(f Burckhardt éyCompression DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 Dr. Norbert Feistel, Dr. Georg Samland, BesimlFejzuli Compressors for a Lifetime

2 HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 Dr. Norbert Feistel received his degree in Mechani-cal Engineering (DipL-Ing.) from the University of Karlsruhe, Germany in 1987. He began his professional career as a design engineer with Mannesmann Demag Fordertechnik in Offenbach/ Main, Germany. In 1988 N. Feistel joined the R&D Group of Burckhardt Compression in Winterthur. After approxi-mately two years, in which N. Feistel's activities concentrated mainly on the labyrinth piston comͭpressors, his responsibilities are now for the development...

HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 3 The need for cooling piston rod sealing systems (packings) has recently been a subject of more intense discussion. This has been accompanied by developments of new cooling systems permitting more efficient heat dissipation. These activities are motivated by a general susceptibility of commonly used cooling systems as well as their poorer heat dissipation properties compared with cylinder cooling. An analysis of these two shortcomings has led to a new configuration of cooling channels. Operators...

4 HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 CHAPTER 2 possessing a high thermal conductivity. At the same time, an attempt is made to minimize friction power by optimizing sealing element design. A key parameter in this context is the sealing elements' axial width, whose reduction results in a corresponding decrease in friction power without any notable deterioration in sealing efficiency4. Given otherwise identical conditions, the shorter distance to the heat sink permits a cooled sealing system to achieve more favourable thermal...

HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 5 2.2.1 COOLING JACKET A technically very simple method of heat removal by means of a fluid is provided by a cooling jacket which surrounds all packing cups of the sealing system and whose coolant inlets and outlets are usually directly connected to the cylinder cooling. Fig. 1 The small number of gastight sealing elements over which the pressure difference is distributed results in a sealing system of widely differing load zones, the maximum values frequently occurring at the packing boundaries....

6 HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 The outer edge of the packing cups in some designs is equipped with screw plugs allowing the channels to be cleaned. In the case of the more widespread designs without cleaning apertures, the cooling channels are very awkward to maintain. 3.2 SHORTCOMINGS OF CONTEMPORARY COOLING SYSTEMS FOR PISTON ROD SEALS Even before the compressor is started, liquid cooling can pose considerable problems if faulty assembly enables coolant to penetrate into the sealing element chambers. Following contact...

HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 7 CHAPTER 4 Fig. 7 Piston rod sealing system with heat dissipation via longitudinal cooling channels THE CONCEPT OF LONGITUDINAL COOLING Compared with the cylinder, indirect heat transfer via the piston rod on the one hand limits the efficiency of heat dissipation from the sealing elements' friction surfaces, and on the other hand does not allow the piston rod temperature to be reduced significantly through improvements to the packing cup region. Accordingly, developments in piston rod sealing...

8 HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 CHAPTER 5 An infrared sensor was used to measure the piston rod temperature during operation3. One problem posed by such comparaͭtive tests is that the large number of variables influencing the piston rod temperature makes it very difficult to achieve similar experimental conditions. Gas leakages through the sealing system play a very influential role here. Fig. 8 shows the piston rod temperatures and gas leakages (measured in standard cubic meters per hour) ascertained for the new longitudinal...

HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 9 integrated directly in the packing cup web. Had the overall length of the sealing system been limited to 150 mm, the large axial dimension of their packing cups would only have permitted a use of four sealing elements. However, since an integration of cooling channels into the packing cup web does not improve piston rod temperature, the sealing system's service life would be shortened in comparison with the remaining two cooling systems. Fig. 9 CHAPTER 6 SUMMARY The highest resistance arising...

10 HEAT DISSIPATION FROM PISTON ROD SEALING SYSTEMS - DIFFERENT CONCEPTS WITH CONSIDERATION OF THE API 618 Notation PTFE polytetrafluoroethylene PEEK polyetheretherketone l ax axial dimension of the packing cup Q heat flow Rfrences 1 Heinrichs, K.; Striimke, M.: Berechnung der Gleitflachentemperatur in trockenlaufenden Kolbenstangen-dichtungen Wiss. Z. Techn. Hochsch. Magdeburg 28, 1984, Heft 4, S. 86-89 2 American Petroleum Institute Reciprocating Compressors for General Refinery Services API Standard 618, Fourth Edition Washington, D.C. 20 005, June 1995 3 Feistel, N.: Bestimmung der Kolbenstangen-Oberflachentemperatur...

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