McNab Model L1/L3 Instrument Sensor Valve

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Valve for insertion of continuous monitoring fluid sensors into pipes and tanks.
  • Operates at full line temperature and pressure
  • Eliminates sample disposal problems
  • Allows for accurate measurement because pressure, temperature and flow remain constant
  • Enables easy installation and replacement of fluid sensors while under pressure - no pipe dewatering or tank drainage
  • Lets you change sensors at the same location or use the same sensor at multiple locations


Typical Uses Include:

  • Organic Chemical Processing
  • Inorganic Chemical Processing
  • Food Processing
  • Beverage Processing
  • Power Generation
  • Condensate Monitoring
  • Plastics Manufacturing
  • Polymer Manufacture
  • Pharmaceutical Processing
  • Wastewater Monitoring
  • Petrochemical Processing
  • Oil Production
  • Paints & Coatings Manufacture
  • Reaction Vessels
  • Hydraulic Fluid Monitoring

Or any process where fluids need to be monitored.

Model L1/L3

If you monitor fluid characteristics such as water impurities pH, turbidity, color, conductivity Oxygen Reduction Potential (ORP), sodium potassium, chloride, ions, and other characteristics of fluids in pipes under pressure or standing in tanks, the patented McNab Model L1/L3 Sensor Valve should be on your system.  Here's why:

No System Interrupt

This unique device allows you to insert and remove fluid sensors without affecting pipeline flow or requiring tank drainage This valve requires no tools to operate and takes only 90 seconds for a qualified technician to remove and replace a sensor-without dewatering.

And, because there is no system interrupt, the fluid is analyzed while under normal operating conditions. Pressure, temperature and flow are not disturbed, so accurate representative readings are assured.

Monitors In-Process Fluids – No Samples

Because the valve allows continuous monitoring of fluids in process, there is no need to pull samples from the system; hence, there are no samples to dispose.

And, the valve's unique operation puts the sensor past the fluid wall and into the main stream.

Sensor Flexibility

model_L1-L3_valve_open_cell_in_stream.JPG (16438 bytes)Because it takes less than two minutes to remove and replace a sensor, you can check the same fluid properties at various locations on the line with only one sensor to ensure accuracy or monitor different properties at the same location just by changing the sensor.

Immediate Action

model_L1-L3_valve_closed_cell_withdrawn.JPG (16610 bytes)With the L1 /L3 valve, you need not wait for the line to drain to check the fluids or change the sensors; any time is convenient. And, field standardization and/or sensor calibration is fast and easy.

Low Maintenance

model_L1-L3_valve_closed_cell_unloaded.JPG (25051 bytes)The L1/L3 valve's unique design will never crush the probe and exerts no pressure or twisting on the probe cables. Because of its few operating parts, the valve requires minimal maintenance and will provide years of trouble-free operation.

Product Description

The L1 /L3 Valve is a cylindrical-type isolation valve that opens and closes by extending and withdrawing the openings at the valve end. It can contain many different types of instrument probes or cells, forming a complete seal that prevents liquid or pressure from escaping. The mechanism is constructed in such a manner that the probe cannot be unloaded unless the valve is closed.


Product Specifications:

Interface: Standard 1-1/4 NPT Tee or by welding, clamping, sanitary clamping or with bolted flanges (consult factory)
Materials: Stainless steel or PVDF (Kynar™)
Maximum Suggested Operating pressure: 150 psi (ss)
Burst Pressure Test: 800 psi (ss)
Maximum Suggested Operating Temperature: 250° F (120° C) (ss)
Probe Types: Various, including the Aqua Purometer I and II family of probes
Weight: 2.5 pounds (typical)
Length: 7 inches

Additional Features: 

  • The L1/L3 valve meets or exceeds the OSHA spec 9/10.11 standard FDA-approved materials
  • The L1 /L3 valve has ultra-low leakage rates, exceeding 108 torr helium
  • Easily back-fitted to existing systems
  • Simpler, quicker and more positive than typical gate or ball-valve arrangements

383-2 East 29th Street | Buena Vista, VA | USA 24416-1293

540.261.1045 voice | 540.261.1268 fax |

Copyright © 1999 - 2010  McNab, Inc. All Rights Reserved.  Last modified: 08.12.2010

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