Product Introduction of Valve Stem Guide
The valve stem guide is a guiding and positioning component in the suction valve and discharge valve assembly at the hydraulic end of the drilling mud pump. It is mainly used to guide the reciprocating opening and closing motion of the valve stem or valve body, limit the radial swing of the valve during opening and closing, and maintain the correct relative position between the valve body's movement axis and the valve seat center.
When the mud pump is in operation, the suction valve and the discharge valve open and close periodically at high frequency in response to the pressure changes at the hydraulic end. After leaving the valve seat, the valve body needs to move within the specified direction and lift range. When the pressure difference drops, it needs to quickly return to its original position under the action of the valve spring and the fluid. The valve stem guide restricts the lateral displacement of the valve stem through the guide hole or guide bushing, helping the valve body move stably along the axial direction.
The size of the guide hole of the valve stem guide, the guide length, the fit clearance between it and the valve stem, and the installation coaxiality will all directly affect the movement state of the valve group. Too small a clearance may cause the valve stem to get stuck, while too large a clearance will reduce the guiding ability and increase the swing of the valve body.
The main function of the valve stem guide
1. Guide the axial movement of the valve stem: Limit the lateral displacement of the valve stem through guide holes or guide bushings, ensuring that the valve body maintains the specified movement direction during opening and closing.
2. Limit the radial swing of the valve body: When the slurry pump valve group opens and closes at high speed, the guide vane can reduce the excessive lateral offset of the valve stem and improve the stability of the valve body movement.
3. Assist the valve body in correct reseating: When the valve stem is in a good guiding state, it is conducive to maintaining the correct center position of the valve body and returning to the valve seat, reducing the local impact and eccentric wear caused by obvious deviation during reseating.
4. Maintain the geometric relationship of the valve group: The valve stem guide works together with the valve, valve seat, valve spring and related supporting parts to maintain the specified movement axis and assembly relationship of the valve group.
Guiding working principle
The valve stem guide is internally equipped with guide holes that match the valve stem, and some structures may also be fitted with replaceable guide bushings. During the opening and closing of the valve assembly, the valve stem moves axially along the guide hole. The guide structure restricts its radial degrees of freedom, thereby reducing the wobbly of the valve body.
A working clearance that meets the design requirements must be reserved between the guide hole and the valve stem. If the gap is too small, mud particles, thermal deformation, corrosion or part eccentricity may all increase the risk of jamming. If the clearance is too large, the valve stem may swing significantly, causing the reseating position of the valve body to be unstable.
Therefore, the valve stem guide cannot be selected merely based on the outer diameter. The valve stem diameter, guide hole diameter, guide length and fit clearance are all important parameters.
Upper valve stem guide and lower valve stem guide
Some drilling mud pump valve groups are equipped with upper valve stem guides, lower valve stem guides or other valve guiding structures at different positions according to the structural design. Guides at different positions may vary in terms of outer diameter, guide holes, total height, positioning steps and installation structure.
The upper guiding structure may form a fit with the valve cover, valve spring and their supporting parts in some pump types. The lower guiding structure may be coordinated with the corresponding positioning structure inside the liquid cylinder. The specific installation relationship is not exactly the same for all mud pumps. It should be determined based on the corresponding hydraulic end drawing and the original part number.
When purchasing, it should be clearly defined whether it is an upper guide vane, a lower guide vane or other special valve guide components. They cannot be directly interchanged just because the valve stem diameters are the same.
The fit relationship with the valve spring
The valve stem guide and the valve spring perform different functions in the valve assembly. The valve spring mainly provides the return force of the valve body, and the valve stem guide mainly controls the movement direction of the valve body.
When the valve is opened, the pressure difference of the fluid pushes the valve body away from the valve seat and compresses the spring. The valve stem moves simultaneously in the direction specified by the guide. When the valve needs to be closed, the spring pushes the valve body back to its original position, and the guide continues to restrict its radial swing, enabling the valve body to return to the valve seat position relatively stably.
The difference from spring supports
Valve stem guide: It mainly centers and guides the movement of the valve stem through guide holes or guide bushings, with a focus on controlling the radial swing of the valve body and the movement axis.
Spring support: Mainly used to support and position valve springs, providing the specified installation position and force-bearing foundation for the springs.
Some parts of mud pumps may have certain supporting and guiding structures at the same time. However, when selecting accessories, it is still necessary to confirm according to the actual structure, part number and matching relationship of the original pump type, and not to judge only based on appearance.
Guide hole and fit clearance
The guide hole is a key working part of the valve stem guide. The size of the guide hole needs to match the diameter of the valve stem, ensuring smooth axial movement of the valve stem while avoiding excessive radial clearance.
As the working time increases, the valve stem and guide hole may wear out, causing the radial clearance to gradually increase. When the clearance exceeds the allowable range of the corresponding pump type, the stability of the valve body movement may decline, and it may be accompanied by valve stem swing, eccentric reseating and local abnormal wear.
For structures with replaceable guide bushings, during maintenance, in addition to checking the wear of the guide holes, it is also necessary to inspect whether the bushings are loose, offset, damaged or abnormally worn. Whether to use an independent bushing should be determined by the specific structure of the pump type.
Common wear and tear and fault manifestations
The valve stem guide is constantly exposed to the high-frequency opening and closing of the valve group and the drilling fluid environment. Common abnormalities include wear of the guide hole, wear or loosening of the guide bushing, erosion, corrosion, damage to the installation surface, deformation, and local cracks.
After the guide hole is worn, the radial movement of the valve stem may increase, which in turn causes the valve body to swing or tilt, affecting the reseating state of the valve body and the valve seat, and may also accelerate the abnormal wear of the valve stem, valve body and valve seat.
If obvious unilateral wear of the valve body or valve seat, abnormal scratches on the valve stem or abnormal opening and closing status of the valve group are found, in addition to checking the valve, valve seat and valve spring, the wear and coaxiality of the valve stem guide should also be inspected.
Key points for selection
When purchasing the valve stem guide for drilling mud pumps, 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. Upper valve stem guide, lower valve stem guide or other installation positions;
5. Matching valve and valve stem model;
6. Valve stem diameter;
7. Inner diameter of the guide hole;
8. Guiding length;
9. Fit clearance between the valve stem and the guide hole;
10. Outer diameter of the guide;
11. Total height or total length;
12. Position the dimensions of the steps and the stop mouth;
13. Installation and fixation of structures;
14. Whether replaceable guide bushings are adopted;
15. The matching relationship with the valve spring, valve cover and supporting parts;
16. Original part number, physical sample or technical drawing.
Installation and Inspection
Before installation, the guide holes, positioning outer circles, steps and installation surfaces of the valve stem guide should be cleaned, and mud, sand particles, metal shavings, corrosion products and burrs should be removed.
At the same time, the working surface of the valve stem should be inspected. If the valve stem has already undergone obvious bending, scratching or abnormal wear, merely replacing the new guide vane cannot solve the problem of abnormal movement of the valve group.
After the guide is installed in place, it is necessary to check whether the valve stem can move axially smoothly in the guide hole without obvious jamming, and at the same time, there should be no radial wobble that exceeds the requirements of the corresponding pump type.
For structures with replaceable guide bushings, when replacing the bushings, installation should be carried out in accordance with the original equipment process to avoid deformation of the bushings, out-of-roundness of the inner holes or deviation of the center position due to press-fitting.
Before disassembling and assembling the valve cover and valve assembly, it is necessary to confirm that the mud pump has been shut down and that the hydraulic end and related high-pressure pipelines have been completely depressurized. Then, operate in accordance with the corresponding mud pump maintenance procedures.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides valve stem guides and hydraulic end valve group accessories for drilling mud pumps. The valve stem guide is mainly used for the movement guidance and center positioning of the valve stem of the suction valve and the discharge valve. It can be selected according to the model of the slurry pump, the model of the hydraulic end, the position of the suction or discharge valve, the upper and lower guiding positions, the diameter of the valve stem, the guiding hole, the guiding length, the positioning size, the original part number and the technical drawing.