Jerguson Gage & Valve
Reflex & Transparent Armored Level Gages
Series 300L · Series 32 · Series 20 · Series L10 — Reflex & Transparent Glass, 750–3270 PSI
Jerguson armored level gages provide direct visual liquid level indication on process vessels, boilers, storage tanks, and heat exchangers. All series feature one-piece bar stock chambers — no weld seams in the pressure boundary — with tempered borosilicate glass retained by forged or bar stock covers and alloy steel hardware. Reflex glass (prismatic) provides self-illuminating level indication; transparent glass (flat, two-piece) allows direct viewing of fluid color, clarity, and interface. Mica shields are available for steam and corrosive service on all series.
Available Series
The Jerguson Series 300L is the standard armored level gage for low-to-medium pressure service. The one-piece chamber is machined from bar stock — A696 Grade C carbon steel or A511 Grade TP316L stainless steel. Bar stock covers, tempered borosilicate glass, and steel bolts and nuts (A193 B7 / A194 2H). Recessed gasket seats in both chamber and cover aid in positioning and retaining the gasket. Replaces the older Series 12 and Series 5 gages.
Reflex & Transparent Styles Shown.
Max Pressure
750 PSI @ 100°F (CS) · 720 PSI @ 100°F (316LSS)
Max Temperature
600°F (316°C)
Glass
Reflex or transparent; tempered borosilicate per BS 3463, JIS B8211, DIN 7080/7081
Body Material
Carbon Steel (A696 Gr. C) or 316LSS (A511 TP316L)
Connections
1/2" or 3/4" NPT female standard; flanged or socket weld optional
Visible Length
Single section 10-1/4" to 19-1/4" visible; multi-section to 124-3/4" visible
Key Features
The Jerguson Series L10 is designed for accurate liquid level readings in liquids that tend to surge, boil, or flash. The large chamber reduces boiling effects from entrained gas released under lowered pressure, liquid vaporization at critical low pressure, and boiling caused by temperatures exceeding the boiling point. A non-frosting unit is available for liquids with unusually low boiling points such as liquid ammonia, liquid oxygen, and liquid nitrogen.
Transparent Style Shown with Optional Flanged Connections.
Max Pressure
Low pressure service — contact NCI for ratings
Max Temperature
Contact NCI for ratings
Glass
Transparent borosilicate glass
Body Material
Carbon Steel or 316 Stainless Steel
Connections
NPT or flanged; contact NCI for available configurations
Visible Length
Contact NCI for available lengths
Key Features
The Jerguson Series 20 is a high-pressure armored level gage for demanding process service. One-piece chamber machined from bar stock, forged steel covers, tempered borosilicate glass, and alloy steel bolts and nuts (A193 B7 / A194 2H). Recessed gasket seats aid in positioning and retaining the gasket. Available in carbon steel, low-temperature carbon steel (A350 LF2), and 316LSS. FM Approved. Aluminosilicate glass option extends temperature rating to 800°F.
Reflex Style Shown with Optional Side Connections.
Max Pressure
3270 PSI @ 100°F (CS) · 2285 PSI @ 600°F
Max Temperature
600°F (borosilicate) · 800°F (aluminosilicate glass option)
Glass
Reflex or transparent borosilicate; aluminosilicate available to 800°F
Body Material
Carbon Steel, Low Temp CS (A350 LF2), or 316LSS
Connections
1/2" or 3/4" NPT female standard; socket weld, flanged, or close hook-up optional
Visible Length
Single section 3-3/4" to 12-5/8" visible; up to 7-section assemblies (111-1/2" visible)
Key Features
The Jerguson Series 32 looks very similar to the Series 20, with the critical addition of mid-span supports (tie-bars) to achieve higher pressure ratings up to 4000 PSI @ 100°F. The mid-span support is recessed — unlike competitive designs — so there is no blind spot in the visible length. Recessed gasket seats in both chamber and cover provide positive location of the seal gasket during assembly and field repair, and help prevent lateral movement that could lead to gasket blow-out. Carbon steel covers are shrouded to protect the glass edges. All gages feature a continuous one-piece chamber regardless of length, and are hydrostatically tested at 1½ times the design pressure rating prior to shipment.
Reflex Style Shown with Optional Flanged Back Connections.
Max Pressure
4000 PSI @ 100°F
Max Temperature
600°F (borosilicate glass)
Glass
Reflex or transparent; tempered borosilicate per BS3463, JIS B8211, DIN 7081
Body Material
Carbon Steel or 316LSS; NACE MR0175 & MR0103 acceptable materials
Connections
1/2" or 3/4" NPT female standard; socket weld or flanged optional
Visible Length
Single section 3-3/4" to 12-5/8" visible; multi-section assemblies available
Key Features
Pressure-Temperature Ratings (PSI)
| Series | Material | 100°F | 200°F | 300°F | 400°F | 500°F | 600°F |
|---|---|---|---|---|---|---|---|
| Series 300L | Carbon Steel | 750 | 730 | 705 | 665 | 620 | 570 |
| Series 300L | 316LSS | 720 | 680 | 640 | 600 | 560 | 510 |
| Series 20 | Carbon Steel | 3270 | 3185 | 3075 | 2900 | 2700 | 2285 |
| Series 20 | 316LSS | 3140 | 2970 | 2790 | 2620 | 2450 | 2130 |
| Series 32 | Carbon Steel | 4000 | 3900 | 3760 | 3550 | 3310 | 2800 |
| Series 32 | 316LSS | 3840 | 3630 | 3410 | 3200 | 2990 | 2600 |
Ratings are for the gage body. Glass ratings may be the limiting factor at elevated temperatures — borosilicate glass is rated to 600°F; aluminosilicate glass (Series 20 option) extends to 800°F. Mica shield required for steam service above 406°F (208°C). Series L10 ratings — contact NCI.
Reflex vs. Transparent Glass — Selection Guide
| Aspect | Reflex | Transparent |
|---|---|---|
| Glass Type | Prismatic (grooved) glass | Flat, clear glass (two pieces — front and back) |
| Visibility | Liquid appears dark; vapor/gas appears bright silver | Direct view of liquid level, color, and clarity |
| Illumination | No illuminator needed — self-illuminating by refraction | Illuminator recommended for dark or opaque fluids |
| Fluid Color | Not visible — level indication only | Fluid color, turbidity, and interface visible |
| Interface Detection | Not suitable | Suitable — two immiscible liquids visible |
| Corrosive Fluids | Mica shield available to protect glass | Mica shield available to protect glass |
| Steam Service | Suitable; mica shield recommended for wet steam | Suitable with mica shield |
| Pressure Rating | Generally higher (single glass piece) | Slightly lower (two glass pieces) |
| Best For | Water, steam, clear process liquids | Colored fluids, interface detection, visual inspection |
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 | 300L · 32 · 20 · L10 |
| 2 | Glass Type | R = Reflex · T = Transparent |
| 3 | Visible Length | Specified in inches (e.g., 10-1/4", 12-5/8") — see series length table |
| 4 | Body Material | C = Carbon Steel · S = 316LSS · LF = Low Temp CS (A350 LF2, Series 20 only) |
| 5 | Connection Type | N = NPT female (std) · SW = Socket Weld · F = Flanged · CH = Close Hook-Up |
| 6 | Connection Size | 1/2" or 3/4" NPT; flange size as specified |
| 7 | Accessories (optional) | M = Mica Shield · I = Illuminator · FS = Frost Shield · D = Drain Plug |
Contact Northeast Controls for multi-section assemblies, special alloys, non-standard connection sizes, or service conditions requiring factory review. The full Jerguson Glass Gage Model Number Spec Guide is available from NCI on request.
Accessories & Options
Mica Shield
Protects glass from corrosive, caustic, or wet steam service. Required for steam above 406°F (208°C). Available for all series.
Illuminator
Recommended for transparent gages with dark or opaque fluids. Electric illuminators available in standard and explosion-proof configurations.
Frost Shield
Insulating cover for cryogenic and low-temperature service. Prevents condensation and frost buildup on the glass. Used with Series L10.
Drain Plug
Plugged drain connection in the lower chamber for draining the gage body. Available on all series.
Isolation Valves
Jerguson gauge cocks and isolation valves for block-and-bleed service. See Jerguson Isolation Valves page.
Multi-Section Assemblies
Two or more gage sections connected with center valves for extended visible length. Available on all series.
Typical Applications
Boiler Water Level
Monitor boiler drum water level in power generation and industrial steam systems. Series 20 for high-pressure boilers.
Steam Drum Monitoring
Continuous visual level indication on steam drums. Mica shield required for wet steam service above 406°F.
Process Vessel Level
General process vessel level indication in chemical, petrochemical, and refining applications.
Storage Tank Level
Visual level indication on storage tanks for liquids, chemicals, and hydrocarbons.
Heat Exchanger Level
Monitor liquid level in heat exchanger shells and condensate pots.
Separator Level
Liquid level indication on gas/liquid separators and knockout drums.
Cryogenic Service
Series L10 with frost shield for liquid ammonia, liquid oxygen, liquid nitrogen, and other cryogenic liquids.
Interface Detection
Transparent gages for detecting the interface between two immiscible liquids (e.g., oil/water).
Jerguson level gage sales & selection assistance
Contact us for series selection, pressure/temperature ratings, glass type, and multi-section assemblies.
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