CHROME REPLACEMENT ON HYDRAULIC ACTUATORS

UPDATE ON HVOF SEAL TESTING AND EXPERIENCE

PRESENTED BY:SON HUYNH

Senior Aerospace Application Engineer

Presentation Outline

Seal Testing and Experience on HVOF Coating

Surface Finish

Recommendations

High Pressure Material - Aerospace Case Study

HARDWARERod (HVOF) – < 5uin. Ra max.Housing (Bare Steel) – 8uin. Ra max.

MOTIONReciprocating – with Dither

APPLICATIONS5000 psi Development Program

SPECIFICATIONSMedia Phosphate EsterSpeed 3 to 4 HzStroke Length (in.) 4” Max.Pressure 0 to 5000 psiTemperature Range -65F to 275F

LEAKAGE MEASUREDZero (insufficient to form a drop)

Turcon VL Seal Turcon Excluder DC

Commercial Aircraft - Aerospace Case Study

SPECIFICATIONSMedia Phosphate EsterSpeed n/aStroke Length (in.) 2.95Pressure 0 to 3000 psiTemperature Range -65F to 275F

LEAKAGE MEASUREDZero (insufficient to form a drop)In service since early 2000. Performed to 30,000 Flight Hours.

Turcon VL Seal Turcon Excluder DC

MOTIONReciprocating – with high Hz dither

HARDWARERod (HVOF) – 4uin. Ra max.Housing (Bare Steel) – 8uin. Ra max.

APPLICATIONSOutboard, Inboard Aileron and Elevator Actuators

Commercial Aircraft - Aerospace Case Study

SPECIFICATIONSMedia Phosphate EsterSpeed n/aStroke Length (in.) .020” to 4”Pressure 50 psi min

5000 psi maxTemperature Range -65 to 275F

Turcon VL Seal Turcon Excluder DC

APPLICATIONSFlight Controls

LEAKAGE MEASURED1 drop every 31,899 cycles

MOTIONReciprocating with dither

HARDWARERod: HVOF apply Wc-Co-Cr Surface finish: per B+S recommendation

Basic Characteristics of Surface Texture

TypicalTraversing

Length

Lay

RoughnessAverageRa

Centerline

WavinessSpacing

WavinessHeightPeaks

RoughnessSpacing

Roughness sampling Length or Cutoff

valleys

PTFE

Elastomer

Influences:Sealing performance, wear and life time

Surface Finish

1

2

A

B

Abrasion – Dry Running

• Particles (2) are torn out of the

soft surface (B) due to peaks of

the hard surface (A)

• Hard particles (1) are removed from the surface

due to wear, corrosion or system non-cleanliness.

These particles become embedded into the soft

surface (B) and cause scratches in the hard surface (A)

• Premature seal wear/failure

• Hardware damage scratching and scoring

• Excessive leakage

• System failure

Improper Surface Preparation can lead to…..

Surface Finish Roughness: Ra

Ra = 1L

Z(x) dx∫L

o

Roughness Average Ra – the area between the roughness profile and it’s mean line, or the integral of the absolute value of the roughness profile height over the evaluation length

Ra is not enough to define a Dynamic Sealing Surface

Rz5Rz1 Rz2 Rz3 Rz4

Lm = 5 x sl

sl

Surface Finish Roughness: Rz

Rz =15 (Rz1+Rz2+Rz3+Rz4+Rz5)

Lm

Rt

Surface Finish Roughness: Rp, RtRp

Material contact area: Tp (Mr)

L1 L2 L3 L4 L5

C

Lm

L1+L2+L3+L4+L5LmTp = x 100 (%)

Definition: Material percentage at defined

depth (C)

Surface Finish Bearing Ratio: Tp (Mr)

Surface Finish Bearing RatioSimply expressed, at a given depth the profile is sliced (horizontally) and the material percentage is reported

Tp = 39%

Tp = 79%

Surface Finish Effects

Wear rate

Leakage rate

Seal friction

High

Medium

Low

32 µin Ra(0,8 µm Ra)

16(0,4)

12(0,3)

8(0,2)

4(0,1)

2(0,05)

Surface Finish

0(0,0)

Aerospace std.

Profiles Rt Ra Mrc=.25 ABBOTT Curves

1

1

1

1

1

1

1

9

9

8

8

3

8

12

75%

15%

85%

20%

7%

25%

38%

Surface Finish Profile Comparison

Static, ExternalDynamic, Internal

Dynamic, External

Surface Finish Recommendations

Surface Finish Recommendations – Static, Internal

The following is Busak+Shamban Aerospace surface finish recommendation for static seals on cylinder (bore) inside diameters (I.D.) and other static locations:

Measurement Std. Recommendation

Ra 32 μin maximum

The following is Busak+Shamban Aerospace surface finish recommendation for dynamic pistons seals on cylinder (bore) inside diameters (I.D.):

Measurement Std. Recommendation

Ra ≤ 16 μin

Surface Finish Recommendations– Dynamic, External

The following Busak+Shamban Aerospace surface finish parameter recommendations for dynamic rod seals or dynamic external sealson HVOF applied coatings:

Measurement Std. Recommendation

Ra < 5μin

Rp ≤ 8μin maximum

Rz (Rtm) 40μin maximum

Tp (Mr)> 70% @ depth of p =

0.25 Rz relative to reference line = 5 %

Rsk -0.1 to –3

Thank You For Your Attention

Contact Information:Son Huynh

Phone: 260-748-5729Email: son.huynh@busakshamban.com