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Metric US
Coefficient of mean linear thermal expansion α acc. to DIN ISO 7991 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Transformation temperature Tg 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Density ρ at 25°C 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Modulus of elasticity E (Young's modulus) 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Poisson's ratio µ 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Thermal conductivity λw at 90°C 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Refractive index (λ = 587.6nm) nd 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
Stress-optical coefficient (DIN 52 314) K 3.3 * 10-6 K-1 (20°C; 300°C) 3.3 * 10-6 K-1 (68°F; 572°F)
SiO2 B2O2 Na2O + K2O Al2O3
81 13 4 2
Main components in approx. weight %
Hydrolytic Class (DIN ISO 719) HGB 1
Acid Class (DIN 12116) Class S 1
Alkali Class (DIN ISO 695) Class A 2



When the glass tube is filled with water, the transmission increases from about 92% to 95.6% due to reduced reflection losses at the inner glass/water interface.

Pressure Resistance of Tubing made of Borosilicate Glass

The following formulas apply to stress free, pristine tubing and cylindrical hollow bodies with a circular profile, uniform wall thickness with open ends, free from thermal load, under internal positive pressure and external negative pressure.

Estimation of the maximum pressure resistance (p):
Estimation of the minimum wall thickness (WT):
OD = Outside Diameter in mm WT = Wall Thickness in mm p = Pressure Resistance in bar

permissible load refferring to standard DIN EN 1595:

Pressure Equipment made from Borosilicate Glass 3.3 General Rules for Design, Manufacture and Testing

Other points to be considered:
AD 2000-leaflet N 4, edition 2000-10:
Pressure vessels made of glass, with encl. 1, edition 2000-10: Evaluation of faults in walls of glass pressure containers
AD 2000-leaflet B 1, edition 2000-10:
Cylindrical and spherical shells under internal pressure overload
According to DIN EN 1595 "Pressure Equipment made from Borosilicate Glass 3.3 - General Rules for Design, Manufacture and Testing", DURAN® is an approved material and may be used for the construction of pressure equipment.

For the optimum construction of a photobioreactor the expected pressure loss in the system must be known. This information is absolutely relevant for the lay-out of an ideal pump design. For the calculation of the pressure drop of the entire photobioreactor system the pressure drops of the individual components must be added together and these individual pressure drops must be calculated for the desired velocity, u.

In the following table the individual pressure drops of representative glass components are shown for a typical flow velocity of 0.7 m/s. The pressure drops depend on the dimensionless zeta-value, which slightly decrease at larger velocities. Please contact SCHOTT technical service for assistance and additional simulations.

u = 0.7 m/s ζ δ p [pa]
Round Tube
(D = 65 mm, WT = 2.2 mm, L = 5.5 m)
1.96 480
U-bend (L = 5.5 m)
(D = 65 mm, WT = 2.8 mm)
0.252 62
Pressure drops of a tube and a U-bend at the given velocity, u. D is the outer diameter, WT the wall thickness. The algae culture’s density was approximated with ρ=1 g/cm3.
In general and under the approximation of a velocity independent zeta-value, the pressure drop can be calculated for any velocity using the formula left.

∆pv: Pressure loss in Pa

ζ : Pressure loss number

ρ: Density in kg/m3

d: Inner tube diameter in m

up: Process velocity in m/s

Q: Volume flow rate m3/s round tube: Q = 0,25 * d2π * up

The investigated oval tubes of SCHOTT with their elevated light absorption need only an electrical power compared to the one of conventional round tubes with the same process velocity. Thus a higher productivity of the photobioreactor can be achieved at similar move to next line so there is no operational energy costs. The electrical power of the pumps, Pel, scales with the pressure drop and the volume flow, Q:
Pel: Electrical power ∆pv-ε: Sum of pressure loss in Pa Q: Volume flow rate in m3/s ηp: Pump efficiency at operating point (ηp<1)