Condition monitoring
Guarding your critical installations by means of vibration measurements enables you to increase the returns of your investment. The key to this is periodical measurements of a number of machinery parameters, of which vibration measurements is the most important one. In standard maintenance, the machines are inspected at fixed intervals. These intervals are usually determined on the basis of experience with other equal machines, or based on the manufacturer’s guidelines. These are often on the safe side, resulting in shorter interval terms than actually necessary, due to a very conservative safety margin. Exceeding this period, means risking a critical failure, and you will not be willing to take such a risk. This means, you will have to stop and open the machine once its time has come…
The advantage: easy planning of maintenance, since a schedule can be made far ahead. The disadvantage: not all machines follow this schedule, and minor errors in, for instance, alignment, mounting conditions, balancing of components, and so on, may cause the installation to fail within its expected "maintenance free" period.
A better method is to determine the actual need for maintenance of a machine. On the basis of vibration patterns resulting from periodic vibration measurements, the behaviour in time, and the presence, or absence, of pre-determined fault frequencies can be determined. From this, the condition of the installations can be established with great accuracy. This is done with the installation running in normal operation, without having it to stop, or even open the case.
Vibration monitoring makes it possible to have better control over the actual need for maintenance of the installation. In most cases, this means a lowering of total maintenance costs, and a decrease in maintenance costs per machine.
There is also a slight disadvantage to this method: since maintenance is determined on the basis of the installations need for maintenance, it makes planning less easy. However, since faults are usually detected in an early stage of development, it is often possible to predict remaining life of the component (usually a bearing). Carefully following the development of such failure does make it possible to plan the best suited moment for a stop.
Condition monitoring can be divided in two mainstreams.
It can be performed just before a planned stop of a complete plant. During this session, all machines which are part of the maintenance plan are measured. This gives a rough impression of the need for maintenance of the machines. The basis for the vibration levels being international standards such as ISO, or comparison with earlier measurements or similar installations. Before the measurement, an overview of possible fault frequencies is made on the basis of the types of bearing, number of gear tooth, couplings, and etcetera. This method gives a brief impression of the state of the installations. It is sufficient for less critical components only, since the most important tool for condition monitoring, the development of wear, or fault-frequencies, in time is missing, and there is no actual monitoring of the machines. Typical examples for such actions are plants, just before a summer or winter stop, or larger ships, which base the order of maintenance for pumps, generator, winches and so on, on the results of the measurements.
The other method of condition monitoring is based on periodical measurement, with the period being determined on the basis of importance of the machines in question, and the type of operation. The deviation of the frequency pattern in time, and especially the development of frequencies related to typical components such as bearings, gears, rotor bars and other, is the basis for judging the machines need for survey. This means the installation is only stopped and opened when it is determined necessary. This lowers, in some cases dramatically, the maintenance cost per engine. Furthermore, and not less important, the number of failures will drop, since a number of failure will be established in an early stage.
We have a long history and good reputation with regards to condition monitoring. In Europe, we are one of the very few companies who hold the ABS certificate for service approval. This certificate allows users of steam turbines, often used in older types of ships, to start up a maintenance program for their turbines.
Maintenance for the turbines and related equipment is than required on the basis of the vibration measurements.
Since the alternative is the requirement to open up the turbine casing every 5 years, together with the cost of opening and the loss of sailing days, the advantage of condition monitoring is clear. The possibilities to start a condition monitoring plan are plenty. We can come by your plant or ship, perform the measurements, go back to the office, and analyze the data. We than present you with a report in which we give an overview of the status of your installations, together with a maintenance advice
When we come for the first time, we will discuss the number of plants and measurement interval with you. We will also make invent the types of machines in your plant which are part of the program, their possible fault frequencies and standard alarm values based on ISO or our own experiences.
Another option is that you perform the measurements, on the basis of a plan as described below. This can be done with your own data collector, or you can rent one from us. You than sent us the measurement data, which we will analyze, and present the results as described above.
We will also help you start up a maintenance program, for which we will help you choose a data collector and software, determine measurements intervals, and train your personnel. Once everything is running to your satisfaction, we will fall back and you will be able to perform the maintenance measurements yourself. Of course, we stay in the background, and will be pleased to be of service in the case of more serious problems, which require more knowledge or equipment than a data collector and basic knowledge of vibration analysis.
When an installation is crucial, and requires constant monitoring, we can provide an on-line measurement and monitoring system. This can be equipped with a data logger system, a wired or wireless connection to a control system, or by a telemetry system to us for continuous monitoring.
Please contact us with your questions regarding the possibilities of implementing a monitoring program within your company.