Keystone Figure 990/920 Resilient Seated Butterfly Valve

Overview

The Keystone Figure 990 is a resilient seated butterfly valve from Emerson with a split body and a thin, one-piece disc-stem, designed for high flow and modulating service. It is supplied in two body styles: Figure 990 is the wafer version that installs between pipe flanges, and Figure 920 is the lugged version with drilled and tapped lugs around the body. Sizes run from DN 25 to DN 500 (NPS 1 to 20) for the wafer style and DN 50 to DN 500 (NPS 2 to 20) for the lugged style, which covers most utility, water and process lines in a typical plant.

Seven Star LLC supplies the Keystone Figure 990 and Figure 920 to utilities, desalination and water treatment operators, HVAC contractors and process plants in the Sultanate of Oman and across the GCC. As a trusted supplier with regional stock and engineering support in Muscat, we help customers choose body, disc and seat materials for the medium and match the valve with a manual operator or an automated actuator package.

Operating Principle

The Keystone Figure 990 is a concentric butterfly valve: the stem passes through the centre of the disc and the disc rotates a quarter-turn inside a resilient seat. The thin profile disc-stem presents minimal obstruction to flow, giving a high flow coefficient, low pressure drop and good control characteristics, which is why Emerson positions the valve for modulating as well as on-off service. The rounded, polished disc edge seals concentrically against the seat, lowering torque and extending seat life while giving tight shut-off.

The Keystone Figure 990 resilient seat performs three functions at once. It isolates the body and stem from the line medium, provides drop-tight shut-off at full rated pressure, and seals against the pipe flanges, so separate flange gaskets are not needed. Bi-directional, self-adjusting double V-cup stem seals stop external contaminants entering the valve, and a heavy-duty corrosion resistant top bushing supports the upper stem and absorbs side loads from the actuator, extending cycle life.

Engineering Design of the Keystone Figure 990

The split body is the defining design feature of the Keystone Figure 990. Because the body is made in two halves, the seat and disc-stem can be replaced in the field, and Keystone actuators can be mounted directly to the valve top plate without separate couplings or brackets. Body materials include cast iron (ASTM A126 Class B / EN-GJL-250), ductile iron for lugged valves and 316 stainless steel. Discs are offered in CF8M stainless steel with as-cast, satin or mirror polished finishes, duplex stainless steel, or steel discs molded with PTFE, EPDM, NBR or urethane, and ceramic-coated versions are also listed, with availability depending on size and region.

Keystone Figure 990 seat choices include food grade NBR and EPDM, white NBR, FKM, PTFE-lined EPDM or NBR, and urethane. Stems are 316 stainless steel or duplex, stem packing is NBR and body screws are 18-8 stainless steel. The Figure 990 wafer body fits between ASME 125/150, PN 10 and PN 16 flanges, while the Figure 920 lug body is compatible with ASME 125/150, PN 10/16 and BS Table E drilling. Emerson also notes the valve is not intended for end-of-line use.

Key Features

The design points below explain why the Keystone Figure 990 is widely used on water and utility systems.

• A one-piece thin profile disc-stem gives high flow capacity, low pressure drop and good control behaviour.
• The rounded, polished disc edge provides concentric sealing with lower torque and longer seat life.
• A triple function resilient seat isolates the body, gives drop-tight shut-off and eliminates flange gaskets.
• The split body allows field replacement of the seat and disc-stem.
• Direct mounting of Keystone actuators is possible without couplings or brackets.
• Self-adjusting double V-cup stem seals keep contaminants out of the valve.
• Pressure rating is 10 bar for DN 25 to 300 and 5 bar for DN 350 to 500, with 7 bar for molded discs up to DN 300.
• PTFE-lined seats suit light corrosive services and rubber lining suits light abrasive services.

Industrial Applications

Emerson lists food and beverage, pharmaceutical, pulp and paper, mining, oil and gas and power industries as heavy-duty applications for the Keystone Figure 990 and Figure 920, wherever modulating service or corrosion resistance is needed. In the region, typical uses include seawater and brine lines in reverse osmosis desalination, filter and backwash valves in water treatment plants, chilled and condenser water in district cooling and commercial HVAC, cooling water in power stations, and utility water in refineries and petrochemical plants. Food grade seats make it suitable for beverage and dairy processing.

For the Keystone Figure 990, choosing the right combination of body, disc and seat for each medium is key to long service life, particularly for chlorinated water, seawater and slurries. Seven Star LLC supports projects in Muscat, Sohar, Salalah and across the GCC as a trusted supplier of the Keystone Figure 990, and can deliver valves bare-stem, with lever or gear operators, or as complete automated packages.

Technical Specifications

The Keystone Figure 990 and Figure 920 data below are taken from Emerson’s technical data sheet; confirm material availability for each size when ordering.

Call To Action

To request a quotation for the Keystone Figure 990 or Figure 920, send Seven Star LLC the size, flange standard, medium, temperature, pressure and whether you need manual or automated operation. Our instrumentation division in Muscat checks material suitability against the Emerson data sheet and supplies from regional stock where possible. The technical data sheet can be downloaded from this page. Related products include the Fisher 8560 high performance butterfly valve, the Johnson Controls VFC-060HB butterfly valve and the AUMA SQ part-turn actuator. Contact us for Keystone valve supply in Oman and the GCC.