VDN Newsletter 2016-2 - December 2016

  Static Equipment & Structures (Piping Vibration & Fatigue)

1  Repairing a pipeline subjected to ground-borne vibration

High-speed compressor in Brazil

Pipeline anomalies discovered under railway

An in-line inspection (ILI) of a 30” crude oil pipeline identified significant features located between two girth welds, 36 meters apart. These features were located beneath and in close proximity to the Bo'ness and Kinneil railway, near Edinburgh, Scotland. The inspection identified several external corrosion clusters and two features with peak depths above 50% wall thickness. In addition, two dents associated with metal loss were identified, which were located under the railway crossing and within an existing concrete sleeve that was installed by auger boring during the pipeline construction. [ACCORDION_1]

2  Coming soon: Viridian — free web tool to assess piping vibration

Viridian - EI web tools for pipework and thermowell assessments

Assess your piping vibration against industry standards with our new web-based tool.​

See your vibration concerns in a graphical and easy-to-use interface, quickly produce detailed reports, and much more.

Pipework assessments are done against the Energy Institute standard document “Guidelines for the avoidance of vibration induced fatigue failure in process pipework”. Thermowells are assessed against ASME PTC 19.3-TW-2016.

Contact us for more information, or watch for the release date in our next newsletter.

  Machinery Analysis

3  New guidelines aim for better high-speed compressors, reduce torsional vibration risks

High-speed compressor in Brazil

Lack of standard for high-speed compressors

Separable reciprocating compressor system technology has evolved greatly in the past 50 years with continual increases in operating speeds and brake horsepower to meet demands of gas storage and transmission applications. However, expertise for the appropriate design, analysis and fabrication of packaged compressor systems for these high-speed, high-power applications has been found lacking by many owner and operators.

One of the main factors identified in problem installations is the lack of a standard relating to high-speed, high-power separable packaged compressors. [ACCORDION_2]

4  Taking a “big picture” view of centrifugal compressor surge

Dynamic surge analysis

Surge control response time factors

A centrifugal compressor’s surge control system is a combination of its recycle valve, valve control system and its integrated control algorithms. It is responsible for detecting the proximity of the compressor operating point to the surge control line. A successful anti-surge control system must meet a certain control response time to restore positive flow to the compressor.

Two factors dictate this response time: [ACCORDION_3]

  Rotating Equipment Reliability

5  Shaft alignment: tackling thermal variation and dynamic forces

Misaligned shafts are costly

Misaligned shafts can be costly for operators. They apply excessive force on bearings, couplings and seals, reducing the operational life of these components and the reliability of the rotating equipment package. This recent case highlights the impact that thermal growth of equipment and pipework has on shaft alignment when going from a cold condition to steady-state operations. [ACCORDION_4]

  Noise Management

6  Noise risks in the gas industry

Noise survey in gas processing facility

Assessing noise risks and undertaking surveys on-site involves a detailed understanding of gas compression equipment and operations.

Noise control is a growing concern for owners and operators of production facilities and pipeline stations. Increasing environmental and occupational regulation on city, state and federal levels often requires a noise impact assessment for new facilities. Risk of hearing damage to workers at a facility, or exceedance of environmental noise limits can lead to re-work, modifications or implementation of noise controls on existing stations. [ACCORDION_5]

  Field Engineering & Troubleshooting

7  Vibration-induced fatigue failures of discharge bottle fitting connections

Predicted shell mode on-discharge bottle (FEA)

Vibration assessment of complex geometries

Field measurements are the most common method to quantify fatigue risks on piping and vessels subjected to vibration. Typically, analysts compare recorded vibration levels against industry-standard acceptance criteria. However, for complex geometries of piping and vessels, using vibration guidelines as an acceptance tool for fatigue risk can be limited. In some cases, where stress raisers and structural discontinuities are present, vibration guidelines can be non-conservative.

Fatigue failures on discharge bottles

An operator found a series of fatigue failures on welded fittings of reciprocating compressor discharge bottle nozzles. Since units of identical design operate throughout the area, any additional fatigue risk to these units had to be assessed. Due to the complex nature of the geometry, a finite element model was built as vibration measurements alone were not accurate enough to quantify the risks.

Vibration measurements and dynamic strain measurements were carried out, and results were compared with strain and vibration levels calculated by the finite element analysis. An acceptance guideline for the specific geometry was determined, which could then be compared with other units in operation.

Paper describes assessment methodology and recommendations

This paper, presented at the Gas Machinery Conference 2016, describes:

  • Methodology to quantify fatigue risks on units with similar pulsation bottle designs, through both field testing and analysis
  • Considerations for minor geometric differences between units
  • Recommendations for performing vibration measurements on complex geometry piping
  • Guidance on when vibration measurements alone cannot be used to determine fatigue risks
  • Lessons learned regarding the design of fittings and welded discontinuities on suction bottles

Read the full paper (PDF)

  Anti-Vibration Products

8  Vibration clamps — an easy way to avoid failures

DamperX damper clamp reduces vibration by 40 to 90%

DamperX™ damper clamp: field testing has proven a 40 to 90% vibration reduction compared to conventional and other lined clamps.

Piping vibration is common near machinery

Pipework near vibrating machinery can be particularly susceptible to problems, often exacerbated by the use of incorrect clamps. If not addressed, this can lead to long-term asset integrity, reliability and safety concerns. Besides loss of production from downtime, there are even greater risks from effects on worker safety, the environment and corporate liability.

Conventional clamps are not made for vibration applications

Standard pipe clamps are not recommended for pipework near vibrating machinery as they lack the required stiffness to restrain vibration loads, and do not prevent vibratory loosening of bolts. With nearly 50 years’ experience in solving vibration problems, Wood Group's vibration, dynamics & noise team (formerly BETA Machinery Analysis)  has developed clamp designs specialized for vibration service.

How vibration clamps prevent failures

Vibration clamps are superior to standard designs due to:

  • Bolt stretch. Insufficient bolt stretch is a well-known issue causing vibration loosening, resulting in failures. Wood Group’s vibration clamps have longer bolts and sleeves, increasing bolt stretch by three times over conventional clamps.
  • Material. An extra-rugged construction ensures reliability even in highly demanding environments. All material is primed for corrosion; additional plating and custom finishes are available.
  • Damping. For additional vibration control, Wood Group developed the DamperX™ clamp. This optional feature is ideal for resonant or higher vibration applications because it absorbs vibration energy while reducing stress on the surrounding piping system.
  • Thermal expansion. Wood Group developed vibration clamps for thermal applications (eg, where temperature cycling occurs). Specialty lined and slotted clamps are designed with vibration control in mind while allowing for thermal growth (providing both stiffness and flexibility).

Vibration clamps are field proven

DamperX vibration damper clamp
Major operators in North America and Asia are now using DamperX in their facilities

Wood Group’s vibration clamps are field proven and have been successfully applied in demanding compressor and pumping applications. Additional support includes:

  • Piping vibration design services; main line, auxiliary piping and small-bore piping.
  • Pipe stress, transients, including water hammer, and other excitation sources (eg, vibration, acoustics and pulsation).
  • Field inspections and troubleshooting.
  • Additional vibration control solutions (damping, absorbers).

Clamp loosening makes this vital piece equipment redundant in minimizing vibration impact. Wood Group’s vibration clamp is a more effective approach to avoid fatigue failures, reduce downtime and extend asset lifetime.

Learn more about Wood Group's vibration clamps

9  New principal in turbomachinery group

Philippe Loustau 

Phillipe Loustau

We are excited to announce that Philippe Loustau (MSc, Mech Eng) will lead the troubleshooting and turbomachinery team in Houston.

Philippe Loustau is a principal engineer with a focus in turbomachinery and machinery analysis. He has over 15 years of consulting experience in Europe and North America. His specialties include rotor dynamics, fatigue, troubleshooting, finite element analysis, root cause failure analysis, material science and machinery design analysis.



10  Upcoming conferences

Date Conference Paper Place
30 Jan - 2 Feb API Inspection Summit “Vibration-Induced Fatigue -
A Risk-Based Approach“ 
Galveston, Texas
31 Jan - 2 Feb Predictive & Preventive Maintenance, Reliability & Asset Integrity Forum "Inspection Planning Using RBI and IOW Best Practice” Brisbane, Australia

11  Training schedule — coming soon

Stay tuned for our training calendar, coming in spring 2017.

Visit the SVT training website for training opportunities in Australia.