Thermowells Material Selection Criteria & Design

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

Thermowells 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 manufacturer.

The instruments shall operate continuously without any degradation and should comply with a minimum -maximum range of 10°C(50°F) to 35°C(95°F) in indoor Air conditioned or a range of 0°C (32°F) to 55°C (32°F) in outdoor sheltered and to a range of 0°C (32°F) to 65°C (149°F) ( in outdoor unsheltered conditions). [ SAES-J-003, Sec. 8.1]
The vendor to provide certification that the temperature instrumentation meet the typical dust (particulate) and gaseous concentration levels in the air as specified in SAES-A-112, Paragraph 4.6 Ambient Air Quality. See Attachment “1”
Equipment which is not enclosed or hermetically sealed, but is situated offshore or near shore, shall be protected against corrosion and operational failure due to wind-borne sea water spray and the accumulation of wetted salt (NaCl). SAES-A-112, Paragraph 4.6.dust (particulate) and gase. See Attachment “1”
“Electrical and electronic installation and wiring of temperature instrumentation shall be in compliance with SAES-J-902.
Exception: Cast Aluminum heads may be used.”
“All temperature sensing elements shall be installed in thermowells.
Exceptions: Sensors for bearing, motor winding, furnace, skin or surface temperature measurement, ambient air, electronic equipment cabinets. (However, a mechanical protection sleeve shall be considered for the sensors in the area where there is possibility of damage such as pump bearings.).”
“Thermowells shall be 316 stainless steel unless alternative metallurgy is
specified or dictated by process conditions. Alternative metallurgy shall
be approved by the Materials Engineering Unit of CSD”
“Threaded thermowells shall be constructed and installed in accordance
with Standard Drawing AB-036019.
Commentary Note: Threaded thermowells with ¾-inch MNPT process connections shall be used only when required to replace existing ¾-inch thermowells.”
“Flanged thermowells shall be furnished with ASME B16.5 flanges.
Flanged thermowells shall be constructed and installed in accordance
with Process Industry Practice PCFTE000 Temperature Measurement
Fabrication Details, Drawing PCFTE102. Flange size shall be 1-½ inch
minimum 300 # RF.”
“Standard thermowell bore selection for Threaded and Flanged
thermowells is 0.260 inch. The thermowell bore may be increased to
0.385 inch where required (e.g. filled systems). For the flanged
thermowell the tip diameter shall then be increased to 0.75 inch.

International Codes and Standards for Thermowells Material

1. Flow Nozzle Material Selection Criteria Design & Flow Measurement
2. Venturi Tube Material Selection Criteria Design & Flow Measurement
3. SAES-J-002 – Technically Acceptable Instrument Manufacturers, 23 June 2008.
4. SAES-J-003 – Instrumentation – Basic Design Criteria, 16 January 2008
5. SAES-A-112 – Meteorological and Seismic Design Data, 31 October 2006
6. SAES-J-400 – Temperature, 31 May 2004
7. PIP PCFTE000 – Temperature measurement Fabrication details April 2000.
8. PIP PCCTE001 – Temperature Measurement Criteria July 1999
9. STD. DWG. AB-036019 Thermowell Assembly and detail rev 21

   ATTACHMENTS:
   1. Attachment 1: Ambient Air Quality

   

   2. Attachment 2: Thermowell Assembly and Details

   

   3. Attachment 3: Fabrication Detail for Flanged Thermowell