What Are the Needle Valves? (2)

Needle valves have the capability of fine adjustments. Along the flow direction of media, these valves are operated to change the flow areas for blocking or regulating the flow.

Nominal Pressure: PN2.5, PN4, PN6.4, PN16, PN32, etc.
Nominal Diameter: from DN5 to DN25
Media: Oil, Water, Gas, etc. (Corrosive and Non-corrosive Media)
Raw Materials: 20#, 1Cr18Ni9Ti, 304, 316, 316L, 12Cr1Mov, etc.

What is the needle lift?
With high precision, general fuel injectors consist of magnet coils and needle valves and belong to magnetic valves actually. 

When the needle valve is opened and then leaves the valve seat of the magnetic valve, the maximum range of the needle valve’s lifting distance is called the needle lift.

When the magnet wire is electrified, the armature and the needle valve are attracted; the gasoline with pressures passes through the annular space between the needle valve and the magnetic valve’s seat; the gasoline is sprayed into the air tube in the form of oil spray and then becomes mixed with air; when the magnet wire is not electrified, the coil spring of the fuel injector makes the needle valve back to the valve seat. 

When the needle lift, the injecting pressure and the injecting time are limited, the quantity of the fuel injection is determined by the annular gap. To ensure the accuracy of the quantity and the atomization quality, the needle valve and the valve seat require fairly high machining accuracy, making the annular gap narrow and instrumental error little. 

The high accuracy and the small gap lead to high sensitivity to the debris clinging to the gap. Thus, even a little debris can cause the clogging of the annular gap and the insufficient oil supply.

Solutions to broken fuel injectors about needle valves
When the orifice of the fuel injector is blocked, the orifice can be dredged by the nozzle cleaner and be cleaned carefully then. 

When the valve body of the needle valve has the large surface in poor contact with the surface of the fuel injector’s main body, the chromium oxide can be daubed on the flat plate and used to abrade the flat plate following a shape of the figure eight .

Moreover, if the cylinder surface of the needle valve wears seriously, the needle valve components should be replaced in pair. 

When the needle valve is poorly sealed so as to cause the poor atomization of the nozzle or the oil dripping, the toothpaste and the fine chromium oxide can be used to add to the sealing tape on the end of the needle valve. At the same time, the cylindrical part of the needle valve has to be kept from being painted when either toothpaste or the chromium oxide is added. And then, the needle valve should be inserted into the valve body. Finally, both two components should be hit repeatedly until they are in close contact. It should be especially noticed that all the toothpaste and the fine chromium oxide must be removed after the abrasive treatment.
Source: China Valve Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

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