Faq

Double-sided forced sealing for gate valves:

This means that whether at the inlet or outlet end of the medium, the gate plate and valve seat sealing surfaces remain sealed. The sealing integrity is forcibly maintained by the axial force of the valve stem. When no medium is present, the positive pressure between the sealing surfaces must not be less than the sum of the medium's static pressure and the sealing force.

Single-face forced sealing for gate valves:

This means that no seal exists between the gate plate and the valve seat sealing surface at the medium inlet end. Here, either no pressure differential exists at all, or the pressure differential is less than the sealing pressure. On the medium outlet side, the seal between the gate plate and the valve seat sealing surface is forcibly maintained by the axial force of the valve stem and the medium pressure. When no medium is present, the pressure differential across the sealing surfaces must not be less than the sealing pressure.

(1) Classified into two types based on the structure of the gate plate

1. Parallel gate valves feature sealing surfaces parallel to the vertical centerline, meaning the two sealing surfaces are parallel to each other. Within this category, there are double-disc and single-disc types. They are further classified as having or lacking flow-through holes.
2. A wedge gate valve refers to a gate valve where the sealing surfaces form a wedge shape by being angled relative to the vertical centerline. Within this category, there are further distinctions between double-disc gate valves, single-disc gate valves, and elastic disc gate valves.

(2) Classified into two types based on valve stem construction

1. A rising stem gate valve is a type of gate valve where the valve stem nut is located on the valve bonnet or bracket. When opening or closing the gate, the valve stem is raised or lowered by rotating the valve stem nut.
2. A stemless gate valve is a type of gate valve where the valve stem nut is in direct contact with the medium inside the valve body, and the gate plate is opened or closed by rotating the valve stem.

The minimum stem diameter refers to the diameter of the portion of the stem that contacts the packing. The minimum stem diameter refers to the diameter of the stem thread relief groove.

The paint color of the handles and handwheels corresponds to the paint color of the sealing surface material, as detailed in the table below.

Valve handle and handwheel paint color：

The opening and closing directions for general valves are specified as follows: clockwise for closing and counterclockwise for opening.

The mandatory and optional markings for general-purpose valves are shown in the table below.

Valve markings：

Note: When the nominal pressure value cast on the valve body equals ten times the megapascal (MPa) figure and is positioned below the nominal pressure value, it is not preceded by the designation “PN”.

Marking method:

(1) Valve marking for nominal sizes greater than or equal to DN50:

1. Items 1 through 4 in the table are mandatory markings and should be affixed to the valve body.
2. Items 5 and 6 in the table are mandatory markings only when specified in the relevant valve standards. They should be marked on the valve body and flange, respectively.
3. Unless otherwise specified in various valve standards, items 7 through 19 in the table are optional markings. When required, they may be marked on the valve body or nameplate.

(2) Marking for valves with nominal sizes less than DN50:

1. Items 1 through 4 in the table are mandatory markings. Whether these markings appear on the valve body or on a label is determined by the product designer.
2. The marking of items 5 to 19 in the table shall comply with the provisions for markings 2 and 3 for nominal sizes greater than or equal to DN50.

(3) Additional markings:

1. Any marking from the table may be affixed at different locations. For example, any marking placed on the valve body may also be duplicated on the nameplate.
2. Any additional markings may be affixed provided they do not cause confusion with the markings on the form. For example: product model numbers, etc.

For pressure reducing valves, in addition to the 19 items specified for general valves, the markings on the valve body shall also include: date of manufacture, applicable medium, and outlet pressure.

For steam trap markings, in accordance with GB/T 12250-2005, the markings may be affixed to the valve body or displayed on a nameplate.

The marking of safety valves shall comply with the provisions of GB/T 12241-2005.

Ball valves, parallel gate valves, and plug valves shall be marked in accordance with API 6D-2014.

The sealing surface material code for surfaces machined directly from the valve body is denoted by “W”. Codes for other materials are listed in the table below.

Seat sealing surface or lining material code:

Note: When the sealing surfaces of a sealing pair are made of different materials, the designation code of the softer material shall be used.

对闸阀、截止阀、止回阀以及球阀和蝶阀来说，密封必须比压 qMF 小于密封比压 q ，密封比压小于密封许用比压 [q] (即： qMF ＜ q ＜ [q] ) 。

The shell test pressure for general-purpose valves is 1.5 times the rated working pressure of the material at 38°C. The high-pressure seal test is 1.1 times the rated working pressure of the material at 38°C. Low-pressure seal test requirements vary by standard.

Among these:

GB/T 13927-1992 、ISO 5208:2008、EN 12266.2-2012 为0.6MPa±0.01MPa；

GB/T 26481-2011、API 598-2009 为0.4MPa~0.7Mpa；

MSS SP61-2013 为0.56MPa；

API 6D-2014 为Ⅰ型：0.034MPa~0.1MPa、Ⅱ型：0.55MPa±0.69MPa；

ISO 14313:2007 为Ⅰ型：0.05MPa~0.1MPa、Ⅱ型：0.55MPa±0.07MPa；

API 6A（idt ISO  10423:2003） 为PSL3G：第一次：额定压力、第二次：2.0MPa±0.2MPa；PSL4：第一次：额定压力、第二次：2.0MPa±0.2MPa。

The specific test pressures for shell tests, high-pressure sealing tests, and high-pressure upper sealing tests are shown in Tables 1-1 and 1-2.

Classification of valves based on their purpose or primary structural characteristics.

General classification categorizes valves by both operating principle and structure, representing the most widely used classification method domestically and internationally. Common types include: gate valves, globe valves, plug valves, ball valves, butterfly valves, diaphragm valves, check valves, throttle valves, safety valves, pressure reducing valves, steam traps, and control valves.

Valve model designations are composed of codes representing valve type, actuation method, connection type, structural configuration, sealing surface material or lining material type, pressure rating or working pressure at operating temperature, and valve body material.

The valve model consists of seven parts, with their meanings shown in the diagram.

NPS：

用于管道系统元件的字母和数字组合的尺寸标识，它由字母 NPS 和后跟的无量纲的整数数字组成。这个数字与端部连接件的孔径或外径等特征尺寸直接相关。无量纲数字可作为没有前缀 “NPS” 的阀门尺寸标识。无量纲的尺寸数字不代表测量值，也不能用于计算。

Class：

与阀门材料的力学性能和尺寸特性相关、用于有关阀门的压力/温度能力的字母和数字组合的标识。它由字母 Class 和后跟的无量纲整数组成。字母 Class 之后的数字不代表测量值，也不应用于计算。除非在有关标准中另有规定，管道元件许用压力取决于 Class 数值、材料以及允许工作温度。许用压力在相应标准的压力-温度额定值表中给出。

DN:

用于管道系统元件的字母和数字组合的尺寸标识。它由字母 DN 和后跟无因次的整数数字组成。这个数字与端部连接件的孔径或外径（用 mm 表示）等特征尺寸直接相关。

Note:

1. 除在相关标准中另有规定，字母 DN 后面的数字不代表测量值，也不能用于计算目的。
2. 采用 DN 标识系统的那些标准，应给出 DN 与管道元件的尺寸的关系，例如 DN/OD 或 DN/ID。

PN:

与管道系统元件的力学性能和尺寸特性相关，用于参考的字母和数字组合的标识。它由字母 PN 和后跟无因次的数字组成。

Note:

1. 字母 PN 后跟的数字不代表测量值，不应用与计算目的，除非在有关标准中另有规定。
2. 除与相关的管道元件标准有关联外，术语 PN 不具有意义。
3. 管道元件许用压力取决于元件的 PN 数值、材料和设计以及允许工作温度等，许用压力在相应标准的压力-温度等级表中给出。
4. 具有同样 PN 和 DN 数值的所有管道元件同与其相配的法兰应具有相同的配合尺寸。

Valves commonly used in pipelines across various industrial enterprises.

A general term for mechanical products with movable mechanisms used to control the flow of media within pipelines.