What are the chemical pipes and fittings valves?

Do you understand chemical pipelines? Start with these 11 types of pipes, 4 types of pipe fittings, and 11 major valves!

11 types of chemical pipes

Types of chemical pipes are divided into materials: metal pipes and non-metal pipes

Cast iron pipes, seamed steel pipes, seamless steel pipes, copper pipes, aluminum pipes, lead pipes.

Cast iron pipe:

Cast iron pipe is one of the pipes commonly used in chemical pipelines.

Due to its brittleness and poor connection tightness, it is only suitable for transporting low-pressure media and is not suitable for transporting high-temperature and high-pressure steam and toxic and explosive substances. Commonly used in underground water pipes, gas mains and sewer pipes. The specifications of cast iron pipes are expressed in Ф inner diameter × wall thickness (mm).

Seamed steel pipe:

Seamed steel pipes are divided into ordinary water and gas pipes (pressure resistance 0.1~1.0MPa) and thickened pipes (pressure resistance 1.0~0.5MPa) according to the use pressure.

Generally used to transport water, gas, heating steam, compressed air, oil and other pressure fluids. Galvanized pipes are called galvanized iron pipes or galvanized pipes. Those that are not galvanized are called black iron pipes. Its specifications are expressed in nominal diameter. The minimum nominal diameter is 6mm and the maximum nominal diameter is 150mm.

Seamless steel pipe:

The advantage of seamless steel pipe is uniform quality and high strength.

Its materials include carbon steel, high-quality steel, low alloy steel, stainless steel, and heat-resistant steel. Due to different manufacturing methods, it is divided into two types: hot-rolled seamless steel pipe and cold-drawn seamless steel pipe. In pipeline engineering, when the pipe diameter exceeds 57mm, hot-rolled pipes are commonly used, and when the pipe diameter is below 57mm, cold-drawn pipes are commonly used.

Seamless steel pipes are often used to transport various pressurized gases, vapors and liquids and can withstand higher temperatures (approximately 435°C). Alloy steel pipes are used to transport corrosive media, among which heat-resistant alloy pipes can withstand temperatures up to 900-950°C. The specifications of seamless steel pipes are expressed in Ф inner diameter × wall thickness (mm).

The maximum outer diameter of cold-drawn pipes is 200mm, and the maximum outer diameter of hot-rolled pipes is 630mm. Seamless steel pipes are divided into general seamless steel pipes according to their uses.

Pipes and special seamless pipes, such as petroleum cracking seamless pipes, boiler seamless pipes, fertilizer seamless pipes, etc.

Copper pipe:

Copper tubes have good heat transfer effect. 

It is mainly used in pipelines of heat exchange equipment and cryogenic devices, instrument pressure measuring tubes or transmitting pressured fluids. However, when the temperature is higher than 250°C, it should not be used under pressure. Because it is more expensive, it is generally used in important places.

Aluminum tube:

Aluminum has very good corrosion resistance.

Aluminum tubes are often used to transport concentrated sulfuric acid, acetic acid, hydrogen sulfide, carbon dioxide and other media, and are also commonly used in heat exchangers. Aluminum pipes are not resistant to alkali and cannot be used to transport alkaline solutions and solutions containing chloride ions.

Since the mechanical strength of aluminum pipes decreases significantly as the temperature increases, the operating temperature of aluminum pipes cannot exceed 200°C. For pressure pipelines, the operating temperature will be even lower. Aluminum has good mechanical properties at low temperatures, so aluminum and aluminum alloy tubes are mostly used in air separation devices.

Lead pipe:

Lead pipes are often used as pipelines to transport acidic media. They can transport 0.5% to 15% sulfuric acid, carbon dioxide, 60% hydrofluoric acid and acetic acid with a concentration less than 80%. They are not suitable for transporting nitric acid, hypochlorous acid and other media. The maximum operating temperature of lead pipes is 200°C.

Non-metallic pipes

Plastic pipes, glass pipes, ceramic pipes, cement pipes.

Plastic pipe:

The advantages of plastic pipes are good corrosion resistance, light weight, convenient molding, and easy processing.

The disadvantages are low strength and poor heat resistance.

At present, the most commonly used plastic pipes include hard polyvinyl chloride pipes, soft polyvinyl chloride pipes, polyethylene pipes, polypropylene pipes, and metal pipes sprayed on the surface with polyethylene, polychlorotrifluoroethylene, etc.

Rubber tube:

Rubber pipes have good corrosion resistance, are light in weight, have good plasticity, and are flexible and convenient to install and disassemble. 

Commonly used rubber tubes are generally made of natural rubber or synthetic rubber and are suitable for situations where pressure requirements are not high.

Glass tube:

Glass tubes have the advantages of corrosion resistance, transparency, easy cleaning, low resistance, and low price. The disadvantages are that they are brittle and cannot withstand pressure.

Ceramic tube:

Chemical ceramics are similar to glass and have good corrosion resistance. In addition to hydrofluoric acid, fluorosilicic acid and strong alkali, they can withstand the corrosion of various concentrations of inorganic acids, organic acids and organic solvents.

Cement pipe:

Mainly used in situations where the pressure requirements and connection sealing are not high, such as underground sewage, drainage pipes, etc.

Category 4 pipe fittings

In addition to pipes, in order to meet the needs of process production, installation and maintenance, there are many other components in the pipeline, such as short pipes, elbows, tees, reducers, flanges, blind plates, etc.

We usually call these components pipeline accessories or pipe fittings. Pipe fittings are an indispensable part of the pipeline. Here is a brief introduction to several commonly used pipe fittings.

Elbow

Elbows are mainly used to change the direction of pipelines. They can be classified according to the degree of bending of the elbows. The common ones are 90°, 45°, 180°, and 360° elbows. 180° and 360° elbows are also called "U" shaped elbows.

There are also elbows with specific angles required for process piping. Elbows can be made by bending straight pipes or tailor-welding pipes. They can also be welded after molding, or made by casting and forging. For example, elbows in high-pressure pipelines are mostly forged from high-quality carbon steel or alloy steel made.

Tee

When two pipelines are connected to each other or a bypass is required, the pipe fitting at the joint is called a tee.

Depending on the angle of the access pipe, there are vertically connected front tees and mitered tees. Miter tees are named according to the miter angle, such as 45° miter tees, etc. 

In addition, they are called according to the diameter of the entrance and exit, such as equal-diameter tees, etc. In addition to the common tee fittings, they are often referred to by the number of interfaces, such as four-way, five-way, mitered five-way, etc. Common tee fittings, in addition to pipe welding, are also made by die assembly welding, casting and forging.

Short pipes and reducers

When there is a short section in the pipeline assembly, or when a small detachable section of pipe needs to be installed in the pipeline for maintenance, a short pipe is often used.

Short pipes are available with connectors (such as flanges, screws, etc.), or are simply short pipes, also called pipe pads.

The pipe fitting that connects two pipe openings of different diameters is called a reducer. Usually called Big Head. This kind of pipe fittings include cast reducers, cut and welded pipes, or rolled and welded steel plates. The reducers in high-pressure pipelines are made of forgings or reduced from high-pressure seamless steel pipes.

Flange, blind plate

In order to facilitate installation and maintenance, detachable connections are often used in pipelines, and flanges are a commonly used connection part.

For cleaning and inspection, it is necessary to set a hand hole blind plate on the pipeline or install a blind plate on the pipe end. The blind plate can also be used to temporarily close a certain interface of the pipeline or to interrupt a certain section of the pipeline from the system.

In general medium and low pressure pipelines, the shape of the blind plate is the same as the solid flange, so this kind of blind plate is also called a flange cover. This kind of blind plate, like the flange, has been standardized. The specific dimensions can be found in the relevant manuals.

In addition, during the maintenance of chemical equipment and pipelines, in order to ensure safety, a solid disc made of steel plates is often inserted between two flanges to temporarily isolate the equipment or pipelines from the production system. This blind board habit is called inserting a blind board. The size of the insertion blind plate can be the same as the outer diameter of the sealing surface of the insertion flange.