Displacement Level Transmitters Material Selection Criteria & Design

This article is about Displacement Level Transmitters Material Selection Criteria & Design For Level Measurement of Instrumentation and Control Systems as per International Codes and standards for Commercial Buildings, Plants and Refinery Projects.

Displacement Level Transmitters Material Selection Criteria & Design

Material Receiving General Checklist for Instrumentation & Control

Purchase Order and Instrument specification sheet criteria shall be confirmed and compared with instrument stainless steel tags / labels and nameplates, and shipment checked for damage, prior to acceptance of the shipment
Verify that all the instruments are from technically acceptable vendors.

Displacement level transmitters may be used for liquid level ranges up to and including 1,830 mm.
Use of this technology shall be limited to non-viscous process fluids with low concentration of solids.
Displacement transmitters shall be considered for a specific application only if GWR or differential pressure level devices are not suitable.
Displacement level transmitters shall normally be installed in cages external to the process vessel, to allow for maintenance without process interruption or hazard.
Internal displacement type instruments shall be used only where the process requires the primary element to be at the same temperature as the vessel liquid, where high sensitivity is required, where the density difference between liquid interface is small, and where the vessel can be opened for maintenance requirements without process interruption or hazard.
“Displacement type instruments shall not be used in highly corrosive
services or services where salts or other deposits may precipitate onto
the displacer or on the walls of the chamber.”
“The displacer shall be installed vertically. The center of the displacer
shall be at the elevation at which the level in the vessel is to be
maintained.”
“An air-fin extension shall be provided between the level sensing
element and the transmitter, for applications where fluid temperatures
will exceed 200°C.”
Mounting flanges and torque tube housings shall be steel. Cast iron shall not be used.
Displacers shall be 316 stainless steel with 316 stainless steel or Inconel torque tubes.
For low temperature and other severe service applications materials compatible with the process shall be specified on the ISS.
Displacer chambers and torque tube housing materials shall meet requirements of the application.
Cast iron shall not be used. As a minimum, displacers shall be minimum 316 stainless steel with 316 stainless steel or Inconel torque tubes.
For low temperature and other severe service applications materials compatible with the process shall be specified on the ISS.
HART or Foundation Fieldbus microprocessor based smart transmitters shall be provided with all displacer units. The use of pneumatic transmitters is permitted only for local indication and control.

International Codes and Standards for Displacement Level Transmitters

1. Flow Nozzle Material Selection Criteria Design & Flow Measurement
2. Venturi Tube Material Selection Criteria Design & Flow Measurement

3. SAES-J-002 – Technically acceptable instruments.
4. SAES-J-300 – Level.
5. SAES-B-057 – Safety Requirements: Refrigerated and Pressure Storage Vessels.