Product Introduction of D-type Sealing Ring
The D-type sealing ring is a dedicated elastic sealing component used at the hydraulic end of the plunger pump, and is often employed at the static sealing positions between the suction cover, discharge cover and the valve box. Its name is derived from the cross-sectional structure of the sealing ring, which is different from the common circular cross-section O-ring.
During the operation of the plunger pump, the pressure of the medium inside the hydraulic end valve chamber changes periodically. A reliable static seal needs to be set at the fit position between the gland and the valve box. The D-type sealing ring is installed in the corresponding sealing groove. After assembly, it forms an initial compression and further undergoes elastic deformation under the action of working pressure to seal the fit clearance, thereby reducing the leakage of the medium from around the cover.
In some plunger pump structures, D-type sealing rings can be used for the suction and discharge covers, but the installation positions, sealing ring sizes and sealing groove structures of different pump types are not exactly the same. Therefore, when purchasing, it should be matched according to the pump model, the position of the gland, the original part number and the size of the sealing groove.
The main function of the D-type sealing ring
The fit clearance between the sealing cover and the valve box: The D-type sealing ring is installed in the sealing groove of the cover or valve box to seal the annular fit area between them, reducing the leakage of the working medium at the hydraulic end to the outside.
2. Establishing a seal through elastic deformation: After the sealing ring is inserted into the sealing groove, it forms a specified compression amount. During operation, it further deforms under the action of the medium pressure, maintaining effective contact on the sealing surface.
3. Adaptation to periodic pressure changes: The suction and discharge processes of the plunger pump generate periodic pressure changes. The D-type sealing ring maintains a sealed state through elastic compression and recovery, in conjunction with the gland and valve box.
4. Protect the joint of the gland cover: A correctly installed sealing ring can reduce the direct leakage of the medium through the fit gap of the gland cover and prevent the leakage medium from continuously eroding the relevant joint position.
Installation location
D-type sealing rings are commonly found at the cover positions of the suction and discharge valve chambers at the hydraulic end of plunger pumps. For example, in the suction end structure, the D-type sealing ring can be installed between the suction cover and the valve box. Some of the discharge end structures also use D-type sealing rings to seal the discharge cover.
The specific sealing groove may be set on the outer circle of the gland cover or at the corresponding position of the valve box according to the design of the hydraulic end. Therefore, the installation direction and position cannot be determined merely by the appearance of the sealing ring. It should be confirmed in combination with the original parts and the structure of the valve box.
The structural characteristics of the D-shaped cross-section
The key difference between D-type sealing rings and ordinary O-rings lies in their cross-sectional shapes. Its cross-section usually features a relatively straight installation surface and an arc-shaped sealing surface. The planar part forms a relatively stable installation relationship with the sealing groove, while the arc-shaped area participates in sealing contact and elastic deformation.
This cross-sectional structure is conducive to maintaining the specified posture of the sealing ring in the groove, reducing the possibility of abnormal rolling or twisting during assembly and force application. However, the specific D-type cross-sectional dimensions, compression amount and sealing groove dimensions must still be determined in accordance with the corresponding pump type design.
The difference from O-rings
O-rings feature a circular cross-section, while D-rings adopt an irregular cross-section with both planar and arc-shaped characteristics. Both can be used in the static sealing position of the plunger pump, but the corresponding sealing groove structure, cross-sectional dimensions and compression state may be different.
Therefore, even if the nominal inner diameters of the D-type sealing ring and the O-ring are similar, they cannot be directly interchanged without confirming the sealing groove and the original equipment design. When replacing, priority should be given to matching according to the original part number and original sealing form.
Common failure forms
D-type sealing rings, when exposed to compression and periodic pressure for a long time, may experience compression deformation, decreased elasticity, surface wear, edge cutting, squeezing, cracking or changes in material properties caused by medium action.
Under high-pressure conditions, if the fit clearance between the sealing groove, the gland or the valve box is abnormal, the sealing material may also be squeezed out into the clearance area, causing local damage to the sealing ring and eventually forming a leakage channel.
If leakage still occurs after replacing the new D-type sealing ring, it is not only necessary to continue replacing the sealing ring, but also to check whether there is erosion, grooves, scratches or dimensional abnormalities on the outer circle of the gland cover, the sealing holes of the valve box, the sealing grooves and related mating surfaces.
Key points for selection
D-type sealing rings are hydraulic end sealing parts with high requirements for size and material matching. 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. Is it used for the suction cap or the discharge cap?
4. Original D-type sealing ring part number;
5. Inner diameter, outer diameter and cross-sectional dimensions of the sealing ring;
6. The specific shape and height of the D-shaped section;
7. Diameter, width and depth of the sealing groove;
8. Requirements for compatibility of working medium and materials;
9. Sealing materials and hardness requirements specified for the equipment;
10. Physical or technical drawings of the original sealing ring.
Installation and Inspection
Before installation, the cover and the sealing groove of the valve box should be cleaned to ensure that there are no metal debris, sand, old sealing materials or other foreign objects in the groove. Also, check if there are burrs or sharp edges on the edge of the sealing groove.
When installing the D-type sealing ring, it is necessary to ensure that the cross-sectional direction is correct to avoid twisting, folding or local stretching of the sealing ring. When the sealing ring passes over steps or sharp edges, care should be taken to prevent the sealing surface from being cut.
When the gland is installed into the valve box, it should be kept coaxial and stable to avoid direct shearing of the sealing ring by the edge of the gland. If the corresponding pump type has specified lubrication, installation tools or assembly methods, they should be carried out in accordance with the equipment maintenance requirements.
Before disassembling the hydraulic end cover and the D-type sealing ring, 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 D-type sealing rings and hydraulic end sealing accessories for plunger pumps. The D-type sealing rings of different pump types may vary in inner diameter, outer diameter, cross-sectional dimensions, materials and installation positions. When purchasing, it is recommended to provide the pump model, hydraulic end model, installation position, original part number, physical size of the sealing ring or technical drawings to accurately verify the product.