1、5-47- /7 SAE AIR*L244A 88 8357340 0003860 5 I Issued 6-73 Revised 10-88 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096 REPORT Submitted for recognition as an American National Standard SELECTING SLIPPER SEALS FOR HYDRAULIC-PNEUMATIC FLUID POWER APPLICATIONS 1. PURPOSE: The purpose of this report is to
2、 provide design and maintenance engineers with basic information on the use of slipper sealing devices when used as piston (OD) and rod (ID) seals in aircraft fluid power components such as actuators, valves, and swivel glands. 2. SCOPE: The slipper seal is defined and the basic types in current use
3、 are described. design requirement are covered in terms of friction, leakage, service life, installation characteristics, and interchangeability. Guide lines for selecting the type of slipper seal for a given 3. REFERENCES : AIR1243 - Anti-Blow-By Design Practice for Cap ARP1233 - Gland Design, Elas
4、tomeric O-ring Sea ARP1281A - Actuators: Aircraft Flight Controls AS568A - Aerospace Size Standard for O-rings 1500 psi max General Specification for Strip Seals s, Dynamic Radial, Power Operated, Hydraulics, MIL-C-5503 - Cy1 inders, Aeronautical, Hydraulic Actuating, General MIL-G-5514 - Gland Desi
5、gn; Packings, Hydraulic, General Requirements for MIL-P-5514 - Packings; Installation and Gland Design, Hydraulic, General MIL-R-8791 - Retainer, Packing, Hydraulic, and Pneumatic, Tetrafluoroethylene MS28774 - Retainer, Packing Backup, Single Turn Tetrafluoroethylene MS28775 - Packing, Preformed, H
6、ydraul i c, +275”F (O-rings) MS28782 - Retainer, Packing, Backup, Teflon MS28783 - Ring, Gasket, Backup, Teflon Requirements for Requirements for Resin SAE Technical Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this
7、 report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cance
8、lled. SAE invites your written comments and suggestions. Copyright Society of Automotive Engineers, Inc. Printed All rights reserved. in U.S.A. c_ SAE AIR*32L14A 88 H 8357340 O003863 7 H AIR1244 A SRE, Page 2 REV. 1 4. INTRODUCTION: 4.1 What Is a Slipper Seal: A slipper seal is a separate circumfere
9、ntial band of PTFE (polytetrafluoroethylene) fitted to the inside diameter (ID), outside dlameter (OD), or face of an elastomer O-ring or other shape of so-called “squeeze type“ molded packing. The cross section of the slipper seal configuration can be a variety of symmetrical or asymmetrical shapes
10、 (see Fig. 11, . . . . . . . . Q FIGURE 1 - Typical S ipper Seals The combination of a slipper seal and a molded packing, when fitted in a gland, acts together to control fluid leakage. When used in a static application, the slipper seal prevents extrusion of the elastomer. When used in a dynamlc ap
11、plication the slipper seal reduces breakout and running friction and protects the elastomer from extrusion and wear. The slipper seal concept became practical with the availability of PTFE resins. 1950. PTFE is a chemically-Inert, tkmperature-resistant (450 - 500“F), low-f r i ction, thermopl as ti
12、c f 1 uorocarbon pl as ti c , compati bl e wi th al 1 industrial and military fuels and hydraulic fluids in commercial use. The first PTFE slipper seals were probably used successfully around Although PTFE is not elastic in the same sense as an elastomer material, it is deformable for good sealing a
13、nd can be stretched and folded for ease in installation. Because PTFE is a plastic, sealing surfaces must be protected from scratches and nicks during handling and installation. Installation tools for both OD and ID slipper seals can be used to advantage where one-piece glands are involved, but are
14、not always necessary (see 9). Most slipper seal commercial standards are designed for use in type I, II, and III hydraulic systems with AS568 O-rin sizes in glands per MIL-G-5514. add1 tional extrusion resistance is provided by reduced clearances or the addition of high modulus backup rings. Other t
15、ypes of commercial standards are also available. No MS standards have been issued for slipper seals. Slipper seals are also used in 8000 lbf/in 4 hydraulic systems when 4.2 Mw Do Slipper. Seals Work: installed with a diametral squeeze and may be pressure energized in service. spiral failure, and wea
16、r and will have a relatively short life compared to O-rings used as static seals in a similar environment. An O-ring in a static or dynamic application is O-rings used in a dynamic application are exposed to extrusion, When an O-ring is used with a backup ring, such as MS28774, it is protected again
17、st extrusion but it is still vulnerable to the effects of friction that cause spiral failure and wear. An O-ring used with a slipper seal in a dynamic environment becomes a static seal and is protected from the effects of friction as well as extrusion. SAE AIR*L24qA 88 8357340 0003862 7 Page 3 AIR12
18、44 IRE“* A 4.2 (Continued): Figure 2 illustrates the simplest of all slipper seal configurations. (X.x.I+ May not stay in place No backup- during assembly width glanl (b) May tip in groove during use (cl Gland dimensions impose high occupancy which increases the unit loading on the slipper seal and
19、reduces the friction advantage of the TFE Friction advantage vs O-ring Static Good Dynamic . Fair Service life vs. other slipper seals . Fair Leakage characteristics . Good Recommended for new design No SAE AIRm1244A 88 8357340 0003b5 4 m; REV. AIR1244 A SAE, Page 6 5.1 (Continued): II SOUARE SEA4 U
20、se on ID and OD (a) May not stay in place during assembly (b) Will not tip in groove during use (cl Gland dimensions Impose high occupancy which increases the unit loading on the slipper seal and reduces the friction advantage of the TFE III CHANNEL SEAL Use on ID and OD (a) Will stay in place durin
21、g (b) Will not tip in groove (cl Gland dimensions impose assembly during use high occupancy which increases unit loading on sllpper seal and reduces friction advantage of the TFE IV PROPRIETARY CAP S TRIP Use on ID and OD (a) Will stay in place during assembly (c) Gland dimensions impose high occupa
22、ncy which increases the unit load1 ng on the slipper seal and reduces the friction (b) Wl11 not tip in groove during use No backup- width gland No backup- width gland No backup- width gland RAT1 NG Friction advantage vs O-ring Static Fair Dynamic . Poor Service life vs other slipper seals . Fair Lea
23、kage characteristics . Good Recommended for new design No Friction advantage vs O-ring Static Fair Dynamic . Fair Service life vs other slipper seals . Good Leakage characteristics . Good Recommended for new design Yes Friction advantage vs O-ring Static Excellent Dynamic Excellent Service life vs o
24、ther s 1 i pper seals Excellent Leakage characterlstics . Good Recommended for new design Yes advantage of the TFE RAT1 NG - -_I- SAE AIR*I Will stay in place during assembly (b) Will not tip in groove during use (c) Thick web improves service life (d) Reduced volumetric occupancy in groove reduces
25、friction Friction advantage vs O-ring Static . Excel -/ Dynamic Excel One backup- Service life vs width gland other slipper seals Excel Le akaae - Characteristics . Good Recommended for new design Yes ent ent ent (e Miniature grooves improve low pressure leakage control; reduce friction PROPRIETARY
26、SEAL Friction advantage vs O-ring V Use on OD (a) Used as heavy duty, high pressure piston seal (b) Will stay in place during assembly (c) Thick web improves service life (d) Special elastomeric energizer required - - Static . Excellent Dynamic Excellent (e) Positive actuation of scarf cut backup re
27、duces incidence of cap extrusion and prevents pressure trapping One backup- Service life vs width gland other slipper seals Excellent Leakage characteristics . Good Recommended for new design Yes - SAE AIR*IJZL/A 88 -835734000038b7 L Page 10 1 5.2 (Continued): DESCRIPTION RAT1 NG VI PROPRI ETAR Y SE
28、AL Use on ID Friction advantage vs O-ring (a Used as heavy duty, Static . Exce lent (b) Seals in one dlrection onlv One backuD- Service life vs high pressure rod seal . Dynamic Exce lent (c) Excellent as first stage seal in dual seal appl i cation (dl Stays in place during assembly (e Thick web Impr
29、oves service llfe (f) Special elastomeric energl zer requl red (g) Positive actuation of scarf cut backup reduces incidence of cap extrusion and prevents pressure trapping VI I PROPRIETARY SEAL Use on ID and OD (a Primarily for rod appl Ications on linear actuators (b) Unidirectional seal Ing B (cl
30、Uses proprietary e 1 as tomer (d) Unique design limits elastomer contact and controls friction “ width gland other slipper seals Exce lent Leakage characteristics . Good Recommended for new design Yes Friction advantage vs O-ring Static . Excellent Dynamic Excellent . One backup- Service life vs wid
31、th gland other slipper seals . Good Leakage characteristics Excellent Recommended for new design Yes SAE AER*L244A 8G A357340 0003870 ai I 1 REV. I AIR12441 A Page 11 5.2 (Continued): DESCRIPTION RATING (e Also excellent as low pressure seal, for example, secondary seal in dual “vented“ appl ication
32、 VI11 PROPRIETARY SEAL Use on ID and OD Friction advantage vs O-ring Static Good Dynamic . Good . . . . . . m . (a Used primarily as a rod seal b- One backup- width gland Service life vs other slipper seals Exce (b) Unidirectional sealing lent 1 ent fe s (cl O-ring contact improves leakage character
33、istics Leakage characteristics Exce Recommended for new design (d) Minigrooves improve low pressure leakage control; reduce friction IX PROPRIETARY SEAL Use on ID only 1 7 Friction advantage vs O-ring (a) Use as heavy duty Static . Excellent Dynamic Excel lent high pressure seal u One backup- width
34、gland (b Seals in one direction only Service life vs other s1 i pper seals Excellent (cl Stays in place during assembly Le a kag e characteristics . Good (d) Thick web improves service life Recommended for new design Yes (e) High modulus backup rings prevent high pressure ex trus i on (f) Special el
35、astomeric energizer required SAE AIR*3244A 88 8357340 0003873 T - AIR1244 =i! Page 12 REV. A 5.3 Slipper Seals for Two Backup -Width Glands per MIL-P-5514 and MIL-G-5514: There are four slipper seal configurations for two backup-width glands. Some types are for general purpose applications and other
36、s are intended for special purposes. DESCRIPTION RAT1 NG CHANNEL SEAL Use on ID and OD Web cracking and folding shorten life O-ring may be damaged adjacent to bottom of 1 eg Gland dimensions are favorable for limiting the effect of occupancy on friction CHANNEL SEAL Use on ID and OD This seal is in
37、wide general use for rod and pi ston application on linear actuators Gland dimensions are favorable for 1 imi ting the effect of occupancy on friction Two backup- width gland Two backup- width gland Friction advantage vs O-ring Static Good Dynamic . Good Service life vs other s 1 i pper seals . Poor
38、 Leakage characteristics . Good Recommended for new design No Friction advantage vs O-ring Static Good Dynamic . Good Service life vs other slipper seals Excellent Leakage characteristics . Good Recommended for new design Yes SAE AIR*1244A 88 = 8357340 0003872 L = Page 13 I -AIR1244 IRE“- A 5.3 (Con
39、tinued): DESCRIPTION RAT1 NG III PROPRIETARY CAP STRIP Use on ID and OD Friction advantage vs O-ring (a) Will stay in place . Static . Excellent during assembly Dynamic Excellent . (b Will not tip in groove Two backup- Service life vs (cl Thick web improves (d) Reduced volumetric during use width gl
40、and other slipper service life Leakage. occupancy in groove Recommended for reduces friction new design Yes seals Excellent characteristics . Good (e) Miniature grooves improve low pressure leakage control ; reduce friction IV MODIFIED FOOTSEAL Use on ID and OD (a Used primarily as a rod seal (b) Se
41、als in one direction only (cl Gland dimensions are favorable for limiting the effect of occupancy on friction (d) Seal contour improves leakage characteristics but tends to increase friction out of propor- tion with an increase in fluid pressure Friction advantage vs O-ring Static Good Dynamic . Fai
42、r Two backup- Service life vs width gland other slipper seals Excellent Leakage characteristics . Good Recommended for new design Yes SAE AIR*L2q4A BB M 83573qO 0003874 5 Page 15 I AIR1244 I REV- A 5.3 (Continued): DESCRIPTION RAT1 NG PROPRIETARY SEAL - Friction advantage vs O-ring Static . Excellen
43、t Dynamic Excellent Use on ID Used as heavy duty, high pressure rod seal Seals in one direction Two backup- Service life vs only width gland other slipper Excellent as first stage seal in dual seal Leakage. application characteristics . Good seals Excellent Stays in place during assembly Thick web i
44、mproves service life Special elastomeric energizer required Positive actuation of scarf-cut backup reduces incidence of cap extrusion and prevents pressure trapping Recommended for new design Yes PROPRIETARY SEAL Used on ID and OD Friction advantage vs O-ring seal Dynamic . Good Used primarily as a
45、rod Static Good Seals in one direction Two backup- Service life vs only width gland other slipper seals O-ring contact improves leakage characteristics Leakage characteristics Minigrooves improve low pressure leakage control; Recommended for reduce friction new design . Excel lent Excel 1 ent Yes SA
46、E AIR*L244A* 88 H 8357340 0003875 7 AIR1244 IRE“* A I Page 16 1 1 5.3 (Continued): DESCRIPTION PROPRIETARY SEAL Use on ID and OD Primari 1.y for rod appi i cations on 1 i near actuators -J . Two backup- width gland Widely used on landing gear shock struts Unidirectional sealing Uses propr i etaiy el
47、astomer Unique design limits elastomer contact and controls friction Also excellent as low pressure seal, for exampl e, secondary seal in dual llventedl application RAT1 NG Friction advantage vs O-ring Static . Excellent Dynamic Excellent Service life vs other s 1 i pper seal s . Good Leakage charac
48、teristics Excellent Recommended for new design Yes m. PROPRIETARY SEAL Use on ID and OD Used as heavy duty, hig Friction advantage vs O-ring Static . Excellent pressure rod seal Dynamic Excellent Stays in place during Two backup- Service life vs assembly width gland other slipper Thick wall improves
49、 service life Le a kage High modulus backup rings prevent high pressure Recommended for ex t rus i on new design Yes seals Excellent characteristics . Good Special el astomeri c energizer required SAE AIR*L244A 88 m 8357340 0003876 3 B Page 17 I AIR1244 IRE“- A 5.3 (Continued): DESCRIPTION XI PROPRIETARY SEAL RAT1 NG Use on ID and OD pressure rod and piston seal (a Used as heavy duty, high Two backup- (b) Minigroove sealing width gland surface provides low fr i c t i on (cl Grooved sealing surface provides greater leakage control Friction advantags vs O-ring Static
