Instrument Tubing

Instrument Tubing for Gas Service

The most important consideration in the selection of suitable tubing for any application is the compatibility of the tubing material with the media to be contained. Stainless steel fittings should be used only with stainless steel tubing.

 

Stainless Steel Type 316 tubing material is recommended for High Pressure, High Temperature, Generally Corrosive Media. The recommended temperature range includes -425°F to 1,200°F1 (-255°C to 605°C).

 

When selecting tubing for oil and gas service, the system operating pressure and temperature must be carefully evaluated. The most important consideration in the selection of suitable tubing for any application is the compatibility of the tubing material with the media to be contained.

The Selection Process

General Selection Criteria

The most important consideration in the selection of suitable tubing for any application is the compatibility of the tubing material with the media to be contained. Table 1 lists common materials and their associated general application. Table 1 also lists the minimum and maximum operating temperature for the various tubing materials.

 

General Selection Criteria

* Dual-certified grades such as 316/316L, meet the minimum chemistry and the mechanical properties of both alloy grades.

Notes:
1. For operating temperatures above 800°F (425°C), consideration should be given to media. 300 Series Stainless Steels are susceptible to carbide precipitation which may lead to intergranular corrosion at elevated temperatures.
2. Consideration should be given to maximum temperature ratings if fittings and/or tubing are coated or plated. All temperature ratings based on temperatures per ASME B31.3 Chemical Plant and Petroleum Refinery Piping Code, 1999 Edition.

System Pressure

The operating pressure is an important factor in determining the type, and more importantly, the size of tubing to be used. In general, high-pressure installations require stronger materials. Heavy walled softer tubing such may be used if chemical compatibility exists with the media.

 

Maximum Allowable Working Pressure Tables

Maximum Allowable Working Pressure Tables (Seamless)

 

Maximum Allowable Working Pressure Tables (Welded)

* Dual-certified grades such as 316/316L, meet the minimum chemistry and the mechanical properties of both alloy grades.
*Notes:
• All working pressures have been calculated using the maximum allowable stress levels in accordance with ASME/ANSI B31.3, Chemical Plant and Petroleum Refinery Piping or ASME/ANSI B31.1 Power Piping.
• All calculations are based on maximum outside diameter and minimum wall thickness.
• All working pressures are at ambient (72°F) temperature.

System Temperature

The operating temperature is also important when determining the proper tubing material. Stainless steel tubing is suitable for higher temperature media

 

Temperature Derating Factors

Table 8 lists derating factors which should be applied to the working pressures listed in Tables 2 & 3 for elevated temperature conditions. Simply locate the correct factor in Table 8 and multiply this by the appropriate value in Tables 2 or 3 for elevated temperature working pressure.

*Example: 1/2” x .49 wall seamless 316 stainless steel tubing has a working pressure of 3700 psi @ room temperature. If the system were to operate @ 800°F (425°C), a factor of 80% or (.80) would apply (see Table 8) and the “at temperature” system pressure would be 3700 PSI x .80 = 2960 PSI.

Tubing Handling & Preparation

After tubing has been properly selected and ordered, careful handling is important. From the receiving dock to point of installation, special attention is necessary to prevent scratching, burring and other injurious damage occurring to the tube. This is especially important for gas service. Low-density gases such as helium and argon cannot be sealed with damaged tubing.

 

Make certain not to drag tubing across any surfaces such as truck beds, shelves, or storage racks, the floor and (or) ground of any plant/construction site. This is important for tubing of all materials. Besides scratching, improper handling can create out-of-round tubing.

 

To discuss an upcoming project with one of our experts, reach out to our team today. 

Stainless Steel Type 316 Tubing Sizes Currently In Stock

 

Tube Outside Diameter Size Wall Thickness
1/4″ 0.035″
3/8″ 0.035″ & 0.049″
1/2″ 0.035″ & 0.049″
3/4″ 0.049″ & 0.065″

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DISCLAIMER

All tables, examples, and notes are provided by Parker Hannifan.