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News
Presentation
Rotating equipment
Skid design
Internal faults
Reciprocating equipment faults
Piping Vibration
Structural vibration

FIELD SERVICE

For more than 30 years, VibraTec has been known for its reliable troubleshooting services.

Onshore and Offshore vibration control is key to ensuring ongoing production reliability and integrity. Leading production operators call VibraTec to address vibration, pulsation, fatigue and other issues affecting their process performance and safety.
Our expert teams are committed to being reactive to our clients’ requests regarding on-site diagnosis and troubleshooting. Such interventions comprise, but are not limited to:

  • Vibration Analysis services:
    • Rotating equipment Condition-Based Monitoring (CBM)
      and remote vibration analysis,
    • Structure and Piping surveys.
  • Advanced Vibration Analysis services:
    • Rotating equipment troubleshooting and Root Cause Analysis (RCA),
    • Structure and Piping failure troubleshooting and Root Cause Analysis (RCA).

Presentation

piping vibration diagnosis
reactivity diagnosis mobilization

Rotating and reciprocating equipment packages are the main sources of vibration on Oil & Gas facilities. However, several faults could lead to vibration level increases. The most significant examples are:

  • Poor rotating equipment skid design,
  • Internal faults (bearings, etc.),
  • Reciprocating equipment faults.

ONLINE MONITORING, CONDITION-BASED MONITORING (CBM)

How much can you benefit from predictive maintenance?

  • 10x Return on Investment (ROI)
  • 25-30% reduction in maintenance costs
  • 70-75% elimination of breakdowns
  • 35-45% reduction in downtime
  • 20-25% increase in production

Moving from scheduled-based maintenance to condition-based maintenance is a paradigm shift across the oil and gas industry. Today, condition-based maintenance is broadly accepted as the best practice for monitoring and preventing plant equipment failure. VibraTec has responded with customized solutions that cover the broad spectrum of safety, quality, value, and cost to fit end-user needs depending on where an organization is in its preventive maintenance journey from reactive to proactive.

The most basic condition monitoring strategy starts with a walk-around program. As a result, portable devices designed for walk-around monitoring can be considered the “gateway to condition monitoring”.

Transform your machines into smart connected things: make the best use of your available PLC data (contact our expert for more details about this solution).

ADVANCED VIBRATION ANALYSIS SERVICES

Detailed field analysis is often necessary to assess and address vibrations issues requiring Root Cause Anaysis (RCA). These on-site diagnoses are performed in 5 steps:

  • Step 1: Installation vibration survey,
  • Step 2: Operating Deformation Shape (ODS),
  • Step 3: Experimental Modal Analysis (EMA),
  • Step 4: Remedial action,
  • Step 5: Validation.

Step 1: Installation vibration survey

The objective of this first approach is to obtain an overview of the vibration issues of the machinery installation. Measurements are performed at selected points all over the package including:

  • Machinery skids,
  • Surrounding piping,
  • Piping supports,
  • Supporting structure.

The measured spectra gives information about the excitation source(s) and critical process conditions. Attention is paid to the equipment rotating frequencies and low frequencies that can be due to flow excitation.

VibraTec mobilizes consultants to site with all necessary measurement equipment to undertake the survey.

Step 2: Measurements when operating – Operating Deformation Shape

The objective is to obtain an overview of the vibration levels for the whole package.

To characterize the package’s dynamic behavior, a mesh of suitably representative points is defined. Depending on the size of the package and the type of problem, 20 to 50 points might be necessary to obtain a complete representation of the faulty installation. If Anti-Vibration Mounts are utilized, their efficiency is verified via measurements above and below the mounts.

Measurements are performed on the equipment body as well as the following components (where relevant):

  • Component bearings,
  • Component fixation points,
  • Package skid,
  • On both sides of Anti Vibration Mountings (if any),
  • Skid fixation points,
  • Discharge and suction piping (if any),
  • Piping supports,
  • Supporting structure.

The measurements are performed during system run up/run down at some points and normal operating conditions for all above points. Measured levels are compared to relevant acceptance criteria to identify critical frequencies. API618 and ISO are used for the machinery and the structure.

The measured spectra are analyzed to obtain necessary information to determine the likely excitation source(s). Specific attention is paid to the component rotating frequencies and their harmonics.

Step 3:  Experimental Modal Analysis (EMA)

Further measurements are undertaken without the package operating. The mesh of points used for the ODS is re-utilized. An impact hammer is used to excite the structure.

The objective of these measurements is to identify the natural frequencies and associated mode shapes of the system. Comparison of ODS and EMA results can identify any natural resonances that might explain the high vibration levels experienced.

When necessary, EMA results can be used during a further step to tune a Finite Element Model in order to evaluate potential structural modifications (in case of resonances) which may provide a solution to the problem.

Step 4: Remedial action

After the measurements are performed, basic analysis is undertaken on-site to determine the likely cause of the vibration. Remedial actions are proposed on-site if they do not require further validation by computation. Typical recommendations that could be proposed on-site include:

  • Additional supports,
  • Modifications of Anti Vibration Mount characteristics,
  • Improvement of rotating part imbalances.

Post-processing

On return to VibraTec offices, data obtained on-site is analyzed in more detail to refine the diagnosis and more precisely identify probable causes (Root Cause Analysis). A summary of the measurements, analysis, etc. is presented in a technical report.

A phone meeting is recommended to discuss results.

Mitigation

Depending on the diagnosis’ findings, it might be necessary to compute the solution using a numerical Finite Element Model (FEM) of the structure. The complexity of the model depends on the diagnosed fault. The modelling process requires detailed information concerning the system (general arrangement, drawings, isometrics etc.).

The FEM is tuned with measured values in order to be representative of the system’s real behavior. Structural modifications are tested and their efficiency evaluated. The FEM tuning helps to reduce errors in the model and greatly improves computation accuracy.

Many causes can explain high vibration levels. Examples include:

  • Supporting structure resonance,
  • Skid resonance,
  • Component support resonance,
  • Abnormal excitation force (unbalance, misalignment etc.),

For the proposed solutions, the criteria that determine efficiency are mainly:

  • The shift of a resonance frequency,
  • The velocity level on a component.

A phone or physical meeting is organized to present and validate the selected mitigation actions.

Step 5: Validation

A validation assessment is recommended by VibraTec after mitigation is implemented on-site, in order to ensure that the vibration issue is fully addressed and resolved.

Rotating and reciprocating equipment

compressor vibration diagnosis
rotating machine skid
offshore pump noise

Excessive vibration levels are often due to a resonance phenomenon corresponding to the coincidence between:

  • The equipment excitation frequency (usually rotation speed and first harmonics),
  • The skid natural frequency corresponding to the first skid flexion or torsion modes or main component rocking modes (driver & driven machines, gearbox).

Poor rotating equipment skid design

equipment structure assembly
pump baseplate mode
skid dynamic stiffness

The damage that can occur on some critical components (bearings, gears), like shaft faults (torsion and flexion modes, unbalance, misalignment), can be an important source of vibration. These faults can be identified by their signature and can usually be anticipated with careful design and maintenance.

VibraTec’s Rotating Equipment Vibration Diagnosis training course gives insight into the identification and comprehension of these types of fault.

Internal faults

oilpan default analysis
machine gearbox diagnosis
time shock signal
ball bearing verification

Diesel engines, reciprocating pumps and compressors are naturally strong vibration sources because of their operational behavior. They generate high levels of excitation over a broad range of frequencies.

The most common faults specific to these equipment packages are:

  • Inefficient Anti-Vibration Mountings;
  • Inefficient decoupling of connected pipework; and
  • Poor design of dampers, anti-pulsation bottles and restricted orifices.

Reciprocating equipment faults

alternating compressor pulsation
anti pulsating bottle vibration-measurements
equipment fixation structure

Piping vibration issues are often highly complex and require the liaison of various technical disciplines (piping, structure, process etc.). The intervention of a specialized piping vibration expert with a global understanding of such issues is often required and highly recommended. With extensive project experience gained from more than 30 years of work in piping vibration studies, VibraTec is a leading international expert in this field.

VibraTec’s piping field services cover:

  • Piping surveys
  • Piping Troubleshooting and Root Cause Analysis (RCA)

Piping survey

Piping survey activities can be split in three phases. The preparation phase comprises the selection of the lines which are the most likely to be subjected to vibration. This line selection is based on basic information:

  • Fluid and piping characteristics (flow-rate, density, diameter etc.)
  • Critical equipment (reciprocating pumps or compressors etc)
  • Reported problems.

VibraTec experts perform a visual inspection of the selected lines, focusing on Small Bore Connections (SBC) and instrument tubing which are known to be among the main locations of fatigue failure. Main line support efficiency is also assessed. Surveys are undertaken in accordance with the Energy Institute document: “Guidelines for the avoidance of vibration induced fatigue failure in process pipework”. During the survey, when a support, an SBC or instrument tubing appears critical, vibration measurements are undertaken.

Vibration levels are measured and compared to vibration limits (VDI, EI Guidelines etc) on the main lines and on the SBC. Levels are measured using a portable measurement device. Following the measurements, data analysis is used to determine the cause of the vibration. Remedial actions are often proposed on-site where they do not require further validation by computation. Typical recommendations that could be proposed on-site include, but are not limited to:

  • Adding new supports,
  • Modifying existing supports,
  • Controlling the unbalance and /or the setup of equipment,
  • Confirming the efficiency of pulsation bottles,
  • Improving design.

If necessary, in-depth diagnosis can be performed on identified critical items

Troubleshooting and Root Cause Analysis (RCA)

The on-site diagnosis is performed in 3 steps:

  • On-site diagnosis (survey, Operating Deformation Shape – ODS, Experimental Modal Analysis – EMA)
  • Mitigation
  • Validation

Prior to undertaking the vibration measurements, it is useful to have all available historic data regarding the piping network (design modifications, issues of concern, process configuration, etc.).

Piping network vibration survey

VibraTec mobilizes consultants to site with all necessary measurement equipment to undertake the survey.

Prior to undertaking any detailed measurements, a visual line inspection is made to detect any abnormal behavior of pipework elements such as small bore connections, inefficient supports, etc. The objective of this approach is to obtain a first pass visual review of the line vibration issues and preliminary measurements to identify critical areas.

Preliminary measurements are performed during system run up/run down and normal operating conditions at selected, representative points on the line(s) in the vicinity of the following elements:

  • Machinery body,
  • Discharge pipe,
  • Piping,
  • Piping supports,
  • Scrubber and cooler,
  • Supporting structure,
  • Valves,
  • Small Bore Connections

Measured levels are compared to relevant acceptance criteria to identify critical frequencies. Energy Institute guidelines and in-house methodologies are used to quantify the vibration risks and identify the sections that may require a more detailed analysis.

The measured spectra are analyzed and provide necessary information to determine the likely excitation source(s). Specific attention is paid to machinery rotating frequencies and low frequencies that can be due to flow excitation.

Where possible, dynamic pressure probes are installed in the pipeline in areas where the highest vibration levels are observed, in order to measure the pulsation levels and identify possible acoustic resonances.

Operating Deformation Shape (ODS)

Representative locations of the pipeline are selected and a subsequent mesh of measurement points is defined. This process serves to characterize the dynamic behavior of the critical area(s) identified during the survey. Depending on the size of the line and the type of problem, 20 to 50 points might be necessary to obtain a complete representation of the problem at hand.

The ODS makes it possible to:

  • Describe the deformation of the line,
  • Validate the efficiency of pipe supports.

Additional strain measurements can be made on the pipe at specific locations using strain gauges. These values are used to validate the mechanical strength of the pipe; they can also be used to tune a Finite Element Model that may be required for mitigation.

Experimental Modal Analysis (EMA)

These measurements are undertaken without fluid flow (non-operating line) using the same mesh of points as that which was used for the ODS. An impact hammer is used to excite the structure. These measurements can be made on critical piping areas and also on Small Bore Connections or Thermowells.

The objective of these measurements is to identify the natural frequencies and associated mode shapes of the system. Comparison of ODS and EMA results makes it possible to identify natural system resonances which may in turn explain the high vibration levels experienced in operating lines.

EMA results can be used to tune a Finite Element Model that may be required to evaluate mitigation actions.

Remedial action

After the measurements are performed, basic analysis is undertaken on-site to determine the likely cause of the vibration. Accordingly, remedial actions can be proposed on-site if they do not require further validation by computation. Typical recommendations that could be proposed on-site include:

  • Additional supports,
  • Modification of existing supports,
  • Improvement of pulsation bottle efficiency.

Post-processing

On return to VibraTec offices, data obtained on-site is analyzed in more detail to refine the diagnosis and more precisely identify the possible solutions. A summary of the measurements, analysis, etc. is presented in a technical report.

A phone meeting is recommended to discuss results.

Mitigation

Many causes can explain the high vibration levels experienced. Examples include:

  • Resonance of the supporting structure,
  • Resonance of the piping,
  • Internal fault of a component (valve, cooler etc.),
  • Abnormal excitation forces (pulsations, mechanical excitation, etc.)
  • Inefficiency of the support.

If a resonance is identified, structural modifications will be required to shift the mode. In the case of a piping resonance, supports may be modified. Depending on the mode shape and the structure design, it might be necessary to compute the solution using a numerical Finite Element Model (FEM) of the structure. The complexity of the model depends on the diagnosed fault. The modelling process requires detailed information concerning the system (general arrangement, drawings, isometrics etc.).

The FEM is tuned with measured values in order to be representative of the real behavior of the system. Structural modifications are tested and their efficiency evaluated. FEM tuning  helps to reduce the errors in the model and greatly improves the accuracy of the computation.

For the proposed solutions, the criteria that determines the efficiency of those solutions are mainly:

  • The shift of a resonance frequency,
  • The velocity level on a component.

A phone or physical meeting is organized to present and validate the selected mitigation actions.

Validation

A validation assessment is recommended by VibraTec after mitigation is implemented on-site, in order to ensure that the vibration issue is fully addressed and resolved.

Piping Vibration

onshore pipe_rack mitigation
piping vibration measurement
welding problem detection

The structures supporting vibrating equipment can amplify vibration levels if not correctly designed. The risk of resonance is important on metallic structures such as platforms, topsides or pipe racks as it can lead to material fatigue and failure. Resonance also needs to be taken into account on concrete baseplates.

When assessing structural vibration, Vibratec typically combines measurements with a Finite Element Model of the structure. The model is tuned with experimental results, after which it becomes possible to compute the efficiency of any proposed modifications. The main objectives are typically:

  • to modify the structure response in order to avoid a coincidence between an equipment excitation frequency and a natural frequency of the structure;
  • to greatly reduce the vibration amplitude by stiffening the structure; and
  • to improve the uncoupling of the vibrating equipment.

Structural vibration

platform structural integrity
platform vibration measurements
well pipe deformation
VibraTec has been approved for French Innovation Tax Credit for 2021. This recognizes our ability to carry out innovative design work for clients.