TEN YEARS OF SUCCESSFUL OPERATION OFTID PISTON RINGS AT HIGH PRESSURE DIFFERENCES Dr. Norbert Feistel Compressors for a Lifetimem

2 TEN YEARS OF SUCCESSFUL OPERATION OF TIO PSTON RINGS AT H E DIFFERENCES Dr. Norbert Matel receiwd his degree in Mechan cal Engineering (DipUngJ from the Univefsrty Df KarLsruhe. Germany in 1967. He began his pro-fessional career as a design engineer with Mannesmann Demag FoerdertechnA in Offenbach/ Main. Germany. In 1988 N. Feistel Jolned the RRD Gfoup of Burckhardt Compression in Winterthur After ap-proxirnately two years, in which M Feistels art i vit tes concentrated mainty on the labyrinth piston compressors. his responsibilities are now for the deveiopment of oil-free sealing Systems....

TEM VEARS OF SUCCESSFUL OPERATION OF TO PISTON RINGS AT HIGH PRFSSURf DIFFERENCES 3 The limits of dry-running frictional sealing Systems can be attained and even exceeded during oil-free sealing of gases at pressures amounting to 200 bar or more. The flow rates required in such applications are often relatively low, hence resulting in very small cylin-der diameters particularly in the final compression stage. This poses a problem of optimization for sealing ͩlments subjected to high loads; Such l驩ments must not only possess the necessary strength and rigtdity, but also be sufficiently capable...

4 TEN YEARS OF SUCCESSFUL OPERATION OF T10 PSTON RINGS AT H E DIFFERENCES rings- To avoid this, segmented designs are also employed prefer-entielly in combination with a pressure relief mechanism*. Finally, dry-running sealing Systems hsndling high loads often suffer from unfavorable friction pairs for a given application. Because "self-supporting" piston rings should comprise h kjh-tempe rature polymers. this notably restricts the choice of matriels avail-able. Ring matriels with better tribological characteristics often prove unfeaslble due to their Inad驩quate strength. thus usually falling...

TEN YEARS OF SUCCESSFUL OPERATION OF TID PISTON RINGS AT HIGH PRESSURE DIFFERENCES 5 Fig. 2 Dviations between a self-tensioning piston ring and the cylinder contour Gap Type: Gap Unit: mm Time: 1 06.07.2009 15:50 Total Dformation Type: Total Deformation Unit: mm Time: 1 06.07.2009 15:48 0 Max -0.055901 -0.1118 -0.1677 -0.2236 -0.2795 -0.33541 -0.39131 -0.44721 -0.50311 Min 17.579 Max 16.18 14.781 13.382 11.984 10.585 9.186 7.7871 6.3883 4.9895 Min two-piece piston rings were not able to prevent the rise in leakage following failure of the twin rings. 2.2 RETAINED PISTON RINGS A retained piston...

6 TEN YEARS OF SUCCESSFUL OPERATION OF TID PISTON RINGS AT HIGH PRESSURE DIFFERENCES 2.3 COMBINATIONS OF RETAINED AND CONVENTIONAL PISTON RINGS Since the performance of the sealing system entirely comprising retained piston rings proved to decline at a relatively early stage, a combination of retained piston rings and conventional twin rings was selected to improve the operational behavior. Four retained piston rings were positioned near the compression chamber to protect the six succeeding twin rings against the high dynamic pressure difference. All sealing elements were again made of modified...

TEN YEARS OF SUCCESSFUL OPERATION OF TID PISTON RINGS AT HIGH PRESSURE DIFFERENCES 7 Fig. 4 Design of a TID piston ring comprising TID segments, a tension ring and a base ring impermissibly high levels, the TID piston rings provided efficient sealing only during the first 1'000 hours, after which the leakage began to fluctuate within the permissible range. It took 8'206 hours for the operational behavior to finally become unsta-ble, the leakage rate then rising above the specified termination threshold. An analysis of the TID piston rings revealed a low average wear of just 1.53 mm. With an original...

8 TEN YEARS OF SUCCESSFUL OPERATION OF TID PISTON RINGS AT HIGH PRESSURE DIFFERENCES Table 1 Comparison of various sealing Systems tested in dry nitrogen at a final pressure of 250 barg Sealing system Conventional piston rings Retained piston rings Retained piston rings / twin rings Retained piston rings / TID rings Retained piston rings / TID rings Material mod. PEEK mod. PEEK mod. PEEK / mod. PEEK mod. PEEK / mod. PEEK mod. PEEK / poLymer bLend Test duration 416-1'070 664-1'545 1'300-4'008 8'206 8'425 Sealing efficiency poor poor good moderate good CHAPTER 4 were made of modified PEEK. The...

TEK YARS OF SUCCESSFUL OPERATION OF TO PISTON RINGS AT HIGH PRFSSURF DIFFERENCES » Flfl.7 Fatlure by fracture (left) and uneven material loss on twin rings made of modified PEEK and subjected to high pressure diffϩrence The use of Injectlon-molded. modified PEEK with much better mechanical properties made lt possible to eliminate fracture failure*. Nonetheless. only operating periods ranglng from 2 000 to 3*000 hours were achieved before the flow rate began to fall below the guaranteed value. An analysls of the dismantled sealing lments showed that unequal wear of cover ring and sealing ring...

10 TEN YEARS OF SUCCE5SFUL OPERATION OF T10 PSTON RINGS AT H RE DIFFERENCES CHAPTER5 POTENTIAL OF THE TID PISTON RING TID piston rings essentially increase the efficiency of heavy-duty piston seallng Systems in three diffrent ways: a) Segmentation of the piston rings, which increases radial dimensions without hlndering wear compensation. b) Very high sealing efficiency of segmented piston rings, attribut-able to the combination of the TID design for the seallng 魩lment and the supplementary base ring for axial sealing of the ring joints. c) Elimination of the seallng rings1 self-supporting function...

TEN YπftS OF SUCCESSFUL OPERATION OF TO PISTON RINGS AT HIGh PRrsSURF DIFFERENCES 11 Notation PTFE Polytelratluoreth^erw PEEK Polyetheretherketone PPS Polyphenylensulfide Rfren驧as 1 Burckhardt Compression AG: Piston compresser for in ollfree gas compression Europen Patent EP0541482 Bl. 1992 2 Burckhardt Compression AG: SeaUng l驩ment for dry runnlng Systems and the use of a seatlng lment of thls klnd Europ驩en Patent EP0985108 811997 2 Burckhardt Compression AG: Method of manufactura a seallng lment, and seallng 驩lment manufactured by trit method Europ颩en Patent EP091B0W Bl. 1997 4 Vetter. G; Feistel....