Description
Product Overview
Spirax Sarco BRV2 bellows assembly is a factory replacement sensing and dynamic sealing component designed for BRV2 direct-acting pressure reducing valves. It isolates process fluid from the adjustment mechanism while transferring downstream pressure forces directly against the control spring on steam, compressed air, and inert industrial gas lines.
The bellows assembly is supplied as a matched service spare kit consisting of the flexible bellows unit (Item 5) and the mating bellows assembly gasket (Item 6). A single assembly size covers all nominal valve diameters in the BRV2 product line, including DN15 (1/2”), DN20 (3/4”), and DN25 (1”).
Key Features
- Material options: stainless steel grade 316Ti/316L for BRV2S, BRV2SP, and BRV2S5 valves, or phosphor bronze/brass to BS 2872 Cz 122 for BRV2B, BRV2BP, and BRV2B5 valves.
- Standardized sizing: one universal bellows assembly fits DN15, DN20, and DN25 host valves without variation in dimensions.
- Dedicated sealing: supplied with a stainless steel reinforced exfoliated graphite gasket (Item 6) to guarantee bonnet-to-body joint containment.
- Sensor configuration support: operates with both standard internal pressure sensing passages and external impulse tubing configurations (BRV2SP and BRV2BP models).
Technical Specifications
| Parameter | Specification Details |
|---|---|
| Compatible Host Valves | Spirax Sarco BRV2S, BRV2B, BRV2SP, BRV2BP, BRV2S5, BRV2B5 |
| Compatible Nominal Sizes | DN15 (1/2”), DN20 (3/4”), DN25 (1”) universal |
| Stainless Steel Bellows Material (Item 5) | Stainless steel 316Ti / 316L |
| Bronze Bellows Material (Item 5) | Phosphor bronze / brass BS 2872 Cz 122 |
| Bellows Gasket Material (Item 6) | Stainless steel reinforced exfoliated graphite |
| Internal Mating Component | Cone shaped washer (Item 9, ASTM A276 316L) |
| Spring Housing Bolt Torque (Item 7) | 18 to 24 N m (13 to 18 lbf ft) |
| Maximum Host Operating Temperature | 207 °C to 210 °C depending on body metallurgy |
| Downstream Pressure Control Range | 0.14 bar g to 8.6 bar g across grey, green, and orange spring bands |
Applications
- Saturated steam branch lines and terminal process heating circuits.
- Industrial compressed air pressure regulation skids.
- Inert gas supply headers requiring strict downstream pressure stability.
- Planned preventative maintenance and corrective rebuild of leaking or fatigue-cycled BRV2 valves.
Installation and Replacement Procedure
Safety Warning: The bellows assembly gasket contains a thin stainless steel support ring which may cause physical injury if not handled and disposed of carefully.
- Relieve all control spring compression by rotating the handwheel (2) fully anticlockwise.
- Loosen and extract the 4 spring housing bolts (7) using a 13 mm A/F spanner, then remove the spring housing (1).
- Lift out the worn bellows assembly (5) and discard the used gasket (6).
- Remove the cone shaped washer (9) from inside the old bellows body.
- Transfer the cone shaped washer into the replacement bellows assembly, place the new gasket on the seating face, and reposition the assembly into the valve body.
- Refit the adjustment spring and spring housing, tightening the M8 housing bolts evenly in a cross pattern to 18–24 N m (13–18 lbf ft).
Troubleshooting and Fault Diagnosis
- Symptom: Downstream pressure rises uncontrollably above the setpoint.
- Diagnosis: Bellows failure or perforation allows upstream or downstream steam to bypass internal sensing areas into the spring bonnet. Verify that rapid pipeline oscillation has not produced metal fatigue. Check chemical compatibility: chlorides cause stress cracking in stainless steel units (BRV2SP), while halides attack phosphor bronze units (BRV2BP). Replace the bellows and gasket assembly immediately when leakage is detected.