Welch 1376N CHEMSTAR Vacuum Pump for Pumping Corrosive Gases, 115VAC, PN 1376N-01

The Welch 1376N Chemstar Belt Drive Rotary Vane is a durable vacuum pump with a superior vapor handling capability, primarily for pumping corrosive gasses. The Welch 1376N Chemstar Belt Drive dual stage rotary vane mechanical vacuum pump offers an excellent ultimate pressure of 1x10-4 Torr. These pumps are commonly used for vacuum furnace evacuation, backing turbomolecular pumps, backing diffusion pumps, rotary evaporation, refrigeration system evacuation, epoxy degassing, vacuum sterilization, backing mass spectrometers, freeze drying, vacuum centrifugal applications, vacuum distillation, space research, and other corrosive chemical vacuum processes.

This unique Welch 1376N CHEMSTAR vacuum pump was designed to give you the maximum possible service life when evacuating corrosive gases. However, corrosive gases can cause damage to the most rugged vacuum pump in an improperly configured or improperly operated vacuum system. Please refer to the recommendations made in the CHEMSTAR Owner's Manual (can be downloaded below under AVAILABLE DOWNLOADS) for operating your CHEMSTAR vacuum pump successfully when pumping corrosive gases. We recommend Welch DIRECTORR Gold Oil for this pump and if the flow of strong acids or halogens exceeds 10% of gas flow, you must switch to a perfluoropolyethers (PFPE) such as Fomblin Y06/6, Fomblin is a registered trademark of Ausimont. In addition, if ozone is pumped and its concentration exceeds 100 ppm of the gas flow, a perfluoropolyether (PFPE) oil must be used. Perfluoropolyethers are very resistant to chemical attack by strong acids. These Welch 1376N CHEMSTAR Belt Drive Pumps have a pumping speed displacement of 10.6 CFM. We repair this model and All Welch Vacuum Pumps. All accessories and oils for this pump can be found on this website.

We often get this question:
How do I switch my CHEMSTAR from factory prepared hydrocarbon oil (DIRECTORR Gold) to the very chemical resistant PFPE fluorinated oils (Fomblin Y06/6), and what should I consider when doing this?

First Part Answer
If you are okay with a small amount of hydrocarbon oil left in the pump, then you are good to drain the new pump of as much hydrocarbon as possible, then fill with PFPE FOMBLIN Y06/6. The oil as seen in the sight glass will become milky, as it still has a small amount hydrocarbon oil inside. Overtime, with future PFPE oil changes, the oil will become less milky. The pump will run fine with no issues having the milky mixture, the pressure will be the same, the pump will last just as long.

Second Part Answer
When should I be concerned? Well, it depends on what you are pumping in your vacuum application and at what concentration. The hydrocarbon oil is not compatible with high concentrations of oxidizers, such as hydrogen chloride (HCl), hydrogen bromide (HBr), Oxygen (O2), Ozone (O3) and other oxidizers. If the percentage of oxidizer is above a small amount, then the pump should be rebuilt, completely taken apart, all hydrocarbon oil removed, and the pump rebuilt using only PFPE oil. Welch gives good guidance on this topic, they state “WARNING Do not use DIRECTORR gold oil when pumping gases containing more than 30% oxygen. The use of DIRECTORR gold which is supplied with the pump is a Flammability Hazard if more than 30% oxygen mixtures are pumped. When gases pumped into a CHEMSTAR pump exceed 30% oxygen of gas flow, the CHEMSTAR pump must be prepared with FOMBLIN Y06/6. In these cases, to switch from DIRECTORR Gold oil To Fomblin, the CHEMSTAR pump must be totally disassembled, and all parts cleaned of oil. The pump must then be assembled using Fomblin. Welch can carry out the conversion for you through our repair department. Call Welch factory at 847-676-8800 ext. 1 for details.”

It is helpful to understand why
Hot hydrocarbon oil is flammable and will burn in air or in the presence of an oxidizer. When hydrocarbon oil is heated inside the pump and an oxidizer is present, it can auto ignite, this is called reaching the flash point, it will burst into flames without even having a spark present. If the oxidizer concentration is high, the hydrocarbon oil can even spontaneously explode. This is not the case with PFPE oils, they are not flammable, in fact, they will actually put out a fire, acting as a fire retardant.

Our Recommendation
There are a lot of things to consider when your vacuum application requires pumping of chemicals. We recommend that you study the document prepared by Welch, it is helpful, it covers pumping of acids, halogens, oxidizers, anhydrides, and other chemicals. The concentration of the evacuated chemicals is important, you can lower the concentration by diluting the system with dry inert gases, Welch gives good guidance on dilution practices. Please refer to Welch Vacuum document, see section “USING YOUR CHEMSTAR® PUMP WITH CORROSIVE GASES” 3rd Edition Applications Booklet, download from our website at: ChemStar Owner's Manual and our Application Note in the Downloads Section.