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Designer's Guide


Tube-Mac® has developed a strong position against the use of welded connections and pipe threads to eliminate leakage in a system. Although our name indicates the use of tube, our systems have been developed to handle high flow rates and pressures, which dictate the use of pipe sizes rather than tubing.

Fluid Power Designers are required to make decisions regarding the flow and velocity to be used for the system design. The first decision to be made is the size of the pipe, more specifically the "internal" bore diameter of the pipe. The Flow capacity and fluid Velocity of the system are two deciding factors in sizing the pipe.

Flow Rate of the system is 185 US GPM
Design or Working Pressure is 3,500 PSI

Ref. Table 1. The recommended Oil Velocity is 20 FPS for a pressure line with a design pressure of 3,500 PSI.

Ref. Table 2. Select the column GPM @ 20 FPS, travel down this column until you find the approximate flow of 185 US GPM. Read across the row horizontally and the nominal pipe size that suits the criteria of this example would be 2" sch 80 pipe with internal bore 1.939".


Once the line size has been established the next most critical selection the designer has to consider is the type of pipe material that meets the Working Pressure of the system.

There are two TMI® Pipe - Pressure Rating tables to choose from:
Table 3. Carbon Steel

Table 4. Stainless Steel

The maximum Allowable Working Pressures are according to ASME/ANSI B31.3. The internal bore diameter of each pipe is also shown beneath the pressure rating as a quick reference.

In this example the Working Pressure is 3,500 PSI and we will assume that the environment is non-corrosive therefore stainless steel pipe is not required. We also assume that temperature does not play a factor.

Ref. Table 3. Carbon Steel – Read vertically down the 2" nominal pipe size column until you find the pressure rating that meets or exceeds the working pressure. There are three pressure ratings, which exceed 3,500 PSI. The most cost effective solution would be to select the pipe with a pressure rating, which is closest to the working pressure.

In our example the designer would select 2" schedule 80 TMP52CD pipe.

Note: See pages A6 through A9 for additional information on carbon steel and stainless steel pipes Tube-Mac® has to offer.


Finally the designer must select the pipe connection that meets the design criteria. Tube-Mac® offers non-welded flanged systems and coupling solutions dependent upon the working pressure of the system.

  • Flared pipe ends with flare flanges.
  • Retain ring grooved pipe ends with retain ring flanges.
  • Roll or cut groove pipe ends with a coupling.

There are two TMI® Pipe Connection - Pressure Rating Guides to choose from:

Table 5. Carbon Steel Pipe Connection

Table 6. Stainless Steel Pipe Connection

These guides will help select the best-suited pipe connection for the application.

In our example the designer has selected 2" schedule 80 TMP52CD pipe.

Ref. Table 5. Carbon Steel – Read vertically down the 2" nominal pipe size column and horizontally across TMP52CD schedule 80 pipe row to confirm the pressure rating meets or exceeds the working pressure of 3,500 PSI.

The left side of this table indicates the pipe connection style. In our example the pipe connection is "flared pipe ends with flare flanges".

To the far right of this table is a column that directs the designer to a "systems" section of the Tube-Mac® catalogue. Here the designer will find more detailed information about the selected pipe connection system.

In our example the designer would be referred to SECTION B, which is the Flared System section of the Tube-Mac® catalogue.