API Pumps design, application and selection

API Pumps
design,
application
and selection

Pumps Technology - Classification of Pumps
٢ @ Pumps Technology Mechanical Dept. June 21
API
STANDARDS
•API 610
•API 674
•API 676
•API 682
•API 685
•API 686
H.I.
•ANSI/HI
9.1-9.5
•ANSI/HI
1.3
•ANSI/HI
6.1-6.5
•ANSI/HI
10.1-10.5
•ANSI/HI
3.1-3.5
•ANSI/HI
2.3
ASME
•ASME
B73.1
•ASME
B73.2
•ASME
B73.3
ISO
•ISO 5199
•ISO 1940
•ISO
10816-1
NFPA
•NFPA 20
Enppi
SPECIFICATIONS
•100-012
•100-014
•100-027
Law 4/1994 amended by the law 9/2009

Introduction to Pumps Technology
Pump Types
٣ @ Pump Design Guide Mechanical Dept. June 21

Pump Types
٤ @ Pump Design Guide Mechanical Dept. June 21

Scope:
• This International Standard specifies requirements for centrifugal pumps, including pumps running in reverse as
hydraulic power recovery turbines, for use in petroleum, petrochemical and gas industry process services.
• This International Standard is applicable to overhung pumps, between-bearings pumps and vertically suspended
pumps (see Table 1).
• Relevant industry operating experience suggests pumps produced to this International Standard are cost effective
when pumping liquids at conditions exceeding anyone of the following:
1. discharge pressure (gauge) 1 900 kPa (275 psi; 19,0 bar)
2. suction pressure (gauge) 500 kPa (75 psi; 5,0 bar)
3. pumping temperature 150°C (300 OF)
4. rotative speed 3600 rlmin
5. rated total head 120 m (400 ft)
6. impeller diameter, overhung pumps 330 mm (13 in)

Why:
The equipment (including auxiliaries) covered by this International Standard shall be designed and
constructed for a minimum service life of 20 years (excluding normal-wear parts as identified in Table 20) and at
least 3 years of uninterrupted operation. Shutting down the equipment to perform vendor-specified maintenance
or inspection does not meet the continuous uninterrupted operation requirement. It is recognized that these
requirements are design criteria and that service or duty severity, mis-operation or improper maintenance can
result in a machine failing to meet these criteria.

6.6.9 Shafts shall be machined and finished throughout their length so that the TIR is not more than 25 µm
(0,001 in).
6.9.1.3 To obtain satisfactory seal performance, the shaft stiffness shall limit the total deflection under the most
severe dynamic conditions over the allowable operating range of the pump with maximum diameter impeller(s) and
the specified speed and liquid to 50 !-1m (0,002 in) at the primary seal faces. This shaft-deflection limit may be
achieved by a combination of shaft diameter, shaft span or overhang, and casing design (including the use of dual
volutes or diffusers). For one- and two-stage pumps, no credit shall be taken for the liquid stiffening effects of
impeller wear rings. For multistage pumps, liquid stiffening effects shall be considered and calculations shall be
performed at both one and two times the nominal design clearances. The liquid stiffness of product-lubricated
bearings and bearing bushings shall be calculated at both one and two times the nominal design clearances.

7.1.7 Unless otherwise specified, motors for vertical pumps shall have solid shafts. If the pump thrust bearings
are in the motor, the motors shall meet the shaft and base tolerances shown in Figure 36

6.8.2 The seal cartridge shall be removable without disturbing the driver.

6.1.25 Except for vertically suspended pumps and integrally geared pumps, pumps shall be designed to permit
removal of the rotor or inner element without disconnecting the suction or discharge piping or moving the driver.

Basic design General Requirements:

6.1.11 Pumps that have stable head/flowrate curves
(continuous head rise to shutoff) are preferred for all
applications and are required if parallel operation is
specified. If parallel operation is specified, the head rise
from rated point to shutoff shall be at least 10 %. If a
discharge orifice is used as a means of providing a
continuous rise to shutoff, this use shall be stated in the
proposal.
6.1.12 Pumps shall have a preferred operating region of 80
% to 110 % of best efficiency flowrate of the pump as
furnished. Rated flow shall be within the region of 70 % to
120 % of best efficiency flowrate of the pump as furnished.

6.1.17 The need for cooling shall be determined by the vendor, and the method shall be agreed upon by the
purchaser. Fan cooling should be the first choice. If fan cooling is inadequate, one of the plans in Annex B shall be
selected. The cooling system shall be suitable for operation with the coolant type, pressure and temperature
specified by the purchaser. The vendor shall specify the required flow. To avoid condensation, the minimum
temperature at the cooling-water inlet to bearing housings should be above the ambient air temperature.

Pumps Technology – Pump Performance
Head is equal to the height of a column liquid that could be supported by the available, or
useful energy.
Energy imparted to the fluid by a pump consists of useful energy in the form of:
Pressure
Fluid temperature rise and velocity
or it may become a loss through conversion to atmospheric heat and noise
All of these values may be arithmetically converted to head
STATIC
HEAD
P

Pumps Technology - Pump Performance
PRESSURE HEAD
STATIC
DISCHARGE
HEAD
DISCHARGE
FRICTION HEAD
STATIC SUCTION
LIFT
SUCTION
FRICTION HEAD
SUCTION
VELOCITY HEAD
DISCHARGE
VELOCITY HEAD
All forms of energy involved in a liquid flow system can be expressed in terms of
meter(feet) of liquid.
The total of these heads is the total system head or the work which pump must
perform in the system

The total head of a pump is the difference between the energy level at the pump discharge
(point 2) and that at the pump suction (point 1).

The change in internal energy is equal to the
amount of energy added by heating minus the
amount lost by doing work on the environment.
The first law of thermodynamics for the pump can be
expressed in the form of the adiabatic steady-flow energy
equation
shaft power Ps is transformed into fluid power, which is
the mass flow rate times the change in the total enthalpy

Hydraulic Losses in
flow passages of the
pump
Mechanical losses in
bearing, seals & fluid
friction on the outside
surfaces og the
impeller shrouds
Leakage Losses past
the impeller and
back into the inlet
eye

Pumps Technology - Pump Performance – NPSHA
PB = Barometric pressure in feet absolute.
VP = Vapor pressure of the liquid at
maximum pumping temperature, in
feet absolute.
P = Pressure on surface of liquid in closed
suction tank, in feet absolute.
Ls = Maximum static suction lift in feet.
LH = Minimum static suction head in feet.
hf = Friction loss in feet in suction pipe at
required capacity
Calculation of system Net Positive Suction Head Available for typical suction conditions

٦٧ @ Pumps Technology
IMPELLER DESIGN VS SPECIFIC SPEED

٦٨ @ Pumps Technology

٦٩ @ Pumps Technology

٧٠ @ Pumps Technology

Pumps Technology - Pump Performance - Curves
Flow
TDH
Impeller
Diam.
Min.
Continuou
s Stable
Flow line
Efficiency
BkW
NPSHR
Rated
Point

Pump Performance – NPSH
NPSH stands for Net Positive Suction Head, and reflects the energy left in a fluid when
the fluid is captured by the impeller and flung out to the casing. There are two
expressions for NPSH: NPSHAvailable and NPSHRequired
NPSHAvailable is a function of the system in which the pump operates.
NPSHavail = hs - hvpa + hst - hfs
NPSHRequired is a function of the pump design.
Vapor Pressure
Vapor pressure is the pressure required to keep a liquid in the
liquid state.

Cavitation occurs when a fluid's operational pressure drops below it's vapor pressure
causing gas pockets and bubbles to form and collapse.
The collapse or "implosion" is so rapid that it may be heard as a rumbling noise, as if you
were pumping gravel.
Pump Performance – Cavitation
Impeller cavitation regions
Collapse of a vapor bubble

Pump Performance – Cavitation
The accompanying noise is
the easiest way to recognize
cavitation. Besides possible
impeller damage, excessive
cavitation results in reduced
capacity due to the vapor
present in the pump. Also,
the head may be reduced
and/or be unstable and the
power consumption may be
erratic. Vibration and
mechanical damage such as
bearing failure can also occur

Pumps Technology - Pump Performance – NPSHR
٧٥ @ Pumps Technology Mechanical Dept. June 21
the pump is supplied from a closed tank in which the
level is held constant and the NPSHA is adjusted by
varying the air or gas pressure over the liquid, by
varying the temperature of the liquid, or by varying
both.
the pump is run at constant rate of flow and speed
with the suction condition varied to produce
cavitation. Plots of head shall be made for various
NPSH values.
As NPSHA is reduced, a point is reached where the
curves break away from a straight-line trend, indicating
a condition under which the performance of the pump
may be impaired.
The 3% drop in head is the standard to determine
NPSHR.

Pumps Technology - Pump Performance – Affinity Law
To reduce cost, pump casings usually are designed to accommodate several different impellers.
Also, a variety of operating requirements can be met by changing the outside diameter of a given radial
impeller or changing pump speed.
3
2
1
2
1
2
2
1
2
1
2
1
2
1
)
N
N
(
=
BHP
BHP
.
C
)
N
N
(
=
H
H
.
B
N
N
=
Q
Q
.
A
3
2
1
2
1
2
2
1
2
1
2
1
2
1
)
D
D
(
=
BHP
BHP
.
C
)
D
D
(
=
H
H
.
B
D
D
=
Q
Q
.
A
With speed N held constant:
With impeller diameter D held constant:

Pumps Technology - Pump Performance – Affinity Law
hp
BHP
BHP
C
ft
H
H
B
gpm
Q
Q
A
30
)
2000
1750
(
20
.
209
)
2000
1750
(
160
.
343
2000
1750
300
.
3
2
1
2
2
2
1
2
2






Approximate characteristics of centrifugal pump

The effect of liquid characteristics on performance
The effect of increased viscosity on centrifugal pump performance can
be significant. Higher viscosity increases the friction losses, hence the
power. In addition, the head capacity curve drops off as viscosity is
increased. Based on higher power, and less head, the overall effect is a
significant drop in efficiency. The Hydraulics Institute has published
curves for estimating pump performance with liquids more viscous
than water.

There are application methods for using the viscosity correction
factors, they are: Initial pump selection
The procedure to use in pump selection is as follows:
1. Locate pump flow - G.P.M.
2. Proceed vertically to pump head - Ft.
3. Move horizontally to specified viscosity - SSU or CTS.
4. Draw a vertical line to locate Efficiency (Ce), Flow (Ca) and Head (Ch)
correction factors.
5. Using the correction factors obtained for flows from 60% to 120%
of flow, generate a head and efficiency curve vs flow for the specified
viscosity.
5. Multiply values on the pump curve (tested on water) by the
appropriate correction factors to obtain the actual values for the
specified viscosity.
As a rule of thumb, centrifugal pumps should not be used for liquids
whose viscosity is greater than 500 SSU. Figure 3.14 presents the effects
of viscosity on centrifugal pump head and horsepower curves.

Figure shows the relationship between specific gravity and head
(energy) produced by the pump to overcome the head (energy)
required by the system, and the horsepower required to deliver the
specified flow rate and head (energy). Also, once the performance of
a pump is known, the discharge pressure and horsepower will be
influenced by changes in specific gravity of the liquid being pumped.

head (energy) required is a result of the difference in static
pressure and elevation head, and friction loss which is plotted
against flow rate. Different process systems have different head
(energy) required curve shapes A reflux loop for example, is
comprised of friction loss only and will have a relatively steep
system resistance curve, whereas a boiler feed pump with a
relative small system resistance, will have a system resistance
curve which is less steep. One can see that the combination of
a relatively flat system curve and pump characteristic curve
which has the shutoff head lower than the maximum head, can
lead to unstable operation. The most common system
characteristic is the intermediate case - examples being
bottoms pump and pipeline pump

Pumps Technology -
Pump Selection Criteria
Process Conditions
(Fluid composition, solids, °C, S.G, cP, Pv, NPSHA, Q, ∆H)
Operating Philosophy
(Continuous, Intermittent, Spare, Criticality, NPSHA, Location )
Hydraulic Coverage Charts
(Head vs Capacity)
Pump Types
(+ve Displacement, Centrifugal, Horizontal, Vertical, High Speed, Seal, Driver ...etc.)

Selecting the right pump
٨٤ @ Pump Design Guide Mechanical Dept. June 21
Operating a pump at or near its BEP not only
minimizes energy costs, also decreases
maintenance requirements.
Over-sized pump; requires flow control
(throttle valve or Bypass line) & efficiency is
reduced

Pumps Technology – Centrifugal Pump Selection
٨٥ @ Pumps Technology Mechanical Dept. June 21
Operating
Philosophy
Hydraulic
Coverage Chart
Capacity
Control
Parallel &
Series
Operation
End of Curve
Operation for
Centrifugal
pump
Process
Conditions

Introduction Pumps Technology
Process Conditions
٨٦ @ Pump Design Guide Mechanical Dept. June 21
 Fluid Composition
 Entrained solids, gases & corrosive materials
 °C, MDMT
 SG, cP, Pv
 Psuc
 Variation in operating conditions
 Flow
 ΔP, ΔH, Pdisch
 NPSH
 Acceleration head basic data

Introduction Pumps Technology
Operating Philosophy
٨٧ @ Pump Design Guide Mechanical Dept. June 21
 Is the intended service critical?
 Is downtime acceptable or should the pump be spared (33%, 50% or 100%)?
 Shall the spare pump be started manually or automatically?
 Is NPSHA sufficient for al modes of operation? (Parallel operation, series
operation).
 What type of foundation will be used?
 Is the site located onshore or offshore?
 Should space and weight be major considerations?
 Is the fluid toxic or flammable?
 Is a special shaft sealing method required?
 Will the service require special construction or pump design? Can operating
experience in this service be verified?
 What utilities are available and what is the preferred driver type?
 Are there abnormal or off-design operating conditions that need to be
addressed?

Shaft Sealing
Sealing area in a typical centrifugal pump
Centrifugal Pump, Liquid End
Leakage along pump shaft can be minimized by
Packing and Mechanical Seal.
Packing is used to minimize leakage along the
shaft by filling the stuffing box but it can’t
prevent leakage by 100%.
Mechanical Seal is used when NO leakage is
required specially in hazard cases mechanical
seal shall be used.

Shaft Sealing – Packing
Packing on shaft sleeve
Lantern ring

Shaft Sealing – Mechanical Seal Basic Design
Pusher
Incorporate secondary seals that move axially along
a shaft or sleeve to maintain contact at the seal
faces. This feature compensates for seal face wear
and wobble due to misalignment. The pusher seals
advantage is that it’s inexpensive and commercially
available in a wide range of sizes and configurations
Non-Pusher
The non-pusher or bellows seal does not have to
move along the shaft or sleeve to maintain seal
face contact. The main advantages are its ability to
handle high and low temperature applications, and
does not require a secondary seal (not prone to
secondary seal hang-up). A disadvantage of this
style seal is that its thin bellows cross sections
must be upgraded for use in corrosive
environments

Shaft Sealing
Plan 11, Single Seal

Shaft Sealing – Mechanical Seal Selection
The proper selection of a mechanical seal can be made only if the full operating conditions are
known:
1. Liquid
2. Pressure
3. Temperature
4. Characteristics of Liquid
5. Reliability and Emission Concerns

Centrifugal Pump – Bearing House
Bearing
House
Cooling Fan
Bearing
House Bulls
Eye
Constant
Level Oiler

Pumps Technology – Shaft Sealing – Packing

٩٩ @ Pumps Technology Mechanical Dept. June 21
A typical pump packing failure

١٠٠ @ Pumps Technology Mechanical Dept. June 21
Advantages Disadvantages
It is relatively inexpensive to purchase. It lower pump efficiency.
It is rarely the cause of catastrophic
pump failure.
Packing and sleeve require regular
replacement.
It can be adjusted or replaced without
pump disassembly.
The packing requires regular
adjustment.
Most maintenance personnel are
accustomed to its use.
Adjustment requires the touch of an
experienced personnel
It often requires considerable volume of
flush water, to ensure lubrication
between packing and sleeve. It is
acceptable if the pumps are handling
clean water.

Firewater Pumps – Pumps Basics - Mechanical Seal
١٠١ @ Firewater Pumps Mechanical Dept. June 21

AS THE PUMP SHAFT ROTATES
A LIQUID IS SUPPLIED TO THE PUMP
“SUCTION”
CENTRIFUGAL FORCE EXPELS THE LIQUID OUT FROM
THE IMPELLER

Firewater Pumps – Pumps Basics – Mechanical Seal
١٠٤ @ Firewater Pumps Mechanical Dept. June 21

Firewater Pumps – Pumps Basics – Mechanical Seal
١٠٥ @ Firewater Pumps Mechanical Dept. June 21

Pumps Technology – Shaft Sealing – Mechanical Seal Basic Design
١٠٦ @ Pumps Technology Mechanical Dept. June 21
Pusher
Incorporate secondary seals that move axially along a shaft
or sleeve to maintain contact at the seal faces. This feature
compensates for seal face wear and wobble due to
misalignment. The pusher seals advantage is that it’s
inexpensive and commercially available in a wide range of
sizes and configurations
Non-Pusher
The non-pusher or bellows seal does not have to move
along the shaft or sleeve to maintain seal face contact.
The main advantages are its ability to handle high and low
temperature applications, and does not require a
secondary seal (not prone to secondary seal hang-up). A
disadvantage of this style seal is that its thin bellows cross
sections must be upgraded for use in corrosive
environments

Pumps Technology – Shaft Sealing – Mechanical Seal Selection
١٠٧ @ Pumps Technology Mechanical Dept. June 21
The proper selection of a mechanical
seal can be made only if the full
operating conditions are known:
1. Liquid
2. Pressure
3. Temperature
4. Characteristics of Liquid
5. Reliability and Emission Concerns

General and Default Materials
Viton O-Rings 316SS Sleeve
316SS Gland Plate
“Premium Grade”
Carbon
Hastelloy C
Springs
Silicon Carbide
Setscrews
harder than
shaft

API Pumps design, application and selection

API Pumps design, application and selection

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