Product Introduction of Valve Spring
The valve spring is an important accessory in the suction valve and discharge valve assembly at the hydraulic end of the drilling mud pump. It is mainly used to provide return force for the valve body, enabling the valve to promptly return to the valve seat position after the end of one working cycle and maintain the specified initial closed state before the start of the next cycle.
When the mud pump is in operation, the suction valve and the discharge valve will periodically open and close in response to the pressure difference generated by the reciprocating motion of the piston. During the valve opening process, the valve spring is compressed. When the pressure difference decreases or the flow direction changes, it releases elastic force, pushing the valve body back to its original position towards the valve seat, thereby helping the valve assembly complete a rapid and stable opening and closing cycle.
The free height, outer diameter, inner diameter, wire diameter, effective number of turns, spring stiffness and installation preloading state of the valve spring will all affect the opening resistance, return speed and closing response of the valve. Therefore, even if the appearances of two valve springs are similar, it does not mean that they can be directly interchanged.
The main function of the valve spring
1. Provide valve body return force: The valve spring is compressed when the valve is open and releases elastic energy when the valve needs to be closed, pushing the valve body back closer to the valve seat.
2. Maintain the initial closed state of the valve: When there is not enough opening pressure difference, the valve spring helps the valve body stay near the valve seat, preventing the valve body from being in an uncontrolled free state.
3. Impact on valve opening response: The spring stiffness and preloading state will form a certain opening resistance, which, together with the fluid pressure difference, determines the dynamic process of the valve body starting to lift and continuing to open.
4. Affecting the valve closing speed: Appropriate spring characteristics help the valve body return to its original position in a timely manner, reducing closing delay and unstable jumping, and maintaining normal switching between the suction and discharge processes.
The working principle of the valve spring
When a sufficient pressure difference is formed on the suction or discharge side, the fluid force overcomes the self-weight of the valve body, the spring force and other motion resistances, pushing the valve body away from the valve seat and forming a flow channel.
After the valve body is lifted, the valve spring is further compressed and stores elastic energy. When the pressure difference drops to a level insufficient to keep the valve open or when the flow direction changes, the spring releases the stored energy and pushes the valve body back to its original position towards the valve seat.
Therefore, the valve spring is part of the dynamic response of the valve group. If the spring is too hard, it may increase the resistance to opening the valve. If the spring is too soft or fatigued, it may cause the valve to return slowly. The actual spring parameters should be determined according to the design of the corresponding mud pump valve group.
Suction valve spring and discharge valve spring
The working pressure, opening timing and flow conditions of the suction valve and discharge valve of the drilling mud pump are different. Therefore, there may be differences in free height, wire diameter, number of turns, stiffness or installation preload between the suction valve spring and the discharge valve spring of some pump types.
When purchasing, it should be clearly stated whether the spring is installed on the suction side or the discharge side. They should not be directly interchanged just because the outer diameter and height are close. For valve groups that partially adopt double-spring or special combined spring structures, the matching relationship between the inner and outer springs should also be verified.
The fit relationship with the valve and valve seat
The valve spring is usually combined with the valve body, valve seat, spring support, valve stem guide and valve cover and other parts to form a complete valve assembly.
The valve spring itself does not undertake the main sealing function. It is the contact surface between the valve body and the valve seat that truly accomplishes the opening and closing sealing. The function of the spring is to help the valve body return to its correct position in sequence, enabling it to come back to the vicinity of the valve seat and establish a closed state.
If the length, stiffness or installation position of the spring is incorrect, it may change the actual lift and closing response of the valve body, thereby affecting the operational stability of the valve group.
The relationship with spring supports and guiding parts
Valve springs usually need to be kept in the correct installation position through spring supports, spring brackets or other positioning structures to prevent obvious deviation of the spring during repeated compression.
In some valve groups, the valve stem guide is responsible for restricting the movement direction of the valve body, the spring support is responsible for supporting and positioning the spring, and the valve spring is responsible for providing the return force. The three have different functions and cannot be mixed as the same accessory.
If the end of the spring does not correctly enter the supporting position, it may cause spring eccentric pressure, local wear, and even affect the normal axial movement of the valve body.
Spring stiffness and preload
The stiffness of the valve spring determines the additional spring force when the spring generates a certain compression amount, and it is an important parameter affecting the dynamic performance of the valve group.
The initial compression amount after installation forms the corresponding pre-pressure, which affects the initial closed state of the valve body and the pressure difference required for opening. The design requirements for different pump types and different valve positions may vary, so uniform empirical values cannot be used to replace the original design parameters.
If a spring experiences a significant decrease in its free height after being used for a period of time, it may indicate that the spring has deformed or become fatigued. At this point, both the actual preload and the return capacity will change.
Common Failures and Inspections
The valve spring is constantly in a state of high-frequency repeated compression and release, mainly bearing cyclic loads. Therefore, issues such as fatigue, deformation and corrosion should be given special attention.
Common abnormalities include shortened free height, spring skew, local wear, rust, coil cracks, fractures, and damage to the end support surface.
During maintenance, it is necessary to check whether the spring has obvious deformation, and compare the free height, outer diameter and actual condition with the original specification. If cracks, broken rings or obvious loss of elasticity are found, it should not be used any longer.
When the valve assembly shows slow return, abnormal jumping, intensified valve seat impact or abnormal working sound, in addition to inspecting the valve and valve seat, the valve spring and its supporting and guiding parts should also be inspected.
Key points for selection
When purchasing springs for drilling mud pump valves, it is recommended to focus on confirming the following information:
1. Brand, series and specific model of mud pump;
2. Hydraulic end or hydraulic cylinder model;
3. Suction valve side or discharge valve side;
4. Matching valve and valve seat models;
5. Spring free height;
6. Outer diameter and inner diameter of the spring;
7. Spring wire diameter;
8. Total number of laps and valid laps;
9. Spring end form;
10. Spring stiffness or load-deformation requirements;
11. Installation height and preloading status;
12. Single spring or double spring structure;
13. Matching spring supports, brackets and guiding structures;
14. Original part number, physical sample or technical drawing.
Installation and Maintenance
Before installation, the valve cavity, spring support position and guiding parts should be cleaned. Mud, sand grains, corrosion products and metal debris should be removed. Also, check whether the spring has cracks, rust or deformation.
When installing, make sure that both ends of the spring are correctly placed in the supporting and positioning positions to avoid the spring being skewed or one side being suspended. For structures with a combination of inner and outer springs, the assembly relationship of the inner and outer springs should be confirmed in accordance with the original design.
After assembly is completed, it should be confirmed that the valve body can move smoothly in the specified direction, and there is no jamming or obvious eccentric wear during the spring compression and return process.
Before disassembling and assembling the valve assembly, it is necessary to confirm that the mud pump has been shut down, and the hydraulic end and related high-pressure pipelines have been reliably depressurized. Then, disassemble and assemble the valve cover and valve assembly in accordance with the corresponding pump type maintenance procedures.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides valve springs and hydraulic end valve group accessories for drilling mud pumps. Valve springs are mainly used for the return position and dynamic opening and closing control of suction valves and discharge valves. They can be selected based on the model of the slurry pump, valve position, valve group model, free height of the spring, outer diameter, inner diameter, wire diameter, number of turns, stiffness, installation height, original part number and technical drawings.