Non-destructive testing (NDT) helps oil and gas operators evaluate equipment condition without damaging the equipment being inspected. But the quality of an inspection does not depend only on the NDT method or inspection equipment. The condition of the surface being inspected can also affect how effectively technicians can examine the equipment.
Oil and gas equipment can accumulate scale, hydrocarbon residue, sludge, corrosion products, dirt, and other process deposits during normal operation. These materials can cover the surfaces that inspectors need to examine and may make it more difficult to identify corrosion, pitting, cracks, weld conditions, or other indications.
That is why cleaning before NDT inspection can be an important part of inspection preparation.
Rock Hill Industrial provides industrial cleaning and NDT testing services for oil and gas and other industrial applications. Its NDT division provides Level I, II and III services along with mobile inspection capabilities.
Why Clean Equipment Before NDT Inspection?
Industrial equipment does not remain clean during normal operation.
Process fluids can leave behind deposits on piping, vessels, valves, heat exchangers, separators, flow iron, and other equipment. Depending on the process, these deposits may include:
- Scale
- Sludge
- Hydrocarbon residue
- Corrosion products
- Sand and sediment
- Grease and oil
- Process residue
- Other accumulated contaminants
When these materials remain on an inspection surface, they can interfere with access and visibility.
RHI’s industrial cleaning guidance notes that deposits can hide corrosion, pitting, cracks, surface damage, and weld conditions. Cleaning can provide maintenance and inspection personnel with better access to the surfaces that need to be evaluated.
The cleaning requirement depends on the equipment, deposit type, inspection method, and condition of the surface. There is no single cleaning method that should automatically be used for every NDT project.
What Equipment May Need Cleaning Before NDT?
The required preparation depends on the equipment and its operating environment.
Oil and gas facilities may require cleaning and inspection support for equipment such as:
Piping and Flow Iron
Piping and flow iron can accumulate scale, corrosion products, hydrocarbons, and other process residue.
Cleaning can expose the inspection area and provide better access for technicians performing the required examination.
Valves and Pressure-Containing Components
Valves, check valves, pressure relief valves, and other components may require cleaning before inspection depending on the type of NDT being performed and the condition of the surface.
RHI’s NDT services cover equipment used in wireline, pump-down, coil tubing, flow-back, and related oilfield applications.
Heat Exchangers
Heat exchangers can develop significant fouling during operation.
Depending on the process, deposits can include mineral scale, hydrocarbons, sludge, biological material, and corrosion products. RHI provides heat exchanger cleaning using industrial cleaning methods selected for the equipment and fouling conditions.
Cleaning may be coordinated with inspection activities so that the equipment is ready when the inspection team begins work.
Separators and Process Vessels
Separators can collect sand, hydrocarbon residue, sludge, scale, and other process deposits.
Cleaning before inspection can help expose internal surfaces and components that may otherwise be covered by accumulated material. RHI specifically identifies cleaning before inspection as an important consideration for industrial separators.
Choosing the Right Cleaning Method
The cleaning method should be based on the equipment, material being removed, surface condition, and project requirements.
Using excessive pressure or an unsuitable chemical process can create unnecessary equipment risks. The objective is not simply to make equipment look clean. The objective is to prepare the required surfaces appropriately for maintenance or inspection.
High-Pressure Water Cleaning
High-pressure water cleaning can remove suitable deposits such as dirt, sediment, loose scale, process residue, grease, and certain other contaminants.
The appropriate pressure, flow, nozzle configuration, and cleaning technique depend on the equipment and material being removed.
Hydro Lancing
Hydro lancing can be used for demanding industrial cleaning applications, including equipment with internal tubes and passages.
For heat exchangers and similar equipment, high-pressure water can help remove deposits that restrict flow or cover surfaces requiring inspection.
Chemical Cleaning
Some deposits are difficult to remove through conventional mechanical cleaning.
Chemical cleaning can be considered when the material is chemically soluble or difficult to remove using water alone. The chemistry must be selected based on the deposit, equipment metallurgy, operating history, and project requirements.
RHI provides chemical cleaning for industrial applications where chemical treatment is appropriate.
Cleaning and NDT Should Be Planned Together
One of the most important parts of inspection preparation is coordination.
Cleaning, equipment isolation, access, inspection, repairs, and return-to-service activities may all be part of the same maintenance window.
If cleaning is completed too late, the inspection team may be waiting for access. If the cleaning scope is incomplete, additional work may be required before inspection can continue.
For planned shutdowns and turnarounds, cleaning should therefore be considered during the early planning stage rather than treated as an unrelated task.
RHI’s shutdown planning guidance identifies cleaning as an upstream activity that can affect inspection and mechanical work during a turnaround.
A Practical NDT Preparation Process
Although every project is different, a typical preparation process can include several stages.
1. Review the Equipment
Identify the equipment requiring inspection, its operating history, previous inspection findings, and the areas that need access.
2. Identify Contamination
Determine what deposits or residue are present.
Scale, hydrocarbons, sludge, corrosion products, and other materials may require different cleaning approaches.
3. Select the Cleaning Method
Choose high-pressure water, hydro lancing, chemical cleaning, or another appropriate method based on the equipment and contamination.
4. Prepare the Equipment Safely
Equipment should be properly isolated, depressurized, drained, and prepared according to the facility’s safety procedures before cleaning and inspection activities begin.
5. Complete Cleaning
Cleaning crews remove the deposits that interfere with access to the inspection surfaces.
6. Confirm Inspection Readiness
Once cleaning is complete, the inspection team can evaluate whether the required surfaces are accessible and suitable for the planned NDT method.
7. Perform NDT
The appropriate NDT method can then be performed according to the inspection requirements.
8. Document Findings
Inspection results, cleaning work, observations, and maintenance recommendations should be documented as part of the equipment record.
How Cleaning Can Support Different NDT Methods
Not every NDT method has exactly the same surface-preparation requirements.
For example, liquid penetrant testing requires a clean and dry surface. ASNT explains that contamination or moisture can interfere with penetrant entering surface discontinuities, reducing the effectiveness of the inspection.
Other inspection methods may have different preparation requirements.
This is why the cleaning scope should be coordinated with the inspection method rather than selecting a cleaning process independently.
The NDT technician, inspection requirements, equipment condition, and cleaning team should all work from the same project scope.
Cleaning Before NDT Can Improve Inspection Access
The purpose of cleaning before NDT is not to replace the inspection.
Cleaning and inspection serve different purposes.
Cleaning removes contamination and deposits.
NDT evaluates the condition of the equipment without damaging it.
When these activities are properly coordinated, inspectors can access the surfaces they need to evaluate while maintenance teams can use the inspection findings to make better decisions about repairs, continued operation, or additional maintenance.
RHI provides both industrial cleaning capabilities and NDT testing services, allowing facilities to coordinate related cleaning and inspection requirements through one industrial service provider.
Preparing for an Oil & Gas Equipment Inspection
Before scheduling cleaning and NDT work, facility managers and maintenance teams should consider:
- What equipment needs to be inspected?
- Which surfaces require access?
- What type of deposits are present?
- Which NDT method will be used?
- Does the inspection require a clean or dry surface?
- Is the equipment part of a planned shutdown or turnaround?
- Are confined-space or atmospheric hazards involved?
- How will cleaning wastewater and removed deposits be handled?
- Does the cleaning scope need to be completed before the inspection team arrives?
Answering these questions early can reduce delays during the maintenance window.
RHI USA for Industrial Cleaning and NDT Support
Rock Hill Industrial works with oil and gas and other industrial facilities on equipment cleaning, inspection preparation, and NDT testing.
Its industrial cleaning services include high-pressure water cleaning, chemical cleaning, heat exchanger cleaning, hydro lancing, scale removal, and other industrial cleaning methods.
Its NDT division provides Level I, II and III services and mobile inspection units for onsite applications. The company lists inspection and testing capabilities for wireline, pump-down, coil tubing, flow-back, reverse units, nitrogen equipment, and related oilfield equipment.
If your equipment needs cleaning before inspection, the cleaning scope should be planned around the actual equipment condition and the NDT requirements.
Contact RHI USA
Preparing equipment properly before NDT can help inspection teams reach the surfaces they need to evaluate and can make cleaning, inspection, and maintenance activities easier to coordinate during a shutdown or turnaround.
RHI USA provides industrial cleaning and NDT services for oil and gas and other industrial applications.
To discuss an equipment cleaning or NDT project, contact RHI USA at 844-762-4455 or visit the company’s website at rhiusa.com. RHI’s current NDT service page also lists Dominic Jones, Regional Manager, NDT Division, at 580-302-4897 and dominic@rhiusa.com for NDT inquiries.