HYDROSPACE manufactures a full range of approved PVHO window geometries. These meet the requirements of the ASME PVHO-1 Safety Standard which are described in detail and available through ASME in the publication below:
ASME PVHO-1 Safety Standard for Pressure Vessels for Human Occupancy
PVHO is a self-regulated code providing safety guidelines for the design, fabrication, testing and life of acrylic windows. The maximum operating pressure of a window depends on the operating temperature, dimension and shape. The PVHO geometries includes:
1) Flat Disc Windows
Flat disc windows are the simplest form. The design is controlled by the window OD and the thickness. Also critical is the window seat ID which determines the internal “unsupported” diameter (Di) of the window. The window ratio of its thickness to the Di is used to determine its max operating pressure. (Refer to ASME PVHO-1 for full details)
Critical Parameters
t ≥ 0.50 inch (12.5 mm)
t/Do ≥ 0.08
Do/Di ≥ 1.25
Standard PVHO Life: 10 years
– (for Life Extension see ASME PVHO-2)
2) Conical Frustrum Windows
Conical frustum configurations are common for high pressure applications. The design is controlled by the window outer diameter (Do), thickness (t) and the angle of inclusion (α) which determines the inner diameter Di. The ratio of the window thickness to the inner diameter Di is used to determine its max operating pressure. The window seat inner diameter Df is important as is the ratio of Di/Df. (Refer to ASME PVHO-1 for full details)
Critical Parameters
t ≥ 0.50 inch (12.5 mm)
t/Di ≥ 0.125
angle α ≥ 60 degrees
Di/Df ratio depends on pressure
Standard PVHO Life: 10 years
– (for Life Extension see ASME PVHO-2)
3) Spherical Sector with Conical Edge
Spherical sector windows present a convex shape on the high pressure side. This offers great strength with optimal thickness. The design is controlled by the inner radius (Ri) and thickness (t). A range of angles (α) are permitted. The ratio of its thickness to Ri determines its maximum operating pressure. The “Conical Edge” is the simplest sealing surface. Spherical Sectors with “Square Edge” are treated very differently. (Refer to ASME PVHO-1 for full details)
Critical Parameters
t ≥ 0.50 inch (12.5 mm)
angle α ≥ 30 degrees
t/Ri ≥ 0.06 for α ≥ 90 degrees
t/Ri ≥ 0.03 for α ≥ 180 degrees
Standard PVHO Life: 20 years
– (for Life Extension see ASME PVHO-2)
4) Hemispherical Dome with Equatorial Flange
Hemispherical domes provide the largest viewing area of the spherical sector windows. The equatorial flange offers a simple retaining mechanism but also limits the window life to 10 years. The maximum operating pressure is controlled by the ratio of the thickness (t) to the inner radius (Ri). The flange dimension (X) is also dependent on the window thickness. Full height of the dome is Ri + 2t. (Refer to ASME PVHO-1 for full details)
Critical Parameters
t ≥ 0.50 inch (12.5 mm)
0.2 ≥ t/Ri ≥ 0.03
Rm ≥ 0.125 inch
2.0t ≥ X ≥ 1.5t
Standard PVHO Life: 10 years
– (for Life Extension see ASME PVHO-2)
5) Cylindrical Windows
Cylindrical windows are very commonly used in medical hyperbaric chamber applications. The design is controlled by the length, diameter and thickness of the window. The maximum operating pressure is determined by both the Length/Diameter ratio (L/D) and the Thickness/Diameter ratio (t/D). Design parameters change depending on whether the window is operated under internal or external pressure. (Refer to ASME PVHO-1 for full details)
Critical Parameters
t ≥ 0.50 inch (12.5 mm)
D = (Do + Di) / 2
L/D and t/D
Standard PVHO Life: 10 years
– (for Life Extension see ASME PVHO-2)
6) Hyper Hemispheres
Hyper Hemispheres are spherical windows that make up a complete sphere with the addition of one access hatch. The maximum operating pressure is controlled by the t/Ro ratio of thickness (t) and Outer Radius (Ro). Because the window is always under compression, this geometry has a life of 20 years. (Refer to ASME PVHO-1 for full details)
