Oxygen Cleaning: A Validated Process Is Critical For Safety

David Escobar, Director of Engineering at Metso Automation


Industrial oxygen is used for many purposes: in a basic oxygen furnace for making steel, water pollution countermeasures, including sewage treatment, habitability and superfund site rehabilitation, and chemical processes such as production of vinyl chloride, nitric acid, epoxyethane and hydrogen peroxide. It is also used for medical treatment, life support in harsh environments and industrial gasses for welding and other processes.

The production of oxygen has risen from approximately 470 billion cubic feet in 1991 to over 1.5 trillion cubic feet in the U.S. and more than 4 trillion cubic feet globally in 2014.

Oxygen is the most common oxidizing gas and is, of course, highly reactive. When dealing with an oxygen-enriched environment, it is important to control the sources of ignition. Ignition can be caused by many things, among them:

  1. Electrical arcs, which can come from electrical equipment or even static discharge
  2. Friction, which can be generated by the sliding contact of materials within the oxygen-enriched environment
  3. Impact of particles or projectiles internal or external to the enriched environment can generate heat
  4. Resonance, which is vibration-induced heating
  5. Heat of compression (HoC) is the most common cause of explosion due to contamination. Heating is caused by the adiabatic compression of a fluid; this is often called auto-ignition.

Auto-ignition is the phenomenon of spontaneous ignition of a fuel source due to the heat generated by the sudden compression of a gas or HoC. When a valve in a high-pressure or high-velocity oxygen flow is opened or closed quickly, the kinetic energy is converted to increased temperature and potential energy in the form of increased pressure. If the temperature generated by the compression exceeds the temperature needed to ignite non-metallic seals or even the pipe itself, the result is a spontaneously explosion or auto-ignition. When this happens in oxygen systems, the effect can be devastating.

A fire in a process plant

Because the HoC is substantial and can generate thousands of degrees of temperature even at moderate pressure ratios, oxygen systems are designed to limit the pressure drops to control HoC and limit temperature within the autoignition temperatures of the system components.

Thus, it is absolutely essential that contaminants, which can introduce lower auto-ignition temperatures than even the non-metallic seats and seals, be removed from any oxygen system. Any method that achieves the desired cleanliness level is acceptable. CGA 4.4 and the recently issued MSS-SP-138 provide excellent recommendations for cleaning processes.

Oxygen Cleaning A Validated Process is Critical for Safety 2
A technician moves hardware in a clean room using proper protective equipment

CONTAMINANTS TO BE REMOVED

Basically, anything that promotes combustion or impact product purity is considered a contaminant. ASTM G93 categorizes contaminants into three types:

Organics

  • Volatile Organic Compounds (VOC)
  • Hydrocarbon-based greases and oils

Inorganics

  • Nitrates
  • Phosphates
  • Water-based detergents and cutting oils
  • Acids/solvents

Particulate

  • Particles, lint and fibers
  • Dust – Weld slag, etc.

Specifications vary on cleanliness level, methods and validation, and include how much residue is acceptable, what method of cleaning can be used and what kind of inspection must be conducted.

CLEANING METHODS

Mechanical cleaning is used to remove scale, coatings, paint, weld slag and other solid contaminants and can include grit or ice blasting, wire brushing and grinding.

Aqueous cleaning can be with hot water and steam cleaning or alkaline cleaning. Hot water and steam cleaning is effective against water-soluble contaminants, and is normally used with detergent. Alkaline cleaning uses caustic salt in water to create a highly alkaline solution. It is effective against hydrocarbon oils, grease and waxes, and generally is enhanced by agitation and/or jet spraying. Typically this is used for industrial parts washers. This process is greatly enhanced by ultrasonic agitation, but the solvent residue must be removed as well.

Semi-aqueous cleaning uses hydrocarbon solvent and water emulsion, which is effective for removing heavy contaminants from parts like heavy grease wax or hard to remove soils. Emulsion may require agitation to maintain the mixture, and parts must be rinsed before the emulsion can dry. Otherwise, contaminants may re-deposit on the part that was cleaned.

Acid cleaning varies substantially based on the acid used.

  • Hydrochloric acid is used to remove scale, rust and oxides. and to strip platings (chrome, zinc, cadmium, etc.) and other coatings
  • Chromic and nitric acid are used to for passivating, deoxidizing, brightening and removing alkaline residues in addition to cutting oils
  • Phosphoric removes oxides, light rust and fluxes

Acids must be removed completely from the part prior to drying and, depending on the acid strength, may need a neutralizing process.

Solvents can be used without water dilution or emulsion. Alcohol is a common solvent often used to revisit areas of concern identified by black (UV) light inspection. Solvents like alcohol evaporate completely, leaving no residue.

Vapor degreasing is a process in which a solvent is heated until it vaporizes, while the part is maintained at a lower temperature. The solvent then condenses and dissolves contaminants. The part must be oriented so that the condensed solvent can drain from the part by gravity. This method is very effective for inaccessible areas on parts but requires a contained environment for the part during the process.

Any combination of cleaning methods that achieve the desired cleanliness level is acceptable.

INSPECTION METHODS

Visual inspection can be direct, including white light, which is effective in detecting contamination down to 500 mg per square meter. UV (black) light visual inspection identifies contaminants that fluoresce and is effective in detecting contamination down to 40 mg per square meter.

Indirect visual inspection is done in two ways: wipe test and solvent filtering. A wipe test can identify contaminants in locations that have no direct line of sight. Typically, both white light and UV light are used on the wipe cloth, and are effective in detecting contamination down to 30 mg per square meter. Solvent filtering rinses the inaccessible area in solvent, which is then filtered to capture contaminants. The filter is then visually inspected and can detect 100 ml per square foot of low residue solvent and it also uses white and UV light.

Oxygen Cleaning A Validated Process is Critical for Safety 3
White light inspection of cleaned surfaces

Quantitative inspection is done by evaporating the solvent used for cleaning and obtaining the weight of the remaining effluent. Acceptable levels of residue vary according to user requirements.

ADDITIONAL CONSIDERATIONS

Clean room: This provides a designated location where the environment limits dust airborne particles, where clean tools and clean assembly and test equipment can be stored. It can also provide controlled lighting for visual inspections.

Clean test equipment: Pressure test equipment contains contaminants in hoses and pumps. If a test machine cannot be dedicated for clean testing, give special consideration to cleaning of test equipment or alternate testing with clean gas.

Packaging: After cleaning, give specific instructions on how to package the product to preserve cleanliness in shipping and subsequent storage. Consider the role of desiccant as a possible contaminant. Use compatible products or control desiccant to prevent contamination. Consider the addition of actuation and accessories to the valve. Can the actuator be installed and set up without violating the protection? If the protection is compromised, are there procedural steps to identify and remediate any contamination?

SUMMARY

Oxygen cleaning is used to remove contaminants that can significantly reduce the temperature of auto-ignition. There are many methods for doing the actual cleaning. CGA 4.4 and the recently issued MSS-SP-138 provide excellent recommendations, but any method that achieves the desired cleanliness level is acceptable. It is important to know what level of cleanliness your standard process produces. Process validation using a quantitative measurement allows the supplier to have confidence in process quality when using qualitative inspections for production work.


Editor’s Note: The following article was posted on April 20, 2015 in Valve Magazine.com. It is reprinted here for the Reaction Research Society (RRS) with permission from the author and Valve Magazine. The information here is very useful in amateur rocketry and is intended to make our readers aware of the importance of a proper oxygen cleaning process for lines and valves. High purity oxidizers must be handled with care and cleanliness is of paramount importance. The RRS would like to thank David Escobar of Metso Automation and Judy Tibbs, Director of Education at the Valve Manufacturers Association and Editor in Chief of VALVE Magazine.

David Escobar is director of engineering at Metso Automation. Reach him at david.escobar@metso.com.

CGA refers to the Compressed Gas Association. Founded in 1913, the CGA is an organization dedicated to the development and promotion of safety standards in the industrial, medical and food industry. The CGA is comprised of over 110 member companies worldwide working together through the committee system to create technical specifications, safety standards and educational materials; to cooperate with governmental agencies in formulating responsible regulations and standards; and to promote compliance with these regulations and standards in the workplace.

For more information, go to the CGA website:

www.cganet.com

MSS refers to the Manufacturers Standardization Society of the Valve and Fittings Industry. Standard practices (SP) documents are available related to many applications including the standardized practice of oxygen cleaning (ANSI/MSS SP-138). ANSI or the American National Standards Institute has adopted the standard for oxygen cleaning of valves and fittings.

https://webstore.ansi.org/Standards/MSS/ANSIMSSSP1382014

ASTM stands for the American Society for Testing and Materials. It is now an international organization known simply as “ASTM International” with its headquarters in West Conshohocken, Pennsylvania. ASTM publishes voluntary consensus technical standards including ASTM G-93 for the Standard Practice for Cleaning Methods and Cleanliness Levels for Material and Equipment Used in Oxygen-Enriched Environments.

For more information, go to the ASTM International website:

astm.org


Build Your Own Rocket Event with Spaceport L.A.

by Larry Hoffing, Educational Outreach Coordinator, Reaction Research Society

The Reaction Research Society (RRS.ORG) is glad to be a part of an upcoming event with Spaceport L.A. The “Rocket Workshop with the RRS” is an excellent opportunity for anyone who wants to get directly acquainted with rocketry. This event is meant for both professionals and non-professionals alike. From younger students to university students of all fields, to adults, this event is meant to give people the experience of assembling and flying your own rocket.

https://www.facebook.com/spaceportla
Spaceport L.A.’s Facebook page has their upcoming events

The event will begin on Saturday, May 4, 2019 with a subsequent launch of the rockets from the RRS Mojave Test Area (MTA) on Saturday, May 18, 2019. At this event, you can learn about the fundamentals and more practical knowledge of rocketry.

The event will be held at the HexLab MakerSpace in Van Nuys. This is laser-cutting service in the Los Angeles area. Check the Spaceport L.A. website for the details and updates.

HexLab MakerSpace is a place for creative people to have the tools they need to make their ideas real

The RRS standard alpha rocket is a very old, but reliable design still used in the society. Although micrograin propellant is not used anywhere else but at the RRS (where it was initially discovered in the 1940’s), it is a simple and powerful propellant combination that makes for an impressive show of raw power. I have attached an earlier description of the RRS standard alpha rocket below.

After the first session, on the second event, you can go out to the RRS’s private Mojave Test Area (MTA) at Koehn Dry Lake, east of Cantil, California in the high desert. The RRS will handle the propellants, you can see the impressive results from the safety of our observation bunker.

alpha launch 03-25-2017
RRS director of research, Richard Garcia, with his brick as a camera tripod
First of ten alphas right at liftoff
Xavier Marshall and Wilbur Owens; Wilbur gets his first RRS alpha

Amateur rocketry is our passion and purpose and the society is glad to hold this event with Spaceport L.A. and the public.

https://www.spaceportla.com/

Spaceport L.A., our sponsor for this Rocket Build Event with the RRS

For questions, look to the Spaceport L.A. official website linked above. For questions about the RRS rocket build event, contact the RRS Educational Outreach Coordinator, Mr. Larry Hoffing.

events@rrs.org

For any questions about the Reaction Research Society, go to our website at RRS.ORG

March 2019 meeting

Dave Nordling, Secretary, RRS.ORG

The Reaction Research Society (RRS) met for our monthly meeting on March 8, 2019, at the Ken Nakaoka Community Center in Gardena, CA. The RRS was glad to welcome our newest associate member, Jaren Li. After our reading of the treasury report, we began the agenda.

[1] Preparing for the RRS symposium, Saturday, April 27, 2019

The first topic was the status of the forthcoming 2019 RRS symposium. This will be an all-day event, Saturday, April 27, 2019. Frank Miuccio, our symposium coordinator, was happy to report we have confirmed Cal Poly Pomona and Northrop Grumman as attendees. With nearly 200 Event-brite tickets sold already, we have 20 exhibitors and nearly a full roster of speakers throughout this all-day event.

https://www.eventbrite.com/e/rrs-2019-rocket-and-space-exhibit-symposium-tickets-54839067126

The RRS will need the help of our membership for setting up on the night before. Also, we expect a good crowd on Saturday and we’ll need our membership again to help support the number of activities going on behind the scenes. The executive council will be contacting our members to enlist their support for specific tasks in the next few weeks. The one thing that everyone can do is spread the word and share our flyers with those interested in coming.

first design of the 2019 RRS symposium flyer, Jan 2019

[2] Improvements to the RRS social media presence

This is to be a regular agenda topic to be led by our two media officers, Bill Janczewski and Alastair Martin. In their absence, the society discussed a few common sense things that will be helpful. Including links in our Instagram and Facebook postings back to the RRS.ORG website should help bring more people to read about us. Also, the RRS should track the number of hits our sites are getting as a way of measuring improvement.

Alastair Martin held the second podcast for “Rocket Talk Radio” at his Hollywood studio. Richard Garcia and I both were pleased to be guests on his show as we talked about the timely subject of Small Launchers. There’s been a lot of recent activity in this area with new businesses such as RocketLab, Vector Space Systems, Relativity Space and Firefly Aerospace entering the market. This project is through Alastair’s company, Production Tribe LLC. You can find Alastair’s podcast at his website at Watch Hollywood -dot- TV:

http://watchhollywood.tv/

Frank Miuccio attended a seminar at the University of Southern California (USC) early this month on leadership of non-profit groups. He said he got a lot of practical advise and suggestions for improvement. He did not have his findings summarized for the March meeting, but he can elaborate on his experiences at the USC seminar at the next meeting.

[3] RRS Mission Statement

A mission statement is a short statement of purpose to describe why an organization exists. After reviewing a few drafts, the society decided to use statements made in our articles of incorporation, but it has not been posted on our website until now. The RRS mission statement can be found near the “Donate” button on the main toolbar of the RRS.ORG website.

[4] RRS Website Articles and Publication Guidelines

It was suggested that RRS ought to publish a set of guidelines for new members and contributors to the RRS.ORG website. The society encourages all of our membership to do more than simply discuss their ideas, but to put them down into writing for the wider audience to see. Our society is one of builders, thinkers and experimenters. We have a long legacy of past articles, but what is equally important is that we continue to contribute to our growing body of knowledge.

The initial set of publication guidelines for website articles was sent to our society membership a couple weeks ago. Although I have not received any formal feedback, the society decided at the March 2019 meeting that those initial publication guidelines will be published both on the RRS.ORG website and on our Facebook page. The society reserves the right to edit and holds the sole discretion to publish articles or not. However, at this time, the RRS is very interested in what kinds of things our membership would like to hear about. More importantly, the society would like our membership to contribute an article.

[5] Loyola Marymount University base11 Liquid Rocket Competition

The RRS has been working with Loyola Marymount University (LMU) in Westchester, CA, providing them with guidance on their liquid rocket vehicle design that will ultimately compete in the base11 Space Challenge. A few members of the LMU team were in attendance at the March 2019 meeting of the RRS. The goal of the competition is to be the first university group to fly a liquid rocket to an altitude of 100 km for a prize of $1,000,000 USD. A link to the base11 home page is below.

The LMU team are very busy assembling their Preliminary Design Review (PDR) submitted presentation which is due in the next few weeks. They were able to ask questions of the society members present on details relevant to their liquid rocket.

Pedro Sales and James Hribal of Loyola Marymount at the March 2019 meeting of the RRS.

Per our charter to support academic groups and our membership, the RRS has supported other liquid rocket competitors in this competition including University of California, Los Angeles (UCLA). Many of the participants in these competitions later become members of the RRS as it is a very exciting thing to build a rocket of your own.

[6] The LR101 Project with Tomorrow’s Aeronautical Museum

RRS members, Wilbur Owens, Xavier Marshall and myself (Dave Nordling) have joined a project hence known as the “LR101 project”. This project is in coordination with Tomorrow’s Aeronautical Museum (TAM) at the Compton Airport in Compton, CA. This project team also includes students at Compton High School and at the local Compton College.

https://www.tamuseum.org/

The short term goal is to build a suitable static test setup to hot-fire an LR101 vernier motor at the RRS Mojave Test Area (MTA). A link to the Heroic Relics website is below for more details on this small auxiliary rocket motor used in both the prior generation of Atlas and Delta vehicles. This small legacy rocket has been the core of a few liquid rocket projects in the past including at least one at the RRS.

http://heroicrelics.org/info/lr-101/lr-101.html

The primary goal of this project is to renew and expand the RRS presence in liquid rocket testing. The team is working out the basic sizing and requirements at this stage. Later this summer, the RRS members on the TAM team can provide an update.

An LR-101 motor sits on the table at the February 2019 RRS meeting at the EAA 96 hangar.

[X1] Update on the RRS Educational Events

Frank, Larry and Osvaldo gave an update on the latest educational event that the RRS started with Compton Elementary on March 8th. The program is well underway and they plan to finish with a scheduled launch event at the MTA on April 6th. The program, known as “Rockets in the Projects” is in partnership with the LAPD Community Safety Partnership (CSP). This partnership has been very successful in the year and half it has been in operation having had over 100 students and counting participating in the project. Not only does the society get the chance to give back to younger students, but also a chance to inspire younger people to be active in rocketry and science as they grow older.

https://www.facebook.com/lapdcsp

[X2] Rocket Statue On Display at the 2019 RRS Symposium

The RRS events coordinator, Larry Hoffing, raised a question about the Rocket Statue designed by our society director of research, Richard Garcia. Although this statue was designed to be a permanent fixture inside the main gate at the RRS MTA, Larry had asked if a model could be assembled in time to have it on display at the Ken Nakaoka community Center when we hold the symposium on April 27, 2019.

Richard Garcia’s rocket sculpture concept; soon to be seen at the RRS MTA

Based on available resources and time, it seems unlikely to happen, but the RRS has managed to do great things in a short amount of time before. We shall see…

[X3] Cal Poly Pomona visit to the RRS

As a last minute addition to the agenda, James McPherson of Cal Poly Pomona made a short presentation to the society. James is the leader of the solid rocket team for the FAR1030 competition. The RRS has had a lot of experience in helping university groups with many aspect of solid motor design and build at the MTA. James had outlined a plan for their motor construction and the RRS was glad to review it. We did not have sufficient time at the March meeting to discuss Cal Poly Pomona’s project in detail, but we hope they can come back for the April meeting.

Jaren, Laila and James of Cal Poly Pomona stopped in to the RRS March 2019 meeting.

IN CONCLUSION

Our next meeting will be Friday, April 12, 2019, at 7:30pm at the Ken Nakaoka Community Center in Gardena. We’ll certainly be talking more about the symposium as it will be happening just two weeks later on April 27th. We also expect to have a summary from the next launch event at the MTA on April 6th.

If there are any questions or corrections, please contact the RRS secretary.

secretary@rrs.org