The Cashco Model 521 is a sliding stem, globe style, bellows sealed, pneumatically actuated control valve designed to provide superior long-term performance and maximum corrosion resistance in pure chemical service. The design allows for all wetted internal parts to be machined from a solid block of isostatically compacted, virgin TFE, thus ensuring maximum density and the lowest possible permeability. An additional design benefit is that the wall thickness integrity is ensured as a result of the TFE body being internally machined after it is secured in a cast 304 SST body shell, thus preventing distortion problems related to the plastic stability of TFE. There is simply no better design or materials available when consideration is given to corrosion resistance and thermal stability.

The Model 521 is designed specifically for corrosive chemical use, including most hazardous or toxic fluids. Ultimate performance when handling chlorine (wet or dry); bromine; hydrochloric, sulphuric, nitric, and hydrofluoric acids; and most industrial reagents. Also performs well in alkaline or strong basic fluids and most organics.
The Model 521 combines the TFE corrosion resistance with superior design and construction for the Chemical Process Industry: .

  • Unibody TFE construction minimises potential leak paths.
  • Dual stem seal design: 100,000 full-cycle bellows primary seal plus V-ring secondary stem seal.
  • Anti-stem rotation device to prevent bellows damage.
  • 304 SST body jacket resists external corrosion.
  • Quick change trim with easily replaceable plug-tip. • Four body sizes - 1/2", 1", 1-1/2", and 2"; (DN 15, 25, 40 and 50).
  • Wide selection of trim sizes and forms.
  • 150# RF, flanged body with “gasketless” pipe-to-valve joint.
  • Optional capability to mate with 300# RF.
  • Optional capability to mate with PN16, PN25, or PN40 DIN flanges.
  • Class VI shutoff.
  • Spring-loaded bonnet seal.
  • All wetted parts are machined from isostatically compacted TFE.
  • May be applied in full vacuum service.
  • Standard Actuator compliant with IEC 60534-6-1 for mounting standardized positioners