Packing, also known as sealing packing, is a crucial sealing material in industrial applications. It is typically made of woven, soft fibers, arranged in square, rectangular, or circular strips and filled into a sealing cavity to prevent fluid or gas leakage.
From early methods of stuffing leak channels with cotton and linen fibers to the widespread use of high-performance fibers today, packing has remained in use due to its wide availability, ease of processing, low cost, reliable sealing, and simple operation. This article will delve into the working principle, types, selection strategies, and installation and maintenance techniques of packing.
1. Working Principle and Structure of Packing
The working principle of packing is based on the "maze effect." At a microscopic level, the shaft surface is not completely flat, and the packing can only partially fit against the shaft, creating tiny gaps. The medium is repeatedly intercepted as it passes through these "maze-like" gaps, achieving a sealing effect.
2. Types and Characteristics of Packing
With the development of materials science, the types of packing are becoming increasingly diverse to meet different working conditions. The following is a comparison of common packing types and their characteristics:
|
SUNPASS Packing Types |
Main Materials |
Impregnation and Reinforcement |
Core Characteristics and Application Scenarios
|
|
Graphite Packing |
Flexible graphite |
Glass fiber, cotton yarn, stainless steel wire, PTFE, stainless steel wire mesh |
High temperature resistance (-100℃–850℃), high pressure resistance (0–30.0MPa), corrosion resistance, suitable for high-temperature and high-pressure valves and pumps. |
|
Aramid Packing |
Aramid fiber |
PTFE, silicone oil |
High strength (tensile modulus >70 GPa), wear-resistant, extrusion-resistant, chemically resistant (pH 2-12), high temperature resistance (-100～+280℃), suitable for centrifugal pumps, reciprocating pumps, slurry pumps, high-temperature and high-pressure steam valves, and reactor agitator shafts. |
|
PTFE packing |
PTFE |
PTFE , silicone oil |
offers excellent corrosion resistance, high cleanliness, and a low coefficient of friction, making it suitable for food, pharmaceutical, and highly corrosive media applications. |
|
Ramie packing |
Ramie fiber |
PTFE and silicone oil |
It has good thermal conductivity, is wear-resistant, and high-temperature resistant, typically used in high-temperature oil pumps and similar applications. |
|
Acrylic packing |
Acrylic |
PTFE, graphite, and silicone oil. |
It is soft, high-strength, wear-resistant, and erosion-resistant, suitable for packing seals in pumps, valves, and reactors operating at high linear velocities and pressures. |
|
Cotton Yarn Packing |
Cotton yarn |
PTFE, Graphite, petroleum jelly, silicone oil |
Offers good flexibility and plasticity, suitable for general sealing of pipes, containers, and equipment. |
|
Glass Fiber Packing |
Glass fiber |
PTFE, graphite |
High temperature resistance, corrosion resistance, wear resistance, high flexibility, suitable for sealing work in high-temperature environments. Used in chemical, metallurgical, power, and dynamic sealing applications. |
3. How to Choose the Right Packing?
Choosing the right packing is the first step to ensuring a good seal. When selecting, the working conditions must be matched with the packing performance.
Key parameters you need to know:
Media Properties: Chemical name of the medium, pH value, whether it contains solid particles.
Temperature and Pressure: Maximum operating temperature and pressure of the equipment.
Linear Velocity: Rotational speed of the shaft.
Dimensions: Shaft diameter, stuffing box diameter, packing width.
Dimension Calculation Formula: Cross Section = (Stuffing Box Diameter - Stem Diameter) / 2
SUNPASS offers free selection and technical consultation based on your needs. For specific customer operating conditions (such as extreme temperatures, highly corrosive media, food-grade requirements), we can design specialized testing programs and acceptance standards, and provide customized quality control reports.
4. Correct Installation and Maintenance Procedures for Packing
In practice, incorrect installation methods are the main cause of seal failure.Following the correct installation procedure can significantly extend the service life of the packing and ensure sealing performance.
Preparation before installation:
Inspection: Inspect the stuffing box, valve stem, or bushing for damage, eccentricity, or corrosion, and repair or replace as necessary.
Cleaning: Thoroughly remove the old packing using specialized tools, clean the cavity walls with a scraper, and blow clean with compressed air.
Cutting and installation techniques:
Cutting: Use specialized cutting machinery or cut around a round bar of the same diameter as the valve stem. The cut should be clean and free of loose threads.
Lubrication: Apply a media-compatible lubricant (such as scaly dry graphite powder) to the packing as needed.
Pressure pressing: Each turn of packing should be pressed in individually.
The valve packing joints should be staggered by 120°or 180°per turn.
The gland insertion depth is generally the height of one packing turn, but not less than 5mm, leaving room for further tightening.
Run-in: After new installation, manually rotate the valve first, then run it at low speed (e.g., 30% of rated speed) for 30 minutes, gradually loading to full load.
5. Our Product Recommendations
Why choose us?
Quality Raw Materials
Raw Material Traceability and Access Control:
Strict Supplier Audit and Management: We conduct technical, production, and quality system assessments of core raw material suppliers such as aramid fiber, carbon fiber, PTFE, and high-purity graphite, establishing a qualified supplier list. Made from high-quality raw materials, our products offer strong sealing, wear resistance, and aging resistance, suitable for various industrial scenarios and with strong operating condition tolerance: They possess excellent high-temperature resistance, low-temperature resistance, high-pressure resistance, and chemical corrosion resistance, and can operate stably in a wide temperature range of -50℃ to 280℃ and under high-pressure environments.
Batch Traceability System: All raw materials are assigned a unique batch number, recording their origin, specifications, and incoming inspection reports. Any finished product can be traced back to the batch of raw materials used, achieving full-chain traceability.
Production Control
Professional Quality Control Team: Led by engineers with backgrounds in materials science and mechanical engineering, all operators undergo rigorous training and certification before starting work. Utilizing a dense structural design, superior substrate characteristics, and high elasticity, a multi-layered sealing protection system is formed, effectively blocking the penetration paths of various media such as gases, liquids, and dust.
Product Quality Assurance: Possesses sealing test reports, SGS and FDA certificates, temperature resistance test reports, and material composition certification, meeting industrial sealing material standards. Under long-term continuous operation, it achieves zero leakage, building a solid safety barrier for industrial production.
Our sealing packings have a service life 40%-60% longer than conventional products on the market, significantly reducing replacement frequency, directly reducing equipment downtime for maintenance and spare parts procurement, and lowering overall operating costs by more than 25% compared to similar products.
③ Comprehensive Service
- Operating Condition Adaptation Analysis: Providing optimal matching solutions for packing materials and braiding methods based on customer-provided pressure and temperature conditions;
- Free small-batch sampling;
- Rapid Response Inventory: Maintaining safety stock of commonly used materials and specifications (such as graphite, aramid, PTFE)
;
- Green channel for urgent orders
