Although gate valves and knife gate valves share many similarities, for example, they are both used in on-off applications, there are more fundamental differences existing.  THE WORKING PRINCIPLE Gate valve is opened by lifting the wedge out of the path of the fluid. It is only used in for shut-off. Previously, normal gate valves are used in the pulp and paper industry, but the stringy pulp would be stuck between the wedge and seat and prevent flow shut-off. To solve this problem, knife gate valve was designed. It is with a sharp edge to cut through the pulp and keep the fluid flowing.  APPLICATIONS As mentioned above, gate valves are applied in many industrial applications requiring shut-off valves, such as power plants, water treatment, mining and offshore applications. They can be used in demanding environments, like high temperature and high pressure environments. Knife gate valves are preferred in slurry applications because their knives can cut right through thick liquids easily. The applications include but not limited to thick flows of heavy oils, light grease, slurry, paper pulp, varnish and waste water etc.  ADVANTAGES AND DISADVANTAGES The advantage of gate valves is that they are bi-directional, suitable for demanding working conditions like high pressure & high temperature. Besides, it is quite efficient that there won’t be much pressure drop when gate valves is fully open. However, the torque of gate valves will be larger compared with other types of valves, so they will need a large force to open and close. For larger sizes, pneumatic or electric actuators will be a must, and this, of course, will lead to higher cost. Also, they take longer time to operate and need more space for installation. By contrast, knife gate valves are cheap, light and easy to operate, but the design makes them only limited to low-pressure working environment. 

Occasionally we will see some relatively large valves installed with a bypass valve. What is the function of a bypass valve? Under what circumstances do you need to install them? What is the size of the bypass valve of the corresponding equipment? In fact, the two main functions of bypass valves are for protection and for emergency. Protection The bypass valve can protect main valve from destruction due to high pressure. Before the high pressure pipeline is opened, the pressure is released through the bypass valve to avoid sudden surge of high pressure and impact on the downstream valve. In addition, the pressure difference between the two ends of the valve is too large, which will lead to high torque that can damage the valve. Thus, the valve is opened after the bypass pressure is released. Emergency The biggest advantage is that when the main valve fails or needs maintenance and repair, the pipeline can be circulated by opening the bypass valve without affecting normal production. When do we need a bypass valve?  When the main valve is with specifications below, we can install a bypass valve. (Just for reference) 2.5MPa, DN400 above 4.0MPa, DN250 above 6.4MPa, DN200 above 10MPa, DN150 above When the main valve is between DN100~DN200,its bypass valve should be DN20; When the main valve is between DN250~DN600, its bypass valve should be DN25; When the main valve is above DN600, its bypass valve should be DN40.

A seal device that prevents the medium from leaking into the stuffing box when the valve is fully open is referred to as backseat. When the gate valve, the globe valve and the throttle valve are in the closed state, there is no or little pressure in the body cavity, thus the pressure on stem packing is small. When it is opened, the packing is subjected to the working pressure. If there is backseat structure, the working medium pressure can be prevented from acting on the sealing packing, and the life of the sealing packing can be prolonged, so that the valve does not have an external leakage. Another function is that when there is leakage at the sealing packing, the valve can be fully opened to seal the upper sealing portion, so that the packing gland or the packing sleeve can be loosened to replace packing. Therefore, the upper sealing device is required for the gate valve, the globe valve and the throttle valve.

Butterfly valve is one of the most frequently used valves, which we commonly comes with concentric soft seal butterfly valve, double eccentric butterfly valve and triple eccentric butterfly valve. Usually, the concentric soft seal butterfly valve is mainly used in normal temperature, low pressure working conditions, such as water supply and drainage, water conservancy engineering, municipal construction and other fields.Then  what is double eccentric butterfly valve? What is triple eccentric butterfly valve? And what conditions do they apply to? Double Eccentric Butterfly Valve PTFE seated double eccentric butterfly valve is Corrosion resistant. Metal seated double eccentric butterfly valve is high temperature resistance. But metal seated double eccentric butterfly valve is not able to withstand high pressure. AS the plate is directly contact with the sealing face which will cause leakage when used in high pressure working conditions. Double eccentric butterfly valve is used in water supply and drainage, sewage, construction, petroleum, chemical industry, light textile, papermaking, hydropower, metallurgy, energy and other fields. Triple Eccentric Butterfly Valve Triple Eccentric Butterfly Valve makes the best of both concentric and double eccentric butterfly valves.There are more choices for the seat material of triple eccentric butterfly valves, and is able to suit both low and high temperature and All kinds of acid, alkali and other corrosive media. In addition,  triple eccentric butterfly valve can achieve zero leakage, especially suitable for large diameter valve, and, in the use of shut-off valve, can replace the gate valve and ball valve. When used to regulate the flow rate, it can replace the cumbersome globe valve. At present, the triple eccentric butterfly valve is widely  used in oil mining, oil refining, petrochemical, energy generation and other important industrial fields of the pipelines. With people's continuous research,it is believed that the triple eccentric butterfly valve will be used in more and more fields.

The butterfly valve, also known as the flap valve, is a simple regulating and isolation valve. The closing member (valve or disc) is a disc that rotates around the valve shaft to achieve opening and closing. From the structure of valve, butterfly valves can be classified into concentric butterfly valve, double offset butterfly valve, and triple offset butterfly. For concentric type, the center of the stem is on the center line of the valve body and passes through the center of the sealing surface section. For double eccentric type, the stem center forms a deviation from the valve seal section and deviates from the valve body centerline. For triple eccentric butterfly valve, the third eccentric is valve body center forms an angular deviation from the center of the valve body sealing surface. From the connection type of butterfly valve, there wafer butterfly valve, lug butterfly valve, flanged butterfly valve and butt-weld butterfly valve. For wafer type, there are two or more center holes to help with valve installation. For lug type, the around bolted holes make lug type a safer choice compared to wafer type. The double flanged butterfly valve are often used for large-size butterfly valves. The butt welded butterfly vale are used in high pressure application. From the seat type, we have soft seat butterfly valve and metal seat butterfly valve. Generally speaking, concentric butterfly valve and double offset butterfly valve own soft sealing. While, the triple offset butterfly valve has metal-to metal seat.

In February, China's crude oil imports rose 20 percent year-on-year to their highest level ever. Due to the current market situation, the number of crude oil importers is rapidly increasing. As the world's second-largest oil consumer, China imported 31.8 million metric tons of crude last month, or a record 8 million barrels a day, DeVos found, according to data released Tuesday by China's General Administration of Customs. . Per day, February's imports were also up about 27 percent from January's 6.29 million barrels per day. Last week, Beijing-based consultancy SIA Energy claimed it hoped China's crude imports would rise by 860,000 bpd, or nearly 13 percent, in 2016, driven by storage needs, strong gasoline demand and fuel exports. China's largest energy group, state-owned China National Petroleum Corporation (CNPC), forecast in January that net crude imports would rise 7.3 percent in 2016.