage control is limited by the ring clearance.
2.1.5 Classification by impeller design
188.8.131.52 Specific speed (nS) and suction specific speed (S)
Advisory note: The user is cautioned to check carefully the basis of calculation of specific speed and suction specific speed before making comparisons because there are subtle but significant differences in methods used throughout industry and in related textbooks and literature.
Preferred terms, units, and symbols to be used in the technology of pump applications are shown in Table 2.2a.
US customary units
When calculating the value for specific speed and suction specific speed, the unit of measurement used for rate of flow is defined in US gallons per minute (gpm).
When calculating the value for specific speed and suction specific speed, the unit of measurement used within thisstandard for rate of flow is cubic meters per second (m3/s).
(An alternative method of calculating this value is to use cubic meters per hour [m3/h] as the unit of measurement for rate of flow, which then results in a value that is 36000.5, i.e., 60 times greater.)
Specific speed: An index of pump performance (developed total head) at the pump's best efficiency point (BEP) rate of flow, with the maximum diameter impeller, and at a given rotative speed. Specific speed is expressed by the following equation:
ns = specific speed
n = rotative speed, in revolutions per minute
Q = total pump flow rate, in cubic meters per second (US gallons per minute)
H = head per stage (measured at the bowl), in meters (feet)
Note: Specific speed derived using cubic meters per second and meters, multiplied by a factor 51.6, is equal to specific speed derived using US gallons per minute and feet.
The usual symbol for specific speed in US customary units is Ns.
An alternative definition for specific speed is sometimes used based on flow rate per impeller eye, rather than total flow rate. In a double suction impeller pump, when this alternative method is used, the resultant value of specific speed is less by a multiplying factor of 1/(2)0.5 i.e., 0.707 times less.
Suction specific speed: An index of pump suction operating characteristics determined at the BEP rate of flow with the maximum diameter impeller. (Suction specific speed is an indicator of the net positive suction head [NPSH] required for given values of capacity and provides an assessment of a pump's susceptibility to internal recirculation.)
Suction specific speed is expressed by the following equation:
S = (nQ0.5)/(NPSH3)0.75
S = suction specific speed
Q = flow rate per impeller eye, in cubic meters per second (US gallons per minute)
= total flow rate for single suction impellers
= one half total flow rate for double suction impellers
NPSH3 = net positive suction head required, in meters (feet) that will cause the total head (or first-stage head of multistage pumps) to be reduced by 3%
Note: Suction specific speed derived using cubic meters per second and meters, multiplied by a factor of 51.6, is equal to suction specific speed derived using US gallons per minute and feet. The US customary symbol Nss is sometimes used to designate suction specific speed.
The value S is an assessment of a pump's inlet design, including both the stationary casing and the rotating impeller design elements. Higher numerical values of S are associated with better NPSH capabilities. For pumps of typical suction inlet design, values range from approximately 120 to 250 (6000 to 13,000). In special designs, including inducers, values up to 700 (35,000) or higher are possible depending on the connected inlet piping, the pump's suction casing arrangement, the range of flow over which the pump must operate, size and power rating of the machine, and other considerations.
184.108.40.206 Radial flow
Pumps with this type of impeller have specific speed values at the lower end of the scale. (See Figure 220.127.116.11-ii, impeller profiles 1 and 2, for approximate specific speed ranges.) The liquid enters the eye of the impeller axially and is turned by the impeller vanes and shroud to exit perpendicular to the axis of the pump shaft.
18.104.22.168 Francis vane (modified radial flow)
This type of impeller usually has higher specific speeds than the radial flow type. (See Figure 22.214.171.124-ii, impeller profiles 3 and 4, for approximate specific speed ranges.) The impellers are normally single suction. In pumps of this type, the liquid enters the eye of the impeller axially and exits semi-radially, at about a 60o to 70o angle to the shaft axis (see Figure 126.96.36.199-ii).
188.8.131.52 Mixed flow
The mixed flow pump has a single inlet impeller with the flow entering axially and discharging about 45o with shaft axis, to the periphery. In many cases, this style impeller has no lower shroud. (For mixed flow impeller configuration, see profile 5 in Figure 184.108.40.206-ii with corresponding specific speed ranges.)
220.127.116.11 Axial flow
An axial flow impeller has a single inlet with the flow entering and discharging axially (or nearly axially). Impellers of this type are sometimes called propellers and do not have shrouds. Axial flow impellers are typically used for lowhead, single-stage applications. (See Figure 18.104.22.168-ii for impeller profiles and for approximate specific speed ranges.)