The corrosion resistance of austenitic stainless steel comes from the protective layer of chromium oxide formed on the metal surface. If this material is heated to a temperature of 450°C to 900°C, its structure changes and chromium carbides form along the crystal edges. This prevents the formation of a protective chromium oxide layer at the crystal edges, resulting in reduced corrosion resistance. This corrosion is called intergranular corrosion. As a result, stainless steel 304L...
Stainless Steel with Low Carbon Content Used for Valves Read
More »
Types of packings Packings of valves can be divided into soft packings and hard packings. Soft packings: they are cotton ropes wovening from mariajuana, flax, cotton and jute, or having metal wire inside with asbestos fibers and coating with graphite powder on the outside. There are also packings formed by pressing, as well as flexible graphite packings developed in recent years. Plant packings are often used for low-pressure valves below 100°C;...
Materials for Valve Components (Part Two) Read
More »
Materials for sealing surfaces The sealing surface is the most critical working surface for the valve. The quality of the sealing surface is related to the service life of the valve. Usually, the sealing surface's material should consider factors such as corrosion resistance, scratch resistance, erosion resistance, and oxidation resistance, which are divided into the following two categories: Soft sealed materials Rubber including nitrile rubber and fluorine rubber...
Materials for Valve Components (Part One) Read
More »
This standard adopts the national standard GB/T13927 Pressure Tests of Industrial Valves. 1. Subject content and scope of application This standard specifies the requirements, methods and evaluation indicators for pressure tests of general valves. This standard applies to the pressure test of gate valves, globe valves, check valves, plug valves, ball valves, butterfly valves, diaphragm valves, etc. 2. Terminology 2.1 Test pressure The gauge pressure born by the inner cavity...
General Pressure Test Standards for Valves Read
More »
The generation of static electricity Static electricity is a common physical phenomenon, which is closely related to our life. Our bodies and clothes will also generate a lot of static electricity, especially in winter. Any two objects of different materials come into contact with each other and then separate; the contact is accompanied by friction, and static electricity will be generated. There are two main key reasons for static electricity: one is the different...
Why Should Soft Sealing Valves Be Anti-static? Read
More »
1. Overview A flange is the most commonly used connection in fluid pipelines, which is convenient for installation, maintenance, and replacement of the pipeline. Flanges are generally used for gate valves, globe valves, check valves, ball valves and plug valves under medium and low pressure. The valve body connected by flanges generally has three parts, two flange ends and one middle flange. For small-diameter valves (DN50...
Hydraulic Automatic Drilling Equipment for Valve Bodies Read
More »
3.6 Stems and packing The threaded part of the valve stem should not be in contact with the conveying fluid, except for the special requirement, and the valve stem and stem nut assembly should be self-locking. The valve stem and packing should be resistant to various corrosion. The packing should meet the requirements of Q/BU.J1502-93. The packing shall be ring shaped packing made of graphite and expanded graphite. 3.7 Hard alloy surfacing Try to avoid surfacing cobalt-based cemented...
Design Requirements for Main Parts of Nuclear Power Valves (Part Three) Read
More »
(2) C2 valves The body of the C2 valve can be made of forged steel and cast steel. When the welding seam on the pressure-bearing boundary can be inspected by radiography, the forged welding structure can also be used. The connection between the valve body and valve bonnet of valves with different pressure adopts pressure self-sealing and sealed bolt connection. For the pressure of 5.0MPa and above, concave-convex mating surfaces and fully embedded gaskets are used. Concave-convex gaskets,...
Design Requirements for Main Parts of Nuclear Power Valves (Part Two) Read
More »
Abstract: The design methods of main parts of gate valves, globe valves, check valves and ball valves for nuclear power plants are introduced and the general requirements for nuclear power valves are discussed in this article. 1. Overview Nuclear power valves refer to valves used in nuclear islands (N1), conventional islands (CI) and auxiliary facilities (BOP) systems of power plants in nuclear power plants. According to the safety level,...
Design Requirements for Main Parts of Nuclear Power Valves (Part One) Read
More »
1. Hot cracks Hot cracks are generated at high temperatures in the welding process of valves, which have characteristics of cracking along the original austenite grain boundary. Different welding metals such as low-alloy high-impact steel, stainless steel, cast iron aluminum alloys and special metals can make forms, temperatures and the main causes of hot cracks different. Hot cracks are divided into crystal...
Hot Cracks, Reheat Cracks & Cold Cracks of Valves Read
More »
