Product Introduction of Hexagonal Head Bolts
Hexagonal head bolts are commonly used structural fasteners in the assembly and maintenance of plunger pumps. They are connected to nuts or internal thread holes on the pump body through threads to tighten and position end covers, bearing housings, brackets, guards, and other detachable components.
The hexagonal head structure is convenient for installation and disassembly using tools such as sockets and wrenches. After the bolts are tightened in accordance with the prescribed method, a preload is established through the axial tension generated by the screw, which presses the connected parts together and keeps the connection parts stable under the vibration, alternating load and mechanical shock conditions produced by the operation of the plunger pump.
The hexagonal head bolts used in different installation positions of the plunger pump are not necessarily the same. There may be differences in nominal diameter, pitch, length, thread length, strength grade, surface treatment and the matching anti-loosening structure. Therefore, when replacing, the selection should be made based on the specific installation position and the original bolt specifications.
The main function of hexagonal head bolts
1. Connect and tighten components: Reliably connect the corresponding structural parts of the plunger pump and maintain the specified assembly relationship among each part.
2. Establish connection preload: After the bolts are tightened, axial tension is generated, which forms a clamping force on the connected parts, reducing the loosening or relative displacement of the mating surface during operation.
3. Maintain the installation position of components: Coordinate with the positioning surface, installation holes, nuts, washers and other structures to keep the end cover, bracket and other accessories in the correct installation state.
4. Facilitate disassembly, assembly and maintenance of the equipment: The threaded fastening structure can be repeatedly disassembled and assembled, making it convenient to disassemble the corresponding components during the maintenance of the plunger pump, inspect the internal parts and then reassemble them.
Working principle
When installing hexagonal head bolts, a wrench or socket acts on the hexagonal head and applies a rotational torque, and the thread pair converts the rotational motion into an axial tensioning effect. When the bolt reaches the specified tightening state, the screw undergoes a certain elastic elongation and exerts a continuous clamping force on the connected parts.
For plunger pumps, a reasonable pre-tightening state of bolts is of great significance. Insufficient preloading may lead to loosening, vibration and abnormal wear of the connection surface. Excessive tightening may cause damage to the threads, plastic deformation of the bolts, and even affect the connected parts.
Therefore, the actual tightening torque cannot be estimated merely based on the outer diameter of the bolt. It also needs to be determined in combination with the strength grade of the bolt, the state of the thread, the lubrication conditions, the structure of the connected parts, and the maintenance requirements of the corresponding pump type.
Structural features
Hexagonal head: It provides the force-bearing position for sockets or wrenches. The dimensions of the hexagonal opposite sides should match the installation tool and the original bolt specifications.
Screw: It is located between the head of the bolt and the thread. Depending on the specific specifications, it can adopt a full thread or partial thread structure.
Thread: It fits with the nut or the internal thread of the equipment. The nominal diameter, pitch, direction of rotation and effective meshing length must be consistent with the original connection structure.
The pressure-bearing surface under the head: Transmits the clamping force of the bolt to the connected part or washer. During maintenance, pay attention to whether there are abnormal indentations, uneven wear or damage.
Full thread and partial thread
The hexagonal head bolts used in plunger pumps may adopt a fully threaded or partially threaded structure. The threads of full-threaded bolts usually extend close to the head, while partially threaded bolts have a certain length of smooth shank section.
The two structures cannot be interchanged at will merely based on the total length. If the original design requires the smooth rod section to pass through the connecting piece, replacing it with bolts of different thread lengths may change the force-bearing position and the effective thread meshing relationship. When making a purchase, both the total length and the effective thread length should be checked simultaneously.
Anti-loosening and matching relationship
The operation of the plunger pump involves continuous vibration and periodic mechanical loads. Some installation positions will be equipped with flat washers, spring washers, lock nuts, lock plates or other anti-loosening structures according to the original design.
The anti-loosening method should be restored in accordance with the original equipment design. It is not advisable to arbitrarily remove or add anti-loosening parts just because the bolt diameters are the same. For end covers or multi-bolt connection positions with specified tightening sequences, they should also be tightened step by step in accordance with the corresponding sequence.
Common failures and inspection sites
When inspecting hexagonal head bolts, special attention should be paid to checking the hexagonal head, the lower fillet of the head, the screw, the thread and the end position of the thread. Observe whether there are any abnormalities such as slippage, scratches, random threading, corrosion, bending, plastic elongation or cracks.
For connection positions that are subject to cyclic loads for a long time, the root of the thread and the area where the cross-section of the rod changes need to be inspected with emphasis, as fatigue damage may occur at these positions.
If bolts repeatedly loosen at the same position, it is not only necessary to tighten them repeatedly, but also to check whether the nuts or internal threads, installation mating surfaces, washers, anti-loosening structures and related components have vibration, deformation or assembly abnormalities.
Key points for selection
When purchasing hexagonal head bolts for a plunger pump, it is not only necessary to confirm the diameter and length. It is recommended to focus on checking the following information:
1. Brand, series and specific model of plunger pump;
2. Specific installation positions of bolts and connecting components;
3. Nominal diameter and pitch of the thread;
4. Metric, imperial or other thread systems;
5. Total length of the bolt and effective thread length;
6. Full thread or partial thread structure;
7. Dimensions of the opposite side of the hexagonal head and the height of the head;
8. Materials and strength grades as required by the original design;
9. Matching nuts, washers and anti-loosening structures;
10. Original part number, physical sample or technical drawing.
Installation and Maintenance
Before installation, the external threads of the bolts and the matching internal threads should be cleaned. Check for burrs, random threads, corrosion and mechanical damage, and confirm that the specifications, lengths and strength requirements of the bolts are consistent with the original installation position.
For multi-bolt connection structures, they should be tightened step by step in accordance with the sequence specified for the corresponding equipment to avoid excessive tightening at one time in some areas, which may cause uneven force distribution on the joint surface.
The tightening torque of bolts, the lubrication requirements for threads, and whether they are allowed to be reused should be carried out in accordance with the specific pump type maintenance manual or technical documents. It is not recommended to apply a uniform torque to the key connecting bolts of the plunger pump in the absence of technical requirements for the equipment.
Procurement Instructions
Juli Petroleum Drilling and Production Equipment Co., Ltd. provides hexagonal head bolts and plunger pump fastening connection accessories. Bolts used in different installation positions may vary in terms of thread specifications, lengths, thread lengths, strength grades and anti-loosening methods. When making a purchase, it is recommended to provide the pump model, installation location, thread specification, original part number, physical dimensions or technical drawings to accurately verify the product.