Level Control Switches

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PT988 Pneumatic Liquid Level Switch

WellMark’s PT988 Pneumatic Level Switch is designed for horizontal mounting in a tank or vessel through threaded or flanged pipe connections (will work in an API 2″ full coupling) and is excellent for applications where space is a factor. It can be externally caged for vessel isolation and can be used as a high or low level alarm, as well as a liquid level control. In addition, it can be switched from direct to indirect action simply by inverting the unit 180˚. The PT988 features a 3-way snap-acting pilot (0 to full output using 20-30 psi supply pressure) or order it with an optional throttling pilot (3 to 15 psi output with a 20 psi supply pressure).

Operation

As liquid within the vessel varies, linear movement of the float is converted to rotary movement of the actuator assembly. In the snap acting mode, as the actuator pad moves closer to the nozzle, supply pressure is diverted to signal pressure, tripping the shuttle pilot to either full output pressure, energizing end-device, or to zero output pressure, de-energizing end-device. In the throttling mode, as the actuator pad moves closer to the nozzle, supply pressure is diverted to output pressure, resulting in modulating pressure to the end-device.

Direct Acting

A rise in fluid level resulting in an increase of pilot output. This is accomplished when the pilot is in the downward position.

Indirect Acting

A rise in fluid level resulting in a decrease of pilot output. This is accomplished when the pilot is in the upward position

  • Snap or Throttle
  • Small, Compact
  • Direct or Indirect Action
  • Economical
  • Max. Working Pressure: 1500 psi
  • Supply Pressure: 20 psi Min. – 100 psi Max.
  • Operating Temperature: -20˚F to 275˚F
  • Process Connections: 2″ MNPT Standard
  • Pilot Connections: 1/4″ FNPT
  • Pilot Mode: Snap Acting Throttling

Materials

  • Body: Plated Steel Std. (S.S. available)
  • Float: Stainless Steel (Collapse pressure: 2500 psi)
  • Wetted Parts: Stainless Steel
  • Pilot: Stainless Steel