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PIPE FLOW FUNDAMENTALS COURSE
Gayungsari Timur 5 Blok MGH No. 923 – 24 Nopember 2013
by Wendi Junaedi
Video
What You Should Know
Course only for two days !!
You may not become a superman nor even goku in 2 days....
Video
Introduction
What is piping system ?
A Piping system consist of tanks, pumps, valves, and components connected together by pipelines to deliver a fluid at a spesific flow rate and/or pressure in order to perform work or make a product. The piping system may also contain a variety of instrumentation and controls to regulate the processes that are occuring within the boundaries of the piping system
What is piping system ?
Video
Introduction
Value of a Clear Picture of a Piping System
To see the piping system clearly, the system boundaries must be defined, including where the system begins and ends, what device are installed in the system, and how all the devices in the system are configured.
Introduction
Value of a Clear Picture of a Piping System
A clear picture of system operation Understanding normal operation (flow, pressure, level,
temperature, etc) Understanding why and how they changed at different operating
condition Understanding the function and expected of hydraulic performance Understanding the processes are occuring inside the piping, and
how the processes measured and controlled.
Introduction
Value of a Clear Picture of a Piping System
A clear picture for troubleshooting Not only provides a better understanding of normal condition Helps to identify abnormal condition
A clear picture for energy consumption and cost Transporting fluid requires energy Energy loss occurs due to friction, noise, vibration, inefficient in the
motor and pump, head loss in the components such as piping, valves, fitting, etc
Surely, energy costs money
Introduction
Understanding Total System
Understand type of piping system Single path open system Branching system Single path closed loop system Multi loop closed system
Understand hydraulic performance
Understand piping system curve vs pump curve
Understand total energy graph
Understand abnormal condition
Terminology, Unit, and Physical Laws
Fluid Properties Any characteristic of a system is called a property.
Familiar: pressure P, temperature T, volume V, and mass m.Less familiar: viscosity, thermal conductivity, modulus of
elasticity, thermal expansion coefficient, vapor pressure, surface tension.
Intensive properties are independent of the mass of the system. Examples: temperature, pressure, and density.
Extensive properties are those whose value depends on the size of the system. Examples: Total mass, total volume, and total momentum.
Extensive properties per unit mass are called specific properties. Examples include specific volume v = V/m and specific total energy e=E/m.
Terminology, Unit, and Physical Laws
Fluid PropertiesThe properties relevant to fluid flow are summarized below:Density:
This is the mass per unit volume of the fluid and is generally measured in kg/m3. Another commonly used term is specific gravity. This is in fact a relative density, comparing the density of a fluid at a given temperature to that of water at the same temperature.
Terminology, Unit, and Physical LawsFluid PropertiesViscosity: This describes the ease with which a fluid flows. A substance like treacle has a high viscosity, while water has a much lower value. Gases, such as air, have a still lower viscosity. The viscosity of a fluid can be described in two ways.
• Absolute (or dynamic) viscosity: This is a measure of a fluid's resistance to internal deformation. It is expressed in Pascal seconds (Pa s) or Newton seconds per square meter (Ns/m2). [1Pas = 1 Ns/m2]
• Kinematic viscosity: This is the ratio of the absolute viscosity to the density and is measured in metres squared per second (m2/s).
Terminology, Unit, and Physical LawsFluid PropertiesReynolds Number:
• Critical Reynolds number (Recr) for flow in a round pipe
Re < 2300 laminar2300 ≤ Re ≤ 4000 transitional Re > 4000 turbulent
• Note that these values are approximate.
• For a given application, Recr depends upon
– Pipe roughness– Vibrations– Upstream fluctuations, disturbances
(valves, elbows, etc. that may disturb the flow)
Terminology, Unit, and Physical LawsFluid PropertiesLaminar vs Turbulent
Video
Terminology, Unit, and Physical LawsPressure Loss in Pipe
Whenever fluid flows in a pipe there will be some loss of pressure due to several factors:
a) Friction: This is affected by the roughness of the inside surface of the pipe, the pipe diameter, and the physical properties of the fluid.
b) Changes in size and shape or direction of flow
c) Obstructions: For normal, cylindrical straight pipes the major cause of pressure loss will be friction. Pressure loss in a fitting or valve is greater than in a straight pipe. When fluid flows in a straight pipe the flow pattern will be the same through out the pipe. In a valve or fitting changes in the flow pattern due to factors (b) and (c) will cause extra pressure drops.
Terminology, Unit, and Physical LawsPressure Loss in Pipe
Pressure drops can be measured in a number of ways. The SI unit of pressure is the Pascal. However pressure is often measured in bar.
This is illustrated by the D’Arcy equation:
Terminology, Unit, and Physical LawsPressure Loss in Pipe
Before the pipe losses can be established, the friction factor must be calculated. The friction factor will be dependant on the pipe size, inner roughness of the pipe, flow velocity and fluid viscosity. Theflow condition, whether ‘Turbulent’ or not, will determine the method used to calculate the friction factor.
Moody Chart can be used to estimate friction factor. Roughness of pipe is required for friction factor estimation. The chart shows the relationship between Reynolds number and pipe friction. Calculationof friction factors is dependant on the type of flow that will be encountered. For Re numbers <2320 the fluid flow is laminar, when Re number is >= 2320 the fluid flow is turbulent.
Terminology, Unit, and Physical LawsPressure Loss in Pipe
The following table gives typical values of absolute roughness of pipes, k. The relative roughness k/d can be calculated from k and inside diameter of pipe.
Terminology, Unit, and Physical LawsPressure Loss in Pipe
Calculate pressure drop for a pipe of 4” diameter. carrying water flow of 50 m3/h through a distance of 100 meters. The pipe material is Cast Iron
Terminology, Unit, and Physical LawsPressure Loss in Components in Piping System
Minor head loss in pipe systems can be expressed as:
Valves
Valves isolate, switch and control fluid flow in a piping system. Valves can be operated manually with levers and gear operators or remotely with electric, pneumatic, electro-pneumatic, and electro-hydraulic powered actuators. Manually operated valves are typically used where operation is infrequent and/or a power source is not available. Powered actuators allow valves to be operated automatically by a control system and remotely with push button stations. Valve automation brings significant advantages to a plant in the areas of process quality, efficiency, safety, and productivity.
ValvesGate Valves
Best Suited Control: Quick OpeningRecommended Uses:
Fully open/closed, non-throttling Infrequent operationMinimal fluid trapping in line
Advantages: High capacityTight shut off, Low cost, Little resistance to flow
Disadvantages:Poor controlCavitate at low pressure dropsCannot be used for throttling
Applications: Oil, Gas, Air, Slurries, Heavy liquids, Steam, Non-condensing gases, and Corrosive liquids
Video
ValvesGlobe Valves
Best Suited Control: Linear and Equal percentageRecommended use-
Throtteling services/flow regulationFrequent operation
Advantages: Efficient throttlingAccurate flow control valvesAvailable in multiple ports
Disadvantages:High pressure dropMore expensive than other
Applications: Liquids, vapors, gases, corrosive substances, slurries
Video
ValvesBall ValvesBest suited control – Quick opening linear.Recommended uses –
Fully open/closed limited throttlingHigher temperature fluids
Advantages – Low costHigh capacityLow leakage & maintenanceTight sealing with low torque
Disadvantages – Poor throttling characteristicsProne to cavitation
Applications – Most Liquids, high temperatures, slurries
Video
ValvesButterfly Valves
Best Suited Control: Linear, Equal percentageRecommended Uses:
Fully open/closed or throttling servicesFrequent operationMinimal fluid trapping in line
Advantages:Low cost and maint.High capacityGood flow controlLow pressure drop
Disadvantages –High torque required to controlProne to cavitation at lower flows
Applications: Liquids, gases, slurries, liquids with suspended solids
Video
ValvesCavitation on Valves
Video
Pump & Pumping System
• 20% of world’s electrical energy demand• 25-50% of energy usage in some industries• Used for
• Domestic, commercial, industrial and agricultural services
• Municipal water and wastewater services
What are Pumping Systems
Pump & Pumping SystemWhat are Pumping Systems
Objective of pumping system
(US DOE, 2001)
• Transfer liquid from source to destination
• Circulate liquid around a system
Pump & Pumping SystemWhat are Pumping Systems
• Main pump components• Pumps• Prime movers: electric motors, diesel engines, air
system• Piping to carry fluid• Valves to control flow in system• Other fittings, control, instrumentation
• End-use equipment• Heat exchangers, tanks, hydraulic machines
Pump & Pumping System
33© UNEP 2006
• Head• Resistance of the system• Two types: static and friction
• Static head• Difference in height between
source and destination• Independent of flow
Pumping System Characteristics
destination
source
Statichead
Statichead
Flow
Pump & Pumping System
Pumping System Characteristics
• Static head consists of• Static suction head (hS): lifting liquid relative to
pump center line• Static discharge head (hD) vertical distance
between centerline and liquid surface in destination tank
Pump & Pumping System
Pumping System Characteristics
• Friction head• Resistance to flow in pipe and fittings• Depends on size, pipes, pipe fittings, flow
rate, nature of liquid• Proportional to square of flow rate• Closed loop system
only has friction head(no static head) Friction
head
Flow
Pump & Pumping System
Pumping System Characteristics
In most cases:Total head = Static head + friction head
System head
Flow
Static head
Friction head
Systemcurve
Systemhead
Flow
Static head
Frictionhead
Systemcurve
Pump & Pumping System
Pumping System Characteristics
Pump performance curve• Relationship between head and flow
• Flow increase• System resistance increases• Head increases• Flow decreases to zero
• Zero flow rate: risk of pump burnout
Head
Flow
Performance curve for centrifugal pump
Pump & Pumping System
Pumping System Characteristics
Pump operating point
• Duty point: rate of flow at certain head
• Pump operating point: intersection of pump curve and system curve
Flow
Head
Static head
Pump performance curve
System curve
Pump operating point
Pump & Pumping System
Pumping System Characteristics
Pump suction performance (NPSH)• Cavitation or vaporization: bubbles inside pump• If vapor bubbles collapse
• Erosion of vane surfaces• Increased noise and vibration• Choking of impeller passages
• Net Positive Suction Head• NPSH Available: how much pump suction exceeds
liquid vapor pressure• NPSH Required: pump suction needed to avoid
cavitation
Pump & Pumping System
Video
Pump & Pumping System
Pumping System Characteristics
Pump & Pumping System
Pumping System Characteristics
Pump & Pumping System
Pumping System Characteristics
Pump & Pumping System
Pumping System Characteristics
Type of Pumps
Centrifugal Pump
Are classified as nonpositive displacement pumps because they do not pump a definite amount of water with each
revolution. Rather, they impart velocity to the water and
convert it to pressure within the pump itself.
Centrifugal Pump
Centrifugal Pump
Video
Centrifugal Pump
Video
Centrifugal Pump
• Pump shaft power (Ps) is actual horsepower delivered to the pump shaft
• Pump output/Hydraulic/Water horsepower (Hp) is the liquid horsepower delivered by the pump
How to Calculate Pump Performance
Hydraulic power (Hp):Hp = Q (m3/s) x Total head, hd - hs (m) x ρ (kg/m3) x g (m/s2) / 1000
Pump shaft power (Ps):Ps = Hydraulic power Hp / pump efficiency ηPump
Pump Efficiency (ηPump): ηPump = Hydraulic Power / Pump Shaft Power
hd - discharge head hs – suction head, ρ - density of the fluid g – acceleration due to gravity
Centrifugal PumpEnergy Efficiency Opportunities
1. Selecting the right pump2. Controlling the flow rate by speed variation3. Pumps in parallel to meet varying demand4. Eliminating flow control valve5. Eliminating by-pass control6. Start/stop control of pump7. Impeller trimming
Centrifugal PumpEnergy Efficiency Opportunities
1. Selecting the Right Pump• Pump performance curve for centrifugal pump• Oversized pump
• Requires flow control (throttle valve or by-pass line)• Provides additional head• System curve shifts to left• Pump efficiency is reduced
• Solutions if pump already purchased• VSDs or two-speed drives• Lower RPM• Smaller or trimmed impeller
Centrifugal PumpEnergy Efficiency Opportunities
2. Controlling Flow: speed variation
Explaining the effect of speed• Affinity laws: relation speed N and
• Small speed reduction (e.g. ½) = large power reduction (e.g. 1/8)
Centrifugal PumpEnergy Efficiency Opportunities
3. Parallel Pumps for Varying Demand
• Multiple pumps: some turned off during low demand• Used when static head is >50% of total head• System curve
does not change• Flow rate lower
than sum ofindividual flow rates
Centrifugal PumpEnergy Efficiency Opportunities
4. Eliminating Flow Control Valve• Closing/opening discharge valve (“throttling”) to
reduce flow
• Head increases: does not reduce power use
• Vibration and corrosion: high maintenance costs and reduced pump lifetime
Centrifugal PumpEnergy Efficiency Opportunities
5. Eliminating By-pass Control
• Pump discharge divided into two flows• One pipeline delivers fluid to
destination• Second pipeline returns fluid
to the source• Energy wastage because part of
fluid pumped around for no reason
Centrifugal PumpEnergy Efficiency Opportunities
6. Start / Stop Control of Pump• Stop the pump when not needed• Example:
• Filling of storage tank• Controllers in tank to start/stop
• Suitable if not done too frequently• Method to lower the maximum demand (pumping at
non-peak hours)
Centrifugal PumpEnergy Efficiency Opportunities
7. Impeller Trimming
• Changing diameter: change in velocity• Considerations
• Cannot be used with varying flows• No trimming >25% of impeller size• Impeller trimming same on all sides• Changing impeller is better option
but more expensive and not always possible
Centrifugal PumpEnergy Efficiency Opportunities
Comparing Energy Efficiency Options
Parameter Change control valve
Trim impeller VFD
Impeller diameter
430 mm 375 mm 430 mm
Pump head 71.7 m 42 m 34.5 mPump efficiency 75.1% 72.1% 77%
Rate of flow 80 m3/hr 80 m3/hr 80 m3/hrPower
consumed23.1 kW 14 kW 11.6 kW
Centrifugal Pump
Video
Pipeline
Generally need to deliver oil or gas at a specified flow rate and pressure Hydraulic design required for preliminary selection of pipeline diameterFluid must be kept above a minimum velocity
• Minimise surging • Prevent build up of solids
Fluid flow must be below a maximum velocity• Prevent erosion • Optimise pumping requirements
Hydraulic Design
PipelineHydraulic Design
Hydrocarbons for transport may beLiquid (incompressible: straightforward to analyse) Gas (compressible & properties vary along pipe:
more challenging to analyse) Multi-phase (e.g. gas & condensate)
(highly complex)
Pipeline
For liquid lines:Max velocity 4 m/secMin velocity 1 m/sec
For gas lines: Max velocity 18-25 m/secMin velocity 4-5 m/sec
Trade off between - CAPEX (Large pipe diameter) and
- OPEX (Lower pumping costs)
Fluid Velocities
Pipeline
Pressure drop in liquid pipelines is principally due to
• Change in elevation (described by change in hydraulic head, or Pressure = gh )
• Friction loss
Pressure Drop
The remainder of the section on hydraulic design will be concerned with liquid pipelines
Pipeline
There are two equations that may be used for calculating the friction loss
Darcy-Weisbach
Fanning
Friction Loss Calculation
2
2L DARCYL Vh fD g
æ öæ ö= ç ÷ç ÷è ø è ø2
2L FANNINGL Vh fD g
æ öæ ö= ç ÷ç ÷è ø è ø
Oil pipelines
Gas pipelines
So, fDARCY = 4fFANNING
Pipeline
Friction Loss Calculation
For Laminar Flow
For Turbulent Flow use the Moody Chart Depends on pipe relative roughness
64ReDARCYf = For Re < 2300
For Re > 4000
Best PracticeCompressed Air System
Best PracticeCompressed Air Leakage
Leaks can be a significant source of wasted energy in an industrial compressed air system and may be costing you much more than you think. Audits typically find that leaks can be responsible for between 20-50% of a compressor’s output making them the largest single waste of energy. In addition to being a source of wasted energy, leaks can also contribute to other operating losses:
• Leaks cause a drop in system pressure. This can decrease the efficiency of air tools and adversely affect production
• Leaks can force the equipment to cycle more frequently, shortening the life of almost all system equipment (including the compressor package itself)
• Leaks can increase running time that can lead to additional maintenance requirements and increased unscheduled downtime
• Leaks can lead to adding unnecessary compressor capacity
Best PracticeCompressed Air Leakage
Best PracticeSteam Distribution
There are numerous graphs, tables and slide rules available for relating steam pipe sizes to flow rates and pressure drops.
To begin the process of determining required pipe size, it is usual to assume a velocity of flow. For saturated steam from a boiler, 20 - 30 m/s is accepted general practice for short pipe runs. For major lengths of distribution pipe work, pressure drop becomes the major consideration and velocities may be slightly less. With dry steam, velocities of 40 metres/sec can be contemplated -but remember that many steam meters suffer wear and tear under such conditions. There is also a risk of noise from pipes.
Pipe Selection
Best PracticeSteam Distribution
Best PracticeSteam Distribution
Recommended Thickness of Insulation (inches) for Mineral Wool
Best PracticeWater Distribution
As a rule of thumb, the following velocities are used in design of piping and pumping systems for water transport:
Best PracticeWater Distribution
If you want to pump 14.5 m3/h of water for a cooling application where pipe length is 100 metres, the following table shows why you should be choosing a 3” pipe instead of a 2” pipe.
If a 2” pipe were used, the power consumption would have been more than double compared to the 3” pipe. It should be noted that for smaller pipelines, lower design velocities are recommended. For a 12” pipe, the velocity can be 2.6 m/s without any or notable energy penalty, but for a 2” to 6” line this can be very lossy.
Best PracticeWater Distribution
Recommended water flow velocity on suction side of pump
Capacity problems, cavitation and high power consumption in a pump, is often the result of the conditions on the suction side. In general - a rule of thumb - is to keep the suction fluid flow speed below the following values:
References
1. Piping System Fundamental, The Complete Guide to Gaining a Clear Picture of Your Piping System, 2012 Engineered Software, inc
2. Best Practice Manual, Fluid Piping System, 2006, Devki Energy Consultancy Pvt. Ltd.
3. Pump Handbook, 2004 Grundfos Industry4. Valve Sizing & Selection, Ranjeet Kumar5. Pumps & Pumping System, 2006, www.energyefficiencyasia.org6. Pumps for Process Industry, Ranjeet Kumar7. Critical Pump Selection, Webinar8. Repair Engineering
Simulation & Modelling