Classification
| Classification method | type | instruction | |
| acting principle | direct-acting | Depend directly on the medium pressure force to overcome the mechanical load of acting on disc to open the valve | |
| not direct-acting | pilot | consist of main valve and pilot valve. Main valve is drived or controled by the medium exhausted from the pilot valve | |
| With additional load-type | before the inlet pressure to achieve opening pressure has always maintained an additional force to enhance sealing. The additional force should reliable release before opening pressure. | ||
| acting characteristic | Proportional-action | Opening height gradually increases by the pressure changes | |
| both ends action Snap Action Type |
Open process is divided into two stages: At first disc ratio opens with the increase of pressure, the pressure increases a little value, the disc is almost rapid opening up to the required height under no increase of pressure | ||
| opening height | low lift type | Open height should be within 1 / 40 ~ 1 / 20 of flow channel diameter | |
| fall lift type | Open height should be greater than or equal to 1 / 4 diameter of flow channel | ||
| middle lift type | Open height is between the low lift type and fall lift type | ||
| whether have back pressure balanced device | back pressure balance type | using bellows, piston or diaphragm and other balanced back pressure acting components, to make the acting of back pressure to disc both up and down sides balance. | |
| normal type | without back pressure balanced components | ||
| disc loading mode | heavy hammer or lever heavy hammer | using heavy hammer to direct load, or using heavy hammer loads through the lever | |
| spring | using spring to load | ||
| air chamber | using compress air to load | ||
（1） according to applicable meidum
steam-used safety valve（Usually represented by A48Y-type）
air and other gas used safety valve（Usually represented by A41Y type）
liquid used safety valve（Usually represented by A41H type）
（2）nominal pressure
low pressure safety valve： nominal pressure PN≤1.6Mpa safety valve
middle pressure safety valve： nominal pressure PN2.5－6.4Mpa safety valve
high pressure safety valve： nominal pressure PN10.0－80.0Mpa safety valve
ultra-high pressure safety valve： nominal pressure PN〉100Mpa safety valve
（3） applicable temperature
Ultra-low temperature safety valve：t≤－100℃ safety valve
low temperature safety valve：－100℃<－40℃safety valve
normal temperature safety valve：－40℃<t≤120℃safety valve
middle temperature safety valve：120℃<t≤450℃safety valve
high temperature safety valve：t>450℃safety valve
Particularly to point out that, according to the actual situation of the domestic spring manufacture, when the safety valve is used for the working conditions more than 350 ℃, mostly use added radiator or made bonnet as basket-style, in order to better for spring heat radiation, to make spring always keep to the following work at 350 ℃ and to ensure its stiffness constant, thus ensuring the proper opening and back seat, and other performance requirements.
（4） connecting mode
Flange connection safety valve. The inlet and pipe connection is flange and outlet form is flexible
Thread connection safety valve. The inlet and pipe connection is thread, outlet form is flexible
Welding connection safety valve. The inlet and pipe connection is thread, outlet form is flexible
（5）structural type
According to structural characteristics or the ratio of largest disc opening height and seat diameter (h / d), the safety valve can generally be divided into the followings：
Lever heavy hammer safety valve
Spring safety valve. Using compress spring force to balance the disc pressure and make it seal safety valve. See as A42Y16C-type safety valve.
Impulse type valve. It is also known as pilot-type safety valve. It designs main valve and secondary valve together, through the auxiliary valve impulse acting to drive the main valve moves. This structure is commonly used for large-caliber, large displacement and high pressure system. impulse-type safety valve, such as WFXD type.
Low lift type safety valve. The disc opening height is 1/40∽1/20 of the seat diameter. Such as A27W-10T, A47H－16C safety valve.
Fall lift type safety valve. Such as A47H－16C safety valve. The disc opening height is 1/4 of the seat diameter.
Completely closed safety valve. Such as A47H-16C type safety valve.
Semi-closed type safety valve. such as A48Y-16C safety valves.
Open safety valve. (A48Y-16C safety valve is also open type)
Pilot type safety valve. Such as WFXD type safety valve.
（6）According to the classification of Sealing
Cemented carbide to cemented carbide sealing pair. Applicable to high temperature and pressure occasion, especially the high-temperature and pressure superheated steam.
Cr13 to 2Cr13r sealing pair. Use in the general situations of the saturated steam and superheated steam, or the temperature below 450 ℃ other media, containers or pipes.
Seat sealing surface is 2Cr13, disc sealing surface is hard alloy. Used in high-pressure steam and large flow relatively, other medium that is easy to cause the sealing surface erosion.
Seat sealing surface is alloy steel, disc sealing surface is PTFE. Apply to oil or gas medium, strict sealing request, but the operating temperature below 150 ℃ occasions.
Sealing is austenitic stainless steel. This safety valve body, bonnet are mostly austenitic stainless steel, used in the medium containing acid, alkali and other corrosive elements occasion
（7） classification according to acting principle
Direct-acting safety valve. Depend directly on the medium pressure force to overcome the mechanical load of acting on disc to open the valve
Pilot type safety valve. It consists of main valve and pilot valve. Main valve is drived or controled by the medium exhausted from the pilot valve
With additional load-type safety valve. before the inlet pressure to achieve opening pressure has always maintained an additional force to enhance sealing. The additional force should reliable release before opening pressure.
（8） according to acting characteristics
Proportional-action type safety valve. Opening height gradually increases by the pressure changes.
Both ends action safety valve (Snap Action Type). Open process is divided into two stages: At first disc ratio opens with the increase of pressure, the pressure increases a little value, the disc is almost rapid opening up to the required height under no increase of pressure
（9）according to opening height
Low lift type safety valve. Open height should be within 1 / 40 ~ 1 / 20 of flow channel diameter
Fall lift type safety valve. Open height should be greater than or equal to 1 / 4 diameter of flow channel
Middle lift type safety valve. Open height is between the low lift type and fall lift type.
（10） whether have back pressure balanced device
back pressure balance typ. using bellows, piston or diaphragm and other balanced back pressure acting components, to make the acting of back pressure to disc both up and down sides balance.
normal type safety valve, without back pressure balanced components
（11） disc loading mode
heavy hammer or lever heavy hammer. using heavy hammer to direct load, or using heavy hammer loads through the lever
Spring type safety valve, using spring to load
Air chamber type safety valve, using compress air to load
