Looking for Spirax Sarco products and services?

Learn about steam

Home
Learn about steam

These tutorials explain the principles of steam engineering and heat transfer. They also provide a comprehensive engineering best practice guide covering all aspects of steam and condensate systems; from the boiler house and steam distribution system up to the point of use; through the condensate recovery system and returning to the boiler. Virtually all major applications and products are discussed.

Steam Insights

Our blog on the latest topics and thought leadership on all things steam

Read it here

Introduction

Why is steam so important to many industries today, its powerful capabilities, and how this sustainable, natural energy source is generated today.

  • Steam - the energy fluid

    Here we look at the many benefits that come from using steam as an energy source. Efficient, economic, flexible, and manageable, steam is widely used by many different industries.

  • Steam and the organisation

    Depending upon your role in your organisation, how steam is relevant to you will vary. From CEOs and managers to technicians and engineers, here we answer common questions about steam systems.

  • The steam and condensate loop

    The steam and condensate loop explained How steam is generated, and why factors like feedwater, level control, and blowdown matter. Discover how steam gets to where it is needed, and why steam quality is important.

Steam engineering principles & heat transfer

The science behind modern steam engineering introduced over 16 topics. These form a solid foundation for understanding the principles and practices relating to steam.

  • Engineering Units

    A detailed look at the globally-agreed units used in steam system engineering. Many you will be familiar with, thanks to their widespread use, whilst we also examine those with specific relevance to steam.

  • What is Steam?

    Here we delve into the physics that lies behind steam. Understand the triple point, saturated steam tables, steam dryness, and what is flash steam.

  • Superheated Steam

    Explore why superheated steam is used, the two theories used to measure its efficiency, the superheated steam table, and its pros and cons.

  • Steam Quality

    Learn about the properties that ensure steam works effectively, why noncondensable gasses matter, and what is a water hammer (and why they should be avoided).

  • Heat Transfer

    A detailed look at how heat is transferred, the thermal conductivity of different materials, barriers to heat transfer, and the various equations needed to measure the efficiency of heat transfer.

  • Methods of Estimating Steam Consumption

    Crucial to an efficient system, we look at the options for estimating your steam needs, both in flow and non-flow applications.

  • Measurement of Steam Consumption

    The three main ways of calculating your steam consumption are considered; a flowmeter, condensate pump, and condensate collection.

  • Thermal Rating

    Why your equipment's thermal rating cannot necessarily be taken as read, and the factors you will need to consider when interpreting it.

  • Energy Consumption of Tanks and Vats

    Widely used to contain liquids, tanks and vats are either open or closed. Here we look at how you can calculate the amount of energy needed for various situations.

  • Heating with Coils and Jackets

    A comprehensive look at submerged steam coils and steam jackets, the two most common ways of indirectly heating liquids in a vessel. The calculations needed, design, and controls are all covered.

  • Heating Vats and Tanks by Steam Injections

    The most common method of heating boiler feed tanks, heat is transferred by direct contact between steam and the liquid. The amount of steam needed, and the factors that might affect the heat transfer rate are dealt with here.

  • Steam Consumption of Pipes and Air Heaters

    Here we investigate how the pipes that carry steam affect the system's efficiency. The difference between warm-up and running loads are considered, and the calculations needed to measure heat loss. We also look at air heating equipment and how to assess these too.

  • Steam Consumption of Heat Exchangers

    This section focuses on shell and tube heat exchangers and plate heat exchangers. How they are used, their design and steam consumption calculations for them are all discussed. Finally, we look at other shell and tube steam heaters.

  • Steam Consumption of Plant Items

    Steam has many other uses. In this module we look at heater batteries, heating calorifiers, hot water storage calorifiers, drying cylinders, presses, and tracer lines. For each, we look at how steam consumption may be estimated.

  • Entropy - a basic understanding

    A practical approach to understanding what entropy is, how it can be measured, and why entropy is so important to steam engineering.

  • Entropy - its practical use

    Find out how Temperature-Entropy and Enthalpy-Entropy charts can help you, how kinetic energy works in steam, and why understanding control valves is so important.

The boiler house

Key to the generation of steam is, of course, the boiler house. This section looks in detail at boilers themselves, issues like feedwater conditioning and water levels, and how the boiler house can best be run efficiently.

  • Introduction

    Factors to consider when choosing boilers, from local regulations, fuel options, and the various pros and cons associated with them.

  • Shell Boilers

    A survey of various types of shell boilers, both wet and dry back. The development of the Lancashire boiler, the arrival of the packaged boiler, through to the reverse flame, or thimble boiler. We also look at the pressure and output limitations of shell boilers.

  • Water Tube Boilers

    How water-tube boilers work, variations using the same principles (drum boilers and the Stirling boiler), and their advantages and disadvantages. We also look at combined heat and power plants (CHP), and combined cycle plants.

  • Miscellaneous Boiler Types Economisers and Superheaters

    Used when steam isn't required all the time, and why economisers and superheaters are used.

  • Boiler Ratings

    The three commonly used methods for measuring boiler outputs, and the equations you will need to calculate them.

  • Boiler Efficiency and Combustion

    How the efficiency of boilers is worked out, and a survey of the different options for burners, their controls, and impact on overall effectiveness.

  • Boiler Fittings and Mountings

    To keep your boiler operating safely and efficiently a range of other valves, controls, and accessories are needed. Here we explain the importance of each.

  • Steam Headers and Off Takes

    Various alternatives to boiler layouts, their smooth operation, the importance of warm-up, and making sure steam is distributed properly.

  • Water Treatment Storage and Blowdown for Steam Boilers

    An examination of the many aspects of water quality and how they might affect steam boilers.

  • Water for the Boiler

    Options for treating water before its use in steam boilers, why carryover should be avoided, and the importance of water quality to different types of boilers are dealt with.

  • The Feedtank and Feedwater Conditioning

    Considerations and calculations needed to optimise your boiler feedtanks, pumps, and piping. We also examine deaerators and other important elements to think about when designing an efficient system.

  • Controlling TDS in the Boiler Water

    See how to measure TDS, maintain the correct level, and how automatic TDS control can lead to cost and efficiency savings.

  • Heat Recovery from Boiler Blowdown TDS Control Only

    Find out how much energy can be saved, and captured, when blowdown is used to control TDS. Both flash steam and heat exchangers are looked at.

  • Bottom Blowdown

    The term used to describe the process of removing suspended solids from a boiler. We look at how this is done, the options for blowdown, and regulations controlling its operation.

  • Water Levels in Steam Boilers

    Crucial to their safe and efficient running, boiler water levels must be monitored and adjusted if necessary. We look at why this is important, and the effect of different loads on levels.

  • Methods of Detecting Water Level in Steam Boilers

    Learn how level controls, low and high water alarms work, and the differences between conductivity and capacitance probes. Float controls and differential pressure cells are also reviewed.

  • Automatic Level Control Systems

    Here we take a close look at how boiler water levels may be automatically detected, and where problems might occur.

  • Water Level Alarms

    Too much, or too little water in your boiler is something that must be avoided. This section looks at your options for warning of either situation.

  • Installation of Level Controls

    How to accurately gauge the water level in boilers, plus the details that will determine which method will be best for your system.

  • Testing Requirements in the Boiler House

    A summary of how boiler testing is regularly carried out, with specific reference to the UK's regulations.

  • Pressurised Deaerators

    A comprehensive look at how these remove unwanted gases from steam system water, and the principles and practices of their use.

  • Steam Accumulators

    Everything you need to know about steam accumulators, from assessing requirements, sizing, design, and operation, to controls, fittings, and injectors. Comprehensive calculations are also included.

Flowmetering

If you want to know exactly how much steam your processes are using, and how much they cost, flowmetering will play a pivotal role. This section details everything you'll need to know, from theory to techniques and practical applications.

  • Fluids and Flow

    An examination of the fundamental principles behind measuring the flow of steam, including density, viscosity, velocity, the Reynolds number, and flow regimes.

  • Principles of Flowmetering

    An in-depth look at the science behind flowmetering, the equations used to maximise its effectiveness, and how ultrasound is used to measure flowrate.

  • Types of Steam Flowmeter

    Discover the seven types of flowmeter used to measure steam and condensate. We consider how each works, their advantages and disadvantages, and where they are often found.

  • Instrumentation

    Here we break down how flowmeters interpret data, why pressure variations must be considered, and understand how dryness fractions and superheat can impact accuracy.

  • Installation

    With over a third of flowmetering problems stemming from poor installation, it's important to get the design and installation right. This section will give you a checklist for selecting the right flowmeters, and a comprehensive set of recommendations for their installation.

Basic control theory

How processes are controlled is fundamental to a safe, stable, and accurate system. In this section, we closely examine the theory behind control, why you might choose one option over another, and how to go about installing and commissioning control systems.

  • An introduction to controls

    Here we investigate why automatic controls are more reliable than manual options, and look at how controls deal with processes that use steam, water, compressed air, and hot oils.

  • Basic Control Theory

    Put simply, the two basic control options are either on/off or continuous control. This module looks in detail at the implications of each, paying close attention to the three elements of continuous control: proportional, integral, and derivative.

  • Control loops and dynamics

    What is a control loop, what are the differences between control loop options (open, closed, single, multi, cascade), what happens in each control loop, and various process reactions are all answered in this topic.

  • Choice and Selection of Controls

    How to Choose Which Controls to Use? An overview of your options (self-activating, pneumatic, electric, electro-pneumatic), a look at valves and actuators, and choices of controllers. Guided by consideration of safety, stability, and accuracy.

  • Installation and commissioning of controls

    A detailed look at the elements involved in the installation and commissioning of controls, including how the Ziegler-Nicholls method can be used for setting controllers.

  • Computers in Controls

    Looking at the evolution of IT helping improve control, up to the introduction of fieldbus technology in streamlining operations.

Control hardware: Electric/pneumatic actuation

How control valves work, their correct sizing, and the role of actuators, positioners, controllers and sensors in steam and water systems.

  • Control Valves

    Get to know the different types of control valves used in steam and fluid systems. The differences between linear and rotary valves, with two or three-ports, is simply explained using animated diagrams.

  • Control Valve Capacity

    Valves work by altering either flowrate or differential pressure. Gain an understanding of the flow coefficient, and how it is used to compare valve performance.

  • Control Valve Sizing For Water Systems

    Here you will find out how to correctly size valves using either equations or charts. The difference between imperial and metric measurements is explained, how two- and three-port valves differ in how they operate, and why valve authority, cavitation, and flashing need to be considered.

  • Control Valve Sizing For Steam Systems

    Your complete guide to unravelling the complicated subject of steam control valve sizing. Find out how to use formulae and steam tables to make sure you have the right sized valve, the issues you may need to consider (velocity, noise, erosion, drying, and superheated steam), together with a checklist of the 20 major factors to assess your system.

  • Control Valve Characteristics

    Different types of valve plug have different flow characteristics. This section gives you a thorough understanding of the three main types (fast opening, linear, and equal percentage), and using detailed case studies, how the flowrates are calculated.

  • Control Valve Actuators and Positioners

    This section looks at how actuators enable valves to work, the differences between pneumatic and electric versions, how reverse acting and direct acting actuators work, and why positioners are sometimes also essential for safe and accurate control.

  • Controllers and Sensors

    What they are, when to use them, and the many variations available. We also look at advanced control systems using the HART protocol and fieldbus standards.

Control hardware: self-acting actuation

Why self-acting controls are needed, the various options available, and their practical application in controlling temperature and pressure in steam and water systems.

  • Self-acting Temperature Controls

    The differences between vapour tension systems and liquid-filled systems are explained, with animated illustrations showing how different options work. We also look at where and why self-actuating temperature controls are used.

  • Typical Self-acting Temperature Control Valves and Systems

    These systems are a vital safety feature. They operate by either adjustment at a sensor, an actuator, or by remote operation. We also examine high limit cut-out devices and the many environments where they are used.

  • Self-acting Pressure Controls and Applications

    Usually used to reduce the amount of steam pressure in a system, self-acting pressure controls tend to be either direct acting or pilot operated. This section illustrates both, looking at choices that determine where each would be used. We also look at pressure maintaining valves, and why these are sometimes needed.

Control applications

This section discusses in detail the ways in which temperature, pressure, flow, and level are controlled in steam systems. We also look at why this is done, and the industries that use these controls.

  • Pressure Control Applications

    In this comprehensive review of the methods used to control steam pressure, we look at the advantages and disadvantages of each, the situations where they are usually employed, and important points to note. We also touch upon alternative methods sometimes used.

  • Temperature Control Applications

    When it is the temperature that must be controlled, there are five main methods for doing so. Here we look at their advantages and disadvantages, and where they are usually used. We also survey some of the other options for controlling steam temperature.

  • Level Control Applications

    An overview of the different types of level control systems used, with particular focus on float and solid probe types, most commonly used in the steam and condensate loop. There is a focus on conductivity and capacitance level controls.

  • Control Installations

    How and where your control system is installed with have a marked effect on its accuracy and lifetime. Here we look at the factors to consider to ensure it works at its best for as long as possible.

Safety valves

This section answers the questions: what is a safety valve, what options are available, and how to choose the right one, and safely install it.

  • Safety Valves

    Safety valves are essential devices used to protect from steam overpressure. Here we look at how this might happen, the range of types available, how they work, and the regulatory frameworks for them.

  • Types of Safety Valve

    Discover in detail the many variations of safety valves, how they operate (including equations illustrating the force needed to do so), and diagrams of each type of valve.

  • Safety Valve Selection

    Including the criteria you will need to consider, how safety valves are properly installed, and where, and the difference between MAWP and MAAP.

  • Safety Valve Sizing

    A detailed look at how to size valves according to various standards, with diagrams and equations for each case. We also look at more complicated solutions like two-phase flow and superheat.

  • Safety Valve Installation

    For it to work correctly, it's vital you know all the factors to make the right decision. Everything you need to know is covered here.

  • Alternative Plant Protection Devices and Terminology

    They might be the most effective, but safety valves are not the only way you can deal with excess pressure. This section looks at the alternatives and gives a full glossary of terms related to this topic.

Steam distribution

It's crucial your steam reaches the point of use in the most cost-effective, energy-efficient way possible. Sizing of pipes, key drainage techniques, how your piping is supported and deals with expansion, venting, and heat transfer calculations are dealt with in this section.

  • Introduction to Steam Distribution

    Here we examine what is the steam and condensate loop, the working pressure of a system, and see why pressure-reducing valves are used.

  • Pipes and Pipe Sizing

    Covering the international standards, schedule numbers, piping materials, and detailed information on the equations, charts, and tables needed to pick the correct piping. Includes comprehensive appendices.

  • Steam Mains and Drainage

    We look at the overall layout, condensate drain points, using branch lines, steam separators and strainers, how to calculate your running load, and what to look out for to avoid waterhammer.

  • Pipe Expansion and Support

    Because they are carrying hot fluids or steam, allowance must be made for expansion. Here we cover the various methods of making sure your pipes are properly installed.

  • Air Venting Heat Losses and a Summary of Various Pipe Related Standards

    How to effectively remove air and noncondensable gases from a steam system, and how to calculate, and reduce, heat losses from pipework. Includes relevant international standards covering the subject.

Steam traps and steam trapping

These 15 sections cover every aspect of steam traps: why are steam traps needed, how do steam traps work, what are the different types and where are they best used? We will also look at how to select the right steam trap, air venting, and why it is so important to maintain your steam traps.

  • Introduction - Why Steam Traps?

    The main job of a steam trap is to remove condensate, air, and any noncondensable gases from a steam system whilst minimising the escape of live steam. Here we look at why this is necessary, how they do this, their basic operation, and the standards applied to steam traps.

  • Thermostatic Steam Traps

    These work by responding to the surrounding steam temperature. There are three main types: liquid expansion traps, bimetallic traps, and balanced pressure traps. We look at each, with animated diagrams showing how they work, and the pros and cons of each.

  • Mechanical Steam Traps

    These use the different densities between steam and water (condensate) to operate. There are two main types: the ball float trap, and the inverted bucket trap. Able to remove large volumes of condensate, mechanical steam traps are used in a wide range of process applications. Discover how each works, and their advantages and disadvantages.

  • Thermodynamic Steam Traps

    It is a very robust form of trap, with only one moving part, that operates using the dynamic effect of flash steam as it passes through the trap. We examine the traditional thermodynamic steam trap, the impulse type, the labyrinth type, and finally fixed orifice traps. How they're made, their uses and pros and cons are discussed.

  • Considerations for Selecting Steam Traps

    Other things to take into account when choosing steam traps: waterhammer, dirt, strainers, steam locking, group trapping, diffusers, and special needs, like vacuum drainage and trapping for temperature-controlled processes.

  • Selecting Steam Traps - Canteen Equipment Oil Transfer Storage Hospital Equipment

    Giving tables and advice on picking the right options for these uses, from boiling pans to bulk storage tanks, to autoclaves and sterilisers.

  • Selecting Steam Traps - Industrial Dryers

    Advice on choosing traps for hot air dryers, drying coils, multi-bank pipe dryers, drying cylinders, and multi-cylinder dryers.

  • Selecting Steam Traps - Laundries and Presses

    Looking at the right steam traps for garment presses, ironers and calenders, tumble dryers, dry cleaning machines, and various types of presses, including tyre presses.

  • Selecting Steam Traps - Process Equipment

    Advice on the ideal steam traps for fixed and tilting boiling pans, retorts, industrial autoclaves, industrial digesters, hot tables, brewing coppers, evaporators, and vulcanisers.

  • Selecting Steam Traps - Space Heating Equipment

    Best and acceptable alternative choices of steam traps for calorifiers, heater batteries, radiant panels and strips, radiators and convection cabinets, unit heaters and air batteries, and overhead pipe coils.

  • Selecting Steam Traps - Steam Mains Tanks and Vats Pressure Reducing Valves

    Covering aspects of the steam mains operations, including horizontal runs, drain pocket dimensions, separators, steam header drainage, and terminal ends. We also look at process vats and small coil-heated tanks.

  • Air Venting Theory

    Because air is an insulator, it works against the efficient heat transfer of a steam system. This section looks at how to detect air in the system, and how to remove it effectively.

  • Air Venting Applications

    Examining many of the cases where air venting will be needed, including the steam mains, jacketed pans, and rotating cylinders. We also consider the use of steam trap bypasses, and how thermostatic steam traps can also be used as air vents.

  • Testing and Maintenance of Steam Traps

    Examining routine maintenance, replacement of internal parts, and potentially replacing steam traps. However, accurately identifying issues with steam traps requires expert knowledge, and we look at manual, remote, and automatic monitoring to determine if there actually is a problem.

  • Energy Losses in Steam Traps

    Often steam traps are blamed for energy losses simply to gain a new sale for an alternative. This section honestly looks at the three types of main steam trap and demonstrates just how little energy steam traps use. trap types.​

Pipeline ancillaries

Additional components are often left out of steam systems to reduce costs. This can be a false economy, since isolation valves, check valves, strainers, separators, gauges, sight glasses, and vacuum breakers are all important to an energy-efficient steam system.

  • Isolation Valves - Linear Movement

    Used to stop the flow of fluid into an area of the system, we look at the different types of gate valves, globe valves, piston valves, and diaphragm valves. We also look at options for valve stems, and how to seal them.

  • Isolation Valves - Rotary Movement

    Sometimes known as quarter-turn valves, we delve into ball valves and their various options, and butterfly valves. This section also gives details on selecting isolation valves, including their sizing, with comprehensive charts and the equations for getting to the right choice.

  • Check Valves

    Also known as non-return valves, a check valve will only allow flow in one direction. The main types used for steam are lift, swing, wafer, and disc check valves. Ball and diaphragm check valves are usually used in fluid applications. Formulae for calculating pressure drops are also given.

  • Strainers

    Usually classified as either Y-type or basket type, strainers prevent damage from debris in flowing liquids or gases, so reducing plant downtime and unplanned maintenance costs. Here we take a detailed look at the options, and how to select the right size, depending upon your processes.

  • Separators

    Important tools in reducing 'wet steam', separators come in various forms. We look at baffle, cyclonic, and coalescence separators, detailing which option to choose, and how to calculate the dryness fraction.

  • Gauges Sight Glasses Vacuum Breakers

    Though relatively small in size, these play a big part in the smooth running of energy-efficient steam systems. We examine what each does, and how they work.

Condensate removal

Vital to the efficiency and long life of a heat exchanger, this section looks in detail at how they operate, what ‘stall’ is, and the best ways of maximising your efficiency.

Condensate recovery

Getting condensate back to the boiler house is key to sustainable operations. This section looks at pipe sizing and layout for drain lines, discharge lines, and pumped lines. Lift, backpressure, and the reduction of costs by using flash steam are also covered.

  • Introduction to Condensate Recovery

    Why condensate recovery and return are useful, saving energy costs, reducing environmental discharges, and keeping water treatment costs down. Covers calculations for potential savings.

  • Layout of Condensate Return Lines

    A fully-illustrated, detailed look at the design and layout of condensate return pipework. This includes the effect of trap types used, how different pressures impact the system, and the discharge of condensate into flooded mains.

  • Sizing Condensate Return Lines

    How to size condensate lines to and from steam traps, with examples and formulae needed using the condensate pipe sizing chart.

  • Pumping Condensate from Vented Receivers

    This comprehensive introduction covers pumping terminology, the operation, application and various benefits of electric centrifugal and mechanical condensate pumps. There are sizing examples for both pumps and pump discharge lines.

  • Flash Steam

    What is flash steam, how much is available, how it can be recovered, controlling flash steam, and its applications.

  • Lifting Condensate and Contaminated Condensate

    Here we look at moving condensate to a higher level return line, and ways to cope with contaminated condensate.

Desuperheating

We examine what superheated steam is, and why it's sometimes necessary to desuperheat it. We also cover the types of desuperheater available, where they're used and how to install them.

  • Basic Desuperheater Types

    First we cover the issues to think about when selecting a desuperheater, such as turndown ratio. Then we survey the types of desuperheater available, including indirect contact, direct contact, water spray, and axial injection desuperheaters. Consideration of the advantages and disadvantages of each is offered.

  • Basic Desuperheating Theory

    The difference between superheated and desuperheated steam is detailed, where both types of steam are typically used, and calculations for desuperheating.

  • Other Types of Desuperheater

    A range of other desuperheaters are commonly used. Here we look at venturi type, steam atomising, variable orifice, combined pressure control valve and desuperheater, and compare the options alongside one another.

  • Typical Installations

    There are a range of factors that must be considered. This section looks at key issues, including the properties of the cooling water itself, the installation of the desuperheater, pressure control, and sensor positioning.