Relationship between valve diameter and medium flow rate

1. The flow rate and flow rate of the valve mainly depend on the diameter of the valve, and also related to the resistance of the structure of the valve to the medium, and at the same time have some internal relationship with the pressure, temperature and concentration of the medium.
2. The flow path area of the valve is directly related to the flow rate and flow rate, and the flow rate and flow rate are two quantities that are interdependent. When the flow rate is constant, the flow rate is large, and the flow path area can be smaller; the flow rate is small, and the flow path area can be larger. On the contrary, the flow passage area is large, the flow velocity is small, the flow passage area is small, and the flow velocity is large.

3. The flow rate of the medium is large, the valve diameter can be smaller, but the resistance loss is large, and the valve is easy to be damaged. The flow rate is large, which will cause electrostatic effects on flammable and explosive media, causing danger; the flow rate is too small, the efficiency is low, and it is uneconomical. For mediums with high viscosity and explosiveness, a small flow rate should be taken. The oil and the liquid with high viscosity select the flow rate according to the viscosity, and generally take 0.1 to 2 m/s.

4. In general, the flow rate is known and the flow rate can be determined empirically. The nominal diameter of the valve can be calculated from the flow rate and flow rate.

5. The valve has the same diameter, the structure is different, and the resistance of the fluid is different. Under the same conditions, the greater the resistance coefficient of the valve, the more the flow rate and flow rate of the fluid passing through the valve decrease; the smaller the coefficient of resistance of the valve, the less the flow rate and flow rate of the fluid passing through the valve.

6. The common flow rates of various media are shown in the table below.
Fluid name
Conditions of Use
Flow rate
 (m/s)
Saturated Vapor
DN>200
 DN=200～100
 DN<100
30~40
 25~35
 15~30
superheated steam
DN>200
 DN=200～100
 DN<100
40~60
 30~50
 20~40
Low pressure steam
ρ<1.0 (absolute pressure)
15~20
Medium pressure steam
Ρ=1.0～4.0 (absolute pressure)
20~40
High pressure steam
Ρ=4.0～12.0 (absolute pressure)
40~60
compressed gas
Vacuum
 Ρ≤0.3 (gauge pressure)
 Ρ=0.3~0.6 (gauge pressure)
 Ρ=0.6~1.0 (gauge pressure)
 Ρ=1.0～2.0 (gauge pressure)
 Ρ=2.0～3.0 (gauge pressure)
 Ρ=3.0~30.0 (gauge pressure)
5~10
 8~12
 10-20
 10~15
 8~12
 3 to 6
 0.5 to 3
oxygen
Ρ=0～0.05 (gauge pressure)
 Ρ=0.05～0.6 (gauge pressure)
 Ρ=0.6~1.0 (gauge pressure)
 Ρ=1.0～2.0 (gauge pressure)
 Ρ=2.0～3.0 (gauge pressure)
5~10
 7~8
 4~6
 4~5
 3 to 4
gas
 
2.5 to 15
Semi-water gas
Ρ=0.1～0.15 (gauge pressure)
10~15
natural gas
 
30
Nitrogen
Ρ=5～10 (absolute pressure)
15~25
Ammonia
Vacuum
 Ρ<0.3 (gauge pressure)
 Ρ<0.6 (gauge pressure)
 Ρ≤2 (gauge pressure)
15~25
 8~15
 10-20
 3~8
Acetylene water
 
30
 5~6
Acetylene gas
ρ<0.01 (gauge pressure)
 ρ<0.15 (gauge pressure)
 ρ<2.5 (gauge pressure)
3 to 4
 4~8
 5
chlorine
Gas
 liquid
10~25
 1.6
Hydrogen chloride
Gas
 liquid
20
 1.5
Liquid ammonia
Vacuum
 Ρ≤0.6 (gauge pressure)
 Ρ≤2.0 (gauge pressure)
0.05~0.3
 0.3 to 0.8
 0.8 to 1.5
Sodium hydroxide
Concentration 0~30%
 Concentration 30%～505
 Concentration 50% to 73%
2
 1.5
 1.2
sulfuric acid
Concentration 88% to 93%
 Concentration 93% to 100%
1.2
 1.2
hydrochloric acid
 
1.5
Water and viscosity
Similar liquid
Ρ=0.1～0.3 (gauge pressure)
 Ρ≤1.0 (gauge pressure)
 Ρ ≤ 8.0 gauge pressure)
 Ρ≤20～30 (gauge pressure)
 Heating network circulating water, cooling water
 Pressure back
 Pressureless backwater
0.5 to 2
 0.5 to 3
 2 to 3
 2 to 3.5
 0.3 to 1
 0.5 to 2
 0.5 to 1.2
Tap water
Supervisor Ρ = 0.3 (gauge pressure)
 Branch pipe Ρ = 0.3 (gauge pressure)
1.5 to 3.5
 1 to 1.5
Boiler feed water
 
>3
Steam condensate
 
0.5 to 1.5
Condensate
Self-flow
0.2 to 0.5
Superheated water
 
2
Sea water, slightly alkaline water
Ρ<0.6 (gauge pressure)
1.5 to 2.5

Note: 
The unit of DN value is: mm;
The unit of devaluation is: MPa.
The resistance coefficient of the gate valve is small, only in the range of 0.1 to 1.5; the gate valve with large diameter has a drag coefficient of 0.2 to 0.5; the resistance coefficient of the shrink gate valve is larger.
The resistance coefficient of the shut-off valve is much larger than that of the gate valve, generally between 4 and 7. The Y-type stop valve (DC type) has the smallest resistance coefficient between 1.5 and 2; the forged steel stop valve has the largest resistance coefficient, even as high as 8.
The resistance coefficient of the check valve depends on the structure: the swing check valve is usually about 0.8 to 2, and the drag coefficient of the multi-lobed check valve is large; the lift check valve has the largest drag coefficient, up to 12 .
The plug valve has a small drag coefficient, usually about 0.4 to 1.2.
The resistance coefficient of the diaphragm valve is generally around 2.3.
The butterfly valve has a small drag coefficient, generally within 0.5.
The ball valve has the smallest drag coefficient, generally around 0.1.
The resistance coefficient of the above valve is the value of the valve in the fully open state.

The choice of valve diameter should take into account the machining accuracy and dimensional deviation of the valve, as well as other factors. The valve diameter should have a certain margin, generally 15%. In actual work, the valve diameter depends on the diameter of the process line.