Industry focus 26 Filtration+Separation July/August 2005 Centrifuge focus: the alternative to ‘new’ – upgrade and refurbishment B CSL’s David Atkinson discusses the options (with examples) available for refurbishing, retrofitting and upgrading existing centrifuges to satisfy a variety of process requirements; namely considerations of cost, operational cleanliness and compliance with national and international legislation. Why bother? The reasons to refurbish or upgrade an existing centrifuge are as many and varied as the processes on which they operate. To obtain the best possible result from any refurbishment or upgrade project, it is of vital importance that the centrifuge refurbishing company has a complete and accurate understanding of the user's process and operating requirement. With regular maintenance, a centrifuge is capable of many years reliable and trouble-free service. Only after long periods of long arduous duty do vital components such as resilient mountings, oil seals, bearings and other moving parts need serious attention or replacement. In many instances the casing and main structure of the machine remain in reasonable condition, and at the end of its life-cycle, can often be refurbished and retrofitted with ‘state- of-the art’ ancillaries – even after 10 to 15 years of continuous operation. Depending on the condition of the original machine, user expectations and financial constraints, centrifuge reconditioning can provide an extremely cost-effective option, offering a wide choice of variables – from basic overhaul/refurbishment to an advanced upgrade more appropriate to current user requirements. As part of this refurbishment process, existing machines can be retrofitted with many of the latest features, including PLC based controls, improved feed and discharge arrangements and other recent refinements which often provide cost-effective benefits such as extended The image shows a centrifuge that has undergone a standard overhaul throughout the machine – including new bearings and bushes; new vibration isolators; the replacement of all elastomers with FDA approved material seals; the use of food grade lubricants; the design and supply of new VFD & S7 siemens based PLC panel + S & I operator panel; fully FAT; the addition of a new door interlock system. Certain upgrade requirements may involve compliance with industry related legislation covering intrinsic safety in hazardous areas (ATEX category 2 Directive 94/EC) or the Good Manufacturing Practice (GMP) requirements of the pharmaceutical industry.
Transcript
Industry focus26Filtration+Separation July/August 2005
Centrifuge focus:
the alternative to‘new’ – upgradeand refurbishmentB CSL’s David Atkinson discusses the options (with examples)
available for refurbishing, retrofitting and upgrading existingcentrifuges to satisfy a variety of process requirements; namelyconsiderations of cost, operational cleanliness and compliancewith national and international legislation.
Why bother?
The reasons to refurbish or upgrade an existingcentrifuge are as many and varied as theprocesses on which they operate. To obtain thebest possible result from any refurbishment orupgrade project, it is of vital importance thatthe centrifuge refurbishing company has a
complete and accurate understanding of theuser's process and operating requirement.
With regular maintenance, a centrifuge iscapable of many years reliable and trouble-freeservice. Only after long periods of long arduousduty do vital components such as resilientmountings, oil seals, bearings and other
moving parts need serious attention orreplacement.
In many instances the casing and mainstructure of the machine remain in reasonablecondition, and at the end of its life-cycle, canoften be refurbished and retrofitted with ‘state-of-the art’ ancillaries – even after 10 to 15 yearsof continuous operation.
Depending on the condition of the originalmachine, user expectations and financialconstraints, centrifuge reconditioning canprovide an extremely cost-effective option,offering a wide choice of variables – from basicoverhaul/refurbishment to an advanced upgrademore appropriate to current user requirements.
As part of this refurbishment process, existingmachines can be retrofitted with many of thelatest features, including PLC based controls,improved feed and discharge arrangements andother recent refinements which often providecost-effective benefits such as extended
The image shows a centrifuge that has undergone a standard overhaul throughout the machine – including newbearings and bushes; new vibration isolators; the replacement of all elastomers with FDA approved materialseals; the use of food grade lubricants; the design and supply of new VFD & S7 siemens based PLC panel + S& I operator panel; fully FAT; the addition of a new door interlock system.
Certain upgrade requirementsmay involve compliance withindustry related legislationcovering intrinsic safety inhazardous areas (ATEX category2 Directive 94/EC) or the GoodManufacturing Practice (GMP)requirements of thepharmaceutical industry.
Industry focus28Filtration+Separation July/August 2005
Certain upgrade requirements may also involvecompliance with industry related legislationcovering intrinsic safety in hazardous areas –Atmosphere Explosible (ATEX) category 2Directive 94/EC – or the Good ManufacturingPractice (GMP) requirements resulting fromthe necessary ultra clean conditions of thepharmaceutical industry – and also conformingwith the latest Good AutomatedManufacturing Practice – level or version 4(GAMP 4) Regulations.
In some instances, operators may requiremachines to be modified and upgraded tocomply with the strict guidelines,recommendations and inspection procedures ofthe Food and Drugs Administration (FDA) thatmaintain high levels of control through theutilisation of ultra-clean processing facilities.
These machines can be refurbished asvalidateable centrifuges with ‘clean-in-place’systems which ensure there is no cross-contamination between batches and that totalcleanliness is maintained during productchange-over.
Modifications to the control systems of existingmachines, including those operating in ATEXcategory 2 areas can include the supply of
purpose-built Programmable Logic Control-based (PLC) systems with Variable FrequencyDrives (VFD), local operator push buttonpanels or Human-Machine Interface (HMI) tosuit a particular process. It is possible to modify
the control philosophy to suit a variety ofprocess applications and maintain compliancewith Functional Design Specification (FDS),Factory Acceptance Test (FAT), and SiteAcceptance Test (SAT) protocols.
A Krauss Maffei peeler centrifuge that has been refurbished. The spec included; new bearings and sealsthroughout; the design and manufacture of new lubrication and hydraulic units; and the design andmanufacture of a new PLC-based control system.
Upgrades – some examples
• BCSL has recently carried out extensivereconditioning work on a number ofKrauss Maffei vertical basket centrifuges,installed to dewater gypsum from a FlueGas Desulphurisation plant at Drax PowerStation, East Yorkshire, UK. Themachines had been operating continuouslyfor more than 10 years and were generallyin need of refurbishment. To ensurecontinuity of the gypsum dewateringprocess, the machines were overhauled ona rolling “one in – one out” basis and werereturned to Drax in “new” condition.Maintenance Technician DuncanMackintosh explains that in addition to ageneral refurbishment, the machines hadtheir original feed control unitsreconditioned and installed with a newdesign of operating arm, which has actuallyimproved the machine's performance. "Toincrease efficiency even further, BCSL isnow in the process of developing a newdesign feed control head which will ensuregreater accuracy in the filling process."
• Another company that recently upgradedis Nobels Enterprises Ltd, of Stevenston,Ayrshire, UK, a manufacturer of industrialNitro Cellulose, which upgraded itshydraulic machines, giving whatengineering manager George Armstrongdescribes as “a more reliable, efficient
centrifuge.” He explained that the upgradehas lead to cycle times that have shorteneddue to quicker ramp times and, as arectifier is used on the drive motor, powerconsumption has been considerablyreduced. “The upgrade exercise hasenabled us to increase production andsupply more product to our customers onshorter lead times.”
• Maintenance Engineers Malcolm Ackerleyand Terry Palmer at Bayer Crop Sciences– a major producer of herbicides andfungicides – also reported that centrifugesmanufactured by Krauss Maffei, Rousselet,Alfa Laval and Broadbent had recentlybeen reconditioned and upgraded in anumber of ways to provide substantialbenefits at the company’s production sitein Norwich. An Alfa Laval centrifuge wasconverted from hydraulic to variable speedelectric drive – making the machinecleaner and much quieter. A new feedpipe, wash pipe and feed controller with allthe wetted parts in titanium were speciallymanufactured and installed as part of theoverall refurbishment process. “Being ableto vary the speed of this machine hasgiven us more process options and the newfeed controller enables us to maximisethroughput,” says Palmer. “Two of theRousselet centrifuge baskets, which wereoriginally clad in titanium, have beenreplaced with solid baskets in the same
material. On one occasion we found that,in the middle of a process run, the casingof a Rousselet centrifuge had beendamaged and needed a fast turn round.The centrifuge casing was relined, in veryreasonable time, with no adverse effects onproduction.”
• And at a pharmaceutical company, anexisting basket centrifuge was proving tobe problematic because of the use of amanual “lift out” bag. This created anumber of product handling issues,including spillages around the productionarea and the possibility of contact with theproduct during transportation to thebagging-off stations. There was also apossibility that, when the lift-out bags wereremoved from the basket, degradation ofthe product’s crystalline structure couldpresent further problems. Followingdiscussions with BCSL, the user agreed tohave the existing centrifuge retrofittedwith a suction discharge system (see imageon page 29.) This was installed on site toremove product from the basket and,under controlled conditions, transfer it to asealed container prior to bagging off. Tocomplete the upgrading of this machine itwas fitted with a pneumatically operatedcover and electric drive – making it notonly safer but eliminating the possibility ofcontamination by oil.
Industry focus 29Filtration+Separation July/August 2005
New machines for old
Standard centrifuge refurbishment work is highly competitive and cost-effective when compared with the purchase of new machinery. Even insituations where spare parts are unobtainable, these can be produced on abespoke basis, from a variety of specified materials, including super duplex,monel and other special alloys. Replacement internal baskets can bemanufactured to user requirements from materials such as stainless steel,Hastelloy and Titanium.
One of the most common concerns of companies using older centrifuges,centres around the need to refurbish machines in compliance with theATEX Directive 94/9/EC. Older machines, operating in the old zone 1hazardous (now ATEX category 2) areas, now need to be modified toinclude safer drive systems, internal atmosphere control, satisfactory
electrical earthing ofrotating parts andcontrol of other sourcesof heat, including themonitoring of bearingtemperature.
Where changingproduction requirementsinvolves the processingof hazardous materialssuch as solvents,machines can usually beretrofitted withnitrogen-purging systemsinstalled to remove thebuild-up of potentiallyexplosive vapour andkeep the atmospherewithin the centrifuge ata safe level of oxygen
during normal operation and discharge. Operating as an integral part of thecentrifuge, the purging system is controlled by the centrifuge control systemand incorporates a separate screen on the operator interface that allows theuser to monitor and control the purge.
Conversion from hydraulic to electric drives
Many centrifuges, currently in service, are fitted with high maintenancehydraulic drives and plough discharge mechanisms that are fast becomingoutdated. The hydraulic power packs installed on these machines areprone to leakages and use expensive filtration systems which require regularoil changes. Over time, many operators invariably find it difficult tomaintain 100% leak-free oil seals.
Hydraulic powered centrifuges can be retrofitted with electric drives andplough units that are totally clean and completely eliminate potentialcontamination from leaking oil. This type of conversion can providesubstantial cost-savings as the machine only uses power when the electricmotor is operating – there is no need to purchase oil and no requirementfor a continuous supply of cooling water. •Contact:David Atkinson is service development manager at Broadbent CustomerServices Ltd (BCSL), which can refurbish, retrofit and upgrade any make ofcentrifuge operating across a wide cross-section of the international [email protected]
A Krauss Maffei peeler centrifuge that has beenrefurbished by BCSL. The spec included; newbearings and seals throughout; the design andmanufacture of new lubrication and hydraulic units;and the design and manufacture of a new PLC-basedcontrol system.
[machines in certain applications] now need to bemodified to include safer drive systems, internalatmosphere control, satisfactory electrical earthing ofrotating parts and control of other sources of heat,including the monitoring of bearing temperature.
