Condition monitoring of LNG plants

Picture of LNG plant at night

Brüel & Kjær Vibro is keenly aware of the challenges in the LNG industry and has been providing successful safety, condition and performance monitoring solutions to the LNG industry for over 15 years.

The crucial quality advantage

  • Fully automated monitoring. This ensures data is captured and analysed for all operating conditions.
  • Early fault detection. Monitoring techniques are implemented to detect potential failure modes in their early phase of development, so action can be taken before a machine trips unexpectedly. Post mortem tools are of course essential, but Brüel & Kjær Vibro’s monitoring concept helps to avoid the machines failing in the first place.
  • High-resolution event monitoring. Brüel & Kjær Vibro records detailed data with extremely high resolution for up to 15 minutes around a user-defined event.
  • Remote diagnostics. Our remote diagnostic team stands by to assist with all levels of diagnostics and analysis support.

Machines in an LNG plant, especially those in the liquefaction process, are subject to extreme operating conditions. The thermal expansion of a refrigerant compressor, pump or hydraulic turbine between start up and full production at cryogenic temperatures is intense, thereby subjecting the bearings and other machine components to severe loads during start-ups and shut-downs. Even small variations in the composition of the natural gas being processed can have significant effects on the overall loading of the machines. Furthermore, many machines are operated at variable speeds and loads; thereby rendering the mean time before failure for the machine components both variable and unpredictable.
Machine trains are becoming larger, over-design margins are diminishing and critical machine components are being grouped on the same shaft. These initiatives were launched over the years to save production costs but they also consequently increase the risk of lost production if a single critical machine is down. This is further compounded by efforts to downsize at the plants and the very competitive nature of the industry.

Despite the increased risk of a larger portion of production being stopped because of a critical machine failure, downtime is tolerated less than ever. In the case of a machine trip in the liquefaction portion of an LNG plant, you only have a few hours to determine the cause and to get the machine up and running again before losing cooling capacity. Failure to do so can result in extended downtime of the entire production train.

As a result of the operation and maintenance requirements of the machines and the increased risks involved with the industry cost-saving initiatives, condition monitoring plays a vital role in safeguarding the company’s competitiveness.

Within the LNG industry as in all other industries, Brüel & Kjær Vibro is completely focused on providing the necessary system, diagnosis and detailed supporting information necessary to help avoid unplanned machine downtime; no matter where the customer is located or what level of technical expertise and resources they have on-site. Brüel & Kjær Vibro helps minimize downtime by preventing machine failures, rather than just understanding what happened after the event! This is based on a dedicated monitoring philosophy that has been developed and refined over the years to ensure optimum results are achieved right from the start-up of machinery.

Monitoring strategy

Machines in an LNG plant, especially those in the liquefaction process, are subject to extreme operating conditions. The thermal expansion of a refrigerant compressor, pump or hydraulic turbine between start up and full production at cryogenic temperatures is intense, thereby subjecting the bearings and other machine components to severe loads during start-ups and shut-downs. Moreover, even small variations in the composition of the natural gas being processed can have significant effects on the overall loading of the machines. Furthermore, many machines are operated at variable speeds and loads; thereby rendering the mean time before failure for the machine components both variable and unpredictable.

The typical LNG plant includes several trains and processes, as shown below. We are currently monitoring many of the machines in each of these processes in a number of different LNG plants around the world. The Liquefaction process is one of the primary processes in the LNG plant.

LNG Plant Machines monitored scheme

These maintenance-intensive machines are often monitored less closely than centrifugal compressors. With our contemporary monitoring strategies, you can monitor reciprocating compressors efficiently and effectively.

Reciprocating Compressor monitoring techniques scheme
Reciprocating Compressor vibration measurements scheme
Reciprocating Compressor dynamic pressure measurements scheme
Reciprocating Compressor dynamic performance measurements scheme
Reciprocating Compressor dynamic tacho measurement scheme
Reciprocating Compressor dynamic process measurements scheme

Of all the machines used in the oil & gas industry, the centrifugal compressor is one of the most widely utilized. There are numerous compressor processes in the oil & gas industry, and equally numerous machine configurations to meet these process requirements. The monitoring requirements are also individualized for each specific process application. The compressor plays an equally important role in the LNG industry. Both axial and centrifugal compressors, sometimes with many side streams, are used for compressing low temperature refrigerant gases in the liquefaction process. The monitoring strategy example described in the images below is based on a typical propane, mixed refrigerant and end flash gas compressor application.

Centrifugal compressor measurements scheme
Table of faults detected at compressors
Monitoring strategies for detecting potential failures.
Centrifugal compressor vibration measurements scheme
Centrifugal compressor tacho measurements scheme
Centrifugal compressor process measurements scheme
Centrifugal compressor performance measurements scheme

The gas turbine is widely used in the oil & gas industry as a prime mover. Although there is not a lot of maintenance needed for operating a gas turbine in comparison to other machines, effective monitoring is crucial to ensure optimal uptime and reliability. As power output and specific fuel consumption have a huge impact on the lifetime operating costs of the gas turbine, plant performance also has to be carefully monitored. The monitoring strategy example described in the images below is based on a single-axel industrial application.

Gas turbine measurements graphic
table of faults detected at gas turbines
Monitoring strategies for detection of potential failure modes.
Gas turbine vibration measurements graphic
Gas turbine tacho measurements graphic
Gas turbine process measurements graphic
Gas turbine performance measurements graphic

The variable-speed hydraulic turbine liquid expander is used for isentropically expanding high-pressure heavy mixed refrigerant or LNG across a turbine to further reduce the temperature of the fluid while at the same time to generate power. The generator and bearings are cryogenically submerged in LNG at a temperature of around -160° C. The thermal stresses on the bearings and other components are high, so maintenance is critical. The monitoring strategy is described in the images below.

Liquid expander measurements graphic
Table of faults detected at liquid expander
Monitoring strategies for detecting potential failure modes.
Liquid expander vibration measurements graphic
Liquid expander tacho measurements graphic
Liquid expander process measurements graphic
Liquid expander performance measurements

The cryogenic pump, like the liquid expander, has the motor and bearings cryogenically submerged in LNG at a temperature of around -162° C. The thermal stresses on the bearings and other components are high, so maintenance is critical. The monitoring strategy is described in the images bellow.

Cryogenic pump measurements graphic
Table of faults detected at cryogenic pumps
Monitoring strategies for detecting potential failure modes.
Cryogenic pump vibration measurements graphic
Cryogenic pump tacho measurements graphic
Cryogenic pump process measurements graphic
Cryogenic pump performance measurements graphic

The electric motor and generator are extensively used in many industrial processes. They come in all sizes, so the specific monitoring strategy used depends on the application. The monitoring strategy example described in the images below is for a large motor used for the end flash compressor.

Motor Generator measurements graphic
Table of faults detected at a motor/generator
Monitoring strategies for detecting potential failure modes.
Motor Generator vibration measurements graphic
Motor Generator tacho measurements graphic
Motor Generator process measurements graphic

The gearbox is not a machine in itself, but a machine component for converting the rotational energy of the prime mover at one speed to the driven machine at another speed. The gearbox is extensively used in many industrial processes, and the specific monitoring strategy used depends on the application. The monitoring strategy example described in the images below is for the end flash compressor train gearbox.

Gearbox measurements graphic
Table of faults detected at a gearbox
Monitoring strategies for detecting potential failure modes.
Gearbox vibration measurements graphic
Gearbox tacho measurements graphic
Gearbox process measurements graphic

Monitoring system

Our products for machine monitoring can be easily interfaced to the user’s process control system (DCS), enterprise and maintenance management systems, emergency shutdown system, operator work stations and even other pre-existing monitoring systems. In many of these applications remote monitoring with secure communications over long distances is a requirement. The image below is an example for the machines in the LNG liquefaction plant.

Monitoring system LNG graphic

Products we use for our condition monitoring solutions

  • Flexible, fast, reliable: Data acquisition platform for more than protection

    Integrates data from any protection system for Condition Monitoring.

    Powerful software package for secure wind turbine monitoring

    Precise acceleration, vibration speed and non-contact displacement sensors

  • Scalable solution beyond machine protection for plant-wide condition monitoring

    VDAU-6000

    The 16-channel system for scalar data reporting and early fault detection

    The allrounders for machine diagnostics, balancing and condition monitoring

    High-quality accessories form the perfect complement to your monitoring solution