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P.C. Engineering Corporation
Spirax Sarco A3S & A3SS Bellows Sealed Stop Valve - Class 800 Forged Steel

Overview

The Spirax Sarco A3S and A3SS are bellows sealed stop valves designed for reliable isolation in steam, gas, liquid, condensate, and water systems. The bellows seal eliminates fugitive emissions and prevents stem leakage, making these valves suitable for applications where environmental compliance and process integrity are critical.

Constructed with a forged steel body (ASTM A105N) and available in screwed BSP, NPT, or socket weld connections, these valves are rated for Class 800 service with a maximum allowable pressure of 136 bar g and temperatures up to 425°C. The A3SS variant features a stellite-faced disc for enhanced wear resistance in demanding applications.

Both models comply with the Pressure Equipment Directive (PED), with bellows fatigue life conforming to ISO 15761 and seat shut-off meeting API 598 and DIN 3230 leakage rate B01 standards.

Key Features

  • Bellows sealed design eliminates stem leakage and fugitive emissions
  • Forged steel body and bonnet (ASTM A105N) for high-pressure service
  • Stellite Grade 6 integral seat for extended service life
  • A3SS variant includes stellite-faced disc for severe service
  • Stainless steel bellows (ASTM A479 Type 321) with ISO 15761 fatigue life compliance
  • API 598 and DIN 3230 B01 seat leakage rating
  • Available with EN 10204 3.1 certification
  • Graphite stem packing for high-temperature sealing

Specifications

ParameterValue
Sizes½", ¾", 1", 1¼", 1½", 2"
Pressure ClassClass 800
Max Allowable Pressure (PMA)136 bar g
Max Operating Pressure99 bar g @ 360°C
Max Operating Pressure (Extended Bellows Life)40 bar g @ 400°C
Max Allowable Temperature (TMA)425°C
Max Operating Temperature (Extended Bellows Life)400°C @ 40 bar g
Min Allowable Temperature-29°C
Body MaterialForged Steel ASTM A105N
Bellows MaterialStainless Steel ASTM A479 Type 321
Disc Material (A3S)Stainless Steel ASTM A276 Type 410
Disc Material (A3SS)Stainless Steel ASTM A276 Type 410 + Stellite Gr. 6
Seat MaterialStellite Grade 6
End ConnectionsScrewed BSP (BS 21 parallel), NPT, Socket Weld (BS 3799/ANSI B16.11)
StandardsPED, ISO 15761, API 598, DIN 3230
Size½"¾"1"1¼"1½"2"
Kv1.33.25.89.017.019.2
SizeA (mm)B – Valve Open (mm)C (mm)Weight (kg)
½"80136701.7
¾"90144902.3
1"1101671103.6
1¼"1271941105.9
1½"1552201308.5
2"17023018011.6

Applications

The Spirax Sarco A3S and A3SS bellows sealed stop valves are used across industries requiring leak-tight isolation:

- Steam distribution and condensate return systems - Chemical and petrochemical processing plants - Pharmaceutical manufacturing facilities - Power generation stations - Oil and gas refineries - Food and beverage processing - Pulp and paper mills - HVAC and utility systems

Frequently Asked Questions

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Contact PC Engineering for pricing, availability, and technical support for Spirax Sarco A3S & A3SS Bellows Sealed Stop Valves. Call us or fill in our inquiry form — our engineers will respond within 24 hours.

Spirax Sarco A3S & A3SS Bellows Sealed Stop Valve - Class