INDUSTRIAL WATER CONSERVATION – A PRIMER

Water being dispersed across the tube bundle of an
evaporative condenser

The industrial sector is diverse and uses water in a variety of ways. Some water uses are common to many industries, for example the use of water as a cooling medium and for the production of steam. Other water uses are very specific to individual industries, for example the use of water as a chemical carrier and rinsing medium in electroplating. The industrial sector has the potential to consume large volumes of water, as well as the potential to contaminate large volumes of water, with both of these impacts reducing the amount of water available to downstream users. The links between industry and the preservation of water resources are therefore indisputable, even for industries which on the face of things are not considered to be water-intensive.

In the industrial sector, water is not only linked to energy, but also to material usage, air quality, health and safety, product quality and other performance dimensions. The relationships may be virtuous or conflicting. Some examples from various industries are outlined in the table below.

Table 1: Links between Water Use Efficiency and other Operational Goals

Linked to	Industry	Detail
Energy efficiency	General	Heat recovery through process integration reduces waste heat and hence cooling tower evaporation. Energy efficiency and water use efficiency work in concert.
Material usage and energy efficiency	Brewing	Increased water usage at lautering increases extract recovery. Increased evaporation rates at boiling could be required to achieve desired sugar concentrations, increasing water and energy use in order to achieve the material usage benefit.
Air quality	Coal-fired Power generation	Wet flue gas desulphurisation (FGD) technologies consume a significant amount of water, but reduce sulphur dioxide and mercury levels in flue gases. The effluents produced must be safely handled to reduce groundwater contamination risks to avoid transference of the risks from air to water resources.
Product quality	Pulp and paper	The quality of bleached pulp is partly dependent on the amount of water used for pulp washing. In the absence of recycling, water use and product quality oppose each other.
Product safety	Food processing	Water is used for cleaning-in-place (CIP), where processing equipment is cleaned and sterilised to prevent microbial contamination of food products. Increased cleaning generally requires more water.
Product quality and effluent volume	Electroplating	Rinses downstream of process baths reduce the carryover of chemicals into successive baths, reducing impurities and improving product quality. Improved quality is a function of water usage, but increased rinsing will increase the volume of effluent produced.

These are just a few examples, and one could get into a lot more detail when examining issues at the industry level. The point here is that in many industries, water usage has to be managed against the backdrop of a large portfolio of constraints of which energy is just one.

Within individual industries, the amount of water used is also heavily dependent on technology choices. These come with trade-offs. For example, a site that employs dry cooling devices will enjoy a reduced consumptive water use over comparable sites that employ wet cooling systems. However, in warm weather dry cooling devices may lack sufficient cooling capacity. In the case of power generation, this translates into reduced turbine efficiency and ultimately, increased emissions.

Quantitative benchmarking of water usage in the industrial sector, if injudiciously carried out, can lead to wildly incorrect conclusions. Consider that product mix typically has an enormous impact on water consumption, and hence that within individual industries, sites producing different products cannot be compared fairly without product-specific benchmarks. A paper mill producing fully bleached Kraft pulp could easily use twice as much water per ton of production than a mill producing newsprint for example.  And of course the issue of technology is important given, as mentioned above, that different technologies imply different water use characteristics. This is not to say that benchmarking is not useful, since every site does need to understand the envelope of what’s possible, both within the constraints of their own technological footprint and product mix and in terms of what could be delivered by alternative technologies. Consider however that not all technologies are equal in terms of the other water-related outcomes of interest mentioned above. Given that water is generally a cheap commodity relative to raw materials, and that product quality problems can be very costly, industrial players will tend to favour performance on these issues, as well as non-negotiables such as safety, over water use efficiency.

To complete the picture of what the challenges of efficient industrial water management entail, consider that the industrial environment is never static. Raw material quality changes continuously, particularly where industries use natural resources, such as in mineral processing and agro-industries. Components fail, even where good preventive maintenance practices are in place. Employees make mistakes, even where automation and mistake-proofing techniques have been applied. Atmospheric conditions vary. All of these variations have a material effect on water consumption, and the most efficient operators are those who design out variation as far as possible and have robust systems in place for identifying risks and responding to non-conformance.  

Given all of these complexities, how does the operator of an industrial concern set about minimising water consumption? Minimising water usage in this context requires deep industry-specific knowledge, without which there is a tremendous risk of incurring unintended consequences. And this is precisely why the regulation of industry from a water use perspective is such a daunting task for policymakers. What should be clear is that industrial water conservation is not simply a case of “closing the tap”. Since water use impinges on so many other critical operational objectives, industrial water conservation has to be tackled in an integrated fashion that balances material usage, safety (for employees, local communities and consumers), hygiene, product quality and environmental considerations. And this is true for every individual aspect of industrial sustainability and sustainability in general. I will get into more details regarding specific aspects of industrial water conservation in future posts, so stay tuned.

RAPID ASSESSMENT OF THE VIABILITY OF MOTOR REPLACEMENT FOR ENERGY EFFICIENCY

Motors driving centrifugal pumps at a water purification plant

Induction motors are prevalent on every industrial site, and are typically responsible for a sizable portion of the total electrical energy consumed (reportedly up to 40%, but it depends heavily on the industry concerned). As technology regarding their construction has moved forward, they have become more efficient, meaning that the amount of energy supplied to an induction motor for the equivalent amount of work performed has reduced. It is widely accepted that most of the life-cycle costs associated with owning an induction motor are due to energy consumption rather than the capital and maintenance costs of the motor itself. Sites with older motor populations can therefore benefit from replacement of older motors with newer, more efficient designs.

Motors are generally classified as being either of standard, high/improved or premium efficiency, with various different standards in use which are not necessarily equivalent (if interested, you can find out more here).

In some parts of the world, minimum efficiency levels are regulated. In the European Community, high efficiency motors became mandatory for new installations in 2011, for example, with stricter standards planned for 2015 and beyond. Various financial incentives are also in place in different parts of the world – in South Africa, the national power utility provides incentives for motor replacement on condition that the motor being replaced is destroyed.

The issues around motor efficiency are diverse, and extend beyond their design characteristics. To begin with, on-site measurement of efficiency is not typically done, and hence the assessment of an existing motor’s efficiency is in most instances an intelligent guess. While the design efficiency of an existing motor is generally available from manuals, and is sometimes displayed on the motor’s nameplate, this efficiency could have changed over time, particularly if the motor has been re-wound. Since in general we are talking about a decrease in efficiency here, using the design efficiency is nevertheless a conservative measure when calculating the benefits of replacement. Note also that the efficiencies quoted are based on full-load conditions. If a motor is poorly loaded, the impacts on efficiency can be very significant, as shown by the typical load-efficiency curve illustrated below.

It is clear that in this example, at loadings of less than 50% efficiency levels fall dramatically. While such loadings are uncommon, I have observed them on occasion, particularly for larger motors. It should however be considered that the illustrated relationship does depend also on motor size, with larger motors able to maintain higher efficiencies at lower loadings.

Use of variable speed drives complicates the efficiency issue further. VSD’s (also called variable frequency drives) contribute to losses directly themselves (these are of the order of 1-3%), but motor speed reduction (caused by the motor operating at lower frequencies than rated) also causes a reduction in motor efficiency. You can find more information in this article. The full-load efficiency levels of new motors are determined according to standard tests and manufacturers are expected to meet the defined efficiency standards in order to classify a motor as being within a specific efficiency class.

Let’s explore a few simple (understanding from the above that it’s not that simple) relationships to illustrate how efficiency increases contribute towards reduced energy consumption.

Motor efficiency% = η = output power (at the shaft) / input power (from the energy source) x 100%. For a given level of output power (OP), an energy-efficient motor requires less input power (IP) than a standard-efficiency motor.  

For any motor, OP = η x IP / 100 (with efficiency in %) and therefore, since we can assume that in evaluating opportunities to install energy-efficient motors the process being driven requires a specific amount of power,  η_standard x IP_standard / 100 = η_new x IP_new / 100

From IP = OP x 100 / η, the change in input power requirements arising from the use of energy efficient motors, ΔIP, is given by: 

ΔIP = OP x 100 x (1/ η_standard – 1/ η_new)               

    = η_standard x IP_standard x (1/ η_standard – 1/ η_new)

So, for a motor drawing an input power of 50 kW, with an efficiency of 92.7% and with a replacement motor of 95% efficiency available, the power savings would be of the order of ΔIP = 92.7% x 50 x (1/92.7 – 1/95) = 1.21 kW.

This is the input power under average conditions, since the power draw of a motor varies with time, particularly under transient conditions like start-up, and also as a function of the specific processes in which the motor is employed. A motor driving a bandsaw will draw different amounts of power depending on the material being cut and the condition of the blade, for example.

The amount of energy saved is the power saving multiplied by the time over which the savings are realised. While motors run continuously in some plants, in most cases you will need to determine the running hours. The energy savings in the case of our example, were this motor to run continuously, would be of the order of 1.21 kW x 24 hours/day =  29 kWh/day. The value of these energy savings would depend on local tariff structures, and there may also be demand savings associated with replacement. 

A few things become apparent (or even self-evident) from the preceding analysis:

·  The bigger the efficiency differential, the better – generally,  the larger a motor is, the smaller is the efficiency differential, since larger motors tend to be more efficient than smaller ones;

·  The longer the running hours, the greater the amount of energy saved. Hence if you run a dayshift operation, expect it to be tougher to justify replacements, even for motors that run continuously;

·   Some measurement is needed to determine input power. While you can log the power drawn, simple spot checks are a useful starting point. If you measure only current and voltage, you will need to make assumptions regarding power factor in calculating the power drawn. This is the least-preferred approach, since like efficiency, power factor varies with motor loading. Alternatively you could measure power factor directly, together with the voltage and current. This would give an accurate indication of power consumption. Better still, hand-held clamp meters are available which measure power directly. 

Conducting such an exercise on a site with a large motor population is possible if you chip away at it over time. It is useful to have such information on record, and to track changes through periodic measurements. These checks could even be incorporated into your preventive maintenance programme, with input power draw triggering further investigations should there be an upward trend. If however you would like a first-order overview of energy-saving opportunities and their potential viability, here is an approach I use to rapidly review opportunities on industrial sites.

·    Construct a record of every motor on the site in terms of its power rating, full-load efficiency level (if available), full-load power factor and rated speed;

o If efficiency is not known, estimate it, either using a standard efficiency value, or correlations for older motors;

o The speed is required in order to calculate the number of poles. This is often indicated on the nameplate. If not, measure it with a tachometer. Often the poles are directly indicated, in which case you do not require the speed value;

·     Assume a loading value - I generally use 80%. At these loading levels, efficiency and power factor levels are typically close to what they would be at full load. Of course, actual loadings could be far lower or even higher;

·  Where a given motor size/speed combination is prevalent for a number of motors, conduct this analysis for just one, which will represent all of them;

·  Find the equivalent high and premium efficiency motors for each individual size/speed combination, and obtain rough prices for the replacement motors. You can generally get a price list from a motor manufacturer - take care to note if the motors are foot mounted or flange-mounted, since there is typically a fairly significant difference in price between equivalent-capacity motors with different mounting arrangements;

·   Determine your unique payback requirements – for example, do you require a payback within 3 years? Bear in mind that the average induction motor can be expected to have a useful life of 100,000 hours.

·  For each motor/speed combination, determine the annual running hours that will lead to a break-even situation over your payback time horizon, based on energy tariffs, energy savings arising from the efficiency differential and the costs of the motor. I use rough costs at this stage – it’s quite simple to construct a correlation between motor price and power rating for premium efficiency motors once you have accumulated a sufficient number of quotations. For simplicity, I don’t include maintenance costs at this stage, but you could do so.

·  Now compare these running hours to the running hours of your facility, the running hours of your individual processes and finally the running hours of individual motors within those processes. If the breakeven running hours exceed the motor’s expected running hours by a significant amount, further investigation is probably not promising. If however the breakeven hours are far lower, investigate further with measurements to determine actual loading and analysis. A firmer motor price could also be obtained by asking a supplier to quote for the specific motor concerned. Recalculate with this firmer data and make a decision.

Wondering how to calculate those breakeven hours?

Annual Energy savings = ΔIP x Running hours/annum x Cost/unit energy

 =η_standardxIP_standardx(1/η_standard–1/η_new)x Running hours/annum x Cost/unit

By setting these annual energy savings to a value which offsets the cost of the replacement motor over the chosen time horizon (e.g. 5 years), the running hours required annually to achieve this can be calculated. Use of a spreadsheet and the goal-seek function is a simple way to do this for multiple motors. An example is outlined in the table below for a sample of 9 power/speed combinations.

RATED MOTOR SIZE (KW)	NO. OF POLES	EXISTING MOTOR   η %	FULL LOAD POWER DRAW (KW)	ESTIMATED AVERAGE INPUT POWER @ 80% LOADING (KW)	PREMIUM MOTOR   η %	SAVINGS OVER 5 YEARS (RANDS)	ESTIMATED MOTOR REPLACEMENT COST (RANDS)	ANNUAL RUNNING HOURS REQUIRED (HRS)
0.75	4	72.1	1.04	0.83	82.5	3900	3900	12392
1.1	4	75	1.47	1.17	84.1	4100	4100	10765
2.2	4	79.7	2.76	2.21	86.7	4700	4700	8787
2.2	6	77.7	2.83	2.27	84.3	4700	4700	8834
3	6	79.7	3.76	3.01	85.6	5240	5240	8415
3	4	81.5	3.68	2.94	87.7	5240	5240	8390
7.5	4	86	8.72	6.98	90.4	7590	7590	7450
11	4	87.6	12.56	10.05	91.4	9500	9500	7582
15	4	88.7	16.91	13.53	92.1	11800	11800	7876

In the calculations in the table, the annual running hours are varied such that for each motor, the savings achieved over a 5-year period are equal to the costs of replacement with an energy-efficient motor, assuming a motor loading of 80% for the existing motor. 

If for example, this site operated for 24 hours a day and for 340 days of the year, total operating hours would be 24 x 340 = 8,160 hours/annum. A glance at the required running hours quickly shows that motors of 7.5 kW, 11 kW and 15 kW should be investigated further. These investigations should involve determination of actual power consumption through measurement, a determination of actual running hours and an assessment of financial viability based on these measurements. In fact, this analysis could be extended to include motors from 2.2 kW in size given that these are relatively close in terms of breakeven running hours.   

As regards the other motors, the overall situation could change (assuming the efficiency differential remained constant) if power prices increased to a higher level, if motor prices decreased and/or if running hours increased. The exercise should also be periodically repeated to account for improvements in motor efficiency arising from technological advances over time.

You could make your approach more comprehensive than the one proposed by assuming a loading level of 100%. This would increase the savings potential due to motor replacement and widen the net in terms of the number of motors that would require detailed measurement. In my experience, motors in most factories tend to be loaded at levels below 80%, so this is just an arbitrary value I have chosen.

A final point: motors form part of a larger system, and before pursuing energy-efficient motor options, don’t lose sight of opportunities such as reductions in running time, installation of more efficient drive systems (belts, chains, gearboxes etc.) where applicable, and increases in the efficiency of the equipment being driven e.g. a different mixer design may require less power to achieve the same degree of mixing. Each system being driven should be examined in its entirety, with energy-efficient motors being a component of that analysis. 

 

5S – SO MUCH MORE THAN A HOUSEKEEPING TOOL

Most of us who have worked in industrial settings for any length of time and have been involved in continuous improvement initiatives would have seen the implementation of the 5S system. Typically elaborated as “sort, set in order, shine, standardise and sustain” (or other “S’s” of that ilk), the approach is typically associated with physical housekeeping, and is a subset of the broader TPM philosophy which spawned the Lean movement. Organisations typically follow a regimented set of steps in “implementing 5S”, often missing the point in the process.

If we are to unlock the true value of 5S, we need to think more deeply into the origins of the approach. In doing so, it soon becomes obvious that here we are dealing not only with a tool for neatening up the shop floor environment, but a powerful management philosophy which, if successfully implemented, can in itself deliver fundamental productivity improvement. This was indeed not intended to be simply a bunch of steps to follow for cleaning up a messy shop floor, but an overarching way of operating, from the top of an organisation to the bottom. Let me explain.  

The first S, SEIRI, is about organisation. It refers to sorting the necessary from the unnecessary. Often, managers allow the hangovers from previous initiatives to remain on their agendas, cluttering the management landscape. Soon daily routine comprises a hotchpotch of unrelated activities, only half of which add any real value. Defunct meeting structures are allowed to continue, unnecessary meetings are held, the wrong people are involved in meetings…the list goes on. Since so much time, money and effort has been invested in these various programmes, we often have a hard time letting go. Take time out to ask yourself what you are trying to achieve, and then sort your management activities to support your objectives. Anything not in support of these objectives must be considered unnecessary and discarded.

The second S, SEITON, concerns neatness. It refers to having “a place for everything and everything in its place”. When trying to manage issues across a broad spectrum, it becomes so easy to lose track of what needs to be done. Things fall through the cracks and often a last-minute charge is needed to catch up. A prime example would be the type of activity witnessed in the days before an audit. There are a few simple things you can do to establish a measure of routine. Schedule different types of activities for different days of the week, and stick to this schedule. Try to get the managers who report to you to do the same, to gain alignment and establish a common “drumbeat” for managerial activities. Map out all of the meetings and forums in your area of influence across the various levels in the organisation, and get these to complement each other. Reduce duplication as much as possible. Soon the limited resources at your disposal will become aligned and you will be able to better apply your efforts to where they can have the most impact.

The third S, SEISO, refers to cleaning and polishing. The aim is not just to make the environment look good, but to expose problems through close inspection. The philosophy is that if problems can be dealt with at this micro level, far bigger problems will be prevented. It is about being proactive. The message from a management perspective is that attention to detail is essential. Merely demanding high performance from your staff without an understanding of the true nature of problems will not deliver results. This does not imply that people must not take ownership of their responsibilities and that you, as the leader, will solve all of their problems. It means instead that you will have empathy for those you lead, allowing you to take a more balanced view around resource allocation, when to back off and give people space and also when to drive harder because complacency has set in.  

You can only deal with the little problems if you are close to the detail. In my humble opinion, the visionary leader who inspires his people with no sense of the detail is inappropriate in a manufacturing and operations environment. You do need to inspire your subordinates, but you also have to have a sense of the detail. It is a rare animal who can successfully do both, but in my experience these types of individuals make the best managers.  Shigeo Shingo emphasised the Japanese management approach, which is for managers to be responsible for performance and workers to be responsible for processes. Managers therefore need to map out the processes which drive performance, with subordinates responsible for the execution of these processes, improving them over time. A manager who is not detail oriented cannot execute on this philosophy.

The fourth S, SEIKETSU, refers to standardisation. At management level, employees are naturally strong-willed and often very innovative. To establish effective routine however, best practices need to be assimilated and followed by everyone. The more certainty you can create, the better the environment becomes for controlled innovation of the kind that adds sustainable value to your business. That means that “bad” management behaviours are simply not tolerated, and everyone on the team has a clear understanding of his/her contribution. All departments need to play by similar rules, for example. If performance standards are vastly different between departments, resentment quickly builds and morale suffers. Standardisation need not mean the same hard standards or specifications for everyone. On the contrary, at management level one needs to be able to assess and appreciate differences between sites, departments and jobs. The standardisation referred to here is a standard amount of stretch in the objectives of each department, site or individual. Everyone should feel equally challenged. This is difficult to do, but for starters, root out glaring discrepancies in standards. Engage with those at the rock face to understand individual operations in more detail and keep an open mind. Management will be viewed as being more objective, and commitment from the lower levels will increase.

The fifth S, SHITSUKE, concerns the aspect of discipline. It is around maintaining established standards. This S is not a stand-alone activity, but permeates all areas of a 5S implementation. If managers display a lack of discipline, don’t expect much more from those lower down the ladder. To gain discipline, individuals need to have a clear understanding of their roles in the business and the importance of what they have to be disciplined about. While management can largely define operating frameworks at shop floor, (though this is changing as teams become more empowered), at management level there is a measure of negotiation involved. People need to buy in to routine – they will not just fall into an unthinking regimen of management activities. There has to be a clear view of the bigger organisational picture and how management activities fit into and drive overall performance. Communicating this vision and how it is to be achieved is the job of senior management.

In summary then, management can benefit immensely by regarding 5S as a central philosophy, the key aspects of which are:

• A sense of order is essential for improved productivity
• Total participation is critical for success
• Focus on the basics and the bigger issues will be more apparent and easier to solve
• Be proactive rather than reacting after the fact
• Follow procedures and standards – short cuts could be costly. Be consistent as a leader.

5S is often viewed as one of the first stages of a lean manufacturing change process on the shop flooor. Consider its principles as the foundation for a world class management approach also.