Flange sealing factors and gasket performance: key considerations for pressure vessel and pipe flange standards

Factors affecting flange sealing

The main factors affecting flange sealing are: bolt pre tightening force, sealing surface form, gasket performance, flange stiffness and operating conditions.

密封面的形式：

Sealing surface form:

平面型：结构简单，加工方便，便于防腐或衬里。但垫片易挤出且不易压紧，用于低压、小尺寸、无毒、密封要求不高的场合。

Plane type: simple structure, convenient processing, easy to prevent corrosion or lining. However, the gasket is easy to extrude and not easy to compress, which is used in low pressure, small size, non-toxic and low sealing requirements.

凹凸型：对中性好，密封性能较好，用于中压且温度较高的场合。

Concave convex type: good for neutral, good sealing performance, used in medium pressure and high temperature occasions.

榫槽型：对中性好，密封可靠，垫片宽度小，所需压紧力也小，适用于易燃、易爆、有毒及高压场合。加工、检修比较困难。压紧面的选择原则为：确保密封可靠，力求加工容易、装配方便、成本低。

Mortise and groove type: good for neutral, reliable sealing, small gasket width, small pressing force required, suitable for flammable, explosive, toxic and high-pressure occasions. It is difficult to process and maintain. The selection principle of pressing surface is: to ensure reliable sealing, to strive for easy processing, convenient assembly and low cost.

 

垫片性能

Gasket performance

在法兰连接中，密封效果在很大程度上取决于垫片的密封性能。

In flange connection, the sealing effect depends on the sealing performance of gasket to a great extent.

1. 材质要求：耐腐蚀，不污染产品，具有一定的弹性，适当的机械强度和柔韧性，在温度变化时不易变质硬化或软化。

1. Material requirements: corrosion-resistant, non polluting, with certain elasticity, appropriate mechanical strength and flexibility, not easy to deteriorate, harden or soften when the temperature changes.

2.  分类

2. classification

 

压力容器法兰和管法兰的标准

Standard for pressure vessel flanges and pipe flanges

容器法兰只用于容器壳体间的联接，如筒节和筒节、筒节和封头的联接。管法兰只用于管道间的联接。

The vessel flange is only used for the connection between the vessel shell, such as the connection between the barrel section and the barrel section, the barrel section and the head. Pipe flange is only used for connection between pipes.

特别注意：两者不能互换！！！

Special attention: the two cannot be interchanged!

容器法兰：JB/T4700~4707《压力容器法兰》

Vessel flange: pressure vessel flange (JB / t4700-4707)

管法兰:

Pipe flange:

HG20592~20635《钢制管法兰、垫片、紧固件》、GB/T9112~9125《钢制管法兰》、JB/T74~90《钢制管法兰、垫片、紧固件》

Hg20592-20635 steel pipe flange, gasket and fastener, GB / t9112-9125 steel pipe flange, JB / t74-90 steel pipe flange, gasket and fastener

法兰标准中的三个重要参数

Three important parameters in flange standard

1、公称直径DN：

1. Nominal diameter DN:

法兰的公称直径是指与法兰配合的容器或管子的公称直径。容器的公称直径是指容器的内径（用管子作筒体的容器除外），管子的公称直径指其名义直径，为介于管子内、外径之间的某一数值，其中大多数接近管子的内径。公称直径相同的钢管，其外径是相同的，由于厚度是变化的，所以内径也是变化的。

The nominal diameter of the flange refers to the nominal diameter of the vessel or pipe matched with the flange. The nominal diameter of the container refers to the inner diameter of the container (except for the container with the pipe as the barrel). The nominal diameter of the pipe refers to its nominal diameter, which is a certain value between the inner diameter and the outer diameter of the pipe, most of which are close to the inner diameter of the pipe. For steel pipes with the same nominal diameter, the outer diameter is the same, and the inner diameter is also variable because the thickness is variable.

2、公称压力PN：

2. Nominal pressure PN:

公称压力是为制定标准而分的压力等级。

The nominal pressure is the pressure class divided for standard setting.

 

3、最大允许工作压力：

3. Maximum allowable working pressure:

 

压力容器法兰标准中的公称压力是按法兰材料16Mn（或16MnR）、设计温度200oC条件下确定的，当法兰材料和温度变化时，法兰的最大允许工作压力将增大或减小。例如表14-3中的长颈对焊法兰的最大允许工作压力。

The nominal pressure in the pressure vessel flange standard is determined according to the flange material 16Mn (or 16MnR) and the design temperature 200oC. When the flange material and temperature change, the maximum allowable working pressure of the flange will increase or decrease. For example, the maximum allowable working pressure of long neck butt welding flange in table 14-3.

 

如何选择压力容器法兰

How to select pressure vessel flange

为一台内径为Di，设计压力为p，设计温度为t的容器筒体或封头选配法兰。

It is an optional flange for the cylinder or head of a vessel with an inner diameter of Di, a design pressure of P and a design temperature of T.

1、根据容器的公称直径DN和设计压力p，参照JB/T4700表1初步确定法兰的结构型式。(甲型平焊法兰、乙型平焊法兰或长颈对焊法兰）

1. According to the nominal diameter DN and design pressure P of the vessel, refer to table 1 of JB / t4700 to preliminarily determine the structure type of the flange. (type a flat welding flange, type B flat welding flange or long neck butt welding flange)

2、根据容器的设计压力p，设计温度t及准备采用的法兰材料，按JB/T4700表6或表7（最大允许工作压力表）确定所选法兰的PN。

2. According to the design pressure P, design temperature T and flange materials to be used, PN of the selected flange shall be determined according to table 6 or table 7 (maximum allowable working pressure gauge) of JB / t4700.

3、根据PN和DN 再查看JB/T4700表1 ，验证初步确定的法兰型式是否符合要求。若不符合，则需变更法兰类型或材料，重新确定PN。

3. Check table 1 of JB / t4700 again according to PN and DN to verify whether the flange type preliminarily determined meets the requirements. If not, the flange type or material shall be changed and PN shall be determined again.

 

4、按JB/T4701(甲型)或4702(乙型)或4703(长颈对焊)查取法兰尺寸。

4. Check the flange size according to JB / t4701 (type A) or 4702 (b) or 4703 (long neck butt welding).