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P.C. Engineering Corporation
Spirax Sarco SG253 Sight Glass - Double Window Flanged Sight Glass for Steam Systems

Overview

The Spirax Sarco SG253 is a double window sight glass constructed from SG iron, designed for visual monitoring of flow in steam, condensate, and process lines. It features flanged connections compatible with EN 1092 PN25 and BS 1560 ASME Class 150 standards, making it suitable for a wide range of industrial piping systems.

The SG253 incorporates borosilicate glass windows conforming to DIN 7080, providing excellent clarity and resistance to thermal shock. Reinforced exfoliated graphite gaskets ensure reliable sealing across the operating temperature range. This sight glass is commonly installed downstream of steam traps to verify trap operation and condensate discharge.

The product fully complies with the EU Pressure Equipment Directive and UK Pressure Equipment (Safety) Regulations, carrying the CE mark where required. Certification to EN 10204 3.1 is available upon request at the time of order.

Key Features

  • Double window design for clear flow observation from both sides
  • SG iron body and cover (EN-JS1025) for durability and corrosion resistance
  • Borosilicate glass windows (DIN 7080) with high thermal shock resistance
  • Reinforced exfoliated graphite gaskets for reliable high-temperature sealing
  • Flanged connections: EN 1092 PN25 and ASME Class 150
  • Available in sizes DN15 to DN50
  • CE marked and compliant with PED/UKCA requirements
  • Optional EN 10204 3.1 certification available

Specifications

ParameterValue
SizesDN15, DN20, DN25, DN32, DN40, DN50
Body MaterialSG Iron (EN-JS1025)
Window MaterialBorosilicate Glass (DIN 7080)
Gasket MaterialReinforced Exfoliated Graphite
Flange StandardsEN 1092 PN25, BS 1560 ASME Class 150
Max Allowable Pressure (PN25)25 bar g @ 100°C
Max Allowable Pressure (ASME 150)17.2 bar g @ 35°C
Max Operating Pressure – Steam (PN25)21 bar g
Max Operating Pressure – Steam (ASME 150)13.8 bar g
Max Operating Temperature280°C
Min Operating Temperature0°C (lower temperatures on request)
Min Allowable Temperature-10°C
SizeA (PN25) mmA (ASME 150) mmB mmE mmF (Window) mmWeight kg
DN151301265545103.2
DN201501425545104.1
DN251601527063155.0
DN321801757063155.9
DN402001999080209.1
DN5023022890802010.9

Applications

- Monitoring steam trap discharge and condensate flow - Visual inspection of process fluids in steam and condensate systems - Flow verification in boiler houses and steam distribution networks - Process monitoring in chemical, pharmaceutical, and food processing plants - Installation on condensate return lines in manufacturing facilities

Installation Note: When installed downstream of blast discharge traps (e.g., thermodynamic type), maintain a minimum distance of 1 metre from the trap to prevent thermal shock. Always fit isolation valves on both inlet and outlet, closing the upstream valve first during maintenance.

Frequently Asked Questions

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