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P.C. Engineering Corporation
Spirax Sarco SGC40 & SGS40 Sight Glasses - Double Window Industrial Sight Glass

Overview

The Spirax Sarco SGC40 and SGS40 are industrial-grade double window sight glasses designed for visual inspection of flow conditions in process pipelines. The SGC40 features a cast carbon steel body, while the SGS40 is manufactured from stainless steel for corrosive or hygienic applications.

These sight glasses are available with multiple connection types including screwed (BSP/NPT), socket weld, sanitary clamp (ASME BPE), and flanged options conforming to EN 1092, ASME, and JIS/KS standards. The dual borosilicate glass windows provide clear visibility while withstanding demanding process conditions.

Both models comply with EU Pressure Equipment Directive and UK Pressure Equipment (Safety) Regulations, carrying the CE mark where required. Optional accessories include visual flow indicator flaps (with spring loading for vertical installations), mica glass protectors for steam and high-pH applications, and glass-filled PTFE gaskets.

Key Features

  • Dual construction options: Carbon steel (SGC40) or stainless steel (SGS40) body
  • Double window design with borosilicate glass (DIN 7080) for safe, clear viewing
  • Wide size range: DN15 to DN100
  • Multiple connection types: Screwed BSP/NPT, socket weld, sanitary clamp, and flanged
  • Optional visual flow indicator flap to verify liquid flow direction
  • Mica glass protectors available (SGC40M/SGS40M) for steam and caustic applications
  • Flanged versions comply with EN 558 Series 1 face-to-face dimensions
  • Certification available: EN 10204 3.1 and manufacturer's Typical Test Report

Specifications

ParameterSGC40 (Carbon Steel)SGS40 (Stainless Steel)
Body MaterialEN 10213 1.0619+N / ASTM A216 WCBEN 10213 1.4308 / ASTM A351-CF8
Cover MaterialC22.8 / A105N (DN15-50), WCB (DN65-100)1.4571 / 316Ti
Window MaterialBorosilicate glass DIN 7080Borosilicate glass DIN 7080
GasketsReinforced exfoliated graphite (std) or PTFE glass-filledReinforced exfoliated graphite (std) or PTFE glass-filled
Size RangeDN15 – DN100DN15 – DN100
Pressure RatingPN40 (40 bar g @ 50°C)PN40 (40 bar g @ 50°C)
Max Temperature (Graphite gasket)280°C280°C
Max Temperature (PTFE gasket)250°C250°C
Min Operating Temperature-29°C-10°C
Max Cold Hydraulic Test Pressure60 bar g60 bar g
Flange StandardsEN 1092 PN40, ASME 150/300, JIS/KS 10/20EN 1092 PN40, ASME 150/300, JIS/KS 10/20
Screwed ConnectionsBSP, NPTBSP, NPT
Sanitary ClampASME BPE (DN15-50)ASME BPE (DN15-50)
ApplicationRecommended Glass
Steam or pH > 9Mica protectors + Borosilicate windows
Temperature > 150°C and pH > 7Mica protectors + Borosilicate windows
Temperature < 150°C and pH < 7Borosilicate windows only

Applications

- Steam systems: Condensate return lines, steam trap discharge monitoring - Chemical processing: Visual inspection of process fluids in reactors and pipelines - Pharmaceutical & food processing: Sanitary clamp versions for hygienic applications - Power plants: Boiler feedwater and condensate systems - Oil & gas: Process line monitoring in refineries and petrochemical plants - Water treatment: Flow verification in treatment process lines

Frequently Asked Questions

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