Emergency Pressure Vent Cover NK-EV30W
API Standard 2000 for Venting / Atmospheric and Low Pressure storage Tanks / SIZING A PRESSURE/VACUUM RELIEF VALVE
API standards are provided as an engineering aid for specification and selection of “normal” and “emergency” pressure and vacuum relief valves for aboveground liquid petroleum storage tanks. Normal venting capacity is obtained without exceeding pressure or vacuum that would cause physical damage or permanent deformation to the tank. The following will help in sizing a pressure/vacuum valve:
1. NORMAL RELIEF : the sum of vapor replacement resulting from emptying or filling and thermal in-breathing or out-breathing.
2. EMERGENCY RELIEF : thermal out-breathing from fire exposure.
3. ALL TANKS : generally require the sizing of a normal pressure and vacuum relief valve to be sized and an independent emergency relief valve to be sized separately.
4. FLOW CURVES : these curves provide pressure and vacuum capacity which is required for sizing.
MODEL NAME : NK-EV30W
NK-EV30W PHOTO
NK-EV30W PHOTO
DESIGN AND FUNCTION
Model No. |
Type | Material |
Setting Pressure Range |
NK-EV30W |
Weight Loaded release to ATM | Aluminum, Carbon Steel, Stainless Steel |
22 ~ 700 mmH2O |
NK-EV30S |
Spring Loaded to ATM | Aluminum, Carbon Steel, Stainless Steel |
Above 700 mmH2O |
Note) Other specification to be consult by factory.
Model NK-EV30, NK-EV33 is designed to protect the tank against rupture or explosion that could result from excessive internal pressures caused by fire etc. Model NK-EV30, NK-EV33 is designed to provide emergency relief capacity beyond that furnished by the normal operating pressure relief valve on the storage tank. The feature of Model NK-EV30, NK-EV33is that the pressure relief cover is designed to lift only far enough to flow its rated capacity should high tank pressure be encountered then reseal automatically when the tank pressure is reduced.
MATERIALS
PART NAME | MATERIALS STANDARD | MATERIALS OPTIONAL |
BODY | C.S / SUS304 / SUS316 / ALUMINUM | Hastelloy, Alloy 20, FRP, PTFE, ETFE LINED |
PALLET | 304 SS / 316 SS / 316L SS | Hastelloy, Alloy 20, FRP, PTFE, ETFE LINED |
WEIGHT | A36 | 304 S.S |
DIAPHRAGM/ORING | Teflon(Diaphragm seal) | NBR, Viton(O-ring seal) |
PRESSURE/VACUUM RELIEF VALVE SETTING
API 2521
Pressure/vacuum valves on atmospheric pressure fixed roof tanks are usually set at 1/2 oz. per square inch pressure or vacuum. Test data indicate that an increase of 1 oz. per square inch in the pressure set point over the usual 1/2oz. per square inch reduces breathing losses by approximately 7 percent. However, the test data indicate that each additional increase of 1 oz. per square inch in pressure set point reduces the breathing losses in progressively smaller increments.
API 2513
The pressure and vacuum setting of a breather valve are dictated by the structural characteristics of the tank and should be within safe operating limits. A certain amount of pressure and vacuum beyond this setting is necessary to overcome pressure drop in order to obtain required flow. Proper size and setting can best be determined by reference to API STD accordance with this publication. The pressure setting for pressure/vacuum valves to be installed on large tanks constructed in accordance with API 12:Specification for Large Welded Production Tanks(1957)usually is limited to 1/2 oz. because roof plates will start to shift when the pressure rises much above 1 oz.
Pressure Relief
As the pressure in the storage tank increases, when the set pressure is reached, the pressure pallet lifts and relieves to atmosphere.
MODEL NAME : NK-EV30W
MODEL NAME : NK-EV30S
MODEL NAME : NK-EV33W
NK-EV33W (Door opening)
DRAWING AND DIMENSION
SIZE | I.D | T | H |
16” | 400 | 20 | 155 |
20” | 500 | 20 | 180 |
24” | 600 | 20 | 200 |
UNIT : mm