Valves have made remarkable progress over the last three decades. Manual shutoff has given way to automated shutdown systems. In-line mounted valves have lost their popularity to pad mounted valves. And, specialized actuator designs have moved to standardized designs in the presence of the European NAMUR standard. These are only a few of the many changes that have occurred to the solenoid valve, the workhorse of the chemical processor's valve system. The solenoid valve has made tremendous leaps in the chemical processing industry. Yet, at the same time, market conditions can dictate the need to continue enhancing solenoid valve technology.
|A 4-way single solenoid pilot-operated valve.|
Historically, newly written standards have been the impetus for many innovations in valve design. As you will see in this article, design standards – from the present and in the future – will also lead to the development of new valve technologies in the years to come.
Higher flow rate
In the 1990s the German chemical industry developed the NAMUR standard, which standardized the actuator interface to the solenoid valve. Initially, the U.S. was slow to accept the European standard; however, by the mid-1990s all actuator manufacturers worldwide embraced it.
Today, a new European CEN standard promises to follow in NAMUR's footsteps. Referred to as CEN/TC69/WG1/SG10/0/ N023, the new standard is an extension of the VDI/VDE3845 requirements. Its significant difference from the original NAMUR standard is that it covers even higher flow rates. To date, few manufacturers have developed valves to conform to this new CEN standard. We can expect future solenoid valve designs to accommodate this product gap.
The European standard RoHS focuses on improving the impact manufacturers in all industries have on the environment. As of July 1, 2006, legislation mandates that any product shipped to Europe has to meet the RoHS standard.
Briefly, RoHS restricts the use of six hazardous substances within electrical and electronic equipment. This includes any product with minimal levels of lead, mercury, cadmium, hexavalent chromium Cr, Polybrominated biphenyls, and polybrominated diphenyl ethers.
Solenoid valves typically have small amounts of some of these restricted substances. For example, hexavalent chromium Cr exists in the standard plating used for corrosion protection in the electrical industry. As a result, we expect that solenoid valves will likely require alternate plating compounds in the near future.
Safety shutdown standard
The International Organization for Standardization (ISO) wrote a safety shutdown standard, S84, which suggests redundant valve design for safety systems. Specifically, four-way solenoid valves traditionally have a single or a dual operator for momentary or maintained position control. With a redundant-type valve, two coils work in tandem. If one coil fails, the other coil can fully operate the solenoid valve on its own. This provides plant personnel with the extra assurance that the valve will function when it must. We expect to see numerous solenoid valve designs incorporating redundancy to ensure safe systems.
A new IEC standard, 61508/61511, requires manufacturers to supply information about their valves' reliability. Manufacturers must obtain a SIL (Safety Integrity Levels) rating to indicate how long the valves will last and how long they will satisfactorily work before replacement or repair. In the future, plant operators will incorporate reliability data into their plans as a way to develop their maintenance schedules.
Another look back
Valve technology has come a long way and will continue to evolve. There are many opportunities to upgrade systems for the sole purpose of improving overall efficiency, reliability, and safety. As standards continue to be written and industries continue to adapt, so will the solenoid valve.
About the author: Russ Fick is the Marketing and Sales Manager at Parker Fluid Control Division (FCD) in New Britain, Conn. He is involved with all aspects of the product sales cycle from product development, launching of the product, and the development of sales channels. Parker FCD's product lines carry trademark names of Skinner, Gold Ring and Sinclair Collins, among others. Fick has a Bachelor of Engineering in Mechanical Engineering from Villanova University. He has 34 years experience in sales and marketing in the solenoid valve industry.
Parker Fluid Control Division