[Difficult Question] How to select the pipe material based on process media, T, P, and other conditions? ?

The choice of material for pipes is primarily determined by the process medium; once the process medium is known, the range of possible materials for the pipes narrows. Subsequently, factors such as temperature and pressure are taken into account to assess issues related to corrosion, stress, and deformation, so as to select an appropriate material. It is not necessary to use the \"Corrosion Data and Material Selection Handbook\", though it can certainly be used as a reference for research.

I don’t quite agree with the view above. The choice of pipeline material requires taking into account the corrosion properties of the process medium, as well as temperature and pressure. Typically, design institutes have tables for selecting appropriate pipes.

The material and wall thickness are determined based on the corrosivity of the process medium, while also taking cost considerations into account； Secondly are the pressure and temperature of the pipes, as well as their coupling.

One must consider cost-effectiveness and suitability; when it comes to suitability, factors such as the medium, temperature, and pressure need to be taken into account

First, select from common materials based on the properties of the process medium, and then calculate parameters such as wall thickness using T and P.

Haha, this is a big question. For those in the materials field, one spends their entire career working on this subject. I’ll mention a few points for your reference. I. The most common rules: 1. The material category is determined by the medium ； For example: oil pipelines, carbon steel ； HCL pipes, fiberglass-reinforced plastic pipes, rubber-lined pipes, and so on... 2. Once the category of material has been determined, the actual material to be used is chosen based on various factors such as industry standards (e.g., those set by the client) and the convenience of installation. For example, for HCL pipes, you selected one option from the category of non-metallic materials. 3. During the above process, attention should be paid to economic comparisons. 4. At the same time, T and P need to be taken into account ； For corrosive environments, references such as the \"Corrosion Data and Material Selection Manual\" can be consulted. Note that corrosion is related to temperature, as well as to pressure; for example, high pressure makes it impossible to use glass fiber pipes. It is also affected by supports and hangers, among other factors. 5. For metal materials, the wall thickness shall be calculated as specified. Pay attention to the temperature and pressure curve. I’ll continue speaking below

Continuing with the speech: II. Special situations 1. Special situations regarding the medium. For example, hydrogen should be selected according to the Nelson curve; materials such as 1Cr-0.5Mo, 0Cr-0.5Mo, and carbon steel are applicable. Note: The operating temperature should be increased by 20~40; the pressure refers to the hydrogen partial pressure. 2. Stress corrosion conditions. For example, in the case of wet fluidized hydrogen, there are requirements regarding the material’s yield strength, tensile strength, operating conditions, carbon equivalent, hardness, heat treatment, and so on. 3. Cases of concentration and temperature combinations. For example, in cases where the combination of NOH concentration and temperature is >40% and >80 degrees Celsius, nickel-based alloys should be considered. 4. Temperature – in combination with pressure, it corresponds to different operating conditions, such as charring, etc. I’ll continue speaking below

Continuing with the discussion: III. Extreme conditions 1. Low temperatures. When the temperature is below -20 degrees, the material must undergo a Charpy (V-notch) low-temperature impact test ； If the carbon content of the material is greater than 0.1%, the same applies...; for low temperatures, steel suitable for such conditions should be used, such as austenitic stainless steel, which can withstand temperatures of >-196 degrees. 2. High temperature. When austenitic stainless steel is used at temperatures above 525 degrees, its carbon content should be no less than 0.04%. In other words, 304 is used, not 304L and so on. 3. Pressure. For example, for 1.0 MPa steam, 20# steel is used, while G20 is required for medium-pressure steam.

Continue speaking. IV. Equipment requirements 1. Pollution requirements. For pipes such as those used for deionized water in catalyst preparation equipment, stainless steel is used to avoid iron contamination. 2. Wear requirements. For example, in FCC plants where pipes transition from three-roll to four-roll configuration, stainless steel cannot be used as it is not wear-resistant; instead, Cr5Mo is generally employed. 3. Cleanliness requirements: For instrument air lines, galvanized pipes should be used, etc.

What are the main reference materials?