[PSUBS-MAILIST] Clearances

[Sean T. Stevenson via Personal_Submersibles]

Rick, is this a flat disc viewport, and not a dome?

See an excerpt from ASME PVHO-1-2023 below. Do, where referenced, is the window major diameter.
2-2.11.4 Flat Disk Windows

2-2.11.4.1 Window External Diameter.

The dimensional tolerance of the external diameter of the window shall be based on the type of sealing arrangement for the window.

(a) The external diameter of the flat disk window shall be within +0.000/−0.010 in. (+0.000/−0.25 mm) of the nominal value if the window is to be sealed in the seat cavity with a radially compressed O-ring.

(b) The external diameter of the flat disk window shall be within +0.000/−0.060 in. (+0.000/−1.5 mm) of the nominal value if the window is to be sealed in the seat
cavity with a seal ring wedged into the annular space between the retaining ring, the window’s bevel, and the cylindrical surface of the seat cavity.

(c) The external diameter of the flat disk window shall be within +0.0/−0.125 (+0.0/−3.2 mm) of the nominal value if the window is to be sealed in the seat cavity with a flat elastomeric gasket axially compressed by the retaining ring.

(d) The external diameter of the flat disk window shall be within +0.00/−0.02 Do of the nominal value if the window is to be sealed in the seat cavity with a room temperature curing elastomeric compound injected into the annular space between the edge of the window and the cylindrical surface of the seat.

(e) The plane bearing surface of the flat disk window shall not deviate more than 0.001 Do from an ideal plane.

2-2.11.4.2 Seat Cavity Diameter.

The dimensional tolerance on the external diameter of the window seat
cavity shall be based on the type of sealing arrangement for the window.

(a) The diameter of the seat cavity for a flat disk window shall be within +0.01/−0.00 in. (+0.25/−0.00mm) of the nominal value if the window is to be sealed in the seat cavity with a radially compressed O-ring.

(b) The diameter of the seat cavity for a flat disk window shall be within +0.06/−0.00 in. (+1.5/−0.00mm) of the nominal value if the window is to be sealed in the seat cavity with a seal ring wedged into the annular space between the retaining ring, the window’s bevel, and the cylindrical surface of the seat cavity.

(c) The diameter of the seat cavity for a flat disk window shall be within +0.125/−0.000 in. (+3.2/−0.00mm) of the nominal value if the window is to be sealed in the seat cavity with a flat elastomeric gasket axially compressed by the retaining ring.

(d) The diameter of the seat cavity for a flat disk window shall be within +0.01 Do /−0.000 of the nominal value if the window is to be sealed in the seat cavity with a room-temperature curing elastomeric compound injected into the annular space between the edge of the window and the cylindrical surface of the seat.

(e) The plane bearing surface of the seat cavity shall not deviate more than 0.002 Do from an ideal plane when measured with a feeler gauge inserted between the mating plane surfaces of the flat disk window or a circular plug gauge and the bare seat cavity. The axial force used to seat the window or the plug gauge shall not exceed 10 Do lb (4.53 Do kg) applied uniformly around its circumference.

Sean
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