Cylinder head product introduction
The cylinder head is an important rigid pressure-bearing accessory at the hydraulic end of the drilling mud pump. It is installed at the corresponding end opening position of the hydraulic cylinder to seal the working chamber of the hydraulic end. Together with the cylinder head sealing ring and the corresponding compression and locking structures, it forms a reliable pressure-bearing sealing system.
When the mud pump is in operation, the piston moves back and forth within the cylinder liner, and the internal pressure of the working chamber changes periodically with the suction and discharge strokes. As part of the pressure-bearing boundary at the hydraulic end, the cylinder head needs to withstand the axial load generated by the pressure of the working medium and the periodic pressure during equipment operation, while maintaining the correct installation and positioning state.
The cylinder head is a detachable and maintainable component. During the maintenance process of the corresponding pump type, after removing the cylinder head and its locking structure, it can provide an operation channel for the inspection, disassembly, assembly and maintenance of the internal related parts of the hydraulic end. There may be significant differences in the outer diameter, length, positioning steps, sealing structure and external locking form of the cylinder heads of different series of mud pumps.
The main function of the cylinder head
1. Seal the opening at the end of the liquid cylinder: After the cylinder head is installed to the corresponding opening of the liquid cylinder, a rigid closed boundary is formed to prevent the high-pressure working medium from being directly discharged from the end of the liquid cylinder.
2. Bearing internal pressure loads: After the hydraulic end enters the high-pressure discharge stroke, the pressure in the working chamber acts on the effective pressure-bearing area of the cylinder head. The cylinder head needs to transfer the generated axial load to the corresponding positioning and locking structures.
3. Provide an installation foundation for cylinder head sealing: The outer circle of the cylinder head, positioning steps or dedicated sealing positions, together with the cylinder head sealing ring and the hydraulic cylinder sealing cavity, form a static sealing interface.
4. Provide maintenance access: The cylinder head adopts a detachable structure, facilitating the inspection and maintenance of relevant internal components at the hydraulic end in accordance with the corresponding slurry pump maintenance procedures.
The working principle of pressure resistance and enclosure
After the cylinder head is installed into the hydraulic cylinder, it maintains the correct radial and axial positions by positioning the outer circle, steps or other structures, and then is axially fixed by the corresponding gland, cap, threaded locking piece or other special structures.
When the working chamber is pressurized, the internal pressure will form an outward axial force on the cylinder head. The cylinder head body bears and transmits this load. The external locking structure restricts the outward movement of the cylinder head, while the cylinder head sealing ring seals the fit clearance between the cylinder head and the hydraulic cylinder.
Therefore, the reliability of the cylinder head system does not solely depend on the cylinder head itself. The correct dimensions and assembly relationships must be maintained among the cylinder head, sealing ring, hydraulic cylinder sealing cavity and external locking structure.
The relationship between the cylinder head and the cylinder head sealing ring
Cylinder head: It is a rigid metal pressure-bearing component, mainly responsible for sealing the working chamber, transmitting pressure loads and positioning the structure.
Cylinder head sealing ring: It is an elastic static sealing component, installed at the sealing position formed by the cylinder head and the hydraulic cylinder, mainly used to prevent high-pressure drilling fluid from leaking out along the assembly gap.
The cylinder head body cannot replace the elastic sealing function of the sealing ring, and the sealing ring cannot bear the main structural load of the cylinder head body either. When making a purchase, the model of the cylinder head and the specification of the matching cylinder head sealing ring should be checked separately.
The difference from the valve cover
Cylinder head: Corresponding to the end openings of the hydraulic cylinder liner and the piston working chamber, it is a pressure-bearing sealing part at the end of the hydraulic end working chamber.
Valve cover: Corresponding to the maintenance opening of the valve cavity where the suction valve or discharge valve is located, it is mainly used to close the valve cavity, facilitating the maintenance of valve group parts such as the valve, valve seat, valve spring and valve stem guide.
Although both belong to the hydraulic end detachable rigid pressure-bearing sealing parts, their corresponding cavities, installation positions, dimensions and matching seals are different. The cylinder head, valve cover and their respective sealing rings cannot be used interchangeably.
Position the outer circle and the step structure
The cylinder head usually fits with the corresponding holes of the hydraulic cylinder through the outer circle, positioning steps or stop mouth. These parts not only affect whether the cylinder head can be correctly installed, but also influence the geometric relationship between the cylinder head and the sealing ring.
When selecting the model, it is important to focus on confirming the maximum outer diameter of the cylinder head, the insertion positioning diameter, the length of the positioning section, the diameter of the step, the position of the step, and the total height or total length. Even if the external profiles of two cylinder heads are similar, they may not be installed correctly as long as the positioning diameters or step positions are different.
Sealing mating parts
The outer circle, step or sealing surface where the cylinder head contacts the sealing ring is a key inspection area. If there are obvious scratches, erosion, corrosion pits or deformations at these positions, even if new cylinder head seals are replaced, repeated leakage may still occur.
For some pump types, the sealing grooves are set on the cylinder head, while for others, the sealing cavities may be formed by the liquid cylinder or adjacent parts. Therefore, when purchasing, it is necessary to confirm exactly which part the sealing groove is located on and verify the cross-section and installation structure of the corresponding sealing ring.
External locking structure
After the cylinder head is installed in place, a reliable axial holding structure is required to prevent internal pressure from pushing it out of the cylinder. Different mud pumps can adopt pressure covers, pressure caps, threaded locking parts or other special pressure-bearing and fixed structures. The specific form shall be subject to the design of the corresponding pump type.
During maintenance, the contact position between the cylinder head and the external locking parts should be inspected simultaneously. If there are abnormal indentations, deformations or fit damages, the relevant pressure-bearing and positioning parts should be further inspected. It is not advisable to simply rely on increasing the locking force for handling.
Common injuries and examinations
The cylinder head is subject to periodic pressure loads for a long time and is in a drilling fluid working environment. During maintenance, the sealing mating surface, positioning outer circle, steps, pressure-bearing end face and structural transition position should be inspected with emphasis.
Common abnormalities include erosion or corrosion of the sealing surface, wear of the positioning outer circle, end face indentation, local deformation, scratches caused by disassembly and assembly, and abnormal damage in the structural transition area.
If mud leakage persists at the cylinder head position, the cylinder head sealing ring, the sealing surface of the cylinder head, the sealing cavity of the liquid cylinder and the locking structure should be inspected simultaneously to avoid problems caused by damage to the metal mating surface only by frequently replacing the sealing ring.
Key points for selection
When purchasing a 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. Original part number of the cylinder head;
4. Maximum outer diameter of the cylinder head;
5. Insert the positioning outer diameter of the liquid cylinder;
6. Positioning section length;
7. Total height or total length of the cylinder head;
8. Locate the diameter, width and position of the steps;
9. Inner pressure-bearing end face and internal profile;
10. Model of cylinder head sealing ring and dimensions of sealing position;
11. Dimensions of the sealing groove, such as when the sealing groove is set on the cylinder head;
12. External compression or locking structure;
13. Disassemble and assemble tool holes, slots or other operating structures;
14. Work pressure level;
15. Material and heat treatment requirements;
16. Physical samples or technical drawings.
Installation and Maintenance
Before disassembling the cylinder head, it is necessary to confirm that the mud pump has been completely shut down and that the hydraulic end working chamber and the high-pressure discharge system have been thoroughly depressified. The cylinder head locking structure must not be loosened in the presence of residual pressure.
Before installation, the outer circle of the cylinder head positioning, the sealing mating surface, the steps and the installation holes of the liquid cylinder should be cleaned. Mud, sand particles, residues of old seals, rust and metal burrs should be removed.
At the same time, the specifications and conditions of the cylinder head sealing ring should be inspected. For irregular-shaped sealing parts with installation directions, the pressure-bearing direction should be confirmed in accordance with the corresponding assembly requirements of the mud pump to avoid twisting, flipping, pinching or cutting of the sealing ring.
The cylinder head should be smoothly installed at the correct position. Only after confirming that the positioning steps are fully in place should the external locking parts be installed. Cylinder heads that do not match the size or are not properly positioned should not be pressed into the liquid cylinder by forcibly knocking or over-locking.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides cylinder heads and hydraulic end accessories for drilling mud pumps. The cylinder head is mainly used for pressure-bearing sealing at the end of the working chamber of the hydraulic cylinder, and together with the cylinder head sealing ring and the external locking structure, it forms the hydraulic end sealing system. The selection and matching can be carried out based on the model of the mud pump, the model of the liquid cylinder, the outer diameter of the cylinder head, the positioning diameter, the step structure, the sealing form, the locking method, the original part number and the technical drawings.