Materials Handling


Oil wiping technology for reciprocating compressors


O


il wiper rings are used on the piston rods of reciprocating compressors. Their job is to


stop crankcase oil from contaminating the gas being compressed in the cylinders, without compromising the lubrication of the machine. Operators of reciprocating


compressors typically waste oil and suffer reduced reliability because of the poor design of conventional metal oil wiper packings. Outward leakage leads to crankcase oil losses as high as 5 l (1 gallon) per day per compressor. At the same time, oil carried back into the crankcase can be contaminated with process gases – such as corrosive hydrogen sulphide – which can damage the compressor and require more frequent oil changes. The design and operating principle of a


new oil film dynamic (OFD) wiper ring from HOERBIGER eliminates the leakage paths, oil pumping action and sharp edges which characterise conventional oil wipers. As a result, it pushes oil back into the crankcase instead of outwards, as conventional oil wipers do. The OFD ring is made from hard-wearing polymer instead of


Fig. 1. HOERBIGER’s oil film dynamic (OFD) wiper.


metal, ensuring long life without damaging the piston rod or impairing lubrication. Four factors characterise the design and


performance of the HOERBIGER OFD oil wiper ring.


The first is geometry. OFD wiper rings feature a two-piece design based on two concentric rings of L-shaped cross-section. Each ring covers the gaps in the other, closing off oil leakage paths. Second is a new spring plate which


applies a side (axial) load to the OFD rings. This stops the rings from moving, eliminating the ‘shuttling’ effect that plagues conventional wiper rings. Third is a change in material. The


radial stiffness of conventional metal wiper rings stops them conforming accurately to the shape of the piston rod. HOERBIGER OFD rings are made from a high-performance polymer that eliminates leaks because it follows the shape of the piston rod accurately. These three design aspects


combine to create the fourth key differentiator of the OFD rings: their innovative working principle. Conventional wiper rings tend to pump oil out of the crankcase, while their sharp edges run the risk of scraping the oil film off the piston rod, leading to inadequate lubrication and damaging the rod surface. OFD oil wiper rings, on the other hand, use elasto-hydrodynamic effects to pump oil back into the crankcase without losing the vital lubricating film, while their soft material avoids rod damage. n


For more information ✔ at www.engineerlive.com/epe


Christian Hold is Team Leader Rings & Packings/Materials, HOERBIGER


Ventilwerke GmbH & Co KG, Vienna, Austria. www.hoerbiger.com


I


Filtration system can be fully automated parts for decades.


nfolabel AG is the manufacturer of Chemap-Filters which have tested in more than 5000 different types of


application. The company’s services range


from the engineering of Chemap-Filters and complete filtration systems to support with spare parts and expert knowledge. The Chemap-Filter system can be constructed to be fully-automated. The Chemap-Filter is designed for process- integrated and efficient filtration, with follow-up treatment levels too if required, in a closed system. Complete project


documentation allows the systems supplied to be provided with spare


Engineers who have specialised in filtration process support customers in the defining and design of instruments and optimise the complex process steps together with the customer, making the filter become an efficient element in the production process. With Chemap-Filter test facilities, performance parameters necessary for the definition of the optimal configuration can be evaluated in Infolabel own laboratories or in a field test on the customer’s premises. n


For more information ✔ at www.engineerlive.com/epe


Infolabel AG is based in Nänikon, Uster, Switzerland. www.funda.ch


www.engineerlive.com 33


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