At Precision Fabrication & Cleaning, one of our most popular services is precision cleaning for ground support systems. Ground support systems, like the kind used at launch pad sites, need to be cleaned to make sure they function properly and to keep all the workers and equipment on the site safe.
In this article, we discuss what exactly precision cleaning is, how it benefits ground support systems, which companies use PFC’s precision cleaning services, and what our precision cleaning process looks like.
Precision cleaning is more in-depth than just a routine cleaning procedure. It involves several steps and can be a long process, but the results are worth it.
The purpose of precision cleaning is to remove all sorts of contaminants – moisture, scale, dirt, oil, grease, wax, gum, fiber or silt, and any other foreign material – from ground support systems, such as fuel systems and oxidizer systems. These systems deliver a product (for example, RP-1, liquid oxygen, monomethyl hydrazine, and nitrogen tetroxide) to a vehicle.
It’s important to remove all contaminants from ground support systems because once contaminated fuel is transferred into a vehicle’s engine, the engine could become damaged. A damaged engine will lead to poor performance or, at worst, failure and hazardous explosions.
Dirty fuel systems and oxidizer systems pose a serious danger to humans, mechanical equipment, and the environment. Hiring a professional industrial cleaning service like PFC that performs precision cleaning is the best way for companies that own launch pad sites to avoid calamity.
Part of the reason that our clients prefer PFC precision cleaning is that we adhere to their specific precision cleaning specifications.
Below are the cleaning specifications for the companies that we continually work with to clean the ground support systems on their launch pad sites.
- KSC-C-123J (NASA – Kennedy Space Center)
- MSFC-SPEC-164 (NASA – Marshall Space Flight Center)
- RPTSTD-8070-0001 (NASA – Stennis)
- MAP-211025 (Orion Program)
- ISO 14952 (International Standards Organization)
- STP-1012 – United Launch Alliance
- STP-0637 – Boeing
- SPX-00006876 – SpaceX
- 24555-SPEC-0002 – Blue Origin
- IEST-STD-CC1246 – Institute of Environmental Sciences and Technology
- RA1110-025 – Aerojet Rocketdyne
At PFC, our typical precision cleaning process involves 8 steps. This can change, of course, depending on the needs of the client. But in general, these steps cover all the bases for fuel systems, oxidizer systems, and more.
1. Mechanical Cleaning / Descaling
Mechanical cleaning and descaling are accomplished by brushing, pressure washing, shot preening, grit blasting, tumbling, or grinding the surfaces of the fuel system or oxidizer system.
Once the dirt, scale, and other debris are jarred or ground loose, they are completely removed from the system by vacuum cleaning, brushing, blowing, or flushing with clean water or a solvent.
Often, when product passes through pneumatic and liquid systems, a layer of residue tends to build up on ground support systems surfaces. This layer of residue must be removed for two primary reasons.
The first reason is that the grease may be incompatible with the intended service media. In other words, it may interfere with the ground support system’s particular function.
Second, the removal of the grease will allow acids to perform the pickling/passivation process later in a later step.
PFC uses many types of cleaners to perform degreasing safely: Turco 4215 NCLT, Naval Oxygen Cleaner (NOC), Brulin 815GD, Micro 90, Daraclean 282, Amway LOC, etc. Degreasing solutions are most commonly used at low concentrations and elevated temperatures. The increase in temperature improves the cleaner’s effectiveness.” The type of degreaser used, temperature, concentration and contact time is
3. Water Break Free Test
Next, we perform a water break free test to check for contaminants we can’t see on the dry surface of the system.
During the test, the part of the system being tested is dipped in and then rapidly withdrawn from a bath of clean water. If a “break” appears in the water on the surface of the part, this indicates that the surface of the part is contaminated. On severely contaminated parts, the water will bead up in disconnected beads of various sizes.
Passivation is the removal of exogenous iron or iron compounds from the surface of stainless steel by means of a chemical dissolution, which typically involves treating the surface with an acid solution. The solution will remove the surface contamination but will not significantly affect the stainless steel itself.
PFC verifies the passivation process through Copper Sulfate Testing.
5. Visual Inspection
The fifth step of PFC’s precision cleaning process is to perform a visual inspection. Often using a flashlight or a borescope, we visually examine the cleaned surfaces of the part to ensure it’s free of contaminants such as moisture, corrosion, scale, dirt, oil, grease, accumulations of fiber or silt, and other foreign material.
Validation is the process of determining the system’s wetted-surface cleanliness level for particulate and NVR contamination.
Measuring the amount of particulate contamination – also called particulate analysis – is an essential part of precision cleaning. It takes cleaning down to the level of the micron, which is a unit of measurement that is smaller than the human eye can see.
During this step, we verify the cleanliness of the system by measuring the level of particulate contamination on the system’s surface, as well as the nonvolatile residue (NVR). NVR is soluble or suspended material and the insoluble particulate matter that remains after the liquid or solution has evaporated.
For the drying step, PFC uses three different techniques: purge drying with gaseous nitrogen (GN2), oven drying, and vacuum drying.
When vacuum drying, the item is subjected to a part specific vacuum, temperature and dwell time. Once the Vacuum drying process is completed, the item is purged with filtered GN2 until it reaches the minimum required dew point. Dew point is the temperature at which condensation of water vapor takes place at the prevailing pressure, and this portion of the drying process is called dew point testing.
Once the parts are completely cleaned and dried, they must be environmentally packaged to preserved the obtained cleanliness level.
Cleaned and verified ground support system parts are packaged within the same environmentally controlled area where the verification step was performed. However, if for some reason it becomes impractical to package a part in the same environment, we make sure that the environment where packaging takes place doesn’t compromise the part’s cleanliness.
PFC’s 8-step precision cleaning process fulfills the purpose of precision cleaning, which is to remove all contaminants from a given system. It’s why we are the preferred choice for clients like NASA to clean the ground support systems on launch pads.
In doing so, and by adhering to the cleaning specifications that our clients provide, we ensure that vehicles and equipment are able to continue functioning properly and that workers stay safe on the job.
If you’re interested in our services and want to learn more, contact us here.