How to choose the right Straight Union material according to the properties and transmission requirements of the fluid?

In the pipeline connection system, Straight Union is a commonly used accessory, which is used to connect two pipes to ensure that the fluid can be transmitted stably. Choosing the right Straight Union material is the key to ensuring the safe, stable and long-term operation of the pipeline system. According to the properties and transmission requirements of the fluid, the correct selection of materials can not only improve the working efficiency of the system, but also effectively avoid pipeline failures and unnecessary maintenance costs. This article will discuss how to choose the right Straight Union material according to factors such as the properties, temperature, pressure and chemical compatibility of the fluid.

1. Fluid type and material selection
First of all, the properties of the fluid are one of the most important factors in selecting the Straight Union material. The fluid may be a gas, liquid or suspended substance, and its physical and chemical properties (such as corrosiveness, viscosity, temperature) will directly affect the choice of material. The following are specific considerations for selecting materials according to the fluid type:

1.1 For water or ordinary liquids
For non-corrosive liquids (such as tap water, clean water, etc.), common materials include stainless steel, copper alloy and PVC. These materials can not only effectively prevent the penetration of water, but also withstand certain pressure and temperature changes.

Stainless steel: high temperature resistant, corrosion resistant, suitable for hot and cold water pipe systems.
Copper alloy: has strong corrosion resistance and good processability, suitable for water supply and HVAC systems.
PVC: suitable for low-pressure fluid systems, lightweight and corrosion resistant, suitable for low-temperature water pipes.
1.2 For chemically corrosive fluids
If the fluid has a certain degree of corrosiveness (such as acid, alkali or chemical solution), it is very important to choose a suitable corrosion-resistant material. For corrosive fluids, commonly used materials include fluoroplastics (such as PTFE), fiberglass, titanium alloy, etc.

PTFE (polytetrafluoroethylene): has excellent chemical stability and can withstand most strong acids, strong alkalis and other chemicals.
FRP: Due to its excellent corrosion resistance, it is often used to transport acid and alkali solutions, chemical raw materials, etc.
Titanium alloy: Titanium alloy exhibits excellent corrosion resistance at high temperatures and is suitable for the chemical and petroleum industries.
1.3 For oils and chemicals
When selecting a straight union for oils, lubricants and other petrochemical products, the oil resistance and high pressure resistance of the material need to be considered. Common materials include stainless steel, alloy steel, and carbon steel.

Stainless steel: oil-resistant and high-temperature resistant, suitable for oil and gas transportation.
Alloy steel: used in high-pressure and high-temperature environments, especially suitable for petrochemical pipeline systems.
Carbon steel: has good oil resistance under low temperature and high pressure conditions, but requires anti-corrosion coating.
2. Influence of operating temperature and pressure
The transmission conditions of the fluid, including operating temperature and pressure, are another important factor that must be considered when selecting the straight union material. Different materials have different strength, corrosion resistance and durability at different temperatures and pressures.

2.1 High-temperature fluids
For high-temperature fluids (such as hot water, steam, hot oil, etc.), the selected straight union material needs to have high-temperature resistance. Commonly used high-temperature resistant materials include stainless steel, aluminum alloy, titanium alloy, etc.

Stainless steel: has excellent high-temperature resistance and is widely used in the transportation of high-temperature steam, hot oil and other fluids.
Aluminum alloy: suitable for medium-temperature fluid systems, with good thermal conductivity, suitable for use in medium and high temperature environments.
Titanium alloy: has excellent high temperature resistance and corrosion resistance, especially suitable for high-temperature chemical fluid transportation in special environments.
2.2 High-pressure fluid
For high-pressure fluid systems (such as natural gas, liquefied gas, etc.), the material of the Straight Union not only needs to have good pressure resistance, but also needs to take into account the impact and friction of the fluid in a high-pressure environment. Commonly used high-pressure materials are stainless steel, alloy steel, and carbon steel.

Stainless steel: high strength and good pressure resistance make it an ideal choice for high-pressure fluid transportation.
Alloy steel: suitable for extremely high-pressure environments, commonly found in high-pressure transportation systems for oil and natural gas.
Carbon steel: suitable for low to medium-pressure fluid systems, but requires coating protection to avoid corrosion.
3. Chemical compatibility and corrosion resistance
The chemical properties of the fluid directly determine whether the material of the Straight Union can be in long-term contact with the fluid without reacting. When selecting the material, the chemical compatibility of the material and the fluid must be ensured. Otherwise, it will not only affect the flow efficiency of the fluid, but may also cause corrosion, leakage or rupture of the equipment.

Plastic materials such as PTFE and PVDF have excellent chemical stability to most chemical fluids, so they are suitable for conveying chemicals such as strong acids, strong alkalis, and solvents.
Stainless steel has a wide range of chemical compatibility and can resist most chemical fluids, but special alloys may need to be selected in strong acid and alkali environments.
Titanium alloy: Suitable for highly corrosive environments, especially with excellent chemical stability at high temperatures.
4. Wear resistance and fluid flow rate
If the fluid contains solid particles or the flow rate is high, it is particularly important to choose a Straight Union material with strong wear resistance. The friction of solid particles in the fluid may accelerate the wear of the material, so it is necessary to choose a material with high hardness and wear resistance.
Stainless steel and carbon steel have good performance in wear resistance and are suitable for conveying fluids with solid particles or high flow rates.
Ceramic coating or cemented carbide: In situations where extreme wear resistance is required, ceramic coating or cemented carbide materials may need to be selected.
5. Environmental and workplace requirements
According to the special requirements of the use environment (such as highly corrosive environment, food grade requirements, etc.), it is crucial to select a Straight Union material that meets safety and hygiene standards. For example, the food and drinking water industries require materials that meet FDA or NSF certification standards to ensure that no harmful substances are leached.

Stainless steel is an ideal material widely used in food, medicine, drinking water and other fields. It meets hygiene standards and is corrosion-resistant.
PFA and PTFE: Suitable for medical, chemical and food industries, with excellent chemical stability and antibacterial properties.