EKasic^® SILICON CARBIDE MECHANICAL SEALS

Mechanical seals are used for sealing rotating shafts with respect to, e.g., housings. One part of the mechanical seal rotates with the shaft; the other part is stationary. The ring that can move axially is called the sliding ring or rotary face, and the other, the counter ring or stationary face. The face surfaces of both rings are machined flat (flatness < 0.6 µm) and are perpendicular to the shaft.

Well-known manufacturers rely on our sliding rings and counter rings for this application. They are generally produced from sintered silicon carbide EKasic^®, exclusively to customers’ specifications.

Applications

Mechanical seals of EKasic^® silicon carbide are particularly suitable for heavy-duty applications, such as:

Contaminated fluids
Abrasive fluids and/or
Extremely corrosive fluids

The rings are pressed together by spring force, and the faces of the rings form the seal. The medium to be sealed penetrates between the seal faces, where it forms a lubricating film (process fluid-lubricated seal). Sealing of the EKasic^® sliding rings with respect to the shaft or housing is performed by means of secondary seals in the form of additional static gasket elements (O rings or sleeves).

Specifications

Mechanical seals are currently available for shaft diameters from approx. 5 mm to 500 mm. They can be used in service pressures up to 200 bar, temperatures from about -200°C to +450°C and sliding velocities up to approx. 150 m/s.

			Silicon Carbide
Material properties	Norm	Symbol/Unit	EKasic^® F	EKasic^® F plus	EKasic^® T
Density	DIN EN 623-2	ρ [g/cm³]	>3.10	>3.16	>3.21
Porosity	DIN EN 623-2	P [%]	<3.0	<1.0	<1.0
Mean grain size		[μm]	<5	<5	<2
Grain size distribution		[μm]
Phase composition			α-SiC	α-SiC	α-SiC, YAG
Vickers hardness	DIN EN 843-4	HV 1 [GPa]	25.5	25.5	22.5
Knoop hardness	DIN EN 843-4	HK 0.1 [GPa]	24.5	24.5	21.0
Young's modulus	DIN EN 843-2	E [GPa]	410	420	420
Weibull modulus	DIN EN 843-5	m	10	15	15
Flexural strength, 4-pt bending	DIN EN 843-1	σ_B [MPa]	400	510	550
Compressive strength		σ_D [MPa]	2200	2200	2500
Poisson ratio		ν	0.17	0.17	0.16
Fracture toughness (SENB)		K_lc[MPa·m^0,5]	4	4	6
Coefficient of thermal expansion	DIN EN 821-1
20°C - 500°C		α [10^-6/K]	4.1	4.1	3.5
500°C - 1000°C		α [10^-6/K]	5.2	5.2	5.2
Specific heat at 20°C	DIN EN 821-3	c_p [J/g K]	0.6	0.6	0.6
Thermal conductivity at 20°C	DIN EN 821-2	λ [W/mK]	125	125	75
Thermal stress parameters	calculated
R₁ = σ_B·(1-ν) / (α·E)		R1 [K]	198	246	314
R₂ = R₁·λ		R2 [W/mm]	25	31	24
Specific electrical resistance at 20°C	DIN EN 50359	ρ [Ω cm]	10⁶-10⁸	10⁶-10⁸	10²-10³

			Silicon Carbide
Material properties	Norm	Symbol/Unit	EKasic^® C	EKasic^® P	EKasic^® G
Density	DIN EN 623-2	ρ [g/cm³]	>3.10	>2.76- 2.89	>3.02
Porosity	DIN EN 623-2	P [%]	<3.0	10-14	<3.0
Mean grain size		[μm]	bimodal	<5	bimodal
Grain size distribution		[μm]	10-1500		10-1000
Phase composition			α-SiC	α-SiC	α-SiC, graphite
Vickers hardness	DIN EN 843-4	HV 1 [GPa]	25.5	23.5	24.5
Knoop hardness	DIN EN 843-4	HK 0.1 [GPa]	24.5	21.6	23.0
Young's modulus	DIN EN 843-2	E [GPa]	410	340	390
Weibull modulus	DIN EN 843-5	m	10	15	14
Flexural strength, 4-pt bending	DIN EN 843-1	σ_B [MPa]	400	225	230
Compressive strength		σ_D [MPa]	2500	2000	2500
Poisson ratio		ν	0.17	0.17	0.16
Fracture toughness (SENB)		K_lc[MPa·m^0,5]	3.5	3	3
Coefficient of thermal expansion	DIN EN 821-1
20°C - 500°C		α [10^-6/K]	4.1	3.5	4.0
500°C - 1000°C		α [10^-6/K]	5.2	5.6	5.0
Specific heat at 20°C	DIN EN 821-3	c_p [J/g K]	0.6	0.6	0.6
Thermal conductivity at 20°C	DIN EN 821-2	λ [W/mK]	125	90	110
Thermal stress parameters	calculated
R₁ = σ_B·(1-ν) / (α·E)		R1 [K]	198	157	124
R₂ = R₁·λ		R2 [W/mm]	25	14	14
Specific electrical resistance at 20°C	DIN EN 50359	ρ [Ω cm]	10³-10⁴	10⁶-10⁸	10³-10⁴