Question 1

How to select graphite material for high/low temperature?

Accepted Answer

Low temperature (-50°C ~ 100°C): Phenolic resin-impregnated medium-fine graphite. Cost-effective with stable performance.
Medium temperature (100°C ~ 250°C): Furan resin or epoxy resin impregnation. Better temperature and corrosion resistance than phenolic.
High temperature (250°C ~ 450°C): Antimony metal or Babbitt-impregnated graphite. Isostatic molded base recommended for dimensional stability at high temperatures.
Ultra-high temperature (450°C ~ 600°C): Carbonized (pure carbon) graphite. No impregnant, relying on graphite's own thermal resistance. Requires inert or reducing atmosphere.

Question 2

How to choose impregnation for wet/dry conditions?

Accepted Answer

Full wet operation (ample lubrication): Phenolic or furan resin impregnation. Resin fills pores, increasing density and reducing wear.
Wet-dry cycling (frequent starts/stops): Impregnation with excellent self-lubricating properties. Metal impregnation (antimony/Babbitt) or PTFE impregnation recommended, forming a transfer lubricating film during dry running.
Complete dry running (no lubrication): Carbonized graphite or special resin impregnation. Design for low PV value (≤ 3 MPa·m/s) with self-lubricating grooves on the seal face.

Question 3

Best graphite for high-speed / heavy-load / low-pressure?

Accepted Answer

High speed (linear velocity > 20 m/s): Isostatic fine-grain high-density graphite paired with SiC counterface. Antimony or carbonized impregnation. Fine grain ensures uniform wear at high speed.
Heavy load (PV > 15 MPa·m/s): Babbitt or antimony-impregnated graphite. Metal filling significantly improves compressive strength and thermal conductivity for timely frictional heat dissipation.
Low pressure (medium pressure < 0.5 MPa): Molded medium-grain graphite with phenolic resin impregnation. Most cost-effective option.

Question 4

Oil-free vs oil-lubricated material selection?

Accepted Answer

Oil-free self-lubricating: High self-lubricating grade graphite required. Carbonized high-purity graphite or PTFE-impregnated graphite recommended. Seal face should have debris grooves or spiral grooves for solid lubrication via graphite transfer film. PV range recommended: 0.5 ~ 5 MPa·m/s.
Oil lubrication: Standard phenolic or furan resin-impregnated graphite suffices. Oil film provides primary lubrication. Graphite acts as the soft mating face for adaptation and emergency running. PV range up to 10 ~ 20 MPa·m/s. Slightly coarser graphite grain can improve wear resistance under oil lubrication.

Question 5

How to fix vibration (excessive clearance) or seizure (too tight)?

Accepted Answer

Excessive clearance: Shaft vibrates radially during operation, reducing seal face tracking, causing leaks, noise, and abnormal wear. Solution: Look up standard clearance table by speed and shaft diameter. Re-machine bushing bore. Check shaft straightness and straighten if out of tolerance.
Insufficient clearance: Friction heat cannot dissipate. Temperature rise causes graphite expansion, further reducing clearance, creating a positive feedback loop ending in seizure. Solution: Increase clearance to recommended upper limit. Confirm bushing housing heat dissipation. Check cooling system flow.
Diagnosis: Measure temperature after 30 min operation. > 90°C = too tight. Noticeable wobble during operation = too loose.

Question 6

Standard fit tolerances by shaft diameter?

Accepted Answer

Common fit tolerance bands (graphite bushing bore vs steel shaft):
Small shaft d ≤ 30 mm: H7/f7 or H7/g6, clearance 0.02 ~ 0.08 mm
Medium shaft 30 < d ≤ 80 mm: H7/f7 or H8/e8, clearance 0.03 ~ 0.15 mm
Large shaft 80 < d ≤ 150 mm: H8/e8 or H8/d8, clearance 0.05 ~ 0.30 mm
Extra large shaft d > 150 mm: H8/d8 or H9/c9, clearance 0.10 ~ 0.50 mm
Note: Actual values must consider speed, temperature, and material thermal expansion coefficients.

Question 7

How to adjust clearance for thermal expansion?

Accepted Answer

Graphite CTE ≈ (2~4)×10⁻⁶ /°C, steel CTE ≈ 11×10⁻⁶ /°C. The difference is significant.
Correction method:
1. Calculate radial change: Δr = (αsteel - αgraphite) × r × ΔT
2. Add result to cold clearance value
3. Example: 80 mm shaft, 150°C rise, radial change ≈ (11-3)×10⁻⁶ × 40 × 150 = 0.048 mm
4. Actual cold clearance = operating clearance + 0.048 mm
5. Note: Clearance shrinks on cooldown. Hot-assembled equipment must be checked for alignment after cooling.

Question 8

Graphite turning, drilling, and grinding precautions?

Accepted Answer

Turning: Use diamond or carbide tools. Rake angle 0°~5°, relief angle 6°~10°. Cutting speed 100~300 m/min, feed 0.05~0.15 mm/r. Maintain continuous cutting; avoid impact feed causing edge chipping. Use dust extraction for graphite dust.
Drilling: HSS or carbide drill, point angle 90°~120°. Speed 3000~8000 rpm, feed 0.02~0.08 mm/r. Entry and exit edges prone to chipping; chamfer both sides, support exit side with wooden backing.
Grinding: Silicon carbide wheel (grit 60~120#), depth ≤ 0.01 mm/pass. Dry grinding preferred. If wet grinding, confirm graphite impregnation grade is coolant-tolerant.
Safety: Graphite dust is conductive. Electrical equipment requires dust protection. Operators must wear dust masks.

Question 9

How to fix press-fit misalignment, edge chipping, and cracking?

Accepted Answer

Misalignment: Uneven bore chamfer or off-axis press force. Solution: Check bore chamfer (≥ 15°), use a guide mandrel, control press speed at 2~5 mm/s.
Edge chipping: Stress concentration at bushing edge or excessive interference. Solution: Increase bushing O.D. entry chamfer (C0.5~C1.0), reduce interference, check bore roughness (≤ Ra 1.6).
Cracking: Interference severely out of tolerance or bore roundness out of spec. Solution: Recalculate interference, measure bore roundness (≤ IT7), consider shrink-fit (heat bore to 150~200°C before assembly).
Monitoring: Use a press with force-displacement sensor for real-time curve monitoring. Stop immediately if curve is abnormal (sudden rise/drop).

Question 10

How to control interference fit tightness?

Accepted Answer

Interference calculation principles:
1. Minimum interference: Ensure bushing does not loosen at max operating temperature; account for thermal expansion differences
2. Maximum interference: Ensure graphite bushing is not crushed by compressive stress; take 1/5 ~ 1/3 of graphite compressive strength
3. Empirical formula: δ ≈ (0.002~0.005) × bushing O.D.

Reference values:
O.D. ≤ 50 mm: interference 0.02~0.05 mm
O.D. 50~100 mm: interference 0.04~0.10 mm
O.D. 100~150 mm: interference 0.06~0.15 mm
O.D. > 150 mm: interference 0.08~0.20 mm

Installation methods:
- Small interference: Press-fit at room temp
- Medium interference: Heat bore to 150~200°C for shrink-fit
- Large interference: Combined liquid nitrogen cooling (-196°C) + bore heating

Question 11

How to handle excessive operating temperature?

Accepted Answer

Inspection sequence:
1. Measure actual temperature — use IR thermometer or thermocouple on seal cavity wall. Check if > 80°C.
2. Check cooling system — is coolant flow adequate? Lines blocked? Heat exchanger efficiency degraded?
3. Check face pressure — spring over-compressed? Seal face width too large?
4. Check clearance — too little clearance causes rapid frictional heat rise.

Emergency measures:
- Increase coolant flow to 1.2~1.5× recommended
- Reduce speed or pressure (temporary)
- Check lubricant cleanliness and filter condition

Long-term measures:
- Evaluate switching to higher thermal conductivity impregnated graphite grade
- Optimize seal face cooling groove design
- Check shaft alignment

Question 12

How to fix minor oil/water seepage?

Accepted Answer

Leakage ≤ 5 drops/min (acceptable minor leakage):
1. Check seal face — if minor leakage during break-in, continue running 24~48 hours for observation; new seals require a break-in period
2. Adjust gland bolts — tighten evenly and diagonally, torque at 50%~70% of recommended
3. Check secondary seals — O-rings/gaskets aged or damaged? Cavity have casting defects?

Leakage > 5 drops/min (requires shutdown):
1. Check seal face — thermal cracks, scratches, warping? Counterface flat?
2. Check installation dimensions — correct compression? Seal face perpendicular to shaft?
3. Check operating condition changes — recent temperature, pressure, or speed fluctuations?
4. Replace seal — disassemble and replace complete seal set, recalibrate installation

Question 13

Causes of noise, vibration, and rapid wear?

Accepted Answer

Noise diagnosis:
- High-pitched squeal → Face dry friction. Check lubrication immediately.
- Low-frequency rumble → Bearing clearance too large or rotating part imbalance.
- Intermittent clicking → Foreign particles on face or localized face chipping.

Vibration causes:
1. Bent shaft or bearing wear causing excessive runout
2. Seal face flatness deteriorated > 0.9 μm
3. Medium vaporization (flashing) causing intermittent face opening
4. Installation alignment deviation > 0.05 mm

Rapid wear causes:
1. Abrasive particles in medium (sand, weld slag, rust) — add upstream filter
2. Wrong material selection (low hardness or mismatched impregnation grade)
3. Actual PV value exceeds material allowable PV
4. Frequent start-stop or extended dry running
5. Medium corrosiveness exceeds impregnant tolerance

Question 14

How to resolve high-temperature carbonization and powdering?

Accepted Answer

Carbonization symptoms: Black powder accumulation on seal face. Graphite surface appears loose, powdered, losing structural strength.

Root cause analysis:
1. Temperature exceeds impregnant tolerance — phenolic resin begins carbonizing > 200°C
2. Localized hot spots — face friction heat + medium temperature exceeding limit
3. Oxidizing atmosphere — oxygen oxidizes graphite at high temperature; CO/CO₂ escape causes structural porosity

Solutions:
1. Shut down immediately and replace; prevent total seal failure from worsening carbonization
2. Select higher temperature-rated impregnation (phenolic→furan→antimony→carbonized)
3. Atmosphere control — inert gas purge or steam sealing for high-temp conditions
4. Optimize cooling — increase seal cavity coolant flow to reduce face temperature
5. Consider face groove design for improved lubrication and heat dissipation

Prevention: Maintain at least 50°C safety margin below rated temperature. Install temperature monitoring probes.

Question 15

Break-in procedure for initial operation?

Accepted Answer

Purpose: Allow seal faces to mate properly, forming a stable fluid film and wear pattern.

Break-in steps:
1. Before start: Check seal cavity is filled with medium, purge air. Hand-rotate 2~3 turns to confirm free movement, no noise.
2. Phase 1 (0~30 min): Run at 30%~50% of rated speed. Monitor leakage, temperature, vibration. Minor seepage acceptable.
3. Phase 2 (30~120 min): Gradually increase to 70%~80% of rated speed. Temperature should stabilize at ≤ 60°C.
4. Phase 3 (120~240 min): Full speed. After temp stabilizes, check leakage is within acceptable range.
5. Break-in period (first 72 hours): Maintain continuous operation if possible, especially for frequent start-stop applications.

If temperature exceeds 80°C or leakage increases significantly during break-in, stop and inspect immediately.

Question 16

Storage and preservation for long-term shutdown?

Accepted Answer

Short-term (≤ 7 days):
1. Keep seal cavity filled with medium to prevent face drying
2. Hand-rotate 1~2 turns weekly to prevent face adhesion
3. Close inlet/outlet valves

Medium-term (7~90 days):
1. Drain medium, flush with clean water or solvent
2. Apply rust-preventive grease or special protective agent to seal faces
3. Coat exposed bushing surfaces with rust oil
4. Nitrogen blanket or add desiccant in seal cavity
5. Hand-rotate once every two weeks

Long-term (> 90 days):
1. Remove seal components and store separately
2. Clean and wrap in anti-rust paper
3. Storage environment: 5~35°C, humidity ≤ 60%, avoid direct sunlight
4. Keep away from acidic/alkaline substances
5. Inspect seals for aging or deformation before reinstallation

Question 17

Wear limits and replacement criteria?

Accepted Answer

Seal rings:
1. Face wear depth > 1.0 mm or defect > 15% of seal face width
2. Through-cracks or chipping
3. Flatness after lapping > 0.9 μm (re-evaluate after re-lapping)
4. Remaining service life insufficient to reach next maintenance interval

Bushings/Bearings:
1. Bore wear > 2~3× initial clearance
2. Visible wear step or groove on O.D.
3. Wall thickness reduction > 20% of original
4. Vibration 50%+ higher than initial value

Assessment procedure:
1. Record initial dimensions and operating parameters
2. Measure wear and vibration trends periodically (every 3~6 months)
3. Schedule replacement early when wear rate suddenly accelerates
4. Prepare spare parts when reaching 80% of theoretical service life

Question 18

Mold considerations for custom graphite parts?

Accepted Answer

Three evaluation factors: 1. Volume & Cost — Mold tooling typically costs ¥3000~15000. Low volume (< 50 pcs): machining recommended. > 500 pcs: consider molding. 2. Precision — Molded tolerance: ±0.5%. Machined tolerance: ±0.05 mm. 3. Geometry — Complex shapes (deep holes, L/D > 5, thin wall < 3 mm): molded blank + finish machining. Mold design notes: - Draft angle ≥ 1°~3° (related to height) - Avoid sharp corners and abrupt section changes (min. radius R ≥ 2 mm) - Keep symmetrical where possible to reduce uneven loading - Leave machining allowance 0.5~1.0 mm (for finished surfaces) - Consider pressing direction effect on density uniformity

Question 19

Groove, oil groove, and rabbet design standards?

Accepted Answer

Oil/Lubrication groove design:
- Depth: 0.3~1.0 mm (based on shaft diameter and PV value)
- Width: 1.0~3.0 mm
- Types: Spiral (unidirectional), herringbone (bidirectional), straight groove (low speed)
- Spacing: 5~15 mm
- Distance from edge: ≥ 2 mm

Rabbet design:
- Height: 1~3 mm (based on wall thickness)
- Angle: 30°~45°
- Fillet radius: R ≥ 0.5 mm
- Avoid stress concentration at rabbet root

Tolerance notation:
- Groove position: ±0.2 mm
- Groove depth: +0.1 mm / -0 mm
- Rabbet concentricity: ≤ 0.05 mm

Question 20

Expedited custom machining with quality assurance?

Accepted Answer

Expedited process:
1. Confirm drawing — 3D model for structure review, 2D engineering drawing with critical tolerances
2. Blank selection — Use in-stock grades and sizes to skip procurement lead time
3. Process route — Order operations efficiently: rough turning→finish turning→drilling→grinding. Minimize setups.
4. Equipment — High-precision CNC lathes (positioning accuracy ≤ 0.005 mm) + diamond tooling

Accuracy levels:
- Standard ±0.05 mm: Standard turning
- Precision ±0.02 mm: Requires grinding
- High-precision ±0.01 mm: CNC grinder + CMM inspection
- Flatness 0.9 μm: Lapping required

Expedited lead times (simple bushings/seal rings):
- Drawing-based: 3~5 business days
- With material procurement: 7~10 business days
- Including mold tooling: 15~25 business days

Question 21

Phenolic Resin

Accepted Answer

-50°C ~ +200°C；Good；Water, oil, mild acid/alkali；General pump seals, water pumps

Question 22

Furan Resin

Accepted Answer

-50°C ~ +250°C；Excellent；Strong acid, strong alkali, organic solvents；Chemical reactors, pickling equipment

Question 23

Epoxy Resin

Accepted Answer

-50°C ~ +180°C；Good；Water, oil, alkali；Food machinery, pharmaceutical equipment

Question 24

10 ~ 25

Accepted Answer

0.08 ~ 0.12 mm；0.10 ~ 0.15 mm；0.15 ~ 0.20 mm；0.20 ~ 0.30 mm

Question 25

25 ~ 50

Accepted Answer

0.10 ~ 0.15 mm；0.15 ~ 0.20 mm；0.20 ~ 0.30 mm；0.30 ~ 0.40 mm

Question 26

50 ~ 80

Accepted Answer

0.12 ~ 0.18 mm；0.18 ~ 0.25 mm；0.25 ~ 0.35 mm；0.35 ~ 0.50 mm

Question 27

Bulk Density (g/cm³)

Accepted Answer

1.70 ~ 1.80；1.78 ~ 1.90；1.65 ~ 1.75；1.55 ~ 1.65；1.70 ~ 1.85

Question 28

Compressive Strength (MPa)

Accepted Answer

≥ 180；≥ 200；≥ 140；≥ 100；≥ 160

Question 29

Flexural Strength (MPa)

Accepted Answer

≥ 60；≥ 70；≥ 45；≥ 35；≥ 55

Question 30

Clean / Fresh Water

Accepted Answer

Medium-fine graphite；Phenolic Resin；200°C；Avoid sandy media

Question 31

Seawater

Accepted Answer

Fine-grain high-density；Furan Resin；180°C；Chloride-resistant impregnation needed

Question 32

Mineral / Hydraulic Oil

Accepted Answer

Medium-grain graphite；Phenolic Resin；200°C；Reduce clearance for low-viscosity oil

Question 33

Carbon Graphite vs SiC

Accepted Answer

200°C；25；18；Oil/water lubrication

Question 34

Carbon Graphite vs Stainless Steel

Accepted Answer

180°C；15；10；Oil lubrication

Question 35

Antimony Graphite vs SiC

Accepted Answer

450°C；20；15；Oil/self-lubricating

Question 36

Clean Water Pump — Continuous

Accepted Answer

Centrifugal pump seal；0.02 ~ 0.05；24 ~ 36 months；Medium cleanliness

Question 37

Chemical Pump — Corrosive

Accepted Answer

Reactor agitator seal；0.05 ~ 0.10；12 ~ 24 months；Medium corrosiveness

Question 38

High-Temp Oil Pump — 250°C

Accepted Answer

Hot oil pump seal；0.03 ~ 0.08；18 ~ 30 months；Temperature stability

Question 39

20 ~ 40

Accepted Answer

0.02 ~ 0.05；5 ~ 15；2 ~ 5；Guide chamfer ≥ 15°

Question 40

40 ~ 60

Accepted Answer

0.03 ~ 0.07；15 ~ 30；2 ~ 5；Bore roughness Ra ≤ 1.6

Question 41

60 ~ 80

Accepted Answer

0.04 ~ 0.09；30 ~ 50；1 ~ 3；Apply lubricant before pressing

Question 42

Internal Balanced

Accepted Answer

0.3 ~ 0.6；0.08 ~ 0.15；0.65 ~ 0.75；< 3000 rpm

Question 43

Internal Unbalanced

Accepted Answer

0.4 ~ 0.8；0.10 ~ 0.20；0.85 ~ 0.95；< 1500 rpm

Question 44

External Balanced

Accepted Answer

0.2 ~ 0.5；0.06 ~ 0.12；0.60 ~ 0.70；< 5000 rpm

Question 45

Blank Drying

Accepted Answer

120°C ~ 180°C；8 ~ 24 h；≤ 30°C/h；Remove forming moisture

Question 46

Carbonization Pretreatment

Accepted Answer

800°C ~ 1200°C；4 ~ 8 h；≤ 50°C/h；Base carbonization strengthening

Question 47

Graphitization

Accepted Answer

2200°C ~ 2600°C；2 ~ 6 h；≤ 100°C/h；Improve crystallinity/conductivity

Question 48

High-pitched squeal

Accepted Answer

Face dry friction / insufficient lubrication；Check lubrication flow rate；Increase fluid supply or improve face groove design

Question 49

Low-frequency rumble

Accepted Answer

Bushing clearance too large / shaft vibration；Measure radial runout；Reduce clearance or straighten shaft

Question 50

Face temp > 80°C

Accepted Answer

Face pressure too high / insufficient cooling；Measure seal cavity temp；Reduce spring compression or increase coolant flow

Impregnation Type	Temp. Range	Corrosion Resistance	Applicable Media	Typical Applications
Phenolic Resin	-50°C ~ +200°C	Good	Water, oil, mild acid/alkali	General pump seals, water pumps
Furan Resin	-50°C ~ +250°C	Excellent	Strong acid, strong alkali, organic solvents	Chemical reactors, pickling equipment
Epoxy Resin	-50°C ~ +180°C	Good	Water, oil, alkali	Food machinery, pharmaceutical equipment
Antimony Metal	-100°C ~ +450°C	Moderate	High-temp oil, steam	High-temp pumps, turbine seals
Babbitt Metal	-100°C ~ +350°C	Moderate	High-temp oil, heavy load	Heavy-duty bushings, large bearings
Carbonized (Pure Carbon)	-200°C ~ +600°C	Excellent	Almost all media (incl. vacuum)	High-temp furnaces, semiconductor equipment
PTFE Impregnation	-100°C ~ +250°C	Excellent	Strongly corrosive media, food	Pharmaceutical, chemical, food

Property	Molded Graphite	Isostatic Graphite	Fine Grain Graphite	Coarse Grain Graphite	High-Purity Graphite
Bulk Density (g/cm³)	1.70 ~ 1.80	1.78 ~ 1.90	1.65 ~ 1.75	1.55 ~ 1.65	1.70 ~ 1.85
Compressive Strength (MPa)	≥ 180	≥ 200	≥ 140	≥ 100	≥ 160
Flexural Strength (MPa)	≥ 60	≥ 70	≥ 45	≥ 35	≥ 55
Shore Hardness (HS)	60 ~ 80	65 ~ 85	50 ~ 65	40 ~ 55	55 ~ 75
Porosity (%)	8 ~ 15	5 ~ 12	12 ~ 18	15 ~ 22	10 ~ 15
Max Temp. (°C)	400	500	350	300	600
Typical Uses	Seal rings, bushings	Premium mechanical seals	General bearings	Low-speed bearings	High-temp, vacuum

Medium Type	Recommended Graphite Base	Recommended Impregnation	Max Temp.	Notes
Clean / Fresh Water	Medium-fine graphite	Phenolic Resin	200°C	Avoid sandy media
Seawater	Fine-grain high-density	Furan Resin	180°C	Chloride-resistant impregnation needed
Mineral / Hydraulic Oil	Medium-grain graphite	Phenolic Resin	200°C	Reduce clearance for low-viscosity oil
Strong Acid (H₂SO₄, HCl)	High-purity fine-grain	Furan Resin	250°C	Avoid antimony impregnation with acid
Strong Alkali (NaOH, KOH)	Fine-grain graphite	Furan Resin	200°C	Phenolic resin not recommended
Organic Solvents	Fine-grain graphite	Furan / PTFE	200°C	Confirm solvent doesn't dissolve impregnant
High-Temp Steam	Fine-grain high-density	Carbonized / Antimony	600°C	Watch for oxidation
High-Temp Hot Gas	High-purity graphite	Carbonized	600°C	Limit oxygen < 1%
Vacuum Environment	Isostatic high-density	Carbonized	500°C	Low outgassing required
Food / Pharmaceutical	Fine-grain graphite	Food-grade resin	180°C	FDA/EU certified

Operating Condition	Typical Application	Monthly Wear (mm)	Est. Service Life	Key Factors
Clean Water Pump — Continuous	Centrifugal pump seal	0.02 ~ 0.05	24 ~ 36 months	Medium cleanliness
Chemical Pump — Corrosive	Reactor agitator seal	0.05 ~ 0.10	12 ~ 24 months	Medium corrosiveness
High-Temp Oil Pump — 250°C	Hot oil pump seal	0.03 ~ 0.08	18 ~ 30 months	Temperature stability
Wastewater Pump — Particles	Sewage pump seal	0.10 ~ 0.20	6 ~ 12 months	Particle hardness/concentration
High-Speed Pump — >3000rpm	Boiler feed pump	0.04 ~ 0.08	12 ~ 20 months	Speed/balance
Dry Running — Intermittent	Fan bearing	0.01 ~ 0.03	36 ~ 60 months	Start-stop frequency
Marine Seawater Pump	Stern shaft seal	0.03 ~ 0.06	18 ~ 36 months	Seawater sand content

Bushing O.D. (mm)	Recommended Interference (mm)	Max Press Force (kN)	Press Speed (mm/s)	Notes
20 ~ 40	0.02 ~ 0.05	5 ~ 15	2 ~ 5	Guide chamfer ≥ 15°
40 ~ 60	0.03 ~ 0.07	15 ~ 30	2 ~ 5	Bore roughness Ra ≤ 1.6
60 ~ 80	0.04 ~ 0.09	30 ~ 50	1 ~ 3	Apply lubricant before pressing
80 ~ 120	0.05 ~ 0.12	50 ~ 80	1 ~ 3	Recommended shrink-fit or heat-fit
120 ~ 160	0.06 ~ 0.15	80 ~ 120	1 ~ 2	Use force-displacement monitoring
160 ~ 200	0.08 ~ 0.18	120 ~ 180	0.5 ~ 1	Step-press, check each stage

Shaft Dia. (mm)	Speed < 500 rpm	Speed 500~1500 rpm	Speed 1500~3000 rpm	Speed > 3000 rpm
10 ~ 25	0.08 ~ 0.12 mm	0.10 ~ 0.15 mm	0.15 ~ 0.20 mm	0.20 ~ 0.30 mm
25 ~ 50	0.10 ~ 0.15 mm	0.15 ~ 0.20 mm	0.20 ~ 0.30 mm	0.30 ~ 0.40 mm
50 ~ 80	0.12 ~ 0.18 mm	0.18 ~ 0.25 mm	0.25 ~ 0.35 mm	0.35 ~ 0.50 mm
80 ~ 120	0.15 ~ 0.22 mm	0.22 ~ 0.30 mm	0.30 ~ 0.42 mm	0.42 ~ 0.60 mm
120 ~ 200	0.18 ~ 0.28 mm	0.25 ~ 0.38 mm	0.35 ~ 0.50 mm	0.50 ~ 0.70 mm

Material Combination	Max Temp.	Max Linear Speed (m/s)	PV Limit (MPa·m/s)	Lubrication
Carbon Graphite vs SiC	200°C	25	18	Oil/water lubrication
Carbon Graphite vs Stainless Steel	180°C	15	10	Oil lubrication
Antimony Graphite vs SiC	450°C	20	15	Oil/self-lubricating
Carbonized Graphite vs SiC	600°C	30	22	Self-lubricating
Carbon Graphite vs Ceramic	250°C	20	14	Water/oil lubrication
Babbitt Graphite vs Steel	350°C	12	8	Oil lubrication
Graphite vs Graphite	300°C	8	5	Self-lubricating

Seal Type	Face Pressure Pc (MPa)	Spring Pressure Ps (MPa)	Pressure Coeff. K	Speed Range
Internal Balanced	0.3 ~ 0.6	0.08 ~ 0.15	0.65 ~ 0.75	< 3000 rpm
Internal Unbalanced	0.4 ~ 0.8	0.10 ~ 0.20	0.85 ~ 0.95	< 1500 rpm
External Balanced	0.2 ~ 0.5	0.06 ~ 0.12	0.60 ~ 0.70	< 5000 rpm
Dual Face Seal	0.3 ~ 0.7	0.10 ~ 0.18	0.65 ~ 0.80	< 4000 rpm
High-Temp Flexible Seal	0.15 ~ 0.35	0.05 ~ 0.10	0.55 ~ 0.65	< 2000 rpm

Process	Temperature Range	Hold Time	Ramp Rate	Purpose
Blank Drying	120°C ~ 180°C	8 ~ 24 h	≤ 30°C/h	Remove forming moisture
Carbonization Pretreatment	800°C ~ 1200°C	4 ~ 8 h	≤ 50°C/h	Base carbonization strengthening
Graphitization	2200°C ~ 2600°C	2 ~ 6 h	≤ 100°C/h	Improve crystallinity/conductivity
Resin Impregnation Curing	150°C ~ 200°C	4 ~ 12 h	≤ 20°C/h	Fill porosity
Metal Impregnation (Sb)	600°C ~ 800°C	2 ~ 4 h	≤ 60°C/h	Vacuum metal impregnation
Babbitt Impregnation	300°C ~ 400°C	1 ~ 3 h	≤ 40°C/h	Bearing alloy filling
PTFE Impregnation Sintering	360°C ~ 380°C	2 ~ 6 h	≤ 30°C/h	PTFE filling and sintering
Stabilization Annealing	200°C ~ 350°C	6 ~ 12 h	≤ 25°C/h	Relieve machining stress

Symptom	Possible Cause	Diagnostic Method	Solution
High-pitched squeal	Face dry friction / insufficient lubrication	Check lubrication flow rate	Increase fluid supply or improve face groove design
Low-frequency rumble	Bushing clearance too large / shaft vibration	Measure radial runout	Reduce clearance or straighten shaft
Face temp > 80°C	Face pressure too high / insufficient cooling	Measure seal cavity temp	Reduce spring compression or increase coolant flow
Slow oil leak (drips/min)	Face flatness degraded / abrasive embedding	Check face lapping quality	Re-lap or replace seal ring
Major leakage	Seal ring cracked / installation misaligned	Stop and inspect seal face	Replace seal and recalibrate installation
Leaks on start-up only	Static seal aged / clearance changed	Check O-ring and bushing	Replace elastic seal
Gradually increasing noise	Bearing wear accumulation	Measure bearing clearance trend	Schedule bushing replacement
Abnormal face wear	Hard particles in medium	Filter and analyze medium sample	Add upstream filter or switch to wear-resistant grade

Symbol	Meaning
C	Operating clearance (mm)
C₀	Initial assembly clearance (mm), typically 0.02~0.08 mm
α₁	Housing material CTE (steel ≈ 11×10⁻⁶ /°C)
α₂	Graphite CTE (≈ 2~4×10⁻⁶ /°C)
d	Shaft diameter (mm)
ΔT₁	Housing temperature rise (°C)
ΔT₂	Graphite temperature rise (°C)
K	Centrifugal force coefficient (≈ 0.001~0.003)
n	Speed (rpm)

Symbol	Meaning
V	Linear speed (m/s)
d	Seal face mean diameter (mm)
n	Speed (rpm)
π	Pi (≈ 3.1416)

Symbol	Meaning
Pc	Face specific pressure (MPa)
Ps	Spring specific pressure (MPa), typically 0.08~0.20 MPa
B	Balance ratio (balanced 0.65~0.85, unbalanced 0.90~1.10)
K	Pressure coefficient (≈ 0.5~0.7)
P	Medium pressure (MPa)

Symbol	Meaning
ΔL	Dimension change (mm)
α	Material CTE (/°C)
L	Original dimension (mm)
ΔT	Temperature change (°C) = operating temp - installation temp

Symbol	Meaning
σ_max	Maximum hoop tensile stress (MPa)
δ	Interference (mm)
E	Graphite elastic modulus (≈ 8000~12000 MPa)
d	Bushing O.D. (mm)
μ	Graphite Poisson ratio (≈ 0.15~0.25)
[σ]	Graphite allowable stress (tensile strength / safety factor)
S	Safety factor (recommended 3~5)

FAQ | Huahao Sealing

Core Reference Tables

Impregnation Quick Selection Guide

Bushing Clearance Standard Calculation

Graphite Material Property Comparison

Medium Adaptation Material Selection

Temperature & Speed Limit Parameters

Wear Life Estimation Reference

Press-Fit Force Safety Reference

End Face Specific Pressure Calculation

Graphite Heat Treatment / Impregnation Temperature Parameters

Noise, Overheating & Leakage Troubleshooting Guide

FAQ Categories

Selection

How to select graphite material for high/low temperature?

How to choose impregnation for wet/dry conditions?

Best graphite for high-speed / heavy-load / low-pressure?

Oil-free vs oil-lubricated material selection?

Assembly Clearance

How to fix vibration (excessive clearance) or seizure (too tight)?

Standard fit tolerances by shaft diameter?

How to adjust clearance for thermal expansion?

Machining & Installation

Graphite turning, drilling, and grinding precautions?

How to fix press-fit misalignment, edge chipping, and cracking?

How to control interference fit tightness?

Operational Faults

How to handle excessive operating temperature?

How to fix minor oil/water seepage?

Causes of noise, vibration, and rapid wear?

How to resolve high-temperature carbonization and powdering?

Maintenance

Break-in procedure for initial operation?

Storage and preservation for long-term shutdown?

Wear limits and replacement criteria?

Custom & Non-Standard Orders

Mold considerations for custom graphite parts?

Groove, oil groove, and rabbet design standards?

Expedited custom machining with quality assurance?

Technical Formulas

Bushing Clearance General Formula

Symbol

Linear Speed Limit Formula

Symbol

End Face Specific Pressure Formula

Symbol

Thermal Expansion Compensation Formula

Symbol

Press-Fit Interference Safety Formula

Symbol

Still have questions?

FAQ | Huahao Sealing

Core Reference Tables

Impregnation Quick Selection Guide

Bushing Clearance Standard Calculation

Graphite Material Property Comparison

Medium Adaptation Material Selection

Temperature & Speed Limit Parameters

Wear Life Estimation Reference

Press-Fit Force Safety Reference

End Face Specific Pressure Calculation

Graphite Heat Treatment / Impregnation Temperature Parameters

Noise, Overheating & Leakage Troubleshooting Guide

FAQ Categories

Selection

How to select graphite material for high/low temperature?

How to choose impregnation for wet/dry conditions?

Best graphite for high-speed / heavy-load / low-pressure?

Oil-free vs oil-lubricated material selection?

Assembly Clearance

How to fix vibration (excessive clearance) or seizure (too tight)?

Standard fit tolerances by shaft diameter?

How to adjust clearance for thermal expansion?

Machining & Installation

Graphite turning, drilling, and grinding precautions?

How to fix press-fit misalignment, edge chipping, and cracking?

How to control interference fit tightness?

Operational Faults

How to handle excessive operating temperature?

How to fix minor oil/water seepage?