Forged Steel Check Valve

Characteristic

The purpose of this type of valve is to allow the medium to flow in one direction only and prevent the flow in the direction. Usually, the valve works automatically. Under the action of fluid pressure flowing in one direction, the valve disc opens; when the fluid flows in the opposite direction, the fluid pressure and the self weight of the valve disc act on the valve seat to cut off the flow.

The internal thread check valve and butterfly check valve belong to this type of valve, including swing check valve and lift check valve. The swing check valve has a hinge mechanism, and a disc like a door freely rests on the inclined seat surface. In order to ensure that the valve clack can reach the proper position of the seat surface every time, the valve clack is designed in the hinge mechanism, so that the valve clack has enough swing space, and makes the valve clack truly and comprehensively contact with the seat. The valve flap can be made of all metal, or inlaid with leather, rubber or synthetic coverage on the metal, which depends on the requirements of service performance.

When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. The disc seat of the lift check valve is located on the sealing surface of the valve seat on the valve body. Except that the valve disc can be lifted freely, the rest of the valve is like a globe valve. The fluid pressure makes the valve disc lift from the sealing surface of the valve seat, and the backflow of the medium causes the valve disc to fall back to the valve seat and cut off the flow.

According to the service conditions, the valve disc can be of all metal structure or inlaid with rubber pad or rubber ring on the valve disc frame. Like the stop valve, the passage of fluid through the lift check valve is narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is limited rarely [1].

Installation mode

1. The disc of the butterfly check valve is disc-shaped, rotating around the axis of the valve seat channel. Because the flow forming line of the channel in the valve, the flow resistance is smaller than that of the rising butterfly check valve, which is suitable for the large caliber occasions with low flow rate and unsteady flow, but it is not suitable for pulsating flow, and its sealing performance is lower than that of the rising butterfly check valve. Butterfly check valve is divided into three types: single disc type, double disc type and multi half type. These three types are mainly divided according to the valve diameter, so as to prevent the hydraulic impact when the medium stops flowing or flows backward.

2. For the check valve with the disc sliding along the vertical center line of the valve body, the internal thread check valve can only be installed on the horizontal pipeline, and the disc can be a ball on the high-pressure small caliber check valve. The body shape of butterfly check valve is the same as that of globe valve (it can be used as globe valve), so its fluid resistance coefficient is large. Its structure is similar to the stop valve, and the valve body and disc are the same as the stop valve. The upper part of the valve disc and the lower part of the valve cover are processed with a guide sleeve. The guide sleeve of the valve disc can rise and fall freely in the guide sleeve of the valve disc. When the medium flows forward, the valve disc is opened by the medium thrust. When the medium stops flowing, the valve disc falls on the valve seat by the self vertical direction, which prevents the medium from flowing backward. The direction of medium inlet and outlet channel of straight butterfly check valve is perpendicular to that of valve seat channel; the direction of medium inlet and outlet channel of vertical lift check valve is the same as that of valve seat channel, and its flow resistance is smaller than that of straight butterfly check valve.

3. Forged steel check valve: a check valve in which the disc rotates around a pin in the seat. The disc check valve has simple structure and can only be installed on the horizontal pipeline with good sealing performance.

4. Wafer butterfly check valve: a valve whose disc slides along the centerline of the valve body. Pipeline check valve is a new kind of valve. It has small volume, light weight and good processing technology, which is one of the development directions of check valve. However, the fluid resistance coefficient is slightly larger than that of swing check valve.

5. Compact check valve: This valve is used for boiler feed water and steam cut-off. It has the comprehensive functions of lift check valve, stop valve or angle valve.

In addition, there are some check valves that are not suitable for pump outlet installation, such as bottom valve, spring type, Y type and other check valves [1].

Main uses

The valve is used as a device to prevent the reverse flow of medium on industrial pipeline.

Structure description edit

During the use of the valve, the medium flows in the direction of arrow as shown in the figure.

1. When the medium flows in the specified direction, the valve disc is opened under the action of medium force; when the medium flows in reverse, the valve disc and the sealing surface of the valve seat are closed due to the self weight of the valve disc and the action of the medium reverse force of the valve disc, so as to prevent the medium reverse flow.

2. The sealing surface of valve body and valve disc shall be welded with stainless steel.

3. The structural length of the valve is in accordance with gb12221-1989, and the flange connection size is in accordance with JB / t79-1994.

Editing of problems in forged steel check valve

The problem of grease injection quantity is often ignored in forged steel valves. After the grease gun is refueled, the operator selects the valve and the grease injection connection mode for the low-temperature stop valve, and then carries out the grease injection operation. There are two kinds of conditions of forged steel gate valve: on the one hand, the amount of grease injection is less, and the sealing surface is worn faster due to lack of lubricant. On the other hand, excessive fat injection results in waste. Because there is no accurate calculation for different valve sealing capacity according to valve type category. The sealing capacity can be calculated according to the valve size and type, and then a proper amount of grease can be injected.

Scope of application

Urban construction, chemical industry, metallurgy, petroleum, pharmaceutical, food, beverage, environmental protection and other industries