Nickel-aluminium Bronze Pressure Temperature Rating 1

[apf]

How do valve manufactures provide an ambient or cold working pressure of 20bar (Class 150) for Nickel-aluminium Bronze B148 C95800?

In basic terms the standards ASME B16.24:2001 (US) and EN 1092-3 / 1759-3:2003 (Euro) do not take into account the higher mechanical properties of Nickel-aluminium Bronze over standard Bronze castings. ASME B16.24 has two tables: Table 1 rates class 150 Bronze at 15.5bar @ ambient to a maximum of 9.3bar @ 232°C. Table 2 rates class 150 Bronze at 13.4bar @ ambient to a maximum of 9.65bar @ 260°C). Similarly, the European standards rate these materials to 15.5bar (16bar - PN rating) but do indicate a higher pressure rating at elevated temperatures.

There is no standard to fully utilise the properties of Nickel-aluminium Bronze: for instance the designation B148 C95800 does not appear in ASME II, the closest material designation is B148 C95200 which gives the PTR for table 2 in ASME B16.24.

Both ASME B16.34 and B16.5 provide an appendix that allows the calculation of a pressure temperature rating. With reference to ASME B16.34:2004 Appendix B for the ambient working pressure of ASTM B148 C95800:

Tensile strength is 85000psi
Yield strength is 35000psi

S1 – selected stress is the lower of:
1. 60% x yield = 60% x 35000psi = 21000psi
2. 1.25 x 25% x tensile = 1.25 x 25% x 85000psi = 26560psi

.: S1 = 21000psi

For class 150, Pr = 115 and C1 = 1
Pst = C1S1Pr / 8750
Pst = 1 x 21000 x 115 / 8750 = 276psi or 19bar

Therefore, using this method you can provide an ambient or cold working pressure of 19bar,
However I do not have the mechanical properties of this material at temperature which would allow me to construct a full pressure temperature rating for this material.

Can any one help me out with this one?

 

[linaldinho]

Hi apf.
I also have the same question too.
In my opinion, I think can't use the formula from either B16.5 or B16.34, C95800 is not consist in B16.5 or B16.34.

 

[vpl]

apf and linaldinho

I wish I had better news, but...

ASME B16.34, Non Mandatory Appendix B provides the method used to determine the pressure and temperature ratings. The introduction notes that the method is general and considers the dimensions used in the standard. A footnote states “This method is appropriate for materials listed in Table 1 of this Standard. It may not be appropriate for other materials.”

The next section in the standard is labeled “Materials.” There is one particular sentence of note in this paragraph: “However, both [the materials used for valve body and bonnet or cover] shall be from materials listed in Table 1.” Unfortunately, as both of you have noted, B148 C95800 is not in Table 1.

Which leads to Interpretation: 2-1; issued May 17, 1990 with a subject of “Materials.” This was a three part question and answer. The third question is directly applicable to your problem:

“Question (3): Can new materials be added to Table l?"

"Reply (3): Yes. This can be done at the next revision or when an Addenda is prepared. In order to facilitate the inclusion of new materials, it is recommended that the requester provide the Committee with the data needed to establish pressure-temperature ratings as provided in Annex F.”

By looking at previous revisions to the standard, it appears that Annex F is now Non Mandatory Appendix B.

The Introduction to the standard (not to the appendix) provides information on submitting requests for interpretations. The address is: “Secretary, B16 Committee, The American Society of Mechanical Engineers, Three Park Avenue, New York, NY 10016-5990.” Page viii has preferred format for interpretations, which is 1) Subject – give paragraph number and topic; 2) Edition – 2004 is the current one; and 3) Question – the question for which you’re seeking an answer.

Although this won't help your short-term situation, I hope it will help in the long-term.


Patricia Lougheed

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[bcd]

Hello,

For what it's worth, I pulled out our old marine valve catalog. We use to make valves out of ASTM B148 Alloy 958. The PT ratings in the buletin were:

Class 150:
-20 to 100 F (250 psi)
200 (230)
300 (210)
400 (190)
500 (170)

Class 300:
-20 to 100 F (700 psi)
200 (600)
300 (550)
400 (500)
500 (450)

This data is old, and the guys who created it are long since dead. However, they were involved with the creation of the Pressure / Temperature rating method in B16.34.

Using the above data and the equations in 16.34, you can calculate the allowable stress at temperature and compare to the Ni-Al-Brz grade listed in the code. At least it will give you some idea where the number are.

bcd