MTA Launch Event, 2021-08-28


by Dave Nordling, Reaction Research Society


The RRS Mojave Test Area (MTA) was used by the student group, Michigan Aeronautical Science Association (MASA) of the University of Michigan at Ann Arbor.  Given the remoteness of the RRS MTA and the great distance that the Michigan team was willing to travel, MASA had planned an extended test campaign to use the site for their cold flow and ultimately hot-fire their RP-1/LOX 2,550 lbf liquid rocket engine.  Originally planned for a week, the team arrived on Monday, August 16th, and continued to use the MTA site through August 28th.  In the end, Michigan faculty called the end of the MASA test series as the new semester was starting and many materials needed to be returned before MASA left southern California.

The MASA logo on the back door of the mobile trailler.
Initial checks of the mobile propellant supply trailer. Over the road travel loosened a lot of plumbing joints.

MASA is a new student group to the society and had very ambitious goals in what they wanted to accomplish in the planned test series.  Typically, the RRS will work with new universities and new clients over a period of many months before agreeing to a first test series at the MTA on a weekend campaign.  Proper planning is an essential requirement for success and the RRS must become thoroughly familiar and comfortable with all planned use of the MTA site.  Like with all attendees to the MTA, indemnification waivers were required from all attendees including spectators.  MASA limited their staff to only essential personnel and ran a day and night shift to both safeguard their equipment through the night and provide continuous support to prepare for the next day’s events.  The team was able to find rented housing accommodations in the local areas of California City and Ridgecrest.

Nate Campbell verified valve functions in conjunction with the mobile control trailler.
The MASA control room was well equipped and was able to safely and remotely conduct test operations.
More leak checks under the rising moonlight and electric lamps at the RRS MTA.

MASA has had a couple years of experience with their propellant flow systems in laboratory tests at the university and was willing to hold several meetings with RRS members sharing their full test procedures and schematics, and answer questions posed by RRS pyrotechnic operators in advance of their arrival.  The MASA fluid systems had many appropriate safety features and used high quality valves and parts.  MASA has developed a control system that uses motorized needle valves in place of a pressure reducing regulator for independent propellant tank pressure controls.  MASA had conducted many tests of this system and held several tests to confirm proper operation in the early steps of their MTA campaign.

The MASA liquid rocket engine, RP-1 and LOX, rated for 4300 lbf thrust but the hot-fire goals of this campaign was 2550 lbf.

MASA’s system designs also had some problems with the nitrogen compressor (booster) system being unable to operate due to a regulator failure. The team was able to bypass the unit, but it limited the top pressure of the blowdown tests to the bottle pressure (2000 psi). A few changes were necessary for vent line routing to improve operational safety. Remote pressurization operations were safely executed but proceeded very slowly and thus a great degree of boiloff in the LN2 limited run time.

The composite overwrapped pressure vessel (COPV) originally was intended for compressed natural gas service in ground vehicles. These vessels have a good safety record in demanding applications and are often used in de-rated aerospace applications.
The MASA team made several changes to their vent line routing for improved safety.

The event was successful in some respects that it gave the students a practical understanding of how to conduct test operations under desert conditions.  It also revealed some of the shortcomings in their plumbing design (leaks) which they were able to fix well enough to get to cold flow with cryogenic LN2 and water on the last day of testing (when this report is dated).  The cold flow tests provided useful data in their control algorithm which will be useful to the next series of tests.  MASA also gained experience in safe cryogenic tanking and operations with these hazardous fluids.

MASA team proceeded into LN2 tanking of their oxidizer propellant tank for the cold flow test through their engine and plumbing.

Logistics was a big challenge for the MASA team due to errors in their communication with local suppliers.  Nitrogen and helium gas bottles were significantly delayed and cryogenic liquid nitrogen cylinders also were very late to arrive at the MTA.  Some of these problems can be easily mitigated for the next test campaign now that relationships have been better established.  sex shop While MASA was disappointed with some of the outcomes from the test series, they are interested in returning to the RRS MTA in the latter part of this calendar year.  This follow-on test series will be discussed at length in the coming months.

A gang of nitrogen bottles sit chained togeither in a pressurant feed manifold.

The society was similarly challenged in supporting this MASA campaign.   The society is grateful to everyone who assisted at the MTA (Osvaldo Tarditti, Waldo Stakes, Bill Inman and myself) or those who gave their comments and concerns (Larry Hoffing, Jim Gross).  Several members spent multiple days at the MTA both during the week and on weekends.   The RRS provided the necessary oversight during the hazardous portions of the testing campaign which was particularly difficult to schedule during weekdays.  The MASA team was very open and disciplined in their interactions with the society.  The RRS was also glad for the University of Michigan’s support and communications throughout this event.

It was a challenging event which was made possible by the contributions of many RRS members over many days.  Frequent communication between MASA faculty and the RRS was a firm requirement on all days of this tenacious campaign and the MASA team provided daily briefings on their progress.

The MASA team showed tremendous dedication and perseverance sex shop over this extended campaign in the summer heat of the Mojave deset.
Cold flow testing complete with pressurized LN2 through the oxidizer path and water through the fuel path.

This testing campaign and current RRS policies will be discussed at the next monthly meeting, 9/10/2021.  Pursuant to our mission statement, the society is glad to support sex shop projects of this kind to universities capable of conducting safe experiments at our unique testing site and to those who are willing and able to provide the society with sufficient advance notice to review their reports, schematics and inspect their hardware.  This campaign is firm proof that we will need more licensed pyro-ops and more members available to support any similarly extended test series in the future if they are accepted by the council.  By building and enforcing a consistent and fair policy for all new and prior clients, the RRS can better operate to the benefit of everyone.

All requests to use the RRS MTA must be made to the RRS president and reviewed by the executive council.  For any questions about this test series or any future test series, please contact the istanbul escort RRS president.

president@rrs.org




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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