Replacing standard alloy fittings on a pressure gauge with gall resistant fittings is a minor change, but doing so eliminates the major issues associated with standard fittings. Fittings in a gall resistant material ensure a leak-tight seal, prevent particulate contamination from silver flaking, and minimize damage to equipment caused by cross-threaded and/or seized fittings.
Galling in a pressure gauge is a common problem caused by friction between sliding metals. In the presence of considerable compression and inadequate lubricity, metals sliding against each other can cause nicks, or galls, to form on the threaded surface of the fitting. Unlike other forms of wear and tear, which occur gradually, galling rapidly worsens and starts a chain reaction of problems in high-purity processes. When the fittings are silver-plated, galling increases the risks of flaking in imperfect seals, which are especially problematic in high-purity processes and semiconductor ultra-high purity media applications.
The Problems with Galling
Applications that require leak-tight connections – such as gas distribution, valve manifold boxes, and integrated sub-components in semiconductor applications – face detrimental consequences when stressed metal between two mated fittings seize together. When seals are no longer reliable, corrosive and/or other aggressive gas medias may be released within the equipment or the atmosphere. There’s a secondary risk of galling, regardless of the process type, if the fitting is plated: The plating may flake off, enter the process medium, and contaminates it.
How to Prevent Galling in a Pressure Gauge Connection
The easiest and most cost-effective way to prevent galling in pressure gauge connections is to switch to gall resistant fittings. This is a small change that brings about big benefits: Gall resistant fittings reduce the risk of contamination through imperfect seals, and prevent both cross-threading and leaks.
The base material of a gall resistant fitting is UNS S20161 stainless steel, which offers greater protection from metal stress and better self-mating than standard fittings. Connectors made of UNS S20161 do not require plating or coated finishes that could potentially contaminate processes.
Reducing Particle Entrapment
Available in all pressure ranges, gall resistant fittings come in both male and female face-seal threads. WIKA’s gall resistant option reduces the risk of particle generation and entrapment caused by the wear and tear of frequently mated process connections.
Take silicon wafer fabrication as an example. If particulates become entrapped in the pressure gauge, they can make their way into equipment and toolsets and possibly ruin millions of dollars of integrated circuits.
Numerous tests demonstrate the superiority of gall resistant fittings. WIKA engineers took male and female fittings and repeatedly tightened and loosened the torque to simulate pressure gauge installations. After 20 of these make-break cycles, the threads were examined under magnification to see if galling occurred. It did not.
What’s more, having just one gall resistant fitting is sufficient to eliminate galling. A follow-up test used a non-gall resistant male fitting with a gall resistant female fitting. The results of this second test showed that galling, again, did not occur.
WIKA USA’s Solutions for Pressure Gauges
Challenges caused by cross-threaded or seized fittings can be readily avoided through this simple solution. Making the switch to gall resistant fittings brings about many positive changes, such as improved durability and potential cost savings through the elimination of scrapped product and/or downtime. Gall resistant fittings are available on UHP models 230.15, 230.25, 230.15w/851.3, and 230.25w/851.3. For more information on gall resistant options, contact WIKA today.