Aerospace sealing systems - All Seals Inc.

1 Aerospacesealing systemsYour Partner for sealing TechnologyAerospace Engineering Guide1 Busak+ShambanEdition April 2004 ContentsSealing system Hydraulic Finish (Recommendations) Finish (Measurement Methods) Quick Reference Criteria for Aerospace Dimensions per MIL-G-5514F and AS4716, Dimensions per MIL-G-5514F and AS4716, (For use in MIL-Standard Grooves) Ring (BUR) manufactured to MIL-G-5514F (Rod and Bore Sizes Only)TurconRDual Piston RingR- For use with MIL-G-5514F/AS4716 Glyd RingR- For use with MIL-G-5514F/AS4716 for Boeing Gland Standard Engineering Guide2 Busak+ShambanEdition April 2004 Selection of the Scraper Scraper , Series Engineering Guide3 Busak+ShambanEdition April 2004 sealing system ExamplesTypical Hydraulic Equipment using Shamban SystemsIn each individual case the type of system should be selectedbased on criteria such as friction, leakage, and cost.

2 In thefollowing examples we have mentioned the main features foreach system as a guideline; however, the section describingthe individual product should always be consulted to ensurethat all operational requirements are Actuator systems : Rod ApplicationsFor general purpose hydraulic actuators, Shambanoffers a variety of simple and reliable sealing systems :TurconRExcluderRDCT urconRWedgpakRpFigure 1 Standard Rod sealing SystemThe WedgpakRand ExcluderRDC standard sealingsystem (Fig. 1) is a simple and effective solution thatcombines long life with good leakage control. TheWedgpakRis an easy to install, foolproof design, offeringexcellent leakage ExcluderRDC is superior to the older garter springenergized scraper because it utilizes an uncut scraper ringand is sealed off by an O-Ring on the static Plus SealRIIpFigure 2 Alternative system IThe GroovedPlus SealRII (Fig.)

3 2) can be substituted for theWedgpakRin cases where an elastomeric contact seal isnot suitable due to high speeds or long rest periods for theactuator. This seal has nearly the same leakage control,but since it is a slipper seal, speeds of up to 15 m/s (49ft/s) are acceptable and adhesion is eliminated. Thegrooves on the dynamic seal surface provide pocketswhere the hydraulic fluid can accumulate and lubricatethe seal, therefore increasing seal SealRFigure 3 Alternative system IIVL SealR(Fig. 3) is a good alternative for applicationswhere a dry rod is critical (and typical slipper Seals allowtoo much leakage). VL SealRis designed to pump anyleakage back into the system . A double acting scraper suchas the ExcluderRDC is used in order to prevent leakage outof the system at the rod end. The VL SealR/ExcluderRDCsystem has the advantage of being extremely leaktight witha surface finish at max.

4 Ra forGroove Distance,seefigure 123 page Engineering Guide4 Busak+ShambanEdition April 2004 Utility Actuator systems : Piston ApplicationsPiston systems are typically simpler than rod must be of symetrical design to cope with thechanging direction of the fluid Piston RingppFigure 4 TurconRDual Piston RingWhere controlled leakage is permissible, the Dual PistonRing offers a good, reliable, low friction seal in a narrowgroove Plus SealRIIF igure 5 TurconRGrooved Plus SealRIIW here leakage is critical, the Grooved Plus SealRII iswidely used and has excellent wear RingRppFigure 6 TurconRGlyd RingRThe TurconRGlyd RingRis a simple, reliable and cost-effective slipper seal that is worthwhile considering as analternative to the Plus SealRII if MIL-G-5514F glanddesign is not 7 TurconRWedgpakRThe Wedgpak is a zero leakage elastomer contact sealwith outstanding dynamic performance and Engineering Guide5 Busak+ShambanEdition April 2004 Advanced Actuator systems :Primary Flight ControlsRod Applications with Dual Unvented SealsWith the increased use of fly-by-wire technology, mostprimary flight controls use a dual unvented sealing system inorder to meet the high performance and long SealRFigure 8 High Frequency SystemThe tandem VL SealRcombines the low frictioncharacteristics of the slipper seal with a leaktightperformance.

5 The dual edge ExcluderRDC closes theleakage by low pressure and static stand-by the HatsealRII and the WedgpakRhave beenused for many years for high frequency systems , thetandemVL SealRsystem provides increased reliability andcan survive high frequency dither stroke applications withincreased service Applications with Pressure Relieving SealsIn some cases an interstage pressure build-up can beexperienced in a dual unvented sealing system . The followingfactors are contributing to this phenomenon:-Stroke frequency-Stroke length-Pressure variation-Extrusion gap-Surface finish-Oil viscosity-TemperatureThe following systems are designed to allow the interstagepressure build-up to be relieved back into the system , whenthe system pressure drops or in the case of the StepsealRKduring the retract stroke of the SealRPRT urconRWedgpakRFigure 9 system with Pressure Relieving Plus SealRPRThe Plus SealRPR is capable of relieving any Plus SealRPR is easily fitted into existing grooves as aretrofit if a pressure build-up is noticed, requires a SealRTurconRExcluderRDCpTurconRWedgpakRF igure 10 system with Pressure Relieving VL SealRPressure relieving can also be achieved by using theVL SealRas a primary seal.

6 The sealing lip will lift if theback pressure exceeds approximately 10 bars (145 psi).VL SealR/WedgpakRconfiguration offers the optimumpressure relieving seal system , due to the VL trapped in between the two Seals is preventedfrom leaking through by the elastomer contact of theWedgpakRand the slight tilt of the VL SealRcaused bybackpressure, allowing the oil back into the Engineering Guide6 Busak+ShambanEdition April 2004 Advanced Actuator systems , :Primary Flight ControlsPiston ApplicationsThe piston Seals in a flight control are working under lesssevere conditions than the rod Seals because they are welllubricated by the Piston RingppFigure 11 TurconRDual Piston RingWhere controlled leakage is acceptable, the Dual PistonRing offers a good reliable low friction solution in a narrowgroove with minimum Plus SealRIIF igure 12 TurconRGrooved Plus SealRIIW here leakage is critical, the Grooved Plus SealRII iswidely used and has excellent wear characteristics.

7 Inflight controls we recommend Back-up Rings with thePlus Engineering Guide7 Busak+ShambanEdition April 2004 Landing Gear Shock StrutsTurconRExcluderRDCT urconRHatsealRIIpTurciteRSlydringRFigure 13 Small Diameter Shock StrutFor smaller diameter shock struts, the HatsealRII/ExcluderRDC has proven to be a cost effective solutiondue to the long service 14 Large Landing Gear with Installed Spare SealFor medium sized landing gear, it is an advantage to usea tandem sealing system with by-pass around the inboardseal. This means that initially the pressure drop is over theoutboard seal, and the inboard seal runs in a lubricatedenvironment. When a leakage is detected, the by-passcan be closed and operations continue on the inboardseal until the next scheduled landing gears where severe shock strut deflection canbe expected, the use of SlydringRis recommended toavoid scoring caused by metal-to-metal contact of themoving SealRIIL uytexRSlydringRLuytexRSlydringRFigure 15 Large Diameter Shock StrutsFor large diameter landing gear where heavydeformations and high pressure shocks may occur, it isessential to use a slipper seal without elastomer contact toprovide the necessary service life.

8 The use of LuytexRSlydringRare critical to good performance becausemetal-to-metal contact is Engineering Guide8 Busak+ShambanEdition April 2004 TurconRVL SealRpTurconRExcluderRDCL uytexRSlydringRTurciteRSlydringRTurconRH atsealRFigure 16 Future Landing Gear sealing SystemTandem sealing systems represent the ultimate sealingsolution for landing gear, with the new Series 600 crosssection, and there is room for it. The TurconRVL SealRasthe primary seal to take up the peak and pulsationpressure, protecting the TurconRHatsealRII as theleaktight performer with the lip. Both seal designs areconsidered the superior strut Seals and the combinationof the seal designs will only improve the Seals and bearings are among othersused for the following Landing Gearapplications:A320, A380/340B737, B747, B757 and B767,ATP, F-5, Eurofighter, J31, HS748, Spitfire, EMB 145, PC7and Vane sealing SystemA rotary vane sealing system consists of a rectangularcap seal with a centerplate, and an O-Ring to energizeand seal between the chambers.

9 The corner seal can bedesigned in various shapes to control the leakpathbetween chambers and rod. The TurconRWedgpakRis positioned as rotary seal with a small elastomercontact to prevent leakage even at low pressure. Finallythe ExcluderRDCprevents contaminationfromenteringthe system . If space is available, a SlydringRisrecommended between the rod seal and consult your Shamban sales engineer for SealCorner SealTurconRWedgpakRTurconRExcluderRDC,Se ries EAAS ection A - AFigure 17 Rotary Actuator sealing SystemAerospace Engineering Guide9 Busak+ShambanEdition April 2004 AccumulatorsThe TurconRAQ-SealR5 is a leak-tight, long-lasting piston seal. The use of SlydringRis recommended to avoid leakageresulting from piston misalignment with the 18 Accumulator sealing systems . Application Example: Sikorsky H60 Spool ValvesReduced gland width can be achieved by using a TurconRGlyd RingRinternally, and a TurconRWedgpakRwithelastomer contact to prevent external RingRTurconRWedgpakRFigure 19 Spool Valve sealing systems .

10 Application Example: IPTNA erospace Engineering Guide10 Busak+ShambanEdition April 2004 BrakesBrake pistons equipped with a spring energized TurconRVarisealRH to take pressure and temperature variation,combined with the tight and efficientTurconRExcluderRDC, Series E, have proven to be veryreliable. The advantage of using VarisealR(springenergized TurconRjackets) instead of elastomer contactor energized Seals is that brake systems often exceed thetemperature capability of the elastomer. Springenergized Seals can go from -100_C/-148_Fto+260_C/500_F, and metallic springs address most fluidcompatility Spring Liner protects the brake housing from wearand abrasion from the RingTurconRSpring LinerpFigure 20 Brake sealing system . Application Example: F-16 A/BAerospace Engineering Guide11 Busak+ShambanEdition April 2004 TurconRSeal MaterialsTurconRmaterials are carefully formulated proprietaryblends and are based on premium-grade PTFE fluoropolymer resins.