MechChem Africa February 2019

Mech Chem FEBRUARY 2019 AFRICA

This month: Coal Ash:Tapping into resource potential

Enhanced production for ion exchange resins

Responsible management of refrigerant gases

SA’s woven geotextile dewatering solution

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Asset, maintenance and risk management 8 Classic wear failures revisited Johannesburg based consulting engineer, Tim J Carter, talks about wear failures and the importance of using the best possible lubricants and lubrication strategies.

P U B L I C A T I O N S CR O WN

10 Local engine remanufacture saves time and money 10 Second extra heavy duty CNC for Metric Automotive 12 Risk management for industrial safety Materials handling 14 Hydroclone shines in diamond processing

Published monthly by Crown Publications cc Cnr Theunis and Sovereign Streets Bedford Gardens 2007 PO Box 140, Bedfordview, 2008 Tel: +27 11 622 4770 e-mail: mechchemafrica@crown.co.za www.mechchemafricamagazine.co.za Editor: Peter Middleton e-mail: peterm@crown.co.za Assistant editor: Phila Mzamo e-mail: philam@crown.co.za Advertising: Brenda Karathanasis e-mail: brendak@crown.co.za Design: Darryl James Publisher: Karen Grant Deputy publisher: Wilhelm du Plessis Circulation: Brenda Grossmann The views expressed in this journal are not necessarily those of the publisher or the editors. P U B L I C A T I O N S CR O WN P U B L I C A T I O N S CR O WN 2015/02/10 01:17:09PM

2015CROWN LOGO february.indd 1

The successful performance of Weir Minerals’ Cavex hydrocyclones at a diamond mine in South Africa’s Northern Cape Province has proved the technology’s applicability in dense medium separation (DMS) plants that treat diamondiferous material.

15 World-class supply for African customers 16 Recent orders put Kwatani above the rest

17 Chute system reduces risk of dust contamination 18 Adapted excavators improve port operations 19 Spiral technology brings value to minerals Heating, cooling, ventilation and air conditioning 20 Responsible management of refrigerant gases MechChem Africa talks to A-Gas sales manager, Mike Labacher, about current trends with respect to refrigerants and the need for more responsible lifecycle management of these gases. Water and wastewater processing 22 Enhanced production for ion exchange resins LANXESS, is investing in its ion exchange resin production facility at its Leverkusen site in Germany. Rainier van Roessel of LANXESS AG explains. 22 New Lewabrane HP reverse osmosis series 25 Cast resin transformers for Zuikerbosch WWTW 26 SA’s woven geotextile dewatering solution Innovative engineering 30 Coal Ash: Tapping into resource potential According to Mark Hunter, general manager of the South African Coal Ash Association (SACAA), South Africans stand to make a fortune out of the tons of ash produced by generators annually. REGULARS 2 Comment: The state of the nation? 4 On the cover: Endress+Hauser’s SANAS accredited laboratory Preston Reddy talks about verification and calibration and the advantages of using the company’s local SANAS-accredited Flow Calibration Centre. 6 SAIChE News: Innovation award for Sasol R&T team 28 Product and industry news 32 Back page: REFLUX Classifier increases mining productivity

Transparency You Can See Average circulation July-September 2018: 5 027 Printed by: Tandym Print, Cape Town

Publisher of the Year 2018 (Trade Publications)

Front cover: Endress+Hauser Contact: Kgomotso Makhobela +27 11 262 8004 kgomotso.makhobela@endress.com www.za.endress.com

February 2019 • MechChem Africa ¦ 1

The state of the nation?

I have never liked the term SONA. It hides from the core purpose of holding the event, which should be to thoroughly analyse where we are as a country so that we can develop improvement strategies. Byhonestly andopenly appraising the state of the nation, we ought to be able to identify the prob- lems holding us back and how best to resolve them. Maybe my views are too system’s bound, though, influenced by technical procedures such as mainte- nance and risk assessments to optimise long-term equipment performance. We have come to expect the annual SONA to be laden with political rah-rah, promises and assurances of abetter future–and in recent times, EFFdisruptions linked to ‘paying back the money’. President Cyril Ramaphosa started off his 2019 address by disarming his entire audience with a joke about his reluctance to sing, while expertly reminding us of his ‘ThumaMina’ catchphrase of 2018andneatly implying thatMmusiMaimanemight be an ally in sing- ing for Julias Malema should he ever have to present the State of the Nation Address himself. Onto the evaluation of our nation: The need for jobs was, as always, highlighted, with the Presidential Jobs Summit mooted in response to double the num- ber of jobs created every year. Ramaphosa also cited his Youth Employment Service, which sets out to put unemployed youth into paid internships. With respect to corruption, he promised to cure our countryof its “corrosiveeffects”; and to implement moves to stabilise and restore the credibility of state institutions such as the NPA, SARS and SAPS. He listed five tasks that will underpin everything Government does this year: accelerating inclusive economic growth and creating jobs; improving the education system and developing the skills we need now and into the future; improving the conditions of life for all SouthAfricans, especially the poor; stepping up the fight against corruption and state capture; and strengthening the capacity of the state to address the needs of the people. On land, he aims to expand agricultural output and promote inclusion, using “massive areas of unproduc- tive land that exist in South Africa”, including land parcels owned by the state. The big anticipated announcement was about the unbundling of Eskom into three separate entities – generation, transmission and distribution – which came with a warning, that bold decisions and decisive action may have painful consequences but would be “even more devastating if we delay”.

Peter Middleton

President Ramaphosa acknowledged that cor- ruption and mismanagement have severely damaged many state-owned companies and assured that evi- dence of criminal activity must be evaluated. “Where there is a basis to prosecute, prosecutionsmust follow swiftly, and stolen public funds must be recovered urgently,” he said. Overall, who can deny that our president is aware of the problems we face and that he is attempting, albeit at a snails’ pace, to address them. He is an astute politician andmuch easier to listen to – and like – than his predecessor. In spiteof reneweddetermination todeal with cor- ruption and to address the challenges at Eskom, the ANC’s disgraced and disbanded provincial executive committee (PEC), which includes its allegedly corrupt leader, Supra Mahumapelo, are back in charge in the North West Province; and Eskom has begun imple- menting Stage 2, Stage 3 and Stage 4 load shedding after up to seven of its generators tripped. In addition, the ‘good news’ that unemployment dropped from27.5%inQ3 last year to27.1%inQ4was reported.Wenowhave6.1-millionunemployedpeople between 15 and 64 years of age and only 16.5-million employed people. Events and statistics such as these bring intomuch sharper focus the real state of our nation. We are in a crisis of our own making and it is very difficult to see how political will alone can drag us out of it. Much has been made of Eskom’s financial failings, which have directly led to maintenance ‘neglect’. More concerning, however, is the recent emergence of poor reliability being experienced at the Medupi and Kusile plants, which were expected to relieve the burden on the older power stations. Suggestions are that this is design-related, which means it will af- fect every unit. According to Titus Mathe, the repair costs may amount to a further R8‑billion and “might take years to fix”. Rating agencyMoody’s is sceptical about the effect of unbundlingEskomas ameans to resolve its financial and technical woes, whileCosatu sees it as a back door to privatisation. What is clear is that, when it comes to strategic, expensive and highly technical SOEs such as Eskom, political interference along with corruption leads to disaster. On the other hand, competence – manage- rial, financial and, most importantly, technical – are absolutely vital. And many of these competences now lie in the private sector. q

MechChem Africa is endorsed by:

2 ¦ MechChem Africa • February 2019

Preston Reddy, business driver for Service at Endress+Hauser SouthAfrica, talks about his company’s verification and calibration offerings, the difference between them and the advantages of using the company’s local SANAS-accredited Flow Calibration Centre to get the best out of the monitoring instruments at the heart of plant control. Endress+Hauser’s SANAS accredited

T echnical experts frequently come across the metrological terms: cali- bration and verification. For some, these two concepts are known and easy to differentiate, but these terms can also cause confusion as their definitions and requirements may not be easily understood. According to the International Vocabulary of Metrology (VIM), the term verification is defined as the ‘provision of objective evidence that a given item fulfils specified requirements’ . An interpretation of verification consists of checking calibration results as ‘objective evidence’ to comply with a ‘specified require- ment’ , such as theMaximumPermissibleError (MPE),definedeitherbyamanufacturer,alegal metrologyorganisationoranend-userinapro- cess application. This situation is illustrated in Figure1, where the device’s relativemeasure- menterrorsobtainedbythecalibrationrigturn out to be smaller than the MPE, meaning that the flowmeter calibration in this example (the item) fulfils the specified requirement. Endress+Hauser’s on-site verification offerings include Heartbeat verification; and In-lineultrasonic clamp-onverification, which each have their own strengths.

nostics solution that continuallymonitors and records data about the functional reliability, safety and accuracy of its instruments. The new Heartbeat-enabled Proline generation flowmeters,forexample,offerunprecedented diagnostic coverage fromthemeasuring tube to the outlet. This ensures an extremely low residual risk of a passive protective function failure. Traceable factory calibration and redundant internal references complement the safety-by-design principle with minimal failure rates in accordance with IEC 61508. In terms of verification, Heartbeat Technology can be used to: • Verify the correct function of themeasur- ing device according to the specifications and generate a protocol – without inter- rupting the process flow. • The automatically generated protocol is structured to support the documentation required by internal and external formali- ties, laws and standards. In-line ultrasonic verification In-line verification involves the temporary use of a second flowmeter inserted into the sameflow line as the instrument that requires verification. The portable ultrasonic Prosonic Flow 93T flowmeter, for example, is ideal for this purpose. Designed for temporary moni-

toring and test measurements with clamp on sensors, these units use batteries, making them independent of mains power. Data from these economical ultrasonic units can be saved via a USB port to a flash driveorotherstoragedevicewithouttheneed for additional software, making them ideal for use for verificationmeasurements at existing flowmetering points. Features of in-line ultrasonic instrument verification include: • The in-line verification is a direct com- parison of the results obtained from the Unit Under Test (UUT) against the In-line Ultrasonic clamp-on flowmeter. • A verification certificate, which indicates the measured error between both the measurements, is generated fromthedata. Calibration made easy According to the VIM, calibration is a proce- dure ‘to establish a relation between a quantity value given by a UUT and a reference quantity value (ref) obtained by a calibration rig, within its associated measurement uncertainty’ . Themainobjective is tocheck theaccuracy of measurements by comparing the device in question with that of a known traceable reference. One fundamental requirement for carrying out a calibration is that the ref-

Heartbeat Technology™ Heartbeat is Endress+Hauser’s built-in diag-

Endress+Hauser’s SANAS-accredited Flow Centre was designed in Switzerland to specifically suit South African requirements. Four Promass Coriolis Master Meters are used to compare the customer’s flowmeter (UUT) response and accuracy across the applicable flow range.

4 ¦ MechChem Africa • February 2019

⎪ Cover story ⎪

verification and calibration laboratory

erence system must have traceability to the fundamental units of measurement needed to reproduce the unit flow. Calibration of devices assist in: • Meeting the requirements of industry regulators and standards such as FDA, IFS, ISO 9000, etc. • Preventing inaccurate measurements influencing thequality of thefinal product. • Preventing energy or material losses due to improper control. • Preventing safety issues arising as a result of poor monitoring. Endress+Hauser’s Calibration offerings fall into two categories on-site and laboratory- based calibration. On-site calibration involves transporting portable rigs and buffer solutions to where the instrument is being used at a plant. On- site calibration is performedby highly trained Endress+Hauser engineers. Convenient and cost-effective, this approach removes the need to send instruments off-site as special- ists come to the plant, which keeps downtime to an absolute minimum. On-site calibration also offers the highest flexibility because calibration can be sched- uled according to the process demands of the application. Laboratory calibration services can be carriedout at Endress+Hauser or a thirdparty laboratory on a single-service or repeat con- tract basis. Endress+Hauser South Africa is now ideally placed to carry out calibrations of customers’ instrumentation from its SANAS accredited facility in Sandton. Calibration Services performed in labora- tories such as this have the advantages of the lowest calibrationuncertainty and thewidest possible calibration ranges. SANAS accredited flowmeter lab Endress+Hauser’s metrology laboratory at its South African Head office in Sandton is a SANAS-accredited flowmeter calibration laboratory, a status that is internationally recognised in accordance with ISO 17025: General requirements for the competence of testing and calibration laboratories. Placing Endress+Hauser ahead of its local competitors, this service ensures that the company’s flowmeters as well as those from third parties can be verified and calibrated to performwithin their expected specifications. The company’s calibration rig supports customers’ process safetyandproduct quality requirements by ensuring that the high preci- sionflowmeters theyuse complywithprocess safety requirements while also delivering optimum process control. SANAS accreditation offers customers

Figure 1: An example of a verification task based on a flowmeter’s Maximum Permissible Error (MPE).

traceability of the calibration results to national and international standards via an uninterrupted ‘traceability chain’ of compara- tive measurements and calibrations. The Flow Centre was designed by Endress+Hauser’s Product Centre − Process Solutions (PCPS) inSwitzerland to specifically suit South African requirements. The rig can accommodate flow calibrations for instru- ment sizes from DN08 to DN100 and flow rates of up to 85 m 3 /h. It uses a closed loop water system with a 200 ℓ tank, and pumps with variable speed drives enable accurate control and optimum stability of flow rates across the calibration range. Four Promass Coriolis Master Meters are used to compare the customer’s flowmeter (UUT) response and accuracy across the applicable flow range. These Master meters are calibrated annually by Endress+Hauser in Switzerland for traceability to ISO 17025 international standards. To meet the requirements of ISO 17025, themeasurement uncertainty – the accuracy and repeatability of the calibration rig – is based on the uncertainty of each component in the measurement process. This enables ISO 17025 accredited rigs to be compared with each other. In addition to the technical requirements, ISO 17025 defines obligatory administrative controls andprocedures tobe followedby the calibration facility. Topics suchas organisation andmanagement, document control andcom- plaint management are addressed to ensure the calibration facility functions in a manner that promoting quality results. Only trained calibration specialists who have completed training inEndress+Hauser’s Product Centres in Switzerland are assigned

Calibration Management Service helps plant operators optimise performance and maintenance so as to deliver the lowest possible product cost. to the local Flow Centre. SANAS accreditation can be seen as a bonus for all South Africans – an assurance of knowing that, for liquids such as petrol, oil or fabric softener, customers are receiving exactly what they are paying for. Calibration Management Service Endress+Hauser also offers an extensive CalibrationManagement Service, which takes theday-to-daymanagementresponsibilityfor a customer’s calibration functions and opti- mises calibration schedules and procedures according to the process needs. The key goals of this outsourcing service are: improving customers’ plant operations; securing calibration process compliance to internal and external regulations; and reduc- ing maintenance and total costs. “We at Endress+Hauser are always look- ing for ways to help clients to optimise their maintenance, ultimately, so that they get the best possiblevalue fromthe instruments used on their process plants,” says Preston Reddy, businessdriverforServiceatEndress+Hauser South Africa. q

February 2019 • MechChem Africa ¦ 5

Innovation award for Sasol R&T team

SAIChE’s 2018 Innovation Award was presented to Sasol Group Technology’s Research and Technology team, consisting of Enrico Caricato, Herman Hoffeldt, Ricky Kotze, Jared Lloyd, Nico Prinsloo and Carel Swanepoel for its work on the development of an automated bench-scale control system for evaluating reforming catalysts. Nico Prinsloo helps MechChem Africa to summarise the innovation.

T he SAIChE 2018 Innovation Award was celebrated with a luncheon at the Wanderers Club in Johannes- burg and alcohol free champagne, in keeping with Sasol’s strict safety protocol. The winning team from Sasol’s Research and Technology division won the award for an automated control systemthey developed for the bench-scale evaluation of new naph- tha reforming catalysts for their continuous catalytic regeneration (CCR) plants. “We at Sasol have an ongoing need to model the performance of commercial catalyst’s on a bench scale, to allow us to continuously improve the performance of our Fischer-Tropsch (FT) syngas-to-liquid process,” Prinsloo says. “Specifically, we need to evaluate new commercial catalysts at a constant research octane number (iso-RON) – and this needs to happen on the benches of our laboratories,” he explains, adding that this is has long been a significant challengebecause theparameter changes that occur while reforming a bench- scale raw naphtha sample happen too fast

for manual control, especially when dealing with naphtha’s derived fromSasol’s FT-based coal-to-liquids (CTL) process. “Sowe needed to automate themanipula- tion of process conditions and this is what we have managed to achieved in this work,” he says. Catalytic naphtha reforming is used at all refineries to convert naphthas – the low-oc- tane raw liquidhydrocarbons usually distilled from crude oil – into high-octane liquid prod- ucts called reformates. “These reformates are then used to blend the high-octane fuels we use in our motor vehicles,” he continues. “The process is a true industry workhorse and almost every refinery in the world has such a processing unit to produce blend products with the octane numbers required,” Prinsloo informs MechChem Africa . Naphtha reforming at Sasol In essence the naphtha reforming process used at Sasol’s coal to liquids (CTL) complex, involves the isomerisation and aromatisation of feeds containing paraffins such as heptane,

Professor Lizelle Van Dyk, associate professor of chemical engineering at the University of the Witwatersrand, presents SAIChE’s Innovation Award for 2018 to Nicolaas Prinsloo, representing Sasol Group Technology’s Research and Technology team. and Vimal Bhimsan, vice president of Process Development at Sasol. Photo: Cara Prinsloo octane and nonane into highly branched and aromatic liquid hydrocarbons. “We typically look for molecules with six or more carbon atoms, which we refer to as C5+ naphthas.

Sasol’s award winning Research and Technology team with SAIChE board members, from left: Enrico Caricato; Lizelle Van Dyk (SAIChE); Carel Swanepoel; Nico Prinsloo; Craig Sheridan (SAIChE); Vimal Bhimsan; Herman Hoffeldt; Ricky Kotze; Jared Lloyd; and Gerhard Marais. Photo: Cara Prinsloo

6 ¦ MechChem Africa • February 2019

⎪ SAIChE IChemE news ⎪

“The critical number for a fuel blending product, however, is its research octane number (RON), which governs the fuel’s suit- ability for use in different modern engines,” says Prinsloo, adding that Sasol’s commercial CTLprocesses strive toproduce fuel products with specific target RONs. “The catalysts are critical for achieving this. They are critical for speeding up the re- action and making it more efficient. But they operate at high temperatures and they coke up, so they need to be routinely regenerated to keep them working effectively. Typically, the catalyst will deactivate within a week under the process conditions in a laboratory reactor,” he says. “The naphtha reforming technology has evolved from a simple fixed bed reactor sys- tem, where the catalyst has to be removed to be regenerated externally, to a highly sophisticated system where the catalyst is continuouslymoved through the reactor into the regenerator and back,” Prinsloo explains. In the regenerator, the catalyst is purged to remove hydrocarbons and hydrogen, the coke is burned off the catalyst before it is re- chlorinated and reduced. “Thewhole process is known as continuous catalytic regenera- tion (CCR) and it is currently used in Sasol’s modern plants in the manufacture of our high-octane fuel blending products,” he says. He adds that the paraffinic feed used in the Sasol process is particularly lean, which requires a much higher temperature to pro- duce the specific octane number required. This lowers product yield and causes catalyst to degenerate far more quickly. “Pushing catalyst andprocessingboundar- ies has always been imperative at Sasol. This has become especially true when targeting reformatewith a RONabove 95while retain- ing an acceptable yield and keeping within commercial fuel specifications, particularly with regard to benzene. The bench-scale challenge Akey role of Sasol’s Research andTechnology team is to seek out new and better catalysts for use in its CTL plants. “We routinely per- form bench-scale tests of catalysts for use in onour FT refinery processes using conditions that are as close as possible to those in our production units,” Prinsloo continues. But doing this manually presents chal- lenges. “First, we are looking to see the effect of the catalyst on the yieldof the targeted fuel anditsRONnumber.Ideally,thewholesample collected needs to have the same RON, but this can be difficult to achieve because the catalyst is slowly deactivating as the test proceeds, sometimes faster than the sample can be analysed,” he says. “We also need to collect a large enough sample of the reformate to do engine analy-

Sasol’s Research and Technology team used a laboratory-scale Zeton catalyst testing system as the basis for its automated bench-scale control system for evaluating reforming catalysts.

ses, which can take a week for each sample,” he adds. The process involves several endothermic and exothermic reactions and temperature swings introduce significant variation in the productcomposition.“Thetemperatureofthe catalyticbeddirectlyaffects theRONnumber and, as well as keeping the temperature as uniform as possible, a gradual increase in bed temperature can be used to counteract the deactivation process,” Prinsloo tells MechChem Africa . Sasol’s new bench scale solution “The control system we developed can compare very small differences in the refor- mate yield when using different commercial catalysts,” he says. “By usingmultidisciplinary analytical and advanced process control techniques, we have achieved substantial im- provementinbench-scalenaphthareforming.” Summarising Sasol’s new bench process, he says that the RON of the product is con- tinuously measured while the temperature and the heat flow over the catalyst bed is accurately controlled. “We slowly ramp up the catalyst bed temperature based on real- time RON measurements of the reformate. In addition, the control loop maintains an exceptionally uniform bed temperature with far less heat flux drift across the reactor zone,” he says. The core innovation involved in achieving this was developing a way of measuring the RON in real time so that it couldbeused in the control loop to automate the whole process. “Octane numbers of reformate samples are measured in a number of ways. The most accurate of these is to use a calibrated CFR engine to determine a motor octane number (MON). But 500 to 1 000 ml samples are required before the test can begin, which takes at least aweek to reformat bench scale, so using this test routinely is impractical for research. “An alternative is to do detailed composi- tional analyses and spectroscopy, but special chromatographic systems have to be used

and, althoughused inmany large laboratories, the equipment requires specialised knowl- edge,isveryexpensiveandtheteststaketime. “Wehavedevelopeda cost-effective alter- native that canapproximate theRONnumber using simple gas chromatography (GC) for component separation, combined with more sophisticated calculations and modelling to arrive at an estimated RON and MON. These values are then occasionally calibrated against more accurate CFR engine tests. “None of these methods were suitable for real time use in a feedback-based control system, however,” Prinsloo says. “We therefore pursued the use of near- infrared (NIR) spectrometry. We used our historical GC RON estimates to calibrate a real time on-line NIR analyser and set it up to continuously monitor the reformate stream from the bench-test system. By adopting error-based feedback control between the output reformate octane number and the preset required RON, we are able to slowly adjust the bed temperature upwards to keep the activity level of the catalyst at the point where it produces a reformatewith the exact RON required,” Prinsloo explains. “This system has enabled us to generate 1 900 equivalent octane number analyses that were corroborated via only 80 CFR engine tests, which translates into a more than 20-fold reduction in the testing load for laboratory octane number determination. “And this has already benefited our pro- duction units. By identifying catalysts better suited to our processes, we are achieving significantly better yields while lowering catalytic reforming demands and associated costs,” he concludes. A project worthy of winning any innova- tion award. q Acknowledgements: This work has been shared with the international community via a keynote lecture byNico Prinsloo at the 2016CATSA con- ference and a paper published in the American Chemical Society’s Industrial Engineering and Chemistry Research journal of May 2017.

February 2019 • MechChem Africa ¦ 7

Johannesburg based consulting engineer, Tim J Carter, B.Tech, C.Eng, FIMMM, talks about wear failures and the importance of using the best possible lubricants and lubrication strategies. Classic wear failures revisited

I n any engineered system, wear is inevi- table and is, ultimately, the life-limiting factor. The life of an engineered system is therefore inevitably linked to thewear properties of the system in the environment in which it is operated. Wear failures are not new and few are novel. They do, however, vary in their impor- tance.Wear lifemust be, of necessity, related to the system inuse. In, for example, an air-to- air missile, a wear life of a few minutes is ac- ceptable, since it then exceeds the flight time and the device will self-destruct. A Formula 1 racing car engine needs only to function for about five hours, after which it will be either re-built or discarded. One motorcycle race engine was known to have had a usable life of only about 750 km. A replacement hip joint, however, needs to operate without maintenance or external lubrication for several decades. This operat- ing period is known as the wear design life, and failure to achieve it will allow an enemy aircraft to escape, a motor racing driver to say rude things about his pit crew, or a person having to return to hospital to have his or her hip joint replaced prematurely. Axle drive gears A load-haul-dump vehicle is a specialised formof front-end loader, designed to operate within the confines of an underground mine. Frequently operated by remote control

because of the hazards of falling rock indeep- level mining operations, these vehicles live, of necessity, ahard life. Failure involves recovery of the vehicle to the surface for repairs and redeployment to the underground work site after repairs, both of which add to the cost of repairs and to prolonging down time, leading to significant production loss. In this example, the vehicles were prone to failure of the drive axle gears after about 8 000 to 10 000 hours for a new axle and about 2 200 to 2 400 hours for a re-manu- factured unit. When a re-manufactured axle suffered gear failure after only 1 800 hours, a warranty claim triggered an investigation into the cause. Metallurgical examination of both com- ponents showed no deficiency to which failure could be attributed. Both were of a suitablematerial andhadbeenproperly case- carburised andhardened. Nomicrostructural anomalies were found, other than a little re- tained austenite in the hardened surface. Also, the case depths, measured by hardness traverse, were considered satisfactory. The investigation therefore turned to the operation of the vehicle. It was reported that the manufacturer specified a lubricant to MIL-PRF-2105E, which contains a range of lubricant grades, and the mine had selected a premium quality 80W90 oil, which was the only gear oil available on the mine to prevent mistakes during top-up. This oil has a maxi-

mum tempera- ture rating of 35EC, which is low when com-

pared to the ambient temperatures found in deep mining operations where the rock temperature canexceed45 °C. Achange toan 85W140grade,withamaximumtemperature tolerance of over 65 °C has eliminated the problemandnofurtherfailureshaveoccurred in more than three years.

Bearings Plainbearings usually give a long and trouble-

a

b

Figure 1: Both the crown wheel and pinion for the underground front-end loader were severely worn. It was noted that neither exhibited any signs of misalignment: a) Crown wheel wear; b) Pinion wear.

Figure 2: Five of the big end bearings from an aircraft engine after a lubrication failure. The sixth bearing was completely destroyed.

Frequently operated by remote control because of the hazards of falling rock in deep-level mining operations, underground downtime associated with repairs of load haul trucks can lead to significant production losses.

8 ¦ MechChem Africa • February 2019

⎪ Maintenance and asset management ⎪

a

a

a

b

b

Figure 5: a) Inner race from a high speed bearing after bearing after lubricant failure; b) Rolling elements from a high-speed lubrication failure showing melted cage debris.

Figure 3: a) Arc pitting on a bearing raceway; b) Micro-cracking within arc pit.

b

Rope sheave The sheaves used to change the direction of a wire rope used for hoisting suffer from wear as a result of the unavoidable metal to metal contact. Whilst this wear can bemitigated by proper lubrication, it is the life-limiting factor for a sheave ineither a craneor aminewinder. Wear occurs in the tread area of a sheave, where the contact pressure is highest, and usually affects one side more than the other due to the angle at which the rope enters the sheave, known as the flight angle. (Figures 6a and b). This wear can be detected either visually or, if the sheave is covered with rope lubricant, by feel, since it leaves an irregular- ity in the tread surface in the shape of the winding rope. Fretting When two surfaces are in relative cyclic motion without lubrication, adhesive wear, known as fretting will occur. This phenom- enon results in pitting, from which fatigue can initiate leading to failure of one or both components, (Figure 7). This phenomenon can be avoided by either preventing the relative movement of the surfaces, or by treating themwith a solid lubricant to prevent adhesion and wear. Conclusion While wear is inevitable wear failures can be avoided by acting in time and by lubri- cating the contact surfaces to best suit the application. q Figure 7: a) Fretting on the external surface of a taper shaft; b) A fatigue failure initiating from of a taper shaft.

a

b

Figure 6: a) Wear of one side of a sheave; b) Failure of a sheave through wear. in service, rolling contact loadingswill initiate rolling contact fatigue leading to spalling of the surface and failure of the bearing. Rolling contact fatigue will affect any two surfaceswhere rolling contact under load oc- curs, and gears are no exception. Pitting due to rolling contact fatigue is common where heavy loading is encountered. If a rolling element bearing is subjected to heavy loadings whilst stationary, the rolling elements can indent the raceways, causing brinelling. A similar effect, known as ‘false brinelling’ occurs when a bearing is allowed to vibrate or oscillate through a small angle of rotation. Whilst the two appear to be similar, the caus- ative factors are different. Whilst brinelling is a purely mechanical mechanism, usually occurring in a single loading event such as an impact, false brinelling is a wear process and occurs over a period of time. If the bearing is operating at high speed, the primary function of the lubricant is that of coolant, to dissipate the heat generated by the elastic strain produced by the loadings on the bearing. If the supply of lubricant is insufficient to remove this heat, the unit will rapidly overheat and the rolling elements and cage will melt.

free life when properly supplied with an ap- propriate clean lubricant at the correct pres- sure and temperature. Lack of any of these, lowpressure,hightemperatureordebrisfrom either external contaminationor normal wear will quickly destroy the bearing, usually with catastrophic results (Figure 2). This set of sixbig-endbearings fromanair- craft engine failed through lubrication failure, resulting in the destruction of the engine and a narrow escape for the pilot. The passage of an electric current through a rolling element bearing will lead to arc pit- ting and the formation ofmicro-crackswithin the pit (Figure 3). Such damage will seriously limit the remaining life of any rolling element bearing, in a heavily loaded unit to a few minutes. Rolling element bearings normally suffer wear in three distinct phases during their life. During initial operation, the raceways and rolling elements are burnished, removing the machining marks left by the manufactur- ing process. Later, the raceways gradually dull, acquiring a grey appearance caused by abrasion from contaminants in the lubricant. It is at this point that the bearing shouldbe discarded and a replacement installed. If left Figure 4: Rolling contact fatigue in a bearing leading to spalling of the raceway.

February 2019 • MechChem Africa ¦ 9

Local engine remanufacture saves time

As South Africa looks to make greater use of natural and landfill gas in the generation of electricity, it’s a reassurance to the market that the country has world-class engine component remanufacturing capacity to optimise the lifespan and reliability of these generating sets.

“ M aking more use of gas as a power source is an exciting prospect for South Africa, both in terms of its reason- able cost and its lower environmental impact. Equally positive is that the expertise and state-of-the-art equipment to remanufacture theseengine components alreadyexists in the country,sodoingtheworklocallysupportsthe economy, reduces turn-around times and cuts costs,”saysAndrewYorke,operationsdirector of Metric Automotive Engineering. Henotes thatwhilenatural gas is generally a clean burning fuel, landfill creates a much harsher environment for an engine, as it is difficult tocontrol the level of contaminants in gas that emanates fromanyparticular landfill. This significantly reduces the intervals that the enginewill require betweenmaintenance interventions.

“The relatively poor quality of gas requires advanced ignition monitoring systems in the en- gine, but the wear rates remain high due to the highly abrasive post-com- bustion residue, de- spite filtering of the gas,” he says.

Heating of the head prior to valve seat sleeve installation.

altogether when it comes to diesel engine component remanufacturing. What is important is that the machining centres provide consistent accuracy levels resulting in a superior quality remanufac- tured engine block. Each centre has the ca- pacity tohandle6.5m long blockswith ease. Yorke notes that operating two of these large three-axis computer numerical con- trolled machining centres will enable the company to offer a faster turnaround to its customer base. He does caution, however, that thenatureof block repair is a significant remanufacturing process and not simply a ‘skim over’. “These are not light repairs which take only a few hours,” says Yorke. “This type of machining, which will see the block being returnedback toOEMspecification, is done over a number of days depending on the condition of the block,” he points out. This equipment is complemented by the company’s almost 50-year track record in remanufacturingdiesel engine components, a capability that has long been acknowl- edged by all engine manufacturers and their distributors who work closely with our company. q the engines is usually between 1.0 MW and 10 MW. The company also provides custom- ers with service exchange units, to enhance efficiency in the maintenance process and reduce downtime. “Service exchange units allow customers to have remanufactured components like cylinder head assemblies readily available to take to site when worn components need replacement,” he says. “These engines are

“With natural gas, for example, cylinder heads will need to be replaced every 20 000 to30000hours.Withengines burning landfill gas, however, they could require attention as early as every 5 000 hours.” Metric Automotive Engineering has al- ready been conducting work for customers in the both the natural gas and landfill gas segments, where the generating capacity of

Second extra heavy duty CNC for Metric Automotive Metric Automotive Engineering recently commissioned its secondRottler F109extra heavy duty multi-purpose CNC machin- ing centre to meet a significant increase in demand for quality large diesel engine component remanufacturing. components is a result of engine users placing greater emphasis on scheduled refurbishment programmes. He says this is an attempt tomitigate against unscheduled downtimecausedbymachine replacements, which can have catastrophic results.

Andrew Yorke, operations director of Metric Automotive Engineering, says the increased demand for large diesel engine

“The trend where operations wait for engines and their components to reach the point of failure before attending to

much needed repairs or refurbishment is start- ing to wane,” say Yorke. “This is apparent across the earthmoving, con- struction, mining, power generation and railway sectors as we see more accurate condition mon- itoring starting to be implemented.” The Rottler F109 machining centres at Me t r i c Au t omo t i ve Engineering’s facility in Johannesburg are two of only 18 operatingworld- wide and place the com- pany in another category

Increased demand from customers has seen Metric Automotive Engineering add a second Rottler F109 CNC machining centre to its facility.

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⎪ Maintenance and asset management ⎪

and money

Above: Machinist fitting valve seat sleeves. Far left: Machinists preparing a cylinder head. Left: Cylinder head with valve seat sleeves fitted. remanufacturing diesel and gas engine components to meet the exacting original equipment manufacturer (OEM) standards,” concludes Yorke. Other items that the com- pany remanufactures include valve-train components,connectingrods,crankshaftsand cylinder blocks. q

maintenance schedule to optimise the performance and lifespan of these engines, while delivering lowest cost of ownership to theoperator and reliableenergy supply to the end-customer. “It is the skilled staff atMetricAutomotive Engineering who have been hard at work

designed to have certain major components replaced in thefield, so itmakes no sense tobe procuring these services from abroad where most of the original equipment comes from.” Lastly, Yorke highlights the vital impor- tanceof highqualityworkmanship inconjunc- tion with a disciplined and well-resourced

February 2019 • MechChem Africa ¦ 11

The Occupational Health and Safety Act (OSH Act) requires companies to take steps in order to protect workers and the public from injury and death in the workplace. The Act has been under review since 2008 to align it with international standards. Risk management company, MMRisk, talks us through risk management, compliance and legislation Risk management for industrial safety

T he Major Hazard Installation (MHI) Regulations, promulgated under the Occupational Health and Safety (OHS) Act (Act No. 85 of 1993) aims to protect personnel and members of the public from the impacts of fires, explosions anddispersionof toxic vapours resulting from industrial accidents. Under the regulations, all industrial facili- ties handling, storing, and processing hazard- ous materials such as liquefied petroleum gas, ammonia, carbon dioxide are required to quantitatively analyse and assess the risk associated with these installations. Another major requirement for these MHI sites is the compilation of an Emergency Response Plan (ERP), which requires a pre- liminary risk assessment to identify potential risk scenarios. “Our initial risk analysis process at MMRisk involves mathematical modelling to determine the types and sizes of fires and explosions that may result from accidental release, as well as statistical modelling to determine the likelihood of accidents occur- ring on these sites,” says Motlatsi Mabaso, director, MMRisk. “From the mathematical modelling we

determine the numerical magnitude or level of risk of each facility and make suggestions of risk prevention and mitigation measures in order to manage the risk and ensure it is reduced to broadly acceptable (BA) levels or levels that are as low as reasonably practi- cable (ALARP).” Mabaso says, determining the hazards is inherent in the design of the process and MMRisk applies these steps to the oil and gas as well as the mining and metals industries. “Weworkwith companies to identify haz- ards in their designs and to suggest methods ofmanaging thosehazards and theassociated risk. The most common method for this pro- cess is our offering of Hazard andOperability (HAZOP) studies. Ourmost popular service is Major Hazard Installation Risk Assessment, a service that is legally mandated in the OHS Act,” he says. Mabaso notes the compilation of ERPs at MHI sites is now standardised through the publication of a South African National Standard, SANS 1514: Major Hazard Installation: Emergency Response Planning (2018). This standard was published in December 2018 and is considered industry best practice for emergency response.

“The purpose of the standard is to ensure adequate organisation and communica- tion within the site and between the site and its neighbours to facilitate an effec- tive response in case of emergencies,” says Mabaso. “SANS 1514 is expected to become a legal requirement once currently underway amendments to existingMHI Regulations are completed.” Mabasoexplains that, as it stands,most stake- holders in the South African MHI industry – including the AIAs, owners and operators of MHI facilities and even the regulators – believe there is some difficulty in interpreting and applying the current MHI Regulations. These include: • Confusionaround thequantities and types of facilities that qualify for exemption. • The definition of ‘Impact on the Public’: Interpretation of the regulations by the various AIAs differ and the meaning of some of the somewhat vague phrases within the regulations is unclear. There is oftena rangeof interpretations depending uponwho is reviewinganMHI report, from an AIA, to the local authorities, and the national Department of Labour. • There is also the problem of standardisa- tion of the MHIs – two AIAs can give MHI Reports that look completely different – which also has cost and quality implica- tions for the client. Mabaso believes with the changes in the regulations, certain topics will be resolved –MHIs will be standardised as well as pricing in the market, for example – so that clients know irrespective of who they employ to conduct their assessment, the quality will be guaranteed. Implications of non-compliance If companies do not undertake some of the studies, they won’t be able to determine the Rationale for revising existing MHI legislation

MMRisk works with companies to identify hazards in their designs and operations and to suggest methods of managing those hazards and the associated risk.

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⎪ Maintenance and asset management ⎪

Summary of new SANS 1514 standard on Emergency Response Rolesandresponsibilities: TheMHIRegulationsdetailtherequirementsfor on-site andoff-site roles and responsibilities and the selectionof personnel who participate in emergency response. It also requires the site to detail what personnel are required to do in an emergency. This includes the roles of communication with neighbours and local authorities. Supporting information: The standard details the required supporting information in the ERP, including, for example, emergency contact details, layout plans, maps, the MHI Risk Assessment, etc. Emergency resources: The regulations details the types of resources the site should have for adequate emergency response planning, both in terms of personnel as well as equipment.

Riskmanagement: TheMHI details the requirements for riskmanagement onsite, including theuseofMHI RiskAssessment information inemergency planning, as well as other forms of risk management the site may choose to perform. Developing and writing the ERP: Techniques for writing the Emergency Response Programme (ERP) and the required content of the ERP are given in the standard. This includes the types of emergency scenarios to be con- sidered onsite aswell as howthe emergency procedures should bewritten. Administration of the ERP: Gives guidance on how the ERP should be controlled and administered to ensure its availability to staff and its cor- rect maintenance. Training and awareness: An ERP is only as good as the people enacting its requirements. An important factor to emergency planning is the training of personnel to ensure that they are aware of the ERP and its requirements and that they respond as expected during an emergency.

Documentation and record keeping: The ERP is required to be adequately documentedandtheregulationsdetailshowrecordssuchastesting,review and update records should be kept. Testing, reviewing and updating the ERP: Testing, reviewing and updating are probably the most important elements of emergency planning. The standard provides guidance on how best these should be done. LPG in bulk quantities: Risk Analysis of sites that handle Liquefied PetroleumGas (LPG) inbulkquantities requiremitigationmeasures includ- ed a review of the fire protection measures onsite, including adjustments based on the requirements of South African National Standard (SANS) 10087, which governs the management of LPG installations. Risk Analysis of bulk petrol and diesel storage terminals: Mitigation measures include studies to determine the impact of the types of bunding on risk to site personnel, the public and their assets. q

rapid growth phase and is growing its client base significantly every year. “The aim is to focus on a small number of niche services and to build our reputation as a thought-leader in the Process Safety and Risk Engineering space. We aim to steadily increase our mar- ket share year-on-year tobecome thebiggest supplier of these services in the country,” he concludes. q

level of risk on the public and personnel and may find themselves non-compliant with Risk Legislation. Consequences can include, amongst others. • Injury and death to people on and offsite. • Negative media coverage. • Reputation and brand damage. • Production stoppages by theDepartment of Labour and others.

• Insurer non-payment. • Litigation costs. • Compensation for injury and death. Future projections for the company MMRisk is currently the only 100% Black owned and, therefore, Level 1 BBBEE pro- vider ofMajorHazard Installation (MHI) Risk services, says Mabaso. The company is in a

February 2019 • MechChem Africa ¦ 13