October 16 2020 Process Analytical
Getting the performance results you want from process or analytical systems requires good design as well as thought toward maintaining the system throughout its life.
At SilcoTek we coat thousands of process and analytical flow path components, like, tubing, fittings, valves, sample cylinders and other flow path components, a year with our inert CVD barrier coatings. We know that for the customer to get the most out of their process or products, they not only need a high purity corrosion resistant barrier coating, they need reliability.
Customers need to understand that proper component selection, careful assembly, and periodic maintenance of silicon coated flow path components can mean the difference between getting reliable results efficiently and system failures. Nobody wants a system failure and they don't want yield or product failures. That's why taking a few simple steps before and after product use make all the difference.
In this blog post you will learn.
When building a process sampling system, analytical flow path, or any product system that utilizes SilcoTek coatings; be sure to use flow path components that assure proper long term operation. Components should be properly sized for the application, our coatings don't significantly impact component dimensions or volumetric calculations but they should be able to be disassembled in order to be properly coated and inspected.
Internal O-rings, plastic components, or other parts not rated for our process temperatures cannot be coated. You'll also need to select the right coating for your application. We have an easy online tool that can help you choose the right coating that best fits your applications. Click on the box below to go to our Coating Selection Guide.
Need help finding the right coated sample cylinder or valve? You can find manufacturers that offer inert coated sample cylinders, valves, fittings, filters and regulators on our Buy Coated Products Page.
HBr Corrosion Rate
Coupons after HBr corrosion testing
When installing SilcoTek coated tubing you should follow the general design criterial outlined by the tubing manufacturer. Our coating will not change the pressure rating or flow characteristics of the tubing. Calculate the flow rate and overall product volume the systems needs to convey. Then match tubing specifications to desired performance. Most tube suppliers offer detailed product data, using an example from Handy Tube Corporation, you can see their data sheets offer extensive information about tube sizing and capabilities.
Assembling Flow Path Components
Inspect canisters, fittings, valve, or regulators or other threaded components for damage, especially on the threads. Check for burrs, gouges or nicks, crossed thread damage, galling damage and damage to the valve seat. If you're using a relief valve, be sure there is no sign of damage to the relief valve or burst disk. Repair any damage and thoroughly clean threads before assembly. Inspect the inside shoulder of the sample cylinder or canister for corrosion and particulate matter.
Galling can occur when two parts of similar material are connected under compression and the heat generated "cold welds" the parts together. Galling can occur when threading valves into stainless steel sample cylinders. Also galling can occur when two SilcoTek® treated threads, compression fittings or NPT fittings are assembled. Be sure to apply PTFE tape to valve threads when assembling sample cylinders.
If both mating parts must be coated, then SilcoTek recommends using anti Seize compounds made from Silver, Moly or Nickel: For sample cylinder applications refer to the instructions pertaining to the use of Teflon tape on the valve NPT prior to installation. Want to learn more about thread galling? Here's a thorough article on galling from Machine Design.
For processes that require optimal cleanliness and purity, clean components before assembly. Components should be cleaned to oxygen service specifications or better, if using for high purity applications. Be sure the solvent used for cleaning will not leave a residue. Solvent residue can be as big a contamination source as the material being cleaned. Here are some tips for cleaning SilcoTek® coated products:
Develop an inspection plan and keep an inspection calendar to be sure sample cylinders and valves, regulators or other critical components are periodically inspected. Inspection tips include:
For Silcolloy® and Dursan® coated cylinders, layer appearance and surface finish can vary from lot to lot. Small variations in surface thickness (measured in angstroms) can impact layer appearance. The surface finish should be bright and free of defects, but original surface condition can have a major impact on final surface quality.
Under normal use, your treated items should deliver outstanding performance for years to come. However; effective lifetime is dependent on the severity of the environment. Factors that can impede performance are:
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