Product Introduction of Threaded Press Cover
The threaded gland is a threaded clamping accessory used in the hydraulic end valve cavity and related installation parts of the plunger pump. Its main feature is that the gland body is provided with connecting threads, which can be directly screwed into the valve box, pump head body or corresponding installation holes. Axial clamping force is generated through the threads to press and hold the internal sealing parts, valve group parts or related positioning parts.
Unlike the press cover structure that uses independent press caps for fixation, threaded press covers usually combine the functions of "press cover" and "threaded fastening" on one part. During installation, the internal parts are kept in the specified axial position through the coordination of the screw-in depth and the clamping end face, while providing reliable mechanical clamping conditions for the sealing structure of the valve cavity or installation port.
The threaded gland of different plunger pumps has different uses and structures. Some are used in the suction valve or discharge valve area, while others are used in other inspection holes, valve cavities or component installation positions at the hydraulic end. Therefore, when selecting a model, in addition to the product name, it is also necessary to confirm the actual installation position, the mating thread, the object to be pressed and the sealing structure.
The main function of the threaded cover
1. Threaded connection and fixation: The gland is directly connected to the valve box or the corresponding installation seat through its own threads, without the need to rely entirely on an independent cap for fixation. After being tightened, a stable axial holding effect can be formed.
2. Axial compression of internal parts: When the threads are screwed in, axial displacement occurs. The end face of the cover further acts on the internal parts, pressing and positioning the seals, valve assembly, bushings or other accessories.
3. Maintain the assembly position of the valve cavity: In the suction valve, discharge valve or other hydraulic end components, the threaded cover can restrict the axial movement of internal parts according to the specific structure, maintaining the correct installation relationship of the valve group and related components.
4. Provide compression conditions for static sealing: For some structures, O-rings, gaskets or other static sealing components are set on the outer circle, end face or adjacent positions of the threaded cover. The threaded gland is responsible for maintaining the required assembly state of these sealing parts. The specific sealing form should be based on the original pump structure.
5. Form a detachable maintenance structure: When it is necessary to maintain the internal valve group or sealing assembly, the threaded cover can be removed and then entered into the corresponding valve cavity, facilitating the inspection and replacement of internal parts.
Working principle
The threaded cover utilizes its external threads to fit with the internal threads of the valve box or mounting seat, converting rotational motion into axial movement. As the cover is gradually screwed in, the clamping end face comes into contact with the internal matching parts and establishes an axial clamping force.
During operation, the threaded connection serves the axial holding function of the cover, while the clamping end face maintains the position of the internal components. If a static seal is set at this position, a sealing fit will be formed between the seal and the gland, valve box or installation hole to jointly complete the sealing of the valve cavity.
Therefore, the thread accuracy, thread insertion length, compression end face size and sealing fit part of the threaded gland all belong to important matching parameters and cannot be replaced merely based on similar outer diameters.
The difference from ordinary press covers
The most obvious structural feature of the threaded cover is that the cover body is directly equipped with connecting threads. Ordinary gland presses may be fixed by independent caps, bolts, pressure plates or other fasteners, while threaded gland presses can be directly installed and axially tightened by using their own threads.
Therefore, when selecting a threaded cover, the thread diameter, pitch, direction of rotation and effective thread length are the key parameters. Even if the shapes and outer diameters of two gland covers are similar, they usually cannot be directly interchanged as long as the thread specifications or the positions of the pressing end faces are different.
Structural and supporting features
Threaded connection part: It is used to form a connection with the valve box or mounting base and is an important structure that distinguishes the threaded cover from other covers.
Compression end face: Located at the inner end of the gland, it cooperates with the valve assembly, bushing, seal or other internal parts according to the specific structure, and is responsible for transmitting the axial compression force.
Center hole or internal passage: Some threaded cover plates are provided with center through holes, inner cavities or steps according to the installation position to avoid valve group parts, rods or form corresponding assembly space.
Disassembly and assembly structure: The outer end can be designed with a wrench face, slot, hole position or other special tool function structure according to the model, facilitating the screwing in and disassembly of the cover.
Common failures and inspection sites
When inspecting the threaded gland, special attention should be paid to checking the connecting threads to observe whether there are any random threads, scratches, corrosion, local deformation or abnormal wear. Thread damage may directly affect the screwing in, positioning and load-bearing state of the gland.
At the same time, the compression end face and internal steps should be inspected. If obvious erosion, indentation, deformation or uneven wear occurs, it may cause uneven force distribution or abnormal positioning of the internal components.
For structures with sealing grooves, it is also necessary to check whether there are scratches, corrosion or deformation in the sealing grooves, and simultaneously inspect the matching O-rings, sealing rings or gaskets. If leakage persists after replacing the sealing parts, further inspection should be carried out on the sealing surface of the gland and the mating surface of the valve box.
The action slots, holes or wrench surfaces of the disassembly and assembly tools should also be inspected. Repeatedly using inappropriate tools to forcibly disassemble may cause deformation of the outer structure and increase the difficulty of subsequent maintenance.
Key points for selection
Threaded gland is a special part that directly matches the hydraulic end installation hole and internal components. When purchasing, it is recommended to focus on confirming the following information:
1. Brand, series and specific model of plunger pump;
2. Hydraulic end or valve box model;
3. Specific installation position of the threaded cover;
4. Diameter, pitch and direction of rotation of external threads;
5. Effective thread length and screw-in depth;
6. Outer diameter, total height and center diameter of the cover;
7. Dimensions of the inner end compression surface and steps;
8. Position of the sealing groove and specifications of the matching sealing parts;
9. The disassembly and assembly structure at the outer end and the form of special tools;
10. Original part number, physical sample or technical drawing.
Installation and Maintenance
Before installation, the external threads of the cover and the threads inside the valve box should be thoroughly cleaned to check if there are any dents, burrs, corrosion or deformation on the threads. At the same time, it should be confirmed that the internal valve groups, seals and positioning parts have been installed in the correct sequence.
When screwing in the threaded cover, it should be kept coaxial. After confirming that the threads mesh normally, gradually tighten it to avoid damaging the threads inside the valve box due to slanting or forced screwing.
For structures with O-rings or other seals, during assembly, it is necessary to avoid the seals being cut when passing through threads or sharp edges. When necessary, assembly protection tools should be used in accordance with the corresponding equipment maintenance specifications.
The final screw-in position of the threaded gland, the tightening torque, and whether locking or anti-loosening measures are required should be carried out in accordance with the specific maintenance manual or technical drawings of the plunger pump. It is not advisable to use uniform empirical values.
The hydraulic end belongs to the high-pressure working area. Before disassembling the threaded gland, the machine must be shut down in accordance with the equipment operation procedures and the pressure must be completely released. Only after confirming that there is no residual pressure in the valve cavity and connecting pipelines can maintenance be carried out.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides threaded gland covers and related accessories for the hydraulic end of plunger pumps. The threaded gland of different pump types may vary in installation position, thread diameter, pitch, pressing end face, internal steps, sealing grooves and disassembly and assembly structure. When making a purchase, it is recommended to provide the pump model, hydraulic end model, installation location, original part number, physical dimensions or technical drawings to accurately verify the product.