Primary Temperature Element Assemblies

IPE Engineering Practice IPE-EP-12-1-6

Document number: IPE-EP-12-1-6 · Section: 12 — Instruments and Controls

SCOPE

Thermowells and primary temperature elements shall be supplied in strict accordance with the attached Data Sheets, this Practice, and the referenced standards and publications.
The use and installation of primary temperature elements shall conform to the appropriate sections of EP 12–1–1 Control Systems.
Any deviation from this Practice must be approved by the procedure described in EP 1–1–3.
A revision bar indicates all changes made to this Revision.

2.0 REFERENCES

The following codes and standards shall be considered as part of this Practice. All documents shall be the latest editions in force on the date of issuance of this Practice.

STANDARDS AND PUBLICATIONS

IPE Engineering Practices
EP 1–1–3 Deviations to IPE Engineering Practices EP 12–1–1 Control Systems EP 12–1–2 Supplemental Requirements for Control Systems EP 12–1–6 Primary Temperature Element Assemblies
ANSI
MC96.1 Temperature Measurement Thermocouples
ASME
Sec VIII Pressure Vessels, Division 1 B 16.5 Pipe Flanges and Flanged Fittings B 31.3 Chemical Plant and Petroleum Refinery Piping
DIN
43760 Electrical Temperature Measuring Instruments, Calibration Tables of Resistance Elements for Resistance Termometers

DEFINITIONS

Contractor - Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
Inspector - A Inflection Point Engineering, LLC. appointed engineer or inspector.
Manufacturer - The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a manufacturer by a contractor or the Owner. An indirect order is one issued to a manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
Owner - Inflection Point Engineering, LLC .

Owner’s Engineer - A Inflection Point Engineering, LLC . appointed engineer.
Purchaser - The party placing a direct purchase order. The purchaser is the Owner’s designated representative.

THERMOCOUPLE ELEMENTS

Thermocouples shall have thermoelectric properties in accordance with ANSI MC96.1
The measuring junction shall be grounded with a single or dual element.
Elements should have a stainless steel sheath with maximum diameter of 3/8 inch and magnesium oxide insulated. Ceramic beads with thermocouple wire may be used with approval of the Owner’s Engineer.
Other sheath materials and thermocouple constructions require the approval of the Owner’s Engineer.

RESISTANCE TEMPERATURE DETECTOR (RTD) ELEMENTS

Elements should have a maximum 3/8 inch stainless sheath with a wire wound element over a ceramic or glass core.
Elements shall have thermoelectric properties have a resistance at 0 o C of 100 Ohms and a temperature coefficient of .00385 ohms/ohm/ o C (DIN 43760).
Other sheath materials and elements may be used with approval of the Owner’s Engineer.

HEADS AND ASSEMBLY

The temperature element head and cover shall be cast aluminum or iron. The cover shall be attached to the body with a stainless steel or zinc coated chain.
The head shall be furnished with a ceramic terminal block with brass or thermocouple alloy terminals for connecting thermocouple wire or RTD leads.
When a complete assembly of well, element, and head is purchased the element shall firmly contact the bottom of the well. Spring loaded assemblies should be used when possible.

THERMOWELLS

Thermowells under 24 inches in length shall be machined from solid bar stock. Welded construction is not acceptable.
Thermowell material identification shall be clearly stamped on the body or flange.
Thermowell design should be in accordance with Figures 1 through Figure 6. The maximum velocity given in the figures should not be exceeded. Thermowells over 24 inches in length shall require approval by the Owner’s Engineer. Other thermowell construction may be required due to corrosion, erosion, or vibrational fatigue. The Owner’s Engineer shall approved all other thermowell designs.Figures 1 6.
Well depth shall be stamped on a stainless steel tag attached to the head of the well.
Welds on flanged thermowells shall be in accordance with the applicable portions of Section VIII, Division 1 of the ASME Boiler and Pressure Code for vessel thermowells. Welds on flanged pipe line thermowells shall be in accordance with ASME B31.3. Flanges shall be in accordance with ASME B16.5.

8.0 FIGURES

FIGURE 1

FIGURE 2

FIGURE 3

FIGURE 4

FIGURE 5

FIGURE 6

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