BRV73 Direct Acting Pressure Reducing Valve

1. Safety information

Safe operation depends on installation, commissioning, use and maintenance by competent personnel in accordance with the operating instructions. Follow the applicable pipework, plant construction and safety requirements and use suitable tools and protective equipment.

1.1 Preparation

Check the installation and maintenance guide, nameplate and technical information to confirm that BRV73 is suitable for the intended service. Check material safety, pressure and temperature limits, and their maximum and minimum values. If the product limit is lower than the system limit, or if a product fault could cause overpressure or overtemperature, provide suitable protective devices.

Confirm the correct installation position and flow direction. The valve must not be exposed to external stress generated by the installed pipework; the installer is responsible for supporting and routing the pipework to minimise such stress. Before installing a steam or other high-temperature service, remove connection protectors and any protective film from the nameplate.

1.2 Access, lighting and hazardous surroundings

Provide safe access and a safe working platform before operating the valve. Arrange suitable lifting equipment where needed and provide sufficient lighting, especially for complex work. Consider the contents and physical state of the pipework, including flammable or harmful substances, extreme temperatures, hot surfaces, ignition hazards, excessive noise and moving machinery.

1.3 Pressure, temperature and competence

Consider the effect of each operation on the complete system. Closing an isolation valve or isolating another service must not put another part of the system or personnel at risk. Isolate pressure and safely vent to atmosphere before maintenance. Consider double isolation, lock-out or tagging. A pressure gauge reading of zero is not proof that the system is depressurised.

After isolation, allow the valve to cool to a safe temperature to prevent burns and use protective clothing, including eye protection, where required. All work must be performed or supervised by competent personnel who understand the equipment and the site's formal permit-to-work and safety arrangements.

1.4 PTFE, other hazards, freezing and disposal

PTFE is inert within its normal temperature range but can decompose or burn at combustion temperatures and produce harmful fumes. Do not smoke where PTFE is handled, prevent contamination of clothing and wash hands after handling particles. During normal service the valve surface can be hot; at the maximum allowable operating temperature some surfaces can reach 210 °C. BRV73 has no self-draining function, so take care when removing it from pipework and provide protection against freezing where an installation can fall below the freezing point.

The product can be recycled when disposed of correctly. PTFE parts must be handled using an approved method and must not be incinerated. Keep PTFE waste in a separate container and do not mix it with general waste. When returning a product, provide information about any residue or mechanical damage that could create a health, safety or environmental hazard.

2. Product information

BRV73 is a direct acting pressure reducing valve for steam, compressed air and inert industrial gases. It is available in DN25, DN32, DN40 and DN50 flanged sizes. The flanges are available in PN16, ANSI 150 or JIS 10 standards. The body is ductile iron and the internal parts are stainless steel.

The valve adjusts by feeding downstream pressure back through a sensing hole in the stem. Pressure acting on the control bellows balances the compressed control spring. A balance bellows reduces the pressure force on the plug face and graphite-reinforced PTFE bushes provide two-point guidance. The maximum upstream pressure is 10 bar g and the recommended maximum pressure reduction ratio is 10:1.

The spring range is marked on the adjustment handwheel. Verify that the installed spring is correct for the application before adjustment.

3. Installation

Locate the upstream and downstream isolation valves 8-10 pipe diameters from each side of BRV73, leaving straight pipe between the isolation valves and the regulator. Do not apply pipe stress caused by thermal expansion or insufficient support to the valve body.

Size the upstream and downstream pipework sufficiently to avoid excessive pressure loss. Use eccentric reducers where a line changes size. Fit an upstream filter to protect the pressure reducing valve and mount it sideways so that collected water does not reduce the effective filter area. For wet steam, fit a separator and trap set, or a suitable drain point and trap. Fit a downstream pressure gauge to set the reduced pressure and an upstream gauge to check the supply pressure. Install a safety valve to protect the downstream system, leaving sufficient margin between its reseating pressure and the BRV73 set pressure.

If installation or operation is difficult, contact Spirax Sarco or the local office before proceeding.

4. Start-up and adjustment

Before operating BRV73, thoroughly flush all pipework to remove dust, excess jointing material and other debris. Pressure adjustment is made by rotating the handwheel: clockwise increases pressure and counter-clockwise decreases pressure. Fully open the upstream isolation valve while the downstream isolation valve is closed. Turn the handwheel clockwise and raise downstream pressure slowly to the set pressure shown on the downstream gauge. Open the downstream isolation valve slowly. Under normal flow the set downstream pressure may fall slightly; re-adjust it if necessary. Under no-load conditions, the set pressure should be slightly higher.

Locking the set pressure

1. When the required set pressure is reached, remove the coloured spring-range disc from the recess in the adjustment handwheel. Insert a small screwdriver beneath the disc to lift it.
2. Remove the small locating pin stored in the handwheel recess.
3. Insert the pin into locking hole A and into one of the ten holes in the top of the spring chamber to lock the pressure setting.

5. Maintenance

Keep the plug and seat clean. The upstream filter and the internal strainer in the valve should be cleaned regularly to prevent restriction in the flow path. Before dismantling, ensure that the adjustment handwheel is released, the valve is fully isolated and pressure has been safely discharged.

Removal

1. Slowly loosen the four bottom-cover bolts and remove the return spring and gasket. The return spring is compressed; use the documented 17 mm A/F socket.
2. Carefully remove the O-ring from the pushrod.
3. Remove the lower pushrod and carefully remove the plug. Use the documented long-reach 15 mm A/F tool.
4. From the top of the valve, loosen and remove the four spring-chamber bolts. Use the documented 13 mm A/F socket.
5. Remove the spring chamber and control spring.
6. Remove the control bellows, gasket, balance-bellows/pushrod assembly and gasket.
7. Remove the internal strainer.
8. The seat is permanently fitted in the body. Clean it by lapping before reassembly; if the seat is damaged, replace the body.

Reassembly

1. Ensure the strainer is clean and install it with the conical face down and the joint away from the inlet.
2. Fit the gasket into the body.
3. Install the bellows and pushrod assembly with the pushrod facing down.
4. Install the gasket and control-bellows assembly.
5. Install the control spring on the bellows assembly.
6. Fit the spring chamber to the valve body and ensure the flanges align correctly.
7. Install the four spring-chamber bolts and tighten to 18/24 N m with a torque wrench.
8. Ensure the O-ring is fitted in the plug and the plug recess is clear of the lower pushrod hexagon. Screw the lower pushrod fully into the pushrod/bellows assembly, then back it off by one quarter turn so the plug can move.
9. Fit the O-ring in the lower pushrod groove.
10. Fit the gasket into the body.
11. Install the return spring in the plug.
12. Fit the return spring in the bottom cover and ensure the cover matches the body.
13. Compress the bottom cover and install two bolts to retain it.
14. Install the remaining bolts and tighten all bottom-cover bolts to 20/26 N m with a torque wrench.

Check that the adjustment handwheel moves freely before returning the pressure reducing valve to service.

Recommended tightening torque

6. Spares

Spares are shown by solid lines in the source figure; dashed components are not supplied as spares. The documented spare groups are common to the available sizes.

When ordering spares, state the valve size, model and pressure range. Before any work on the valve, ensure that it is completely isolated.