Product Introduction of Cylinder Head Sealing Ring
The cylinder head sealing ring is an important static sealing accessory at the hydraulic end of the drilling mud pump's cylinder head section. It is installed in the corresponding sealing cavity or mating position between the cylinder head and the hydraulic cylinder, mainly used to seal the leakage channel between the hydraulic end working chamber and the external environment, preventing high-pressure drilling fluid from leaking out from the cylinder head installation interface during the operation of the mud pump.
When the mud pump is in operation, the piston moves back and forth within the cylinder liner, and the internal pressure of the hydraulic end working chamber changes periodically with the suction and discharge cycles. The cylinder head and its sealing structure are located at the pressure-bearing boundary position of the hydraulic end. The cylinder head sealing ring needs to maintain reliable sealing under the specified installation compression state and adapt to changes in working pressure and the environment of the drilling fluid medium.
The cylinder head sealing rings of different mud pump models may adopt different cross-sectional profiles, sealing cavity structures, materials and anti-extrusion methods. Therefore, when purchasing, it is not only necessary to check the inner or outer diameter of the sealing ring, but also to confirm the model of the cylinder head, the structure of the hydraulic cylinder, the sealing cross-section and the original part number.
The main function of the cylinder head sealing ring
1. Seal the cylinder head installation interface: The cylinder head sealing ring is located between the cylinder head and the hydraulic cylinder, sealing the fixed mating interface formed by the two to prevent the working medium from leaking out along the assembly gap.
2. Establish the pressure-bearing boundary at the hydraulic end: The cylinder head is a rigid pressure-bearing sealing part at the hydraulic end, and the cylinder head sealing ring is responsible for sealing the tiny leakage channels between the cylinder head and the hydraulic cylinder. Together, they form part of the sealing structure of the hydraulic end working chamber.
3. Adapt to periodic pressure changes: During the discharge stroke of the mud pump, the pressure at the hydraulic end rises. The sealing ring needs to maintain stable sealing contact under the action of periodic pressure to avoid external leakage.
4. Facilitates maintenance of the hydraulic end: After the cylinder head is disassembled for inspection, the cylinder head sealing ring can be inspected or replaced based on its wear and deformation status to restore the sealing performance of the cylinder head interface.
The working principle of static sealing
The cylinder head sealing ring is installed in the specified sealing groove or sealing cavity. After the cylinder head is inserted into the hydraulic cylinder, it causes the sealing element to produce the elastic compression as required by the design, thereby establishing an initial contact pressure between the cylinder head and the sealing surface of the hydraulic cylinder.
For special-shaped or lip-shaped sealing structures with self-tightening pressure, the pressure of the working medium can also make the effective sealing parts further adhere to the adjacent sealing surfaces, thereby enhancing the sealing capacity under pressure. The specific compression method depends on the cross-section of the sealing ring and the installation direction.
The cylinder head sealing ring is not the tighter it is pressed, the better. The size of the sealing cavity, the cross-section of the sealing ring and the assembly clearance must be matched with each other. Excessive compression may cause shearing, permanent deformation or installation damage to the seal, while insufficient compression may result in insufficient contact pressure of the seal and lead to leakage.
The difference from the valve cover sealing ring
Cylinder head sealing ring: Installed at the mating position between the hydraulic end cylinder head and the hydraulic cylinder, it is mainly responsible for the static sealing of the cylinder head sealing interface.
Valve cover sealing ring: Installed at the valve cover position corresponding to the valve cavity of the suction valve or discharge valve, it is mainly responsible for the static sealing between the valve cover and the liquid cylinder or valve box.
Although both types of seals belong to hydraulic end static seals, their installation positions, sealing diameters, cross-sectional dimensions and sealing cavity structures may differ. When selecting the model, it should be confirmed respectively according to the specific part name, installation position and the original part number.
The difference from the cylinder liner sealing ring
Cylinder head sealing rings cannot be mixed with cylinder liner sealing rings either. The cylinder head sealing ring seals the closed interface between the cylinder head and the hydraulic cylinder. The cylinder liner sealing ring mainly seals the interface between the external installation area of the cylinder liner and the liquid cylinder, wear-resistant disc or corresponding sealing cavity.
Although both are usually static seals, the corresponding parts, sealing diameters and sealing cavities are completely different. They should be selected respectively according to the cylinder head system and the cylinder liner system.
Sealing cross-section and installation direction
According to the design of the hydraulic end of the mud pump, the cylinder head sealing ring can adopt O-shaped, lip-shaped, special-shaped cross-section or other special sealing structures. The specific form should be based on the original parts or technical drawings of the corresponding pump type.
For sealing rings with lips, pressure chambers or other asymmetrical structures, the pressure-bearing direction should be particularly confirmed during installation. If the installation direction is incorrect, it may cause the seal to fail to form a normal pressure self-tightening effect and increase the risks of lip curling, extrusion and leakage.
Therefore, not all annular cylinder head seals can be treated as ordinary O-rings, nor can the installation method be determined solely based on the appearance diameter.
Sealing cavity and anti-extrusion requirements
The sealing performance of the cylinder head sealing ring is closely related to the diameter of the sealing cavity, the width of the groove, the depth of the groove, the assembly clearance and the sealing cross-section. When selecting the type, the sealing ring should be checked as a whole against the sealing structure of the cylinder head and the hydraulic cylinder.
Some high-pressure structures may be equipped with anti-extrusion parts such as retaining rings and support rings on one or both sides of the sealing ring to restrict the elastic sealing parts from entering the fit clearance of the parts under high pressure.
If the original design is equipped with anti-extrusion parts, during maintenance, their wear and deformation conditions should be inspected simultaneously, and they should be restored according to the original assembly relationship. The installation positions should not be cancelled or changed at will.
Compatibility of materials with drilling fluids
The material of the cylinder head sealing ring should be determined based on the original equipment requirements, drilling fluid system, working temperature, pressure and medium environment. Different elastomers vary in terms of oil resistance, water resistance, heat resistance, resistance to chemical media and resistance to permanent compression set.
The color of the sealing ring cannot be used as a reliable basis for judging the material grade and hardness. Even if the dimensions are exactly the same, problems such as expansion, softening, hardening or decreased elasticity may occur if the material is not suitable for the actual drilling fluid system.
Common failure and leakage checks
Common failures of cylinder head sealing rings include compression set, aging and hardening, cutting, extrusion, tearing, lip damage, and expansion or performance degradation caused by incompatible media.
If there are local cuts on the seals, it is necessary to check whether there are burrs or sharp edges at the cylinder head inlet, the sealing groove and the liquid cylinder orifice. If obvious extrusion damage occurs, the sealing specifications, assembly clearance and anti-extrusion structure should be further inspected.
When leakage occurs repeatedly in the cylinder head area, it is not advisable to simply replace the new sealing rings continuously. It is also necessary to check whether there is erosion, corrosion, scratches or dimensional abnormalities on the sealing mating surface of the cylinder head and the sealing cavity of the hydraulic cylinder, and confirm that the cylinder head has been correctly installed and locked.
Key points for selection
When purchasing the sealing ring of the drilling mud pump cylinder head, 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. Cylinder head model and original part number;
4. Diameter of the cylinder head sealing position;
5. Inner and outer diameters of the sealing ring;
6. Cross-sectional dimensions and profile of the sealing ring;
7. Diameter of the sealing groove or sealing cavity;
8. Width and depth of the sealing groove;
9. Whether there are requirements for the installation direction and pressure-bearing direction;
10. Whether a retaining ring or support ring is configured;
11. Sealing materials and hardness requirements;
12. Working pressure, temperature and drilling fluid system;
13. Original part number, physical sample or technical drawing.
Installation and Maintenance
Before disassembling the cylinder head and the sealing ring, it is necessary to confirm that the mud pump has been shut down and that the hydraulic end and the high-pressure discharge system have been completely depressified. It is strictly prohibited to disassemble the cylinder head when there is residual pressure in the working chamber.
Before installation, the sealing surface of the cylinder head, the sealing groove and the corresponding installation holes of the liquid cylinder should be thoroughly cleaned to check for sand particles, metal shavings, burrs, rust and sharp edges that may damage the sealing parts.
The new sealing ring should be confirmed to match its size, cross-section and material with the installation position. For sealing structures with directionality, the pressure-bearing direction should be confirmed in accordance with the original equipment assembly requirements to prevent reverse installation.
During the assembly process, it is necessary to prevent the sealing ring from twisting, curling, cutting, pinching or partially coming out of the groove. The cylinder head should be correctly positioned before installing the corresponding clamping and locking parts. It is not advisable to compensate for incorrect sealing specifications or damaged sealing surfaces by abnormally increasing the locking force.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides cylinder head sealing rings and hydraulic end sealing accessories for drilling mud pumps. The cylinder head sealing ring is mainly used for high-pressure static sealing between the cylinder head and the hydraulic cylinder. It can be selected based on the model of the mud pump, the model of the hydraulic end, the model of the cylinder head, the inner and outer diameters of the sealing ring, the cross-sectional structure, the size of the sealing cavity, the material, the anti-extrusion structure, the original part number and the technical drawings.