DeZURIK BOS-US Resilient Seated Butterfly Valve 2-20 in

A compact lugged or wafer butterfly valve for water, air and utility lines

The DeZURIK BOS-US is a resilient seated butterfly valve with a one-piece body, a one-piece shaft and a high-performance seat of EPDM or NBR that is bonded to the body. The bulletin covers sizes 2 to 20 in and offers lugged or wafer bodies with nickel plated ductile iron, 316 stainless steel or aluminum bronze discs.

The off-center disc produces an uninterrupted seat and dead-tight shutoff in isolation and dead-end service without downstream flanges. Integral flange seals remove the need for flange gaskets. The valve is meant for continuous modulating control, dead-end service to 250 psi and vacuum service to 24 in Hg.

BOS-US technical specification

Seat, bearing and shaft design

The seat bonding process holds the seat firmly in the body, which prevents the premature failure that comes from flexing and fatigue and helps when the line holds vacuum or carries viscous liquids that would dislodge a loose seat. Four sealing components protect the shaft: the disc hubs form the primary seal and two more seals are molded into the seat.

Three heavy-duty bearings carry the shaft load and stop binding, and the shaft seals protect them from internal and external corrosion. The splined disc-to-shaft connection is blowout proof per API 609, and shaft diameters meet the AWWA C504 Class 75B standard.

Materials of construction

The bulletin lists matching disc and shaft pairings with their pressure ratings, so a 316 stainless disc and shaft pair is rated lower (200 psi, 1380 kPa) than a ductile iron or aluminum bronze disc with a 410 stainless shaft (250 psi, 1725 kPa) on the non-seat side. Pick the pair according to the fluid and the differential pressure.

Standards, ordering and operators

Listed standards include ASME B16.42 Class 150 body and pressure-temperature ratings, ASME B16.104 Class VI shutoff, API 609 Category A, AWWA C504 shaft and wall thickness requirements, MSS SP-25 marking and MSS SP-67 butterfly valves. Every valve is tested for leakage, for shell pressure and for operation with its actuator.

The printed ordering example is BOS,6,W1,DI,NBR,NBR,DI-S8*LT, where W1 is ASME Class 125/150 wafer drilling and LT is a lever actuator. The ten-position lever on 2 to 6 in valves latches in open, closed and eight intermediate positions and can be mounted standard or turned 180 degrees. MG-Series gear actuators with handwheel or chainwheel cover 2 to 20 in (bulletins 72.00-1 and 72.00-2). G-Series cylinder actuators use a rack and gear design for larger valves needing constant high torque (bulletin 73.00-1), and double-acting or spring-return PowerRac actuators suit high-cycle on-off duty (bulletins 74.00-1 and 74.00-4).

Applications and what to check

As general engineering context, a bonded-seat lug valve of this kind is a common choice for chilled water, cooling water, fire pump test lines, compressed air and process water in utilities across Oman and the GCC. Check the fluid against the seat compound, and note that 16 to 20 in sizes have a lower seat-side rating than smaller valves.

More valves of this family are grouped under Butterfly Valves. Bulletin 46.00-1A (02/2025) is attached for torque, Cv and dimension tables; quote the size, body style, seat, disc and shaft pairing and actuator when requesting a price from Seven Star LLC.

Using the BOS-US in Oman and the GCC

Compact resilient-seated butterfly valves are common in the region on water treatment plants, pumping stations, HVAC and district cooling systems, irrigation networks and general industrial utilities. The bonded seat and integral flange seals make installation simpler, and the lugged body allows dead-end service where downstream pipework may be removed for maintenance.

Choose EPDM for water and many dilute chemicals, and NBR where oils or hydrocarbons are present. For seawater or brine, the aluminum bronze or stainless steel disc options are more suitable than plated ductile iron. Outdoor valves should have operators and actuators suited to heat and dust, and the gearbox or handle should be checked during routine maintenance. Where valves are used for modulating control, the actuator and positioner should be selected together with the valve so the operating torque and control signal match.

Information to send with an enquiry

• Size, lugged or wafer body, and flange standard
• Fluid, pressure and temperature
• Seat and disc materials
• Lever, gear operator or actuator
• Quantity