Material Science and Testing Matter: What You Need to Know to Ensure Reliable Regulator Performance
August 28, 2019 | Jon Kestner, Product Manager, General Industrial Regulators
As the requirements of any industry evolve, product portfolios must be adjusted to align product performance to what is required to achieve success across any application, from commonplace to extreme. This paradigm holds true in the world of fluid systems, where the boundaries of performance for valves, fittings, regulators, and other components are continuously being redefined.
Design sophistication and stringent testing are what ultimately guarantee fluid and gas system components will perform under pressure in real-world applications. Testing not only gives confidence that products work as expected, but it also helps experts discover how variables that were not directly being evaluated could impact performance in the field. Especially when products are used in environments with challenging operating conditions, nothing should be taken for granted—otherwise productivity or even personnel may be at risk.
Pressure regulators rated for use at subzero temperatures present a strong example of a component that requires thorough testing to confirm performance in extreme conditions. They must control pressure while reacting to system changes in applications where failure can lead not only to loss of profit and property, but could impact the safety of operators, as well. In cases where cold temperatures threaten crucial component functionality, meticulous regulator engineering and well-thought-through, lab-based analysis stand between success and failure.
Why Performance Matters in Low-Temperature Regulator Applications
Low-temperature regulators are frequently used in applications such as industrial or bulk gas supply. Regulators are used to control system pressure at varying flow rates, and if they fail, it can lead to major problems. Loss of fluid or gas into the environment can be costly, but that is far from the worst-case scenario. Pressure loss due to regulator failure can also jeopardize overall system performance or cause significant safety hazards.
A key reason a regulator might fail is its inability to stand up to extreme temperatures inherent to the application, such as bulk gas supply. Gas supply pressure reduction systems are frequently installed outdoors, often in non-climate-controlled environments. As a result, containers are exposed to temperature extremes found throughout the globe, ranging from the heat near the equator to much colder climates nearer to the poles. The effects of cold-temperature environments can be compounded by the drop in gas temperature as the pressure is reduced. For most gases, a substantial drop in gas pressure will result in a significant Joule-Thomson cooling effect, causing a major decrease in temperature as energy transfer occurs. This can result in industrial regulators experiencing temperature exposures of -40°C or even lower.
These cold conditions can pose a problem for regulator performance, as cold temperatures frequently stiffen and shrink elastomeric components, causing leaks or impacting responsiveness. The main sensing element in regulators is either an elastomer diaphragm or a piston sealed with an elastomer O-ring. If either the diaphragm or piston O-rings get too brittle, they can crack and cause leaks or stiffen so much that they impact the regulator’s ability to react to changes in system flow demand. A variety of other regulator components are also usually comprised of elastomers, including the main seat on which the poppet seals, separating high- and low-pressure areas, the dynamic sealing between the poppet to the body, the diaphragm or piston seal, and static seals in the body that contain pressure. Regulators also contain nonelastomeric polymers, such as hard plastic seat materials, that can become so hard at extremely low temperatures that sealing is difficult or impossible. As a result, regulators are inherently vulnerable to cold-related performance degradation.
To minimize risk of costly or hazardous gas leaks, it is crucial to choose the right materials when designing regulators specifically for these low-temperature applications.
Finding the Right Fit for Low-Temperature Regulator Applications
Material selection makes a big difference in selecting the right regulator, not only because components in applications like bulk gas supply could require low-temperature resistance, but also because not every elastomeric material is compatible with every chemical. For example, ethylene propylene performs well in cold temperatures but is not chemically compatible with hydrocarbons, which are especially likely to be present in compressed natural gas (CNG) and related applications. In order for a material to be effective in an end-use regulator setting, both the environmental performance and chemical resistance must be matched to the application.
Regardless of the material chosen, testing is crucial to confirm reliable performance of the regulator’s seals at extremely cold temperatures. Testing is the only way to make sure no internal leaks occur at the regulator seat, no shell leaks occur due to seal failure, and that the regulator will continue to perform the dynamic functions for which it was designed, constantly self-adjusting to deliver a designated pressure level.
A Look at the Low-Temperature Testing Landscape
Not all temperature testing methodology is created equally. There is no single standard test for low-temperature performance recognized across industries, and thus there is wide variance in the thoroughness of equipment testing. The American Society of Mechanical Engineers (ASME) and American National Standards Institute (ANSI) have low-temperature tests that can be utilized, as well as more specialized bodies like the American Petroleum Institute (API). These tests are often designed for specific applications with specialized requirements, however, and are not broad enough to account for all the applications to which fluid system products are exposed.
Another complicating factor is the challenge of conducting a full flow-curve analysis for extremely cold temperatures due to the inherent limitations of working in a warmed facility. Regardless, testing needs to be conducted to confirm the regulator properly flows gas, will open and close, will remain sealed, and will not otherwise have performance degraded by significant temperature changes.
A customized approach to temperature testing is needed to know a low-temperature regulator will perform as rated when conditions are most extreme. To understand what that looks like, consider the steps taken by Swagelok’s product development team when analyzing the capabilities of a recently released low-temperature version of the RHPS Series of pressure regulators that featured components designed to maintain strong seals in cold conditions.
Case Study: Designing a Plan for Low-Temperature Regulator Testing
The standard RHPS Series industrial regulator catalog includes roughly 900 product variants, and before a testing methodology was established, it was necessary to find a way to reasonably assess them all. Every feature was tested, both from a static performance standpoint (ensuring any seals and O-rings were properly containing pressure and sealing against environmental leakage) and from a dynamic performance standpoint (ensuring O-rings and diaphragms with dynamic movement around them would maintain ideal performance).
The engineering team looked at existing standard low-temperature testing for valves and fittings. A series of temperature cycles from room temperature to low or high temperatures is common practice. This works for most products across a broad spectrum of applications, as it confirms seals will work, valves will actuate, and any performance degradation is captured over the course of multiple temperature cycles.
To properly evaluate low-temperature regulators, specifically, testing was expanded to cover all the functionality needs of pressure regulator applications. The testing team knew low temperatures can degrade performance, creating situations such as valves requiring high actuation torque or seals exhibiting leakage at low temperatures due to shrinkage. As a result, the testing plan was designed to catch any potential issues such as these so customers did not end up with unwelcome surprises when deploying products in the field.
Working from proven testing protocols, the team employed a hot-cold, hot-cold cycle for the RHPS Series low-temperature regulators. The temperature between extreme cold and ambient room temperatures fluctuated to ensure any degradation occurring during cycling that may go unnoticed during a single drop in temperature would be apparent in the subsequent drops to cold temperatures. The careful approach made sure products would function as expected across a wide range of low-temperature applications.
Separate procedures were employed for back pressure and pressure-reducing regulator designs, ensuring all products were tested in a manner appropriately customized to their design. In the end, a dedicated industrial regulator low-temperature cycle test for the company was developed, as well as a product line that performed in extreme conditions.
Before Purchasing Products, Be Sure They Will Perform as Required
Testing should be a standard part of any R&D process, but it should also never be taken for granted. As the case study above demonstrates, great care is needed to be sure a product will perform at extreme temperatures. Temperature ratings cannot be based off the sum of the product’s parts; real lab data is essential to know the product will perform safely and reliably. It is also not enough to simply expose a product to the cold—manufacturers must employ carefully crafted temperature cycle tests to be sure it will hold up, and that no unforeseen issues might jeopardize performance in the field.
If you need help finding the right components rated to perform in your applications, contact your local Swagelok sales and service center for guidance at any time. And if you have any doubts around the current performance of existing fluid or gas systems or need expert insights when designing new systems, consider tapping into the knowledge of Swagelok’s Evaluation and Analytical Services professionals for on-site inspection and recommendations around fluid system performance improvement.