THE CHANGING NATURE OF DIESEL ENGINE FUEL FILTERS FOR HIGH PRESSURE COMMON RAIL (HPCR) DIESEL INJECTION SYSTEMS
Bradley Crook (pages 86-93)
Over recent years the world has gradually witnessed the introduction of diesel engines equipped with advanced High Pressure Common Rail (HPCR) fuel injection systems. The introduction of new designs is primarily the result of new emission regulations, which now requires these engines to improve their overall performance and reduce harmful pollutants with the culmination of requirements being 2015 when all new diesel engines shall be rated to Tier 4.
In order to reduce emissions, advanced HPCR injection systems operate at pressures in excess of 30,000 psi and in some designs, pressures approaching 40,000 psi can be achieved. These advanced systems are capable of multiple injection events per cycle and involve clearances between moving parts in the order of 1-4 µm. For these reasons, HPCR systems are far less tolerant to contamination than previous Electronic Unit Injector (EUI) designs. This increased demand on diesel fuel cleanliness presents new challenges to engine based contamination control solutions and the fuel filters that are intended to protect the injector and high pressure pump from damage or failure.
To protect HPCR components, much lower concentrations of fine particles and water need to be maintained within the fuel system than were previously accepted. This paper will discuss some of the challenges that are faced and provide recommendations to achieving the required reliability.
EVALUATION OF THE FILTRATION PERFORMANCE OF A RAPID PROTOTYPED SINTERED FILTER ELEMENT
Eric Dimla (pages 94-103)
Laser Sintering is a Rapid Prototyping (RP) technique used for the direct manufacture of solid objects layer by layer, with the aid of CAD models. In this investigation, a sintered bronze filter element was produced by the Direct Metal Laser-Sintering (DMLS) process and its performance data obtained and compared to more conventional elements. The tests showed that the elements had a narrow pore size distribution, a high pressure drop and a low contaminant holding capacity compared to a random fibre element of a similar rating. The ISO 16889 multi-pass β = 1000 rating was 12 µm which was maintained up to the maximum test differential pressure of 10 bar.
The element would be unsuitable for conventional filtration as its limited dirt holding capacity would mean a very short service life, but it could be suitable for Last Chance Filter applications or backwash and blowback applications. Further development would produce an optimum configuration.
DEVELOPMENTS IN LARGE SCALE FILTRATION PLANTS
Jason Palmer (pages 103-106)
Filtration is a well known and effective method for dewatering slurries in the mining and mineral processing industries. Filters have principally been utilised for mineral concentrate dewatering where tonnages are moderate and the separation is targeted to producing cakes dry enough for transport. Water as a resource is becoming scarce and there is legislative pressure to utilise desalinated water or increase the water consumption efficiency of mineral processing operations. The scale of operation has increased dramatically with the trend towards tailings dewatering, forcing equipment manufacturers to adapt and increasing the size of equipment to suit.
Tailings filtration, with a focus on water recovery and dry stack characteristics of the filter cake, has different requirements to product dewatering. Ore variability is significantly higher than the variability of products and plant reliability is essential for robust solutions in tails dewatering. Equipment scale changes have a large effect on the infrastructure required for operation and filtration plants are being developed to integrate the ancillary services required, and to facilitate safe and effective maintenance.
STANDARDS FOR THE COMPRESSED AIR INDUSTRY
Stephen N. Smith (pages 107-114)
Standards for the compressed air industry are broadly divided into two categories, those for the measurement of compressed air purity specification and compressed air treatment equipment performance. The ISO 8573 series of standards for compressed air purity measurement contains 9 parts of which Part 1 enables manufacturers and end users to specify compressed air purity. Compressed air treatment equipment can be validated against ISO 7183 for air drying technology or to ISO12500 Parts 1 through 4 for the removal of oil aerosol, oil vapour, particles and bulk water, respectively.
Combined with the vocabulary standard, ISO 3857 Part 4 Vocabulary they number in total 15 published standards that have been in development since the mid 1980’s under the management of ISO Technical Committee ISO/TC 118/SC4 ‘Compressed air treatment technology’. Over the last 18 months the working group has completed a full review of all standards in the series and set priorities for the changes required to meet environmental legislation and where appropriate to adopt new methods since they were first published. As a priority the working group has identified that significant changes are required to ISO8573-2:2007 ‘Test methods for oil aerosol content’ due in no small part to recent EU regulations and the availability of suitable reagents to undertake the infrared (IR) analysis method detailed.
This paper discusses the changes that are being proposed and provides an overview of a timetable for their adoption.
ASPECTS OF THE DESIGN AND USE OF SEDIMENTING CENTRIFUGES
Clive Grimwood (pages 114-120)
The effects of bowl geometry on the liquor clarification and solids dewatering characteristics of solid bowl decanting centrifuges are discussed. The requirements for centrate clarity and throughput are contrasted with those required for dry decanter cakes and high solids capacity on the assumption that the solids in the decanter feed are crystalline and incompressible. The aim of this paper is to provide a basic understanding of some of the compromises necessary in the selection of decanter centrifuges.