Background

The evolution of pressure regulators for the fledgling semiconductor industry dates back to the 1980’s. General industry regulators used for applications such as welding were made from 316 stainless steel with threaded connections (NPT). As cleanliness was less of a concern, the regulators had guided parts, such as the poppet, which generated particles. Diaphragm seals were typically Teflon rather than metal to metal seals. The first major changes were to welded connections to improve leak integrity and better parts cleaning to improve purity. The concept of Ultra High Purity (UHP) was evolving. Regulator manufacturers worked to develop new ultraclean pressure regulators which brought the first springless designs in the late 80’s.

The question of springless being better than spring type is one that was answered many years ago. The question reoccurs every few years as the next generation of gas system engineers relearn things known to their predecessors – thus this blog.

Springless Marketing

Springless regulators were hyped as the latest and greatest improvement for UHP in the early 90’s. The new designs were compared to the old, existing generation of gas welding regulators used by the industry.  The improvements were striking to say the least. Industry perception was that springless made all the difference in purity when in fact it was simply designing products with ultraclean concepts. Spring type ultraclean regulators were developed with ultraclean design rules that were free of guided parts in the flow path and had metal to metal seals to atmosphere. The particle and dry down performance of these new ultraclean regulators compared to springless were equivalent, but the springless was still thought to be better. There was no data or evidence to prove that a springless regulator was better than an ultraclean spring type, it was just a conceptual preference driven by aggressive marketing.

Spring Type to Springless Comparison

First, the term springless is misleading. A springless regulator still has a non-wetted range spring and the diaphragm itself is in essence a wetted spring. Springless means there is no wetted poppet spring for a regulator.

In the early 90’s AP Tech compared particle performance of equivalent spring and springless UHP regulators at both 0.1 and 0.02 micron. The testing proved that there was no difference in particle generation. Further testing over the years confirmed these early results. Particles in a regulator are generated by the seat and the interaction of the poppet with the seat. PCTFE and most regulator seat materials are machined, not molded. The machining makes a difference in the particles generated due to the surfaces generated. The surface finish of the poppet along with alignment of the poppet relative to the seat also impacts particle performance. A proper poppet spring for UHP applications does not contribute to particle generation.

Some may argue that fewer parts in the flow path is better, meaning springless is better. Some would say that if there were corrosion, the flexing spring would shed particles.  There is no data to prove fewer parts are better. In terms of corrosion, moisture tends to separate from the gas at the point of pressure drop which is where the poppet meets the seat. The corrosion typically occurs on the low pressure side of the regulator which is downstream of the spring. If there is moisture in the gas, there are much bigger problems to address than a poppet spring.

Nothing in life is free, there are always tradeoffs. A springless regulator is more complex than a spring type which makes it inherently more expensive. Attaching the poppet to the diaphragm to enable removing the poppet spring generally involves creating entrapment zones not found in spring type regulators or creating additional seals to atmosphere. The tradeoff of removing a poppet spring which is of questionable benefit to add an entrapment zone which are known to adversely impact purity or an outboard seal which is another leak point. There are different springless designs with different ways of attaching the poppet. One needs to examine a complete sectional view of a springless regulator.  The point where the poppet is attached to the diaphragm should have an apparent entrapment zone or an extra seal on the bottom of the regulator body will be evident. Going springless comes at a higher cost, as in 40% to 200% more, along with the other downsides as explained.

Conclusion

Regulator selection decisions should be made with quantifiable performance standards and not subjective design differences, such as whether there is a poppet spring. Stated differently, a particle performance specification is appropriate whereas a feeling without data that springless is better is not. Today, spring type and springless regulators are used interchangeably. Some manufacturers only produce springless UHP regulators whereas others offer spring type.

AP Tech has both spring type and springless regulators. Our recommendation of spring type over springless is not because we do not offer springless. We believe it is the correct choice due to the higher cost and complexity of springless without a tangible benefit.