There are two types of gate valves: parallel gate valves and knife gate valves, and they can be used with either a straight or a circular actuator. It the function of the valve actuator is, to move the position of an automatic control, it can be hydraulic, pneumatic or electrical in nature. A control valve is an electrical device that opens and closes valves in order to regulate the flow of fluid through a system of pipes.
In order to integrate smooth and positive sealing into the thin gate itself, the gate body is fitted with either elastomers or flexible metal seals that are mounted on the mounting surface. The gate is sealed at the bottom on the edge with an elastomer or spring insert. Having the bottom seal flush with the valve body allows solids to be eliminated from accumulating in the pockets. Axial spacing of the seals is sufficient to provide positive interference, and the gate provides bubble tight sealing, regardless of the operating conditions.
It is possible to install cones of deflection on some designs to direct solids away from the seals to keep them from damaging them. Unlike other gate valves, the knife gate valve is not completely encased in the body, which is why it is different from the others. While the valve is open, the gate will lift out from the body and will leave the body. Rather than being circular, the packaging box is rectangular in shape.
The packing encapsulates the gate itself so that it cannot be moved by the wind or animals. In some cases, it is necessary to place screws or unions on the glands in order to hold them in place. The valves cannot be installed easily and may not be suitable for products with complex packing arrangements. The valves are only suitable for non-hazardous products.
Due to the thinness of the gate, the valve body is able to be slimmer. This body style is similar to the lugged body style in the sense that it has a cast body finish. This is to ensure that all fasteners are made in a timely manner.
Gate valves are not intended for the purpose of regulating flow. High velocities are the only way by which we can increase the pressure losses across the valve. Due to the fluids’ interaction with the gate, some gate valves may “chatter” during opening or closing. In order to prevent leakage of the knife gate valve, the seals work effectively as dampeners. Typically, valves are the design with a spiral screw rising to a point, which is usually located on the outside. As long as the valve does not open or close by itself, there should be no issue with water hammer effects.
In order to accommodate the installation of knife gate valves in concrete tanks and pits, substantial framed versions of the valves can be manufactured in large sizes. There is usually only a slight difference in pressure ratings between atmospheric pressure and the pressure rating. There is also the option of referring to this type of valve as a “penstock valve”. In order to clean these valves, mechanically a pigging tool can be used.
There are valves called conduit gate valves and conduit pipeline valves or they may be called simply “conduit gate valves”. As an application, conduit gate valves are different from conventional valves from the standpoint that they do not simply uncover a seat to allow fluid to flow. As an alternative to the solid part of the gate that seals the seats, there is a section of the gate that has a hole of the same size as the bore of the seat. When a seat is in contact with a gate, the gate is always in contact with it. A longer gate is necessary for constant seat contact. You may notice this by the size and shape of the body and you can also discern it by the size and shape of the gate.
There is about double the length of the gate in comparison to a normal one. By closing the valve, the flow port portion of the gate moves below the pipe middle line so that it is level with the valve. To accommodate for this, an extension is fitted to the body of the vehicle. Large valves may have three pieces – an upper and lower section that connect to the central section, plus a cast steel body made up of two sections attached by bolts. The stems of valves are generally inclined upwards. Water hammer is caused by manual operation which is slow.
In order to guide the gate, we have seats along the sides and a plain, smooth gate. The seats in this model are replaceable and are available both in metallic and non-metallic finishes. PTFE inserts can be used to help seal metal seats and reduce friction, as elastomer inserts are able to aid in this process. It is possible to secure metal seats against gates by having coil springs or disc springs in place or by using “O” rings in order to prevent leakage around the seats. A gate that “chatters” is a sign that the spring loading is wrong, which cannot happen to a gate that is properly loaded. It would be unfair to say that the gate would have to bind due to temperature fluctuations given how the seats are spring loaded against the gate. In order for the bore in the gate to line up with the seats, the plain portion of the valve gate is lifted into the upper part of the valve body upon opening. A casting’s body usually has flange or buttweld connections. The bottom section of the drain is normally connected to a drainage system.