311-312 Midi-Diaphragm Seals

The Ashcroft® 311 and 312 midi-diaphragm seals are fitted in confined areas to protect measuring instruments. Used to ensure process compatibility, they are also applied when process media exhibit pulsation. Ideal for limited space installations.

Key Features:
  • Compact and lightweight design
  • Choice of diaphragm and lower housing materials
  • All-welded construction
  • Volumetric displacement allows attachment to:
    3 1/2″ gauges (Vac to 1,000 psi)
    4 1/2″ gauges (30 to 1,000 psi)
    Transducers and Switches
  • Rated up to 1,000 psi

Process Market:
Oil and Gas
Chemical and Petrochemical
Water and Wastewater

Process Applications:
Oil and Gas Fracking
NACE Compliant Processes (Sour Gas Separation)
Biogas and Biodiesel


Certifications & Approvals

Data Sheets & Instruction Manuals

Drawings & Product/Technical Information

Resources & Tools

Min/Max Guide

IMPORTANT! When selecting a diaphragm seal or isolation ring, refer to the Min/Max Guide (PI page) for compatibility with this gauge. 

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Materials Selector

Use the selector to review compatible wetted materials and requirements of your application.

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Unit Converter

Need to convert measurement units? Check out our quick and easy tool to convert pressure, temperature and flow units of measure.

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Product Information

To learn more about the technical details for options available, review our product information (PI) pages.

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Contact Ashcroft

Ashcroft is a trusted source for pressure, temperature, and test instruments around the world. Learn more about how we can help you protect your people, processes, and profits.

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