Low-Pressure Circular Sight Glass Fittings

John Moncrieff’s low-pressure circular sight glass fittings provide a compact, economical, and reliable solution for direct process observation. Designed for welding into or onto vessel walls, these units deliver robust visibility without the full dimensional requirements of the DIN 28120 series—making them ideal for lower-pressure duty where cost efficiency and compact design are key.

Supplied as complete assemblies—including gaskets, sight glass disc, and hexagon head screws—these fittings enable fast installation and dependable performance across a wide range of industrial vessels, tanks, pipelines, separators, and gear housings.

Key Features

• Circular Pad Flange Design: Suitable for welding into or onto vessel walls for a secure, permanent installation.
• Cost-Efficient Construction: A compact alternative to DIN 28120 sight glasses for low-pressure duties.
• Complete Assembly: Delivered with matching gaskets, precision sight glass disc, and fastening hardware.
• Wide Viewing Range: Viewing diameters from 50 mm to 600 mm.
• Temperature Capability: Up to 280 °C (up to 900 °C with special materials).
• Pressure Rating: Suitable for operating pressures up to 5 bar.
• Material Options: Stainless steel, carbon steel, and specialty alloys including Hastelloy.
• Custom Builds: Tailored solutions available for specific process, mounting, or dimensional requirements.
• Optional Wipers: Manual or mechanical wiper systems available to maintain clear visibility.

Typical Applications

• Tanks and storage vessels
• Mixers, blenders, and separators
• Silos and hoppers
• Pressure vessels (low-pressure service)
• Pipelines and flow observation points
• Gear trains and rotating equipment housings

When you need a rugged, compact, and cost-effective viewing solution for low-pressure service, John Moncrieff’s circular weld-on sight glass fittings deliver proven performance and dependable process visibility across a wide range of industrial environments.

Technical Specifications: