Settings for the operating conditions of the flame arrestor vent valve, hydraulic safety valve, and breathing manhole on fixed-roof tanks (equipped with nitrogen sealing)
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This post was last edited by 2005180005 on 2017-11-20 at 17:41. 1. The design pressure of the storage tank is -0.3 to 2 KPa(G); for the flame arrestor vent valve, the minimum and maximum pressures are -0.0003 to 0.0015 MPa(G). The setting pressure for the hydraulic safety valve is 0.00165 MPa(G), and for the breathing manhole, the minimum and maximum pressures are -0.0004 to 0.0019 MPa(G). Are these three sets of values reasonably set? 2. If the breather valve is operational around the clock, is it then unnecessary to install a hydraulic safety valve? ? ? 3. Does the hydraulic safety valve only discharge air and not draw in any air? ? Why? Logically, the hydraulic safety valve is a backup to the breather valve; it should allow both inhalation and exhalation, but safety valves generally only facilitate exhalation
The hydraulic safety valve is an important accessory installed on the top of the oil tank to ensure its safety. When the breathing valve fails, the hydraulic safety valve can take over from the mechanical breathing valve to exhaust or release air. The pressure or vacuum level controlled by the hydraulic safety valve is 5%-10% higher than that of the mechanical breathing valve; therefore, it does not activate under normal conditions. Oils with a high boiling point, slow evaporation rate, and low freezing point are used as sealing fluids inside the valve. The hydraulic safety valve can be used for both exhaling and inhaling. The flame arrestor breather valve and hydraulic safety valve seem to be fine from a design perspective. I’m not sure what a breathing manhole is; I’ve never seen one before. Generally, storage tanks are equipped with emergency pressure relief manholes. When the tank is under excessive pressure and neither the breather valve nor the hydraulic safety valve can handle the pressure release, the pressure is discharged through these relief manholes once the set pressure is reached. These manholes are usually of DN500 or DN600 size. It can only release pressure.
A hydraulic safety valve can replace a breathing valve for venting or releasing air. “It mentions “exhausting” or “venting”, but not inhaling, so there’s always some uncertainty regarding this
If it can only vent air, then it cannot replace a breathing valve. Hydraulic safety valves also have set values for positive and negative pressures, right?
There is no issue with the pressure progression of the breather valves; the problem lies in the fact that the design pressure of your storage tank is so low, at only 2 kPa, which is higher than the pressure levels of those breather and safety valves. Was the pressure value entered incorrectly?
If high requirements are placed on the breather valve, it is generally configured with two inlets and three outlets. That is, dual functions for replenishing air: a breathing valve + a vacuum-breaking valve. Triple exhaust system: breathing valve + hydraulic safety valve + breathing manhole (emergency pressure relief manhole). These are safety protection measures that are not mandated by standards; they can be applied as appropriate based on the actual circumstances.
It is a fixed-roof tank with nitrogen sealing; the design pressure of the storage tank is -0.5 to 2 kPa, with this value taken from HG 21502.1-92 as a reference
Can the hydraulic safety valve and the breathing manhole also be used for air supply?