Jerguson Gage & Valve
Series 20 Armored Level Gage
ANSI 600# Class · 3270 PSI @ 100°F · FM Approved · Reflex & Transparent · CS, 316LSS & A350 LF2
The Jerguson Series 20 is a medium-to-high pressure armored level gage rated to ANSI 600# class — 3270 PSI at 100°F in carbon steel. The one-piece chamber is machined from bar stock, eliminating weld seams from the pressure boundary. Recessed tie-bar supports span the chamber mid-section, providing structural reinforcement without creating a blind spot in the visible length. Bar stock covers, tempered borosilicate glass, and alloy steel hardware (A193 B7 / A194 2H) complete the assembly.
The Series 20 is FM Approved and available in carbon steel, low-temperature carbon steel (A350 LF2) for cryogenic and cold service, and 316LSS. An aluminosilicate glass option extends the temperature rating to 800°F. Multi-section assemblies provide up to 111-1/2" of visible length.
Reflex Style Shown with Optional Side Connections.
Max Pressure
3270 PSI @ 100°F (CS) · 3140 PSI @ 100°F (316LSS)
Max Temperature
600°F (316°C)
Approvals
FM Approved
Glass
Reflex or transparent; borosilicate standard; aluminosilicate to 800°F
Body Material
Carbon Steel · 316LSS · Low Temp CS (A350 LF2)
Connections
1/2" or 3/4" NPT female standard; flanged or socket weld optional
Single-Section Visible
3-3/4" to 12-5/8"
Multi-Section Visible
Up to 111-1/2" (7 sections)
Hardware
A193 B7 / A194 2H alloy steel bolts and nuts
Key Features
Pressure-Temperature Ratings (PSI)
| Body Material | 100°F | 200°F | 300°F | 400°F | 500°F | 600°F |
|---|---|---|---|---|---|---|
| Carbon Steel | 3270 | 3185 | 3075 | 2900 | 2700 | 2285 |
| 316LSS | 3140 | 2970 | 2790 | 2620 | 2450 | 2130 |
| Low Temp CS (A350 LF2) | 3270 | 3185 | 3075 | 2900 | — | — |
Ratings are for the gage body. Borosilicate glass is rated to 600°F; aluminosilicate glass extends to 800°F. Mica shield required for steam service above 406°F (208°C). Low Temp CS (A350 LF2) not rated above 400°F — contact NCI for exact limits.
Single-Section Visible Lengths
Multi-Section Assemblies
| Number of Sections | Maximum Visible Length |
|---|---|
| 2 sections | 31-1/4" |
| 3 sections | 47-7/8" |
| 4 sections | 64-1/2" |
| 5 sections | 81-1/8" |
| 6 sections | 97-3/4" |
| 7 sections | 111-1/2" |
Multi-section assemblies use center valves between sections. Contact NCI for specific length configurations.
Reflex vs. Transparent Glass — Which to Choose?
Reflex (Prismatic) Glass
- →Liquid appears dark; vapor/gas appears bright silver
- →Self-illuminating — no external illuminator needed
- →Single glass piece — generally higher pressure rating
- →Best for water, steam, and clear process liquids
- →Mica shield available for steam and corrosive service
Transparent (Flat) Glass
- →Direct view of fluid color, clarity, and turbidity
- →Interface detection between two immiscible liquids
- →Illuminator recommended for dark or opaque fluids
- →Two glass pieces (front and back)
- →Best for colored fluids and interface detection
How to Order — Model Code
Specify series, glass type, visible length, body material, connection type, connection size, and any accessories. Example: 20-R-12-5/8-C-N-3/4-M = Series 20, reflex glass, 12-5/8" visible, carbon steel, 3/4" NPT, mica shield.
| Pos. | Field | Options |
|---|---|---|
| 1 | Series | 20 |
| 2 | Glass Type | R = Reflex · T = Transparent |
| 3 | Visible Length | Specified in inches (e.g., 10-1/4", 14-1/4") |
| 4 | Body Material | C = Carbon Steel · S = 316LSS |
| 5 | Connection Type | N = NPT female (std) · SW = Socket Weld · F = Flanged |
| 6 | Connection Size | 1/2" or 3/4" NPT; flange size as specified |
| 7 | Accessories | M = Mica Shield · I = Illuminator · D = Drain Plug |
Accessories & Options
Mica Shield
Protects glass from corrosive, caustic, or wet steam service. Required for steam above 406°F (208°C).
Illuminator
Recommended for transparent gages with dark or opaque fluids. Standard and explosion-proof configurations available.
Drain Plug
Plugged drain connection in the lower chamber for draining the gage body.
Isolation Valves
Jerguson gauge cocks and isolation valves for block-and-bleed service. See Jerguson Isolation Valves page.
Multi-Section Assemblies
Two to seven gage sections connected with center valves for extended visible length up to 111-1/2".
Typical Applications
High-Pressure Process Vessels
Level indication on process vessels up to 3270 PSI in chemical, petrochemical, and refining service.
Boiler Drum Level
Medium-to-high pressure boiler drum water level monitoring. Mica shield required for wet steam above 406°F.
Gas/Liquid Separators
Liquid level indication on high-pressure gas/liquid separators and knockout drums.
Cryogenic & Cold Service
Low-temperature A350 LF2 body option for cryogenic storage vessels and cold process service.
Hazardous Location (FM)
FM Approved for installation in classified hazardous locations in petrochemical and refining plants.
Interface Detection
Transparent glass option for detecting the interface between two immiscible liquids at elevated pressure.
Heat Exchanger Level
Monitor liquid level in high-pressure heat exchanger shells and condensate pots.
ANSI 600# Class Service
Rated to ANSI 600# class pressure-temperature envelope. Suitable for demanding process services up to 3270 PSI.
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