North American Observation Ports
Bulletin 8790
8790 Observation Ports allow visual checking of flames and are available in many sizes with male NPT threaded connections. The 3/8" through 1-1/2" NPT sizes feature a non-replaceable clear glass lens with fused construction. The body is made from Nickel plated steel or Brass. The 2” 8790-4-A has three replaceable lens options; clear Pyrex glass, blue Pyrex glass for luminous flames or a high temperature quartz lens with a heat reflective coating. The body, cap and fasteners are made from series 300 stainless steel (ports made before 2024 were painted cast iron). It may be beneficial in some higher temperature applications to install observation ports with cooling air or a purge air adapter assembly.
8790-02 8790-01 R530-2028 8790-1 R530-2040-ES R530-2011
8790-0
8790-4-A 8790-4-AB 8790-4-AC
3/8" TO 1-1/2" NPT(M) WITH FUSED CONSTRUCTION
dimensions in inches
Part
Max.
Max.
pipe size
Hex
Max.
Overall Length
Installed
Body
Designation psi (bar) temp. °F (C) NPT(M)
Width"
Ø
Length
Material
300+
500
0.88 (22.2)
0.75 (19.1)
0.38 (9.5)
8790-02
0.75
Nickel plated steel
3⁄8
(21+)
(260)
300+
500
1.06
1.25
0.44 (11.2)
8790-01
0.94
Nickel plated steel
½
(21+)
(260)
(26.9)
(31.8)
10
500
1.25
1.00
0.63 (15.9)
8790-0
1.13
Brass
¾
(0.69)
(260)
(31.8)
(25.4)
300+
500
1.25
1.00
0.63 (14.4)
R530-2028
1.06
Nickel plated steel
¾
(21+)
(260)
(40.1)
(31.8)
300+
500
1.58 (51.1)
1.25
0.57
8790-1
1
1.38
Nickel plated steel
(21+)
(260)
(31.8)
(13)
300+
500
2.01 (51.1)
1.219
0.51 (13)
R530-2040-ES
1 ¼
1.75
Nickel plated steel
(21+)
(260)
(31)
300+
500
2.30
1.219
0.50 (12.6)
R530-2011
1 ½
2
Nickel plated steel
(21+)
(260)
(58.4)
(31)
Spare parts are available for the old 8790-0 with removable lens R530-2026 (gasket), R530-2025 (lens)
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