This article is intended to provide useful information for users such as valve design engineers , valve procurement engineers , and pipeline system design engineers , who are dealing with valve material selection in their daily work . Valve material selection includes material selections for the valve body , and valve trim ( typically includes a ball , plug , disk , seat , stem , and sleeves needed to guide the stem ). Valve material selection is a big topic to be discussed , however , this article is only focused on the material selection for the valve body .

By Dongcheng Li , FBV , and Gobind N . Khiani

Background

Valves are one of the most important components for a pipeline or piping system , because valves enable process engineers to open , close , and redirect the flow , control the flow rate , adjust the pressure of the system , release pressure , and more . Based on functions , working conditions ( including type of media , flow rate , pressure , and temperature ) and other requirements , proper valves need to be selected for each specific application .

In general , the valve body , bonnet or cover , and body joint , bolting shall be constructed of material as listed in the respective ASTM specifications referred to in Table 1 of the ASME code B16.34 . 1 Materials for different services proposed in this standard come from real world experience including failures and successes , therefore are tested and proven .

Criteria for Material Selection

Criteria for the selection of the materials are not detailed within the scope of the ASME code B16.34 . The possibility of material deterioration in service and the need for periodic inspections are the responsibilities of the user , i . e ., carbide phase conversion to graphite , oxidation of the ferritic materials , decrease in ductility of carbon steels at low temperatures , susceptibility to intergranular corrosion of austenitic materials , or grain boundary attack of nickel-based alloys , are among the items requiring attention by the user .

The following key factors apply to valve material selection : 2

1 . Operating conditions ;

2 . Effect of internal flow media properties and external environment ;

3 . Fabrication performance ;

4 . Market availability or cost ; and ,

5 . Weight reduction .

Among these factors , the most important factors are the operating conditions , and internal flow media properties .

Materials in Table 1 of the ASME code B16.34 are given in four groups . Generally speaking the materials can be grouped as : carbon steel , low alloy steel , alloy steel , stainless steel , and exotic metals . Considering service temperature limitations , Table 1 below should only be

Table 1 : Temperature range . used as general reference for commonly used materials .

Other than temperature , another factor in selecting the valve material is the internal flow media chemical properties . Some applications require the use of stainless steel or exotic alloys to withstand the extreme corrosive properties of the flow media . But , for applications

-267.8 Austenitic Stainless Steel A182 Grade F304 , F304L , F316 , F316L

-315.0 Alloy Steel A182 Grade F51 , F53 , F55 537.8 Carbon Steel A105 , A216 Grade WCA , WCB , WCC 648.9 High Temperature Alloy A182 Grade F304 , F304L , F316 , F316L 815.6 High Temperature Alloy Inconel 600 , 625 1204.4 High Temperature Alloy Hastelloy , Inconel 601

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