Accessories | Observation Ports
2" NPT(M) WITH REPLACEMENT LENS AND RUGGED STAINLESS STEEL BODY CONSTRUCTION
The design of the 8790-4-A family of observation ports was up- dated in early 2024. The body, cap and fasteners are upgraded to series 300 stainless steel from previous cast iron construction. Three replaceable lens options are available; clear Pyrex glass, blue Pyrex glass for luminous flames or a high temperature quartz lens with a heat reflective coating. Gaskets are mode from 1⁄16 " thick flexible graphite (GRAFOIL).
replacement part numbers
dimensions in inches
Part
2" Ø Lens
Max.
Max.
Hex
Max. Overall
Installed
Gasket
Designation
1/4" thick psi (bar) Temp. °F(C) Width
Ø
Length
Length
(2 Req'd)
Lens
800 (427) 800 (427) 1300 (704)
8790-4-A
Clear Pyrex
R530-2069
5
2.75 (70)
3.00 (76.2)
2.00
1.50
8790-4-4B
Blue Pyrex
4-3903-1
R530-2068
(0.35)
(51)
(38.1)
8790-4-AC
Coated Quartz
R530-2071
8790-4-A = Clear Pyrex glass 8790-4-AB = Blue Pyrex glass for luminous flames or high temperature furnaces 8790-4-AC = Ground & polished high temperature quartz with heat reflective coating
1.75 Ø (43)
2.75 (70)
2.0 (51)
2" NPT(M) LEGACY 8790-4-A WITH REPLACEABLE LENS AND CAST IRON CONSTRUCTION
The legacy 8790-4-A observation ports were made from cast iron and are no longer available. The replacement lens and gaskets for the current design (shown in the replacement part table above) still work in the legacy observation ports.
Legacy cast iron 8790-4-A (pre-2024)
Bulletin 8790 page 2
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