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FP2: Component selection for hydraulic systems

Details of our CPD course, covering hydraulic component selection including more advanced topics such as non linearities, dynamics and physical principles.


This course is run in conjunction with the IMechE.

Our course covers the selection and sizing of actuators, valves, pumps as well as associated equipment like oil coolers, accumulators, and filters. It introduces you to the theoretical background of orifices, pressure losses, hydraulic stiffness, and component efficiency.

You'll learn through worked examples, design exercises, computer simulations classes and laboratory sessions. These will help you understand how to select commercially available hydraulic units to use in practical open and closed-loop hydraulic circuits, taking the constraints imposed by application-specific design requirements into account.

Who should apply

Our course is for engineering professionals and graduates interested or working in designing, developing, installing, maintaining or simulating fluid power systems.

To take this course, you must have either:

  • completed our FP1: Introduction to hydraulic circuits and components
  • or have some work experience and knowledge of hydraulic systems equivalent to CETOP level 3

You will also need fairly good mathematical skills.

Prices and dates

All our course prices and dates are listed on our Centre for Power Transmission & control cpd courses for industry page.

Course objectives

When you complete the course, you should:

  • have a thorough understanding of the fundamental hydraulic principles
  • appreciate factors that influence the specification and performance of hydraulic components and circuits
  • understand technical specifications of components and use this information to select and size actuators, valves, pumps, motors, filters, coolers, and accumulators for given applications
  • know the principles of system design taking into account duty cycles, system efficiency, and reliability issues
  • have knowledge of pipework and component installation, and follow good design practices for pipework and reservoirs
  • be aware of computer simulation methods for predicting the functionality and performance of hydraulic systems

Course contents

Fundamental principles

  • causes, effects, and quantitative description of pressure generation, pressure losses, heat generation, fluid leakage, cavitation, noise, and vibration
  • effects of fluid compressibility on component and system performance
  • relationship between Reynolds number, laminar/turbulent flow, and flow resistance
  • thermodynamic properties of fluids and gases, and principles of heat transfer
  • duty cycles for hydraulic systems
  • nonlinearities and their influence on system design and analysis

Orifice characteristics

  • orifice equation: relationships between flow and pressure difference, orifice area, fluid density, discharge/flow coefficient
  • variation of flow coefficients with Reynolds number
  • flow control characteristics in meter-in and meter-out systems, force/velocity relationship during extension and retraction

Velocity control using modulating valves

  • relationship between valve opening, available force, and velocity for equal and unequal area actuators
  • effects of pump capacity, relief valve settings, and actuator geometry
  • graphical methods for determining and understanding system performance

Central bypass valves and load sensing circuits

  • central by-pass valve construction and principle of operation
  • tandem, parallel, and series circuits
  • characteristics of systems with single and multiple load sensing valves

Pressure losses

  • influence of fluid properties (density, dynamic and kinematic viscosity) and pipe parameters (length, diameter, roughness)
  • laminar and turbulent flow conditions
  • calculation of losses in straight pipes, bends, fittings, and valves - Poiseuille's and Darcy's equations

Actuator stiffness

  • effects on fluid compressibility, expansion/contraction of pipes/hoses, and mechanical compliance of mountings on static position accuracy and dynamical response
  • stiffness for interconnected volumes; combination of mechanical and hydraulic stiffness
  • nonlinear relationship between bulk modulus and pressure, and influence of entrained air
  • stiffness of rotational systems

Pump and motor characteristics

  • linear and nonlinear pump and motor models, steady-state flow and torque characteristics
  • influence of leakage and friction losses, and effect of fluid compressibility
  • optimisation of efficiency

Hydrostatic transmission design

  • review of performance characteristics, volumetric/mechanical efficiency, and principle of power transfer
  • transmission design procedure - load, flow, and power requirements, motor/pump selection, motor/pump sizing, selection of additional transmission components
  • analysis of operating characteristics

Oil cooler sizing

  • principle of return flow, leakage flow, and purge system cooling
  • basic theory or thermodynamics and heat exchange: motor/pump flow/power balance, heat generation due to friction and leakage
  • practical design and cooler selection example for a hydrostatic transmission

Accumulator sizing

  • basic pressure/volume relationship for pneumatic accumulators - isothermal and adiabatic gas expansion/compression
  • refinements: compressibility factor and variation of adiabatic index with pressure and temperature
  • design procedure for given duty cycles

System component selection

  • overview of design process: specification, design, check, selection
  • selection of operating parameters - system pressure, flow requirements, thermal effects
  • component selection: actuators, valves, pumps, pipes, and auxiliary equipment

System filtration

  • filter construction (housing, element, media), filtration mechanisms, and filter test methods
  • filter location: pressure/return/suction line, bypass, off-line
  • filter selection: contaminant sensitivity and performance degradation, BFPA guidelines

Pipework, connectors and reservoirs

  • pipe and hose materials and construction, types of couplings and fittings
  • pipework layout: vibration, external/internal stresses, maintenance considerations
  • reservoir design: size, location, instrumentation, fillers, breathers, baffles, connections


  • wave generator tutorial (system component selection)
  • computer simulation exercise
  • forklift truck design exercise (linear actuator circuits and components)
  • marine engine loading system design exercise (hydrostatic transmission circuits and components)

Laboratory sessions

  • central bypass valve
  • pressure losses
  • accumulator sizing
  • advanced pump characteristics


The University of Bath is regulated by The Office for Students (OfS). We continually improve our course by integrating feedback from academic staff and students.

Learning, assessment and final award

Our teaching is carried out by people experienced in the field, mostly academic staff and PhD candidates as well as select guest speakers. There is no formal assessment and to successfully complete the course and receive the certificate of competence, you must attend the course in whole and participate in the exercises.

Continue your professional development with us

Find out more about what other CPD courses we offer.


If you have any questions, please contact us.

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