WHY THE ABILITY TO IDENTIFY AND DEVELOP SUSTAINABILITY OPPORTUNITIES SHOULD BE VIEWED AS A CORE COMPETENCY

Logging of a large induction motor. Measurement
is a vital aspect of the assessment process.

Realigning an industrial site onto a more sustainable trajectory is a long-term process. It should begin with a strategy or plan, and be supported with the development of scorecard comprising the various measures considered to be indicators of sustainability performance. If the strategy is the GPS determining your direction, the scorecard can be considered to be the dashboard for your efforts as you drive your site towards a more sustainable level of operation.

Your strategy will outline the broad philosophies and focus areas management believes will drive sustainability, while the scorecard will reflect the desired outcomes of the process. However, neither gets into the detail of the precise actions you are going to take to achieve the performance improvements you are after. This is where the rubber hits the road, and where a lot of organisations tend to fall short. Without this detail, there can be no meaningful implementation, and without implementation there can of course be no improvement. The way to get to this detail is through the assessment process. I believe that the ability to conduct assessments is something that industrial companies need to develop internally if they are to integrate sustainability into their operations successfully ,and will explain why in this post.

Assessment is the process through which the various sustainability opportunities on an industrial site are identified and developed into projects that can be implemented to improve performance. While I am often requested to carry out “one-off” assessments at sites I have never seen before, I often find myself thinking of a number of opportunities on these sites long after I have left. The thing is, industrial sites are complex systems, and it is only on deep reflection that all potential opportunities can be unearthed, particularly those that are system-related. So I much prefer longer-term engagements where I get to fully understand the system, since these can lead to richer and more profound sustainability opportunities than those one would find in a typical audit.

The point I am making here is that assessments should not be activities that are only carried out at the outset of a sustainability programme. They should be a routine part of the programme, carried out continuously, open to being updated and revised on an ongoing basis. In this way you can use assessments to feed into a live portfolio of sustainability projects, all at different phases of their life cycles, and all contributing towards the achievement of the targets you have set for your site as defined in your scorecard.

Typical steps in the assessment process would be:

 

Qualitative identification of an opportunity e.g. the furnace is not insulated and is losing a lot of heat energy

Identification of required data for development of the opportunity e.g. dimensions of the furnace, surface temperatures, atmospheric conditions such as typical temperatures and wind speeds, supporting information e.g. the furnaces typical annual operating hours, its temperature profile, seasonality of operation etc.

Carrying out of measurements and specification of assumptions e.g. use of an infra-red thermometer to measure surface temperature,  using an assumption of 0 m/s for wind speed in order to be conservative with respect to convective heat loss effects etc.

Quantification of the resource efficiency potential of solutions. In this example this will mean quantification of the heat losses with and without insulation (with the difference being the potential saving), and then translating those losses into a gas usage value, based on the calorific value of the gas used.

Technical evaluation of the solution e.g. what will the surface temperature of the insulated furnace be, what are the emission reductions associated with this solution etc.

Financial evaluation of the solution, which would mean translating the gas usage into a financial value, determining the costs of insulating the furnace and then assessing the financial impact, using approaches such as the calculation of payback, NPV or ROI.

Identification of any risks associated with the chosen solution e.g. the correct insulation material should be chosen to avoid potential fire risks, critical materials (e.g. asbestos) should be avoided etc.

Insulation is clearly not the only solution when it comes to improving the energy efficiency of a gas-fired furnace. For example, since it important to deal with root causes rather than symptoms, an important question to ask would be: are surface temperatures too high due to poor maintenance of the refractory lining of the furnace? There could be more leverage in approaches such as improved control of air-to-fuel ratio, ensuring that the furnace is not idle at full-flame conditions, limiting the temperature to the minimum required and minimising rework, among others.   Each of these solutions would require an evaluation of their potential, both individually and when considered in an integrated way. Lower operating temperatures would reduce the potential of a solution involving insulation, for example - so one would need to assess how individual approaches may interact with each other.

Carrying out the analyses outlined above requires skills and capabilities that are typically not in evidence on industrial sites, where the focus tends to be more on addressing deviations in process performance rather than ongoing structural change in order to raise performance levels. How then can such capabilities be developed? The answer is – through concerted investments, on the understanding that such investments will have a favourable financial return. Investments would need to be made in:

1.      Skills development – the diversity and quality of training solutions available is growing in areas such as energy efficiency, water conservation and industrial sustainability in general

2.     Measurement equipment – opportunities cannot be developed from assumptions alone, and it is important to build a comprehensive toolbox of specialist measurement equipment that can be used to carry out the required investigations. These measurement tools would require maintenance and calibration, and of course training for users

3.     Software tools – once data has been downloaded or captured it needs to be analysed, and the use of software can make this process faster and easier to do. There are a number of free tools available, as well as very powerful proprietary software for specialist applications. Be sure to use tools from a reputable source

4.     Relationships – it is important to stay close to experts and solutions providers, as well as others in your industry, in order to be aware of the latest trends

5.     People – sustainability is an important enough issue to require dedicated focus. While it needs to be integrated into existing job roles as far as possible, a champion is needed to focus and consolidate efforts and lead the change process. This would probably be someone already in a technical role and senior enough to be able to influence staff from various disciplines in support of the sustainability effort. Project management is a vital skill for anyone in this role

In essence, achieving superior performance in areas such as energy and water use efficiency and waste minimisation is not achievable on a sustainable basis unless assessment capabilities are developed inside your organisation. While you can buy in expertise (this is after all how I make my living) building capacity internally is the only real way to ensure the necessary integration between operational excellence and sustainability. Assessments need to be taking place all the time, with constant revision of the portfolio of potential projects, and must incorporate the learning that comes out of implementation.

 Copyright © 2013, Craig van Wyk, all rights reserved

ENERGY-EFFICIENT MOTORS – NOT NECESSARILY A NO-BRAINER

Induction motors are ubiquitous in industry and invariably

offer energy-efficiency opportunities. These opportunities are

however not necessarily in the form of viable motor

replacement options.

Induction motors are used extensively in industrial facilities, and consequently can be responsible for a significant proportion of energy consumption and demand. Older designs are inefficient, and there are now a range of motors available which require less input power (for the equivalent amount of shaft power) than these older designs. In many countries, the use of high-efficiency designs is becoming mandatory. This is not the case in South Africa, and in my experience the uptake of these motors remains quite low, despite sustained increases in electricity prices. This got me thinking about why this is the case, and in this post I will explore some potential reasons for the relatively poor penetration of these devices, and also what you need to consider when assessing motor replacement opportunities. I won’t get into issues of torque in this post, but will remind you of the fact that a motor’s torque characteristics are an important factor, and the torque requirements of the driven process must be well understood when assessing replacement options.

Motor efficiency refers to the ratio/percentage of input power to output or shaft power for a given motor. The efficiency values you will see on a motor’s nameplate are quoted for full-load conditions. Energy-efficient motors require less input power for a given amount of shaft power. However, it is wrong to speak of a motor having a specific efficiency level. As discussed in a number of previous posts, motor efficiency is a function of load, with load being the proportion of the motor’s capacity that is actually used. If a motor is poorly loaded, replacement with an energy-efficient alternative of the same capacity would yield lower levels of efficiency improvement than replacement with a standard-efficiency motor of the correct capacity. Hence for poorly-loaded motors, correcting the loading problem is a higher priority than motor replacement.

Running hours are important, since the more hours that a motor runs, the more energy can be saved (remember that energy = the product of power and time). The energy savings are the product of the input power differential between the existing motor and its replacement and the running hours: Energy savings = (kW_existing – kW_replacement) x running hours. Clearly, even where a large power differential exists, if running hours are low, energy savings will be low, and the costs of replacement become difficult to justify.

As outlined above, if you can find motors with long annual running hours and which are well-loaded, high-efficiency replacement options should be further investigated. However, motor efficiency is not the only driver of operating cost for induction motors. A further consideration is the difference in power factor between the existing motor and the replacement motor. Power factor is the ratio of real power (in kW) to apparent power (in kVA). The lower a motor’s power factor, the higher the flow of current to the motor for a given real power requirement, and the greater the line losses (also called I²R losses) incurred in operating the motor. For a site that does not have power factor correction systems installed, a motor with a lower power factor (which could be a replacement motor with higher efficiency than the existing motor) will result in increased demand charges as well as some energy losses (these are typically small) due to the increased current flow in the site’s internal distribution system. A reduction in both of these costs can be achieved through the use of local capacitors close to the motor. Sites that have power factor correction systems installed at the point of supply will experience reduced site demand levels, but will not reduce I²R losses in their distribution systems, since excess current will still flow between the capacitor banks and the motor. For such sites, motor efficiency gains are still generally a bigger economic driver than these efficiency losses, particularly when you consider that it is the difference in power factor that is of interest, not only the power factor of the replacement motor.

The above are however not the only important issues when considering motor replacement. Something to bear in mind is that high-efficiency motors tend to operate at slightly higher speeds than standard-efficiency models, due to reduced slip. For fixed speed applications, this can have significant consequences for energy consumption. For example, for centrifugal pumps and fans, flow is proportional to speed, but power varies with the cube of speed. Small increases in speed can result in significant power increases for motors used in these applications. The situation could therefore be one in which the high-efficiency motor uses less energy than a standard-efficiency equivalent would have used for the same output power, but with this benefit negated by operation at a higher output power than was the case before the replacement. Such a situation is only acceptable where the increased power output is actually required, or can be managed - for example through reductions in operating time. How big a problem could this be? Consider a motor replacement option with a speed that is 1.3% faster than a standard-efficiency motor. Input power would increase such that P_final = P_initial x (speed_final / speed_initial)³ = P_initial x (1.013 x speed_initial / speed_initial)³ = P_initial x 1.013³ = 1.04 x P_initial, which is a 4% power increase! This could easily match or exceed the efficiency differential.

 

One final thought is that motors are part of systems, and system efficiency is the product of the efficiency levels of the individual components of the system. No matter how efficient a motor is, if it is driving an inefficient machine or process, replacement of the motor will have a limited impact on the efficiency of the system. For example, an inefficient motor driving a machine producing products in which only 50% of production meets specification with the balance ending up as scrap cannot be considered a high-leverage energy efficiency opportunity.  Not until the scrap problem has been resolved. This highlights the relationship between operational excellence and sustainability on industrial sites, something I will explore more in future posts.

What I've tried to show is that motor replacement on the basis of efficiency improvement is not a straightforward matter, and that hasty replacement without a considered analysis can actually lead to higher operating costs. Motor replacement is certainly not a "no-brainer" and calls into question moves to regulate motor efficiency standards.

Copyright © 2013, Craig van Wyk, all rights reserved

ALIGNING JOB ROLES TO SUSTAINABILITY OBJECTIVES

Sustainability requires involvement at all levels,
not just by a project team. This involvement has to be well defined if it is to become meaningful.

Implementing sustainability is necessarily about change. It starts with a change in mind-set in the very upper reaches of management, where it is realised that from a strategic perspective, sustainability makes business sense, is essential for organisational survival and in fact is a strong source of competitive advantage. This realisation is then translated into concrete action, in order for the organisation’s sustainability goals to be realised. This includes a review of current operations, where often there are many positive organisational attributes that are already sustainable, but may not be recognised as such. Then of course there are those factors which are not sustainable and need to changed or phased out. Finally, there is the very structure of the organisation, which needs to be modified such that it has the capacity to adapt on an ongoing basis, on the understanding that becoming sustainable is not a project, but a process.

This process will involve changes in technology, changes in relationships with suppliers, customers, regulators and other stakeholders, revision of work practices, the development of new products and markets and fundamentally new ways of doing business. It cannot be about a few piecemeal projects that while positive in their own right, are not part of a broader transformation.  It will also be difficult to make sustainability “stick” if it is one of many other “initiatives” in the organisation. Instead, it should be integrated into everything the organisation does, sending a consistent message to all employees and stakeholders that this is the path that has now been chosen.

 

Warm and fuzzy messages do not in themselves bring about change. Yes, it is of course important for all employees within an organisation to understand why change is necessary, and the broader impacts of that change. It is however vital to understand exactly how different levels of the organisation will have an impact on sustainability performance, and then to build sustainable practices into job roles at all levels. Without this level of detail, it is difficult to make sustainability something “real”.

It is a good idea to engage employees on this issue, making them a part of the process of uncovering sustainable work practices. It is however the work of management to analyse each level of the organisation in detail, to assess precisely how every job impacts on sustainability, and then to build the infrastructure around each job to support sustainable work practices. This gives employees a point of departure, a foundation upon which to build new job roles that they can make their own. Of course, I’m referring hear to organisations that are participative in nature, which I think you have to be if you want to become more sustainable.

 

To give you an idea about the types of tasks and behaviours I’m talking about, below is an overview of how an issue like energy efficiency touches on the job roles of different groups of employees on an industrial site.

 SUSTAINABILITY AFFECTS EVERYONE – ENERGY EFFICIENCY EXAMPLE

STAFF	ROLE IN ENERGY EFFICIENCY	MECHANISMS FOR EFFECTING CHANGE
Executive management	Highlight energy efficiency as a strategic issue	Communication channels such as newsletters and site forums
	Set short, medium and long-term site-wide targets	Build into performance goals for managers and departments
	Provide resources for  attainment of targets	Budgeting processes
	Foster integration of sustainability	Include in all areas of operations at the strategic level
Middle Management and technical staff	Identify energy efficiency opportunities	Technical audits and facilitation of shop floor focus groups
	Improve work practices to enhance energy efficiency	Review of work instructions and procedures Training of staff on the energy efficiency issues within their control
	Optimise efficiency of existing operations	Plant settings that minimise energy use e.g. lower operating temperatures and pressures Preventive maintenance programme development and implementation to eliminate failures
	Modify equipment and source new technologies	Investigations into the efficiency of current equipment Research into technological alternatives Identification of alternative suppliers Justification of modifications and capital investments
Shop Floor staff	Operate equipment more sustainably	Addressing failures that may not affect throughput, but waste energy e.g. compressed air leaks Switching off of lighting and equipment when not needed Following agreed best operating practice rigorously
	Minimise defects and rework	Prompt action for quality problems that may lead to rework and wasted energy
		·         Etc…

The table is by no means comprehensive, and there are many other staff functions that are not shown here who all have a role to play. What the above is meant to show is that if you limit the scope of sustainability within an organisation to a few people and treat it as a project, opportunities are lost. There is a role for all employees to play, and it is up to managers to identify what that role is, and then to engage with employees to develop the role further. In doing so, use must be made of existing management infrastructure, and where there are already positive sustainability practices in play, these should be enhanced and reinforced.

This is not a “top-down” process. Senior management need to lead, this is true, but there should be mechanisms in place for continuous feedback from the strategic to the operational levels and back again. The entire organisation should be engaged in a conversation about sustainability, and prepared to modify plans and actions at all levels in response to results achieved. 

Copyright © 2013, Craig van Wyk, all rights reserved

HOW OVER-SIZED EQUIPMENT CAN BE A DRAIN ON YOUR RESOURCES

Where resource efficiency is concerned,
bigger is certainly not always better!

Capacity is such a vital aspect of manufacturing success that it is not unusual to find industrial sites where equipment is far bigger than it needs to be. Part of the reason for this is the need for production plants to be flexible, in which case excess capacity is probably justifiable. It is also often the case that over-sized equipment is installed with an eye on future expansion. The thinking in this case is that the slack will eventually be taken up. Then of course there is the case of the "prudent" engineer, who installs over-sized equipment simply to be absolutely sure that required production levels are reliably met. This “just in case” approach is in my experience probably the most prevalent reason for the large amount of over-sized equipment I come across.

Specifying equipment that is too large for the duty obviously incurs unnecessarily large capital costs. But a far more insidious impact is the inefficient manner in which oversized equipment consumes resources. When you consider that the life cycle costs associated with most process equipment are typically dominated by the costs of resource consumption rather than the initial capital outlay, it is easy to see how what seems like a prudent capacity decision at the time of purchase can have seriously detrimental impacts on profitability.

In general, equipment tends to operate best at the capacity level for which it was designed. To illustrate this point, let’s look at a few examples of oversized equipment and explore the impact of operating them at capacity levels significantly below design ratings.

CASE 1: UNDER-LOADED INDUCTION MOTORS

Induction motors have a nameplate capacity that determines the amount of shaft power they develop when under full load. The input power to the motor under full-load conditions may be estimated by dividing the rated capacity by the full-load efficiency of the motor. Hence, as an example, a 7.5kW motor with a full-load efficiency of 88.6% would have an input power at full load of 7.5 kW / 88.6% = 8.47kW.

Motors rarely operate under full load for extended periods of time. The loading of a motor may be assessed by measuring input power and then dividing it into this full-load input power figure.    

Motor loading = measured input power / (Rated full-load power / ƞ_full-load)

Hence, say for the 3-phase induction motor in our example we measured the input power of the individual phases under typical operating conditions and determined the total input power to be 4.3 kW. The loading of this motor would then be 4.3kW / 8.47kW = 51%. This motor would clearly be significantly under-loaded. A loading of less than 100% is not necessarily a bad thing, the key consideration is where the loading level places the motor along its efficiency continuum.

The efficiency of an induction motor varies significantly with load. Below is a typical induction motor efficiency curve.

As shown, at loadings slightly below 100%, motor efficiency is actually greater than at full load. However, at low loadings, we see that motor efficiency drops off sharply. Based on this efficiency curve, running a motor at the loading we calculated above would result in the motor operating at an efficiency level of some 90% of full-load efficiency. Hence the efficiency level of the motor would be 90% x 88.6% = 79.74%. Should this particular motor operate continuously, this efficiency deficit can cause operating costs to mount up very quickly.

For this situation, it should be clear that the use of a motor with a higher full-load efficiency than the one installed would not solve our problem. The solution would be to specify a smaller motor, which would mean operating at a higher loading and hence a movement up the efficiency curve to a level closer to full-load efficiency.

 CASE 2: UNDER-LOADED BOILER

Boilers are rated to deliver a specific quantity of steam at a given temperature and pressure, using a given fuel. At this “maximum continuous rating”, the boiler would operate at its optimal efficiency. However, when operated at throughput levels lower than the MCR, efficiency tends to decline. The reasons are to do with the fact that burners and other auxiliary equipment are designed to work best over a specific throughput range, and that shell losses, which are fixed, become a larger proportion of the overall boiler losses at lower throughputs. In addition, remember that boilers are heat transfer devices, and as such, reductions in the rate of gas flow through a boiler, as happens at lower throughputs, result in reduced heat transfer coefficients on the combustion side.

A typical boiler efficiency curve is as indicated below.

It is clear that operating a boiler at 30% of its design capacity can result in a significant efficiency drop, as compared to operating it at say, 60% of its design capacity. The difference in efficiency results in a significant increase in the amount of fuel required to produce a given mass of steam.

 CASE 3: UNDER-LOADED CIP SET

Cleaning in place (CIP) refers to the process of cleaning the product-side surfaces of processing equipment in the food industry. This is typically accomplished by pumping water and cleaning solutions through pipelines, or using spraying devices to distribute water and cleaning solutions inside process vessels. The CIP set itself comprises a series of tanks, pipelines, valves and pumps. Each tank holds an individual solution or process fluid, such as water, acid solutions, sterilising agents, caustic solutions or recovered rinse water. There are several ways in which an oversized CIP set can lead to wastage of resources. Some of these could include:

• If the tanks are too large, more fluids than are necessary will be heated and pumped for cleaning. This translates into more water, chemical and energy use than is necessary for constituting the cleaning solutions. Large tanks also translate into more heat transfer surface and hence more heat loss to the surroundings;
• If the flows employed are too high, a significant amount of energy could be wasted. Since centrifugal pumps are typically used for pumping CIP fluids, and energy consumption for these pumps varies with the cube of flowrate, small deviations in excess of minimum required flows could result in significantly more pumping energy being used;
• While CIP sets are typically designed to recover water and cleaning solutions, thereby reducing their resource consumption, some water discharge and loss of cleaning solution is unavoidable – essentially the water used for cleaning becomes too contaminated for reuse.  It is also necessary to periodically drain the system and make up fresh solutions. In the case of an oversized CIP plant, the resource losses associated with ongoing operation and intermittent refreshing of cleaning fluids tends to be higher.

There are many other common examples of oversized equipment I could cite, and in all cases, the amount of resources they consume per unit of production is higher than it would have been had they been correctly specified. Of course, it is not always possible to justify the removal of equipment and its replacement with a correctly-sized alternative, so what would the solutions to this challenge be in practical terms?

The first approach I would recommend would be to try to identify the drivers of the inefficiency behind each individual process. For example, if an under-loaded boiler performs poorly due to poor control of the air-to-fuel ratio at low throughput levels, investigate the control system. It may be the damper valve characteristic that is the problem, in which case use of a variable speed drive on the forced draft fan could help to increase efficiency levels. If the driver of inefficiency for an oversized heated vessel is the excessive surface area, look into insulation as an option. In short, try to establish cost-effective plant modification strategies as far as possible.

In many cases, modifications to the equipment itself may not be possible. For example, an under-loaded induction motor cannot be modified and requires replacement. However, this need not be expensive. It may be that a motor with the correct characteristics may be available elsewhere on your site. This is one of the reasons I recommend retaining redundant motors as spare units, even when replacements are made on the basis of installing higher-efficiency units. Old, standard efficiency motors that are properly loaded are more efficient than high-efficiency motors that are under-loaded, so there are often opportunities to deploy such motors more efficiently elsewhere should they have been replaced with more efficient alternatives. Of course, these motors need to be in good working order.

A final approach I would recommend would be to investigate production planning and scheduling to assess how this may be changed to take advantage of excess capacity in ways which minimise resource consumption. Can larger batches be produced less frequently, for example? Is there scope to operate at higher instantaneous capacities and extend maintenance and cleaning breaks as opposed to spreading production over longer periods while operating the facility at low throughput levels? Much of this approach comes down to business decisions, and considerations that impact on entire supply chains. Product characteristics also play a significant role – for example, perishable products have to be produced as close as possible to time of sale. It is therefore a case of intimately understanding your processes and taking advantage of the unique opportunities on offer, on the understanding that each facility will be different.

So, is over-sized equipment hurting your environmental performance and bottom line? Your first step should be to gather all capacity data for your facility, take the necessary measurements and find out. I can almost guarantee that you will find resource efficiency opportunities in this area.

Copyright © 2013, Craig van Wyk, all rights reserved

A GLOSSARY OF STEAM SYSTEM OPTIMISATION TERMINOLOGY

Steam systems comprise the generation of steam, its distribution to point of use, its deployment in various processes and the recovery of the condensate produced. The efficiency of steam systems is a complex subject area with lots of terminology, some of which can be confusing to those starting out with resource efficiency projects in this area. The attached glossary is meant to assist with the various terms you will come across. I will update it with additional terms over time, so you can use this as a reference.

Approach temperature	The temperature difference between the process fluid leaving a heat exchanger and the service fluid entering the heat exchanger. The smaller this difference, the greater the heat exchange area required and the higher the cost of the heat exchanger.
Backpressure turbine	A turbine that discharges steam at a pressure greater than atmospheric pressure. This type of turbine typically discharges into a steam header, with the steam then used for heating or other process uses. The turbine can be used to generate electricity or to drive a piece of equipment.
Balanced draft	When the air and flue gases in the boiler stack are maintained at a pressure equal to atmospheric pressure
Ball float steam trap	A mechanical type of steam trap that uses a ball that floats on the condensate in the trap. The ball is attached to a lever that is connected to a condensate release valve. The valve is closed when the level of condensate is reduced and the ball is lowered. The trap can also be fitted with a thermostatic air vent, which increases its capacity during start-up. Its biggest advantage is that since it does not rely on temperature, condensate is discharged under all conditions, as soon as it is formed. Hence both saturated and sub-cooled condensate are released through this trap.
Balanced pressure steam trap	A thermostatic type of steam trap comprising a capsule containing a fluid with a boiling point lower than that of water. In cold conditions, the capsule is relaxed and air and condensate can leave the system.  When warm condensate approaches, the fluid vaporises, closing the trap.  Cooling causes the trap to open again, and steam causes the cycle to repeat.
Bimetallic steam trap	A type of thermostatic steam trap that uses a bimetallic strip for its operation. The metals are dissimilar, and expand at different rates with increasing temperature. The deflection in the strip is used to close the condensate release valve at higher temperatures when steam is present, and open to release condensate at lower temperatures.
Blowdown	As steam and condensate are lost from the overall steam system, the concentration of salts in the boiler increases. If the concentration of these salts becomes too high, this can impact on boiler integrity and also cause scaling and heat transfer problems. It is therefore necessary to remove suspended and dissolved solids by draining a portion of the concentrated water and replacing this with fresh make-up water with low salt concentration. This process is called “blowing down”.
Blowdown flash tank	The water in the boiler is under pressure, and when it is exposed to a lower pressure, a portion of it will flash as steam. This can be achieved in a blowdown flash tank, which is simply a vessel large enough to allow the liquid and vapour streams to disengage. The flash steam can be recovered into a low pressure header, or used to heat make-up water (this is less preferable). Heat can also be recovered from the remaining liquid stream using a blowdown recovery heat exchanger.
Boiler	Device used to heat water and produce steam. The two main types of boilers are fire-tube boilers and water-tube boilers.
Boiler efficiency	The efficiency with which the energy contained in the boiler fuel is converted into energy contained in steam. It is important to distinguish between whether the higher heating value (HHV) or lower heating value (LHV) is being used for the calculation, and to be consistent when making comparisons.
Boiler feedwater	The water fed into the boiler to produce steam. This typically comprises a mixture of fresh make-up water (which is typically treated) and recovered condensate.
Boiler feedwater pump	The pump used to pump feedwater into the boiler. Since this pump has to overcome the pressure inside the boiler, it is often a multi-stage pump capable of generating significant head.
Bottom ash	Large non-combustible residues from the burning of solid fuels which typically are too heavy to be conveyed by the combustion gas stream and are hence removed from the bottom of the boiler.
Bottom blowdown	This blowdown removes solids that have settled in the boiler “mud drum” and in the bottom of the boiler tubes in the case of watertube boilers. Firetube boilers may also have a blowdown outlet near the bottom of the water level.
Cogeneration	Also known as combined heat and power (CHP). This is the simultaneous production of electricity and heat energy from a single fuel source. It could entail the recovery of heat from the exhaust gases of a gas turbine to produce steam, for example, or the production of steam with concomitant production of electricity in a manufacturing plant.
Combustion air pre-heater	A heat exchanger used to heat up combustion air using heat recovered from hot flue gases.
Condensate flash tank	A vessel used to allow condensate leaving a high-pressure system to flash as it encounters a lower pressure. The flash can then either be diverted into a lower-pressure steam header or condensed using a flash recovery heat exchanger.
Condensate tank	A vessel used to store recovered condensate. It may also serve as a boiler feedwater tank, in which case it would typically be combined with a deaerator.
Condensate polishing	The process of removing corrosion products and dissolved minerals from returning condensate. In very high pressure systems, demineralisation may be carried out using processes such as ion exchange.
Condensate recovery	The recovery of condensate from processes that condense steam and the return of this condensate to steam generation.
Condensing economiser	Heat exchanger used to heat up boiler feedwater using heat recovered from combustion gases that are cooled sufficiently to condense the water vapour in them, so that it gives up its latent heat. Condensing economisers are typically used with low-sulphur fuels which do not produce a strongly acidic condensate.
Condensing turbines	These turbines exhaust saturated steam (typically with a quality less than 1) at pressures below atmospheric pressure to a condenser, where the steam is condensed and the resulting condensate is typically returned to the boiler. They are typically used in power generation applications and to drive large pieces of equipment.
Condensate recovery	After steam gives up its latent heat it becomes a saturated liquid, and may cool down further to become sub-cooled condensate. The resulting water is of very high quality and also contains significant amount of thermal energy. It is hence a valuable commodity that can be recovered for reuse as boiler feedwater to produce steam.
Conductivity	A measure of an electrolytic solution’s ability to conduct electricity. Used to assess boiler feedwater and boiler water quality, in order to determine when a boiler should be blown down to reduce the build-up of ionic salts in the boiler. At high concentrations these salts could form scale or cause corrosion.
Deaerator	A vessel used to remove air (or more specifically, oxygen) from boiler feedwater, thereby limiting corrosion. Usually achieved using live steam and an arrangement which maximises the residence time of the water and the contact area between the steam and the water being deaerated e.g. a system of trays or a spray system. The vessel is fitted with a vent through which the air and some steam can escape.
Dealkalisation	Removal of carbonate and bicarbonate alkalinity. If they are not removed, these chemical species can cause priming, foaming and carryover in the boiler, and also decompose to form carbon dioxide, and carbonic acid, causing corrosion. Dealkalisation is usually done downstream of softening using a technique such as ion exchange.
Demineralisation	The removal of minerals, typically using ion exchange or reverse osmosis.
Desuperheating	The process whereby superheated steam is transformed into steam with fewer degrees of superheat or to saturated steam through the addition of water. This reduces the specific enthalpy of the steam, but increases the mass of steam.
Distillation column	A device used to separate materials on the basis of their boiling points, using a heat input (typically steam) and a heat exchanger.
Distribution	This is the process whereby steam produced in the boilers is distributed to point of use, using pipelines, valves and pressure reducing devices as appropriate.
End use	This is where the steam is actually employed, either for heating, direct injection or to drive turbines.
Enthalpy	The measure of the total energy content of a thermodynamic system. When analysing steam systems we typically use the specific enthalpy, which is simply the enthalpy per unit mass.
Excess air	A certain minimum amount of air (or more specifically, oxygen) is required in order to meet the stoichiometric requirements of combustion. A small excess is needed to account for imperfect mixing. Too much air will however lead to inefficiency, since the mass of hot flue gases leaving the boiler would be more than optimal for a given mass of fuel combusted. Control of excess air is therefore a critical aspect of boiler efficiency management.
Extraction turbine	With this type of steam turbine, steam is extracted from various stages of the turbine (after having been expanded) and used for process requirements.
Generation (steam)	This is the process whereby steam is produced using boilers. Boilers can use a number of fuels, or can even be powered by waste heat.
Generator (electrical)	A device that converts kinetic/mechanical energy to electrical energy. In the electricity generation process, a conductor is rotated inside a magnetic field, generating a flow of electrical current perpendicular to the field.
Feedwater economiser	A heat exchanger used to heat up boiler feedwater using heat recovered from the hot combustion gases leaving the boiler.
Fire tube boiler	A boiler type in which the hot combustion gases pass through the tubes and heat the water (in the “shell”) to produce steam.
Fly ash	Light particulate residues that are conveyed by the combustion gas stream and are removed from the flue gas stream using equipment such as bag filters or electrical precipitation units.
Forced draft	Control of the combustion zone pressure such that the pressure of the air and combustion gases in the stack is maintained at a level above atmospheric pressure.
Header	A steam pipeline carrying steam at a given pressure and distributing this steam to users.
Heat Exchanger	A device used to exchange heat between two or more fluids. The fluids do not come into physical contact with each other, but are separated by heat transfer surfaces, such as tubes or plates.
Higher Heating Value (HHV)	Also called “higher calorific value – HCV”. The amount of energy liberated upon combustion of a fuel, including that recovered by condensing of the water vapour formed during combustion.
Induced draft	Control of the pressure at the stack entrance such that the air and combustion gases are maintained at a pressure below atmospheric pressure.
Inverted bucket steam trap	A type of mechanical steam trap containing an inverted bucket attached by a lever to a condensate release valve. In the presence of condensate, the bucket sags and the valve remains open, releasing the condensate. When steam arrives, the bucket is buoyed by the steam, and the valve is closed. The bucket typically has a small vent/bleed hole through which air can escape. A small amount of steam is therefore lost through this vent.
Liquid expansion trap	A type of thermostatic steam trap that uses an oil-filled element which contracts when contacted with cooled condensate, and allows the condensate to vent, and expands when contacted with steam, causing it to expand and shut the release valve, trapping the steam. Since these traps tend to activate at a fixed temperature, they are best used to discharge condensate after a shutdown period. They are better at releasing sub-cooled rather than saturated condensate.
Log mean temperature difference	A means of expressing the driving force for heat transfer in a heat exchanger (remember that Q=UA ΔTLM). If A and B are the two ends of the heat exchanger, then LMTD = (ΔTA – ΔTB) / ln(ΔTA/ ΔTB). For crossflow and multi-pass heat exchangers a correction factor has to be applied to calculate the LMTD.
Loss on ignition	The proportion of unburnt carbon and other combustibles in the ash remaining after combustion of solid fuels.
Lower Heating Value (LHV)	Also called “lower calorific value (LCV)”. The amount of energy liberated during the complete combustion of a fuel, excluding heat that would be recovered by condensing water vapour in the flue gases.
Maximum Demand	The peak apparent power drawn by a site over the course of a month, measured in kVA. This may be of interest for sites wishing to generate power using their steam systems.
Mechanical steam traps	Steam traps that rely on mechanical means to operate. They typically exploit the density difference between steam and condensate.
Orifice plate steam flow meter	A plate with a hole in the middle of it through which the steam flows. The flow of steam is inferred from the pressure drop across the plate, the square of which is proportional to the velocity of the steam. A differential pressure measurement device such as a DP Cell is used to measure the pressure difference. The data can then be fed to a computer/PLC and used either on its own or together with additional measurements (such as temperature) to calculate the mass flow of steam.
Oxygen scavengers	Chemicals (such as sodium sulphite) used to remove oxygen from boiler feedwater. Deaerators cannot remove all of the oxygen, and even the low oxygen levels after deaeration may be enough to cause corrosion.
Pressure reducing station	Also called a “pressure reducing valve – PRV” or a “letdown station/valve”. These are systems comprising a control valve and pressure sensing which reduce the pressure of the steam from the pressure in the header to a reduced pressure, either in another header or for a specific individual user. They are always fitted with a bypass to allow for maintenance.
Reboiler	A heat exchanger used to heat distillation column bottoms. It is called a reboiler rather than a boiler since the bottoms are circulated continuously through the heat exchanger, and boiled over and over again.
Refractory	Heat-resistant material used to line high-temperature furnaces and boilers.
Saturated steam	Water vapour in equilibrium with liquid. When heat is removed from saturated steam, it immediately begins transforming back into the liquid phase to form condensate. Saturated steam has a pressure that is completely determined by its temperature and vice versa. The thermodynamic properties of saturated steam can be found from steam tables if either the temperature or pressure are known.
Steam ejector	A device which uses steam as a motive fluid to entrain another fluid (the suction fluid) using a venturi. The steam is injected into the throat of the venturi, where its velocity increases, decreasing its pressure. The lower pressure “sucks” in the fluid being transported and the steam-fluid mixture then enters the wider area of the throat, where the pressure increases again, mixing the steam and the suction fluid.  The word “ejector” implies that the fluids are discharged to the atmosphere, for example where steam is used to generate a vacuum.
Steam injector	This is a variant of an ejector, in that the same principle is used to entrain water with steam, and then mix the two to condense the steam and produce hot water at a high pressure that can be injected into a process or a boiler.
Steam quality	A number between 0 and 1 that reflects the fraction in the saturated mixture that is vapour, with the balance being liquid. At a steam quality of 1, all of the steam is saturated vapour, while at a quality level of 0 all of the steam is saturated liquid.
Steam reforming	The process of reacting steam with natural gas (methane) to produce hydrogen and carbon monoxide in the presence of a nickel catalyst. The carbon monoxide can be reacted with additional steam to produce yet more hydrogen, this time accompanied by the production of carbon dioxide.
Superheated steam	Steam that has been heated to a temperature above its saturation temperature. When heat is removed from superheated steam, it does not immediately begin to condense, but first cools to the saturation temperature corresponding to its pressure. Once it has become saturated, it will begin to condense if more heat is removed from it. The pressure and temperature of superheated steam are independent of each other and both have to be known to assess the thermodynamic properties of superheated steam from steam tables.
Thermodynamic steam trap	This trap works using a disc which either allows condensate to pass, or traps steam inside the steam system. The pressure exerted by cold condensate simply lifts the disc, allowing the condensate to flow. When hot condensate arrives and flashes, the high velocity creates a zone of low pressure underneath the disc, causing it to seat. At the same time, flash steam in the enclosed space above the disc is trapped, creating a positive pressure above the disc. Since force = pressure x area, and the area above the disc is larger than the area below the disc (by virtue of the design of the body of the trap), the flash steam above the disc applies a larger force than the steam below it. This force will remain higher until this flash steam condenses sufficiently for the force of the condensate below the disc to exceed it.  It is important for the top of this trap to be well insulated in order to prevent rapid condensing of steam above the disc, and hence too high an opening frequency.
Reheat turbine	With this type of steam turbine, steam is extracted from the turbine, sent to the boiler to be reheated and then returned to the turbine, from where it continues to expand.
Reverse osmosis	In natural osmosis, water moves from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane, until the solute concentration is equalised on both sides of the membrane. Increasing the pressure on the side of the membrane containing the high solute concentration can slow or oppose osmosis, and if this pressure is made high enough, water can be forced in the opposite/reverse direction. Reverse osmosis is used to purify water containing dissolved solids.
Softening	The process of removing “hardness” from water (calcium, magnesium, iron and other metals). These form scale which impacts on heat transfer.
Soot blowing	The process of removing soot from the surfaces of boiler tubes, using either compressed air or steam. The reduction in fouling improves heat transfer rates.
Steam trap	A device used to “trap” steam inside a system until it condenses, after which it is released as condensate. Steam traps ensure that the latent heat of the steam is released, thereby allowing heat transfer equipment to work as designed. In addition to releasing condensate, they also release air and other non-condensable gases which could compromise the rate of heat transfer.
Steam turbines	Devices that convert the thermal energy in the steam into shaft work, which can be used to drive mechanical devices (e.g. pumps, compressors and the like) or to generate electricity using a generator.
Steam Stripping column	A column in which a liquid product containing volatile components is contacted with live steam, stripping the volatile materials out of the liquid. The column may contain packing or trays to maximise the surface area for mass transfer and the residence time of the material being stripped.
Surface blowdown	This blowdown removes concentrated water from the boiler, but generally does not remove solids. It is therefore carried out close to the surface of the liquid in the boiler.
Thermocompressor	A device used to compress low pressure steam using high pressure steam, resulting in a mixed steam stream at an intermediate pressure. The principle of operation is the same as that of a steam ejector i.e. a venturi is used.
Thermostatic steam traps	These traps operate on the basis of the temperature of the steam or condensate around them. Condensate tends to cool down, leading to a contraction of a component in these traps, which is leveraged as a means of releasing condensate.
Turndown ratio	The ratio of the boiler’s maximum capacity and the minimum capacity it can be operated at by virtue of its design. If a boiler is rated at a maximum capacity of 10 tons/hr of steam and a minimum capacity of 3 tons/hr, its turndown ratio would be 10/3 = 3.33.
Water tube boiler	A boiler type in which the water being heated passes through the tubes, with the hot combustion gases outside the tubes.

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