Product Introduction of Cylinder Head Plug
The cylinder head plug is a special rigid blocking accessory in the hydraulic end cylinder head of the drilling mud pump and its related closed structure. It is mainly used to seal the process holes, through holes, maintenance holes or special connection openings set on the cylinder head or adjacent hydraulic end structure, preventing the working medium from leaking out along this channel and maintaining the complete closed state of the relevant cavity of the hydraulic end.
Depending on the model of the mud pump, the cylinder head plug can adopt threaded insertion, step positioning, press-in or other special fixed structures, and may be used in conjunction with O-rings, sealing gaskets or other static sealing parts. The main body of the plug mainly undertakes the functions of blocking, positioning and mechanical bearing, while the matching elastic sealing parts are mainly responsible for sealing the tiny leakage channels between the parts.
The cylinder head plug is a type of mud pump accessory with a strong model correlation. Even if the outer diameters of the two plugs are similar, they cannot be directly interchanged if the thread specifications, effective thread lengths, positioning steps, sealing grooves or internal end face structures are different.
The main function of the cylinder head plug
1. Seal the relevant openings of the cylinder head: Mechanically seal the process holes, through holes or special openings at the corresponding positions of the cylinder head or hydraulic end to keep the internal working chamber isolated from the external environment.
2. Withstanding internal pressure: For the plug structure communicating with the pressure-bearing chamber at the hydraulic end, the plug needs to withstand the axial load generated by the internal medium pressure and transfer the load to the installation body through threads, steps or other fixed structures.
3. Provide an installation foundation for static sealing: Plugs with sealing grooves or sealing end faces can be used in conjunction with O-rings, sealing gaskets or special sealing parts to establish a stable static sealing interface.
4. Facilitates maintenance and parts replacement: For structures with detachable plugs, during maintenance, the plugs can be removed as per regulations to inspect and maintain the corresponding channels, seals and internal parts.
The principle of sealing and pressure-bearing
After the cylinder head plug is installed in the corresponding hole position, it is kept in the specified position through the meshing of the external thread and the internal thread, the fit of the positioning step or other mechanical fixing structures, thereby forming a rigid closed boundary.
If the plug is directly connected to the pressure-bearing chamber, the internal pressure will act on the effective pressure-bearing area of the plug, generating an axial load that pushes the plug outward. Therefore, the threads of the plug, the locating shoulder, the pressure-bearing end face and the installation body must fit each other correctly.
For structures with independent seals, the plug body is mainly responsible for mechanical sealing and bearing, while the O-ring or other seals are responsible for blocking the leakage path in the fit clearance. The plug itself and the matching sealing ring should not be regarded as the same functional part.
Threads and positioning steps
For cylinder head plugs installed by threads, the thread is one of the key selection parameters. It is necessary to confirm the thread diameter, pitch, thread profile, rotation direction and effective meshing length. It is not allowed to match only according to the outer diameter of the plug.
Some plugs are also equipped with positioning outer circles, shaft shoulders or steps to control the installation depth and end face position. If the size of the positioning step is incorrect, problems such as the plug not being fully positioned, abnormal compression of the seal, or the pressure-bearing end face not being correctly fitted may occur.
The specific thread form and size should be determined based on the corresponding mud pump model, original part number or technical drawing. It is not recommended to use approximate threads to replace the original design.
Sealing groove and matching sealing parts
According to the structure of the cylinder head plug, the sealing position may be set at the corresponding position on the outer circle of the plug, the positioning step, the end face or the installation hole. The matching sealing forms may be O-rings, sealing gaskets or other special static sealing structures.
For plugs with O-ring grooves, the diameter, width, depth of the sealing groove and the cross-section of the matching O-ring should be verified. For structures that adopt end face sealing, the integrity of the end face of the plug and the sealing surface of the installation seat should be inspected with emphasis.
When a plug leaks, it cannot be simply solved by continuing to increase the tightening force. It is necessary to check whether there is any damage to the matching sealing parts, sealing grooves, positioning surfaces of the plugs and the sealing surfaces of the installation holes.
The difference from the cylinder head and the cylinder head sealing ring
Cylinder head: It is a relatively large rigid sealing and pressure-bearing part at the hydraulic end, used to seal the corresponding working chamber or maintenance opening.
Cylinder head sealing ring: It belongs to elastic static sealing parts, mainly sealing the fit clearance between the cylinder head and the hydraulic cylinder.
Cylinder head plug: A rigid sealing component belonging to the relevant hole positions or special openings of the cylinder head, fixed by threads, steps or other structures, and used in conjunction with independent sealing components as designed.
The three types of parts may be located in adjacent areas, but they perform different functions. When purchasing, they should be confirmed respectively based on the specific installation location and the original part number.
The difference from the valve cavity plug
Cylinder head plugs cannot be directly equated with suction plugs, discharge plugs or valve cavity plugs. The valve cavity plug cover is mainly used to close the inspection holes corresponding to the suction valve or discharge valve, and usually has a clear matching relationship with the valve cover, gland or external locking structure.
The cylinder head plug should be identified according to the relevant structure of the cylinder head and its specific hole position. If there are differences in product names, the original part number, installation diagram and physical dimensions should be used for confirmation first to avoid judging the interchange relationship solely based on the Chinese name.
Common injuries and examinations
When inspecting the cylinder head plug, special attention should be paid to checking the external thread, the positioning outer circle, the shaft shoulder, the pressure-bearing end face, the sealing groove and the tool action area.
Common abnormalities include thread wear or scratches, thread deformation, sealing groove scratches, positioning surface erosion, end face indentations, corrosion, tool groove damage, and body cracks.
If the plug repeatedly loosens or leaks, in addition to inspecting the plug itself, the internal threads of the installation hole, the positioning hole, the matching sealing parts and the adjacent pressure-bearing surface should also be checked to determine whether there are any abnormal fit dimensions or structural damage.
Key points for selection
When purchasing the cylinder head plug 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. Cylinder head model and specific installation position of the plug;
4. Original part number;
5. Maximum outer diameter of the plug;
6. Total length of the plug and installation depth;
7. Thread diameter, pitch, tooth profile and direction of rotation;
8. Effective thread length;
9. Position the outer circle and the dimensions of the steps;
10. Pressure-bearing end face and shaft shoulder structure;
11. Position and size of the sealing groove;
12. Specifications of matching O-rings, gaskets or other sealing parts;
13. Tool slots, hexagon socket, hexagon socket or other disassembly and assembly structures;
14. Working pressure and medium conditions;
15. Materials, heat treatment and surface requirements;
16. Physical samples or technical drawings.
Installation and Maintenance
Before disassembling and assembling the cylinder head plug, it is necessary to confirm that the mud pump has been shut down, and the hydraulic end and related high-pressure system have been completely depressurized. The plug must not be loosened when there is residual pressure.
Before installation, the thread of the plug, the thread inside the installation hole, the positioning step and the sealing groove should be cleaned. The drilling fluid deposits, sand grains, rust and metal debris should be removed, and the thread should be checked for any scratches, missing teeth or deformation.
If the plug is equipped with O-rings or other seals, it is necessary to confirm that the model and cross-section of the seals are correct. During the installation process, avoid twisting, cutting or pinching. The plug should be screwed in after the threads are correctly aligned and should not be forcibly tightened when there is obvious jamming.
The method of tightening the plug and the torque should be carried out in accordance with the corresponding slurry pump maintenance manual or technical drawings. The threads, materials and pressure-bearing structures of different plugs are different, and it is not advisable to use a uniform empirical torque.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides cylinder head plugs and hydraulic end blocking accessories for drilling mud pumps. Cylinder head plugs are mainly used for sealing special holes in cylinder heads or related hydraulic end structures. They can be selected and matched according to the model of the mud pump, the model of the hydraulic end, the model of the cylinder head, the installation position, the outer diameter of the plug, the thread specification, the positioning step, the sealing structure, the original part number and the technical drawings.