Breathing discharge calculation of breather valve
The respiratory emissions of the fixed roof tank can be estimated by the following formula:
In the formula:
- LB-respiratory discharge volume of fixed top tank (Kg/a);
- M-the molecular weight of the vapor in the tank;
- P-In a large amount of liquid state, the true vapor pressure (Pa);
- D-The diameter of the tank (m);
- H-average vapor space height (m);
- △T- the average temperature difference within a day (℃);
- FP-coating factor (dimensionless), the value is between 1 and 1.5 according to the paint condition;
- C-Adjustment factor for small diameter tanks (dimensionless); For tanks with a diameter between 0-9m, C=1-0.0123(D-9)^2; C=1 for tanks with a diameter greater than 9m;
- KC-product factor (Petroleum crude oil KC is 0.65, other organic liquids are 1.0).
Working discharge calculation of Breather valve
Work emissions are losses due to man-made loading and unloading. As a result of charging, when the pressure in the tank exceeds the release pressure, the vapor is forced out of the tank; while the discharge loss occurs when the liquid is discharged, and the air is drawn into the tank, and the air becomes a gas saturated with organic vapor and expands. Therefore, the capacity of the vapor space is exceeded.
The working emissions of the fixed roof tank can be estimated by the following formula:
In the formula:
- LW-Work loss of fixed roof tank (Kg/m3 input);
- KN-Turnover factor (dimensionless), the value is determined by the number of annual turnover (K).
Turnover times=annual input/tank capacity
- K>220, KN=0.26
Pressure test of Breather valve
1. Test preparation
Install the fire-stop Breather valve on the test bench correctly, the device should not leak, and the inner wall of the test tube should be flat and smooth.
2. Detection medium
The detection medium for the opening pressure, ventilation and leakage of the fire resistance Breather valve is air, the absolute pressure is 0.1Mpa, the temperature is 20℃, the relative humidity is 50%, and the density is 1.2kg/m3. If the air is not in this state, Should be converted to gas in this state. The detection medium for the pressure of the flame retardant Breather valve body is 5-35 ℃ clean water.
3. Air pressure detection
First detect its leakage, and then detect its sensitivity and ventilation volume one by one.
4. Water pressure detection
The water pressure test of the fire retardant Breather valve is 0.2Mpa, and the pressure holding time is 10min.
5. Pressure detection
Install the fire-resistance Breather valve on the connecting flange of the gas storage tank, adjust the valve to gradually increase or decrease the pressure in the gas storage tank, adjust the valve disc to make it open, and read from the connected micromanometer Output the pressure value, read the value once every minute, and then rotate the valve disc by 90° and 180° respectively, repeat the above test, repeat each working condition three times, and take the average value.
6. Leakage detection
The leak detection pressure is 0.75 times the operating pressure, and this value is read on the micromanometer. The value of the leakage is read from the flowmeter (the accuracy of the flowmeter is 0.5-1.0 level). Read each measurement value once per minute for a total of three readings, and take the average.
7. Low temperature detection fire resistance Breather valve. Install the fire resistance Breather valve on the test frame and put it in the low temperature box. The temperature in the low temperature box will drop to 4-15℃, and the continuous input relative temperature of the low temperature box should not be less than 70%. The air at room temperature reaches the end of the breather valve before the end of the valve disc is opened, and then the temperature in the low temperature box is reduced to -30 ℃, after 24 hours of constant temperature, connect one side of the test frame to the micromanometer, and the other side passes through A surge tank containing room temperature air is connected to the aerodynamic force. When the valve disc of the breather valve is in the open state, read the pressure value. repeat three times.
Maintenance of Breather valve
The Breather valve is maintained and maintained once a month and twice a month in winter. The method: first slightly open the valve cover, take out the vacuum valve disc and the pressure valve disc, check the valve disc and valve disc seal, valve disc guide rod and guide rod sleeve for oil and dirt, such as oil and dirt The objects should be cleaned up, then put back in place, and pull up and down a few times to check whether the opening is flexible and reliable. If everything is normal, then tighten the valve cover. In the maintenance and maintenance, if there is any abnormal phenomenon such as scratches or wear on the valve disc, it should be replaced immediately or contact the supplier company to solve it in time.
Breather valve selection should first follow the four principles of safety, reliability, applicability, and economy in sequence, and then follow the six aspects of on-site working conditions (namely, pipeline parameters, fluid parameters, pressure parameters, action methods, and special requirements). select).
The following factors are mainly considered when selecting the breather valve:
- 1. For the requirements of the installation location and temperature range, such as cold areas, all-weather Breather valves should be used, and pipeline breather valves should be used for installation in pipelines.
- 2. The control pressure of the mechanical Breather valve should be compatible with the relevant pressure bearing capacity.
- 3. The specifications (flange diameter) of the mechanical Breather valve should meet the requirements of the maximum flow rate of breather gas in and out of the oil tank.
- 4. Consider the exhalation volume caused by the increase in the evaporation of liquid in the tube caused by the heating of the tank during a fire.
- 5. Under the influence of climate, the increase of vapor pressure in the tank decreases, resulting in the thermal effect of breather.
- 6. Anti-freeze Breather valve should be selected for selection in northern cold regions.
- 7. The maximum amount of liquid in and out of the tank.
First, determine the breather volume of the breather valve according to the working conditions of the specific occasions where the breather valve is set up and the prescribed calculation method or formula, and then select the breather valve according to the various specified performance curves of different constant pressure values provided by the breather valve manufacturer size. It also determines the take-off pressure and ventilation pressure of the breather valve. When a single breather volume cannot meet the requirements, more than two Breather valves can be set.
Confirm the minimum pressure of the vessel design and the maximum allowable pressure of the vessel, that is, the determination of negative pressure and positive pressure, and the operating pressure range.
Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)