Description
Product Overview
Spirax Sarco BSA6T bellows sealed stop valve is an all-stainless steel, flanged PN40 isolation and throttling unit engineered for demanding industrial media. It prevents fugitive emissions along the valve stem across steam, gas, liquid, condensate, and treated water networks, providing maintenance-free spindle sealing and EN 12266-1 Rate A shut-off tightness.
Standard BSA6T units incorporate a twin ply stainless steel bellows seal, an engineered throttling plug, and a stem locking device to secure manual flow settings without external spindle leakage.
Key Features
- All-stainless steel body (EN 10213 1.4408 / ASTM A351 CF8M) and bonnet (EN 10213 1.4581) construction rated for PN40 service up to 400 °C.
- Twin ply DIN 17440 1.4571 stainless steel bellows isolates process media from atmospheric gland packings.
- Standard throttling plug configuration enables manual flow moderation alongside tight positive shut-off.
- Seat tightness conforms to EN 12266-1 Rate A and ISO 5208 Rate A zero-bubble leakage criteria.
- Handwheel locking screw and threaded nut accept external stroke limiters to control valve position and suppress flow vibration.
- Secondary graphite stem packing provides redundant sealing above the bellows collar.
- Optional carbon-filled R-PTFE soft seat insert available for resilient shut-off requirements across DN15 to DN100 sizes.
- EN 10204 3.1 inspection certification available upon order placement.
Technical Specifications
| Parameter | Metal Seat Specification | R-PTFE Soft Seat Specification |
|---|---|---|
| Flange Rating | EN 1092 / ISO 7005 PN40 | EN 1092 / ISO 7005 PN40 |
| Size Range | DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100 | DN15, DN20, DN25, DN32, DN40, DN50, DN65, DN80, DN100 |
| Maximum Allowable Pressure (PMA) | 40 bar g @ 50 °C | 40 bar g @ 50 °C |
| Maximum Allowable Temperature (TMA) | 400 °C @ 25 bar g | 400 °C @ 25 bar g |
| Minimum Allowable Temperature | -10 °C | -10 °C |
| Maximum Operating Pressure (PMO) | 29.8 bar g @ 236 °C (saturated steam) | 27.0 bar g @ 230 °C (saturated steam) |
| Maximum Operating Temperature (TMO) | 400 °C @ 25.6 bar g | 230 °C @ 27.0 bar g |
| Minimum Operating Temperature | -10 °C | -10 °C |
| Cold Hydraulic Test Pressure | 60 bar g | 60 bar g |
| Shut-off Leakage Standard | EN 12266-1 Rate A / ISO 5208 Rate A | EN 12266-1 Rate A / ISO 5208 Rate A |
| Maximum Differential Pressure (On/Off) | Limited to PMO | Limited to PMO |
| Maximum Differential Pressure (Throttling, DN15-DN80) | 2.0 bar | 2.0 bar |
| Maximum Differential Pressure (Throttling, DN100) | 1.5 bar | 1.5 bar |
Applications
- Saturated and superheated steam isolation and manual throttling.
- High-pressure condensate return systems up to 40 bar g design rating.
- Industrial compressed air and gas distribution requiring Rate A bubble tightness.
- Treated boiler feed water and demineralized water distribution networks.
- Aggressive chemical and process fluid pipelines compatible with 1.4408 and 1.4581 stainless steel grades.
Stroke Limiter and Throttling Control
Spirax Sarco BSA6T handwheel nuts include an internal threaded hole designed to receive an external hexagon bolt as a stroke limiter. Once the handwheel is turned to establish the required flow rate, the locking screw and stroke limiter are engaged to eliminate position drift and minimize valve vibration.
| Valve Size | Stroke Limiter Hexagon Bolt | Maximum Permissible Throttling ΔP |
|---|---|---|
| DN15 - DN80 | M8 x 50 mm | 2.0 bar |
| DN100 | M12 x 75 mm | 1.5 bar |
Operating the valve in throttling duty above these differential pressure thresholds creates elevated noise and pipe vibration levels.
Materials of Construction
| Item No. | Component | Material | Specification Standard |
|---|---|---|---|
| 1 | Body | Stainless steel | EN 10213 1.4408 or ASTM A351 CF8M |
| 2 | Bonnet | Stainless steel | EN 10213 1.4581 |
| 3 | Seat | Stainless steel | EN 10213 1.4408 or ASTM A351 CF8M |
| 4 | Disc (DN15 - DN40) | Stainless steel | EN 10088 1.4571 |
| 4 | Disc (DN50 - DN100) | Stainless steel | EN 100222 1.4571 |
| - | Soft Seat Insert (optional) | R-PTFE | 25% carbon filled |
| 5 | Bellows | Stainless steel | DIN 17440 1.4571 (twin ply) |
| 6 | Stem | Stainless steel | EN 10088 1.4571 |
| 7 | Handwheel | Pressed steel | BS 1449 CR4 |
| 8 | Stem packing | Graphite | High-purity die-formed |
| 9 | Bonnet studs | Stainless steel | A4-70 |
| 9 | Bonnet nuts | Stainless steel | A4 |
| 10 | Body/bonnet gasket | Graphite | Stainless steel reinforced laminate |
| 11 | Locking screw (DN15 - DN80) | Stainless steel | M8 x 14 mm A2-70 |
| 11 | Locking screw (DN100) | Stainless steel | M8 x 20 mm A2-70 |
Dimensions, Weights, and Flow Capacities
Face-to-face dimensions conform to EN 558. Volume flow rates derive from Kv ratings tested to EN 60534-2-3 with water at 20 °C via the relationship Q = Kv × √(ΔP):
| Size | Face-to-Face A (mm) | Height Open B (mm) | Handwheel Diameter C (mm) | Weight (kg) | Full Lift Flow Coefficient Kv (m³/h) |
|---|---|---|---|---|---|
| DN15 | 130 | 205 | 125 | 4 | 4 |
| DN20 | 150 | 205 | 125 | 5 | 7 |
| DN25 | 160 | 217 | 125 | 6 | 12 |
| DN32 | 180 | 217 | 125 | 8 | 19 |
| DN40 | 200 | 243 | 200 | 11 | 30 |
| DN50 | 230 | 243 | 200 | 14 | 47 |
| DN65 | 290 | 263 | 200 | 19 | 77 |
| DN80 | 310 | 287 | 200 | 26 | 120 |
| DN100 | 350 | 383 | 315 | 44 | 193 |
Spare Parts and Maintenance
Spares are supplied in kits to ensure replacement integrity during overhaul. Reassembly requires clean mating faces and tightening across opposing flange diameters to prevent bending stress.
| Spare Assembly | Included Components | Order Specification Notes |
|---|---|---|
| Body/bonnet gasket & stem packing | 10 (2 off), 8 (2 off) | Specify BSA6T, size, and PN40 rating |
| Stem and bellows assembly | 5, 6, 8, 10 | Specify BSAT throttling configuration and size |
| Disc kit | 4, 8, 10 | Specify BSA6T metal seat or R-PTFE soft seat |
| Handwheel | 7 | Specify valve size |
Handling note: gaskets contain a thin stainless steel insert; handle with care. The R-PTFE soft seal insert must be disposed of in compliant landfill facilities and must never be incinerated.