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.

Dervos, not only do business with clients, we also make friends with our clients. Every year, one of our biggest clients from Argentina will come to visit us. We work with each other happily, at the same time we enjoy leisure time together. T is the first big client of Dervos in the past ten years. This friendship has been lasting for 10 years. We will keep it to another 10 years. Hope you could be our next best friends.

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.

On July 8 th, three of our clients from Malaysia visited us. We arrived at Wenzhou branch on July 9th, and introduced our company to help them better understand Dervos. After introduction, we started business talk to communicate the point they care about and the details we need to pay more attention in the future. In the afternoon, we visited factories of forging and casting gate, globe, check valves and ball valves. In this way, clients can know much more about our products. Lastly we had traditional Chinese food together. This trip is quiet big step between clients and us to cooperate closely in the future. Welcome to China and welcome to Dervos!!

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.