Globe valve Also known as the shut-off valve, is a kind of forced sealing valve. The valve head can be driven by the lifting of the valve stem, which can not reach the control of the opening and closing system by changing the distance between the valve disc and the valve seat. The stop valve is the most widely used cut-off valve in the production and management of chemical enterprises. In the actual production, we mainly include the control of water, steam, compressed Chinese air and other pipelines, but should not be directly applied to materials with different viscosity and easy crystallization.
The structure of the shut-off valve is more complex, but the actual operation is simple and labor-saving. It has better performance in regulating the flow and closing the channel, and slowly lifting a small amount of water hammer. The stop valve is compact in structure and has more prominent features, and is connected with the top of the valve stem and hand wheel, with the middle thread section and the sealing packing box.
The main way to judge the opening and closing state of the globe valve is to observe the height of the valve stem above the valve cover, so as to effectively control the operation of the system valve. Some students who connect the valve stem and the valve cover may have a certain gap, which is easy to cause different media leakage. We can solve this problem through packing seal at the same time. The thread of the stem of small-sized globe valve is set in the valve body, so it is often used in enterprises to contact with the medium for a relatively long time and is easy to be corroded by the medium.
The installation of the stop valve should refer to the direction of the fluid, pay attention to keep the low inlet and low outlet of the pipeline fluid, that is, from bottom to top through the valve seat. The purpose of the device is to reduce the fluid resistance in the valve body, thereby reducing the opening and closing force of the valve, and keep the valve stem and stuffing box from contacting with the medium when the valve is closed, so as to reduce the occurrence of damage and leakage.
Precautions for use of stop valve:
1. Check the leakage of the stop valve before opening to determine whether there is no leakage defect in the valve and the stuffing box.
2. If the operation of the stop valve stem cannot be completed by hand, the wrench can be used to replace the special F. in the case of wrench, f is still not connected, and it is safe to open and close the valve without using a long spanner to avoid damaging the valve, even in case of accidents.
3. When the stop valve is applied to the medium pressure steam pipeline, the condensate water should be removed before opening, and then the pipeline system should be studied. The steam preheating should be kept between 0.2 and 0.3MPa. The main purpose of this is to avoid the seal damage caused by the sudden change and development of the ambient temperature and pressure. After the learning state is determined and the stability is ensured, the pressure can be adjusted to the desired value Technical level is required.
Cut off benefits:
It is simple in structure and convenient in manufacture and maintenance. Working small stroke and short opening and closing time. Moreover, the sealing surface has longer friction life. The disadvantages of the stop valve are as follows:
The flow resistance of the fluid is large, and the force required for opening and closing is large. It can be used in the medium with particles, high viscosity influence and easy coking. The performance of the regulating system is relatively poor.
The type of globe valve is divided into external thread type and internal thread type according to the position of stem thread. According to the flow direction of the medium, there are straight through, direct current and angle. The stop valve is divided into sealing form, packing sealing stop valve and bellows sealing stop valve.