The high-velocity relief valve (pressure/vacuum valve for cargo oil tank) generally uses High-velocity relief valve (pressure vacuum valve) is the controlled venting system which is necessary for oil tanker and chemical tanker. The series of DF-type P/V valve is a new generation production without vibration and anti-collision...The pressure/vacuum valve is installed on the vent pipe of oil tanker and chemicals tanker. It is the only entry and exit for liquid cargo tank. 1. When loading the liquid cargo or ballasting, the pressure valve in the high velocity relief will open, then jet out combustible liquid cargo vapour/air-mixture in liquid cargo tank with the rate of more than 30m/s, and dilute in the air so that it will never drop on the deck. 2. When unloading the liquid cargo, the vacuum valve in the high velocity relief valve will open, then supply air to cabin safely so as to avoid the cabin is over-vacuumed. 3. When the tank navigate on sea, the high velocity valve can automatically adjust the pressure oscillation in the cabin which caused by temperature changes. The experiment of pressure/vacuum valve for cargo ships is done in the lab that is approved by the state organs. It is ratified by China Classification Society and some other classification societies through the following tests according to the above standards: 1. Fire Resistant Test 2. Re-burning Test 3. Frozen Test 4. Corrosion Resistant Test 5. Flowing Test

Main Parts of the DF-ISO high velocity relief valve

Serial No.	Parts	Quantity	Material
1	P-valve base	1	20#
2	P-valve seat	1	316
3	P-valve body (a)	1	20#
4	P-valve body (b)	1	20#
5	Director (P-valve disc )	1	316
6	Clump weight	1	316
7	P-valve spindle	1	316
8	Lifting shaft	1	316
9	Climbing cam	1	316
10	Positioning board	1	316
11	Lifting handle	1	316
12	Bush	1	304
13	Nameplate	1	304
14	Lifting pin	1	316
15	V-valve body	1	20#
16	V-valve disc	1	316
17	V-valve seat	1	316
18	Small spacer ring of flame screen	1	316
19	Flame screen	2	316L
20	Big spacer ring of flame screen	1	20#
21	Flame screen gland	1	20#
22	V-valve cover	1	20#

Remarks : The materials mentioned before are basic materials , ship-owners can choose better materials , Such as SUS304,SUS304L ,SUS316L .

Main performance parameter

Model	Opening pressure (kPa)		Rated working pressure (kPa)			Flow rate (m3/h)			Outlet air flow velocity of pressure valve(m/s)
	Pressure valve	Vacuum valve	Pressure valve	Vacuum valve	Air removal cover	Pressure valve	Vacuum valve	Air removal cover
DF50	14.0-21.0	-3.5~-7.0	21.0	-7.0	2.0	＞350	＞350	＞250	＞30

Remarks: The high-velocity relief valves with different specification have the same diameter and performance parameter; The opening pressure of the vacuum valves are -3.5kpa; the opening pressure of the pressure valves on the oil tank is 14kpa,on the chemical tank is 20kpa.The opening pressure of the pressure may be different, but the differences of opening pressure and flow range if the pressure valves have the same diameter.