What Makes a Good Valve
Whether east valve or west valve, a good valve is one that meets application needs. Both domestic and imported valves are good if they satisfy application requirements.
It is well known that scientific research aims to answer "why," while technological research and development aims to solve "how to do it to meet human needs." Therefore, hydraulics exists to meet human needs. Hydraulic drives require control of pressure, flow, and direction, and valves serve this purpose. The cross hydraulic valve is a prime example of such a component designed to manage these critical parameters.
For over two hundred years, hydraulic technology has been widely applied, and different applications have placed varying performance requirements on valves. For instance, some must adapt to different working environments such as extreme cold, intense heat, or exposure to sun and rain. Others need corrosion resistance or explosion protection. Those used in mobile hydraulics often require small size and light weight. A cross hydraulic valve must often be engineered specifically to meet these diverse environmental challenges.
Valves used in industry differ from those in agriculture; those for grasslands differ from desert applications; those for metallurgy differ from mining applications; and those for iron mines differ from coal mines. Even within coal mining, underground applications require different specifications than surface operations. Valves used in hospitals or offices not only need to be leak-free but also odorless. In a market economy, whether we're talking about a cross hydraulic valve or any other type, the principle remains: a valve that meets application needs is a good valve, regardless of its origin.
Key Requirements for Hydraulic Valves
Relative importance of different requirements across various hydraulic applications
1. Regulation Performance
Precise adjustability, including but not limited to high stability and repeatability. It's crucial to clearly understand that function ≠ performance!
Function refers to what can be done; performance refers to how well it is done. Over the 200-plus years of hydraulic valve applications, predecessors have invented many ingenious structures. Following these designs can basically achieve corresponding functions, but does not guarantee excellent performance. This is particularly true for the cross hydraulic valve, where minor design variations can significantly impact overall system performance.
It's not just about steady-state performance; transient performance is even more challenging. This is the main battlefield for valve performance competition, as detailed in sections 4.9 and 4.10.
The regulatory performance of a valve, especially a cross hydraulic valve, involves numerous design, processing, and assembly details. It is achieved through continuous exploration and improvement, verified through testing, and supported by data. There is always room for improvement—no such thing as "optimal."
2. Pressure Resistance
Modern hydraulic systems experience significant pressure fluctuations and often encounter high instantaneous pressure shocks. Hydraulic valves, including the cross hydraulic valve, must withstand these conditions.
Therefore, during research and development, pressure resistance tests are conducted at least 125% of the rated pressure. At high pressures, the performance of a hydraulic valve may differ from its performance at normal operating pressures, which is acceptable.
What's important is that after the high pressure subsides, the regulatory performance remains normal. Therefore, after conducting pressure resistance tests, performance testing under normal operating conditions should be performed (see section 5.3 for research and development testing). This is particularly critical for cross hydraulic valve applications where pressure variations are common.
3. Durability
Most applications expect hydraulic valves to operate durably (long service life). Advanced enterprises are using new materials and processes to improve the durability of hydraulic valves, including innovative approaches to cross hydraulic valve design.
However, durability requirements are not absolute. Some equipment operates around the clock, while other equipment may only be used once every few days, months, or even years. Marine vessels and wind turbines expect hydraulic valves to function for 20 years, while hydraulic valves in missiles only need to work for tens of minutes.
Key Factors Affecting Durability
- Wear is the primary factor affecting durability of mechanical components
- Valve spool movement speed is much slower than that of pump friction components
- Normal pressure on valve friction surfaces is significantly lower than in pumps
- Compared to pumps, valve durability, including that of the cross hydraulic valve, is easier to achieve and not a major challenge
For critical applications, manufacturers often implement special surface treatments and lubrication systems to enhance the durability of cross hydraulic valve components, ensuring they meet the extended service life requirements of modern machinery.
4. Product Stability
Not just one valve should perform well, but all valves should perform consistently. This is measured using PPM (Parts Per Million) – how many defects appear in one million possible defect locations. This is particularly important for high-volume manufacturers of main equipment such as automobiles, excavators, and loaders, where consistent performance of every cross hydraulic valve in their systems is critical.
It's impossible to achieve zero defects. It's better to honestly and objectively inspect and count current defect rates, then identify causes and research ways to reduce them. Persistently, defect rates can decrease from 0.1% to 0.01% or lower.
Quality Management Systems
Stable manufacturing quality is achieved through proper management and established processes, which is why ISO 9001 exists.
Advanced hydraulic component manufacturers implement these standards to ensure consistent quality across all products, including every cross hydraulic valve they produce.
IATF 16949 Core Tools
- Advanced Product Quality Planning (APQP)
- Production Part Approval Process (PPAP)
- Failure Mode and Effects Analysis (FMEA)
- Measurement Systems Analysis (MSA)
- Statistical Process Control (SPC)
Some hydraulic component manufacturers in China, especially those doing OEM work for international brands, have begun implementing Germany's "VDA63" standards for supplier evaluation and classification to improve product quality control processes. This has led to significant improvements in the consistency of cross hydraulic valve production.
However, for very low-volume production, even one-of-a-kind products that allow on-site debugging, the requirement for performance consistency is not as high. The ability to adjust valves, including the cross hydraulic valve, is actually a significant advantage of hydraulic technology.
5. Reliability
Reliability is theoretically defined as: the ability to complete specified functions within specified time under specified conditions.
For hydraulic valves, high reliability means:
- Individual valve performance must meet requirements, not just initially but also after long-term operation
- Due to unavoidable manufacturing variations, a realistic requirement is that very few valves fail to meet standards – for example, fewer than 100 in a million, or even fewer than 10
Therefore, for hydraulic valves like the cross hydraulic valve, reliability is actually a comprehensive reflection of excellent design performance and stable manufacturing quality.
Since a single component failure can affect an entire hydraulic system, users often prefer to pay higher prices for more reliable components. Since the 21st century, the international community has begun using "Mean Time To Dangerous Failure (MTTFd)" to measure hydraulic valve reliability. World-class cross hydraulic valve products have achieved MTTFd levels exceeding 150 years.
6. Market-Adapted Pricing
In the market economy of modern society, all commodities involve price considerations. Some markets are highly price-sensitive, while others prioritize reliability. This balance is particularly evident in the cross hydraulic valve market, where different applications demand different price-performance ratios.
| Market Segment | Characteristics | Key Requirements |
|---|---|---|
| OEM Market | Supplying valves according to main equipment manufacturers' requirements. Typically involves larger orders after qualification. |
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| Aftermarket | Providing replacement parts for existing equipment. Serves maintenance and repair needs. |
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It's not necessary to be innovative; studying existing products thoroughly, perfecting them, and continuously testing and improving can also lead to market success. Hydraulic technology has been in practical use for over 200 years, and there are almost no undiscovered hydraulic valve designs left, including variations of the cross hydraulic valve.
However, materials, processing techniques, fixtures, assembly processes, yield rates, and sales channels – can anyone claim these have reached optimal levels with no room for improvement? Chinese manufacturers of hydraulic valves, including cross hydraulic valve products, have predominantly relied on reverse engineering and imitation. By understanding principles, grasping essentials, identifying weaknesses, developing solutions, and understanding requirements, improvements can be made. Improvement is also a form of innovation!
Conclusion
These requirements for hydraulic components serve as benchmarks for measuring hydraulic valve quality and differentiating between various grades. Of course, excellence is relative; there's no absolute standard. Being more suitable for application requirements than competitors' products is what matters, whether we're evaluating a cross hydraulic valve or any other type.
Some Chinese enterprises, which have manufactured components for various domestic and international companies with mature processes and high qualification rates, are now venturing into producing complete hydraulic valves. This is achievable, but they must clearly recognize that producing qualified OEM components only demonstrates mastery of geometric dimensions and consistent heat treatment – foundational elements for excellent hydraulic valve performance, but not the entirety of hydraulic performance. When producing their own cross hydraulic valve products, customers will be purchasing hydraulic performance, not just geometric dimensions.
Ultimately, whether evaluating a cross hydraulic valve or any other hydraulic component, the fundamental principle remains unchanged: regardless of origin or brand, a valve that meets the specific application requirements is a good valve.