Keystone K-LOK Series 36/37 High Performance Butterfly Valve

Overview

The Keystone K-LOK Series 36 and 37 are high performance double-offset butterfly valves from Emerson for isolation and modulating duty at higher pressures and temperatures than a resilient seated valve can handle. Series 36 covers PN 10/16 and ASME 150 ratings, while Series 37 covers PN 25/40 and ASME 300. The ISO version described here is offered from DN 50 to DN 300 in wafer and lug body styles, with polymer seats that seal drop-tight in both directions, in vacuum as well as at full rated differential pressure.

Seven Star LLC supplies the Keystone K-LOK to refineries, petrochemical plants, power stations, utilities and HVAC contractors in Oman and across the GCC. As a trusted supplier with regional stock and engineering support in Muscat, we help engineers select the pressure class, body style, seat material and actuator so the valve matches the service conditions on each line.

Operating Principle

The Keystone K-LOK uses a double-offset disc and shaft arrangement. The first offset places the shafts downstream of the seat centre-line, which leaves an unobstructed 360 degree sealing surface. The second offset moves the shafts off the vertical axis of the seat. Together the two offsets create a camming action: the disc lifts quickly out of the seat in the first few degrees of opening and does not touch the seat again until it is nearly closed. This removes wear points between disc and seat, reduces operating torque and extends seat life, and it supports high cycling duty with a rangeability of 33:1.

The Keystone K-LOK seat is a true interference design that does not depend on line pressure to seal, so it closes drop-tight bidirectionally at low and high pressure and in vacuum, and it keeps working in dirty services where pressure-assisted seats often fail. In PTFE and RTFE seats, a stainless steel braided wire winding inside a U-shaped envelope gives the seat energy and memory, allowing flexibility as the disc approaches the seat and stiffness once the disc is closed.

Engineering Design of the Keystone K-LOK

Standard Keystone K-LOK bodies are carbon steel ASTM A216 WCB or stainless steel ASTM A351 CF8M, discs are CF8M 316 stainless steel with super duplex as an option, and the two-piece shaft is 17-4PH stainless steel. Disc taper pins sit tangentially, half in the disc and half in the shaft, so they are loaded in compression rather than shear. A blow-out resistant shaft is standard: a snap ring locks into a groove in the shaft and is captured by the packing gland follower, giving positive retention in the unlikely event of a shaft break.

The Keystone K-LOK shaft packing uses three rings of braided PTFE between PTFE V-rings and seals in both pressure and vacuum without modification. Inverted adjustment bolts let the packing be adjusted without removing the actuator, and a gland bridge with a spherical radius gives even compression even when nuts are tightened unevenly; the EN 15848 version has live-loaded packing as standard. An integrally cast disc stop locates the disc in the seat, an extended neck allows 50 mm of pipe insulation, and the top flange follows ISO 5211 for direct actuator mounting. Seats can be replaced in the field by removing the retainer ring, without disturbing the disc and shaft.

Key Features

The following points make the Keystone K-LOK a common choice for demanding butterfly valve duties.

• Double-offset geometry lifts the disc off the seat early in travel, reducing torque and seat wear.
• Interference polymer seats give bidirectional drop-tight shut-off in vacuum and at full rated pressure.
• Series 36 is rated PN 10/16 and ASME 150, and Series 37 is rated PN 25/40 and ASME 300.
• Temperature rating is -40 to +260 °C for the ISO version.
• A blow-out resistant shaft is fitted as standard on every valve.
• Lug style valves are fully rated for bidirectional dead-end service as standard.
• All valves carry PED CE and UKCA marking and are certified to EN 15848-1 for fugitive emissions.
• Field-replaceable seats and externally adjustable packing simplify maintenance.

Industrial Applications

Emerson lists modulating service, airport refuelling, hydrocarbon processing, chemical and petrochemical processing, purified gas, steam and vacuum services, power and utilities, refrigeration, HVAC and alumina refining as typical applications for the Keystone K-LOK. In refineries and gas plants it is used for process isolation, tank and loading lines and utility steam; in power stations for steam, condensate and cooling water; and in district cooling and large HVAC plants for chilled water isolation and control where higher pressure classes are needed. RTFE seats are suggested for HVAC, steam, chlorine, ammonia, nitrogen, water, gasoline and vacuum, and PTFE seats for pharmaceuticals, air, potable water and dyes.

For the Keystone K-LOK, the fugitive emissions certification and live-loaded packing option also support plants working to tighter environmental requirements. Seven Star LLC supports operators in Muscat, Sohar, Duqm and across the GCC as a trusted supplier of the Keystone K-LOK, supplying bare-stem valves, gear-operated valves and automated packages with pneumatic or electric actuators.

Technical Specifications

The following Keystone K-LOK Series 36 and 37 ISO data are taken from Emerson’s technical data sheet.

Call To Action

To request a quotation for the Keystone K-LOK, send Seven Star LLC the size, pressure class, body style, medium, temperature range and operator or actuator requirements. Our instrumentation team in Muscat confirms the configuration against the Emerson data sheet and supplies from regional stock where available. The K-LOK Series 36/37 technical data sheet can be downloaded from this page. Related products include the Fisher 8580 high performance butterfly valve, the Masoneilan 39005 high performance butterfly valve and the Fisher 1061 pneumatic piston rotary actuator. Contact us for Keystone valve supply in Oman and the GCC.