Analysis of oil in use
Introduction
Analysis of oil in use – Considering the importance and benefits of monitoring lubricants in use, an important aspect to consider is sample collection.
It is the first stage of the analysis of oil in use and is extremely important for the success of the monitoring program. The sample needs to be as representative as possible of the lubricant in circulation in the equipment.
Collection frequency
The frequency of collection depends on several factors such as:
- Criticality of the equipment;
- Type of equipment – crankcase volume, access;
- Operating regime.
Critical equipment requires a higher frequency of sample collection since its unscheduled shutdown significantly affects production.
As for the type of equipment, some aspects should be considered. When the crankcase has a small volume, frequent sampling will require level replacement. In these cases, the ideal is to plan the monitoring of only the load changes to evaluate the lubrication condition, identifying changes in the process, or even the possibility of extending the exchange period.
Equipment of difficult access makes the collection more laborious and this should be considered in the frequency of collection. In these cases, it is important to take stock of various factors such as criticality, operating condition of the equipment, time required for sample collection to be done, etc. It is possible, for example, to consider training an operator to perform the collection at the time it is necessary to perform some operation, verification or inspection.
The operating regime is another important aspect, especially when the equipment does not operate 24 hours a day every day of the week (for these, the collection can be scheduled according to prior planning). For those operating during the week or on shift, sample collection should be done at the end of the shift, immediately before being switched off. At this time it will be more representative of what is occurring in the lubrication system.
Equipment that is idle for long periods requires specific planning, according to the following items:
- Sample collection before long shutdown – this way you have a reference of the lubricant conditions before the shutdown;
- Cleaning of the equipment, heating of the lubricant and/or circulation of the lubrication system before collection for return to operation;
- Off-line filtration of the load before return to operation to remove contaminants that may be deposited at the bottom of the crankcase;
- Cargo exchange
Collection points
The lubricant sampling point must allow you to reach places where the sample is representative of what is circulating in the equipment. Unfortunately, there are few equipment manufacturers that previously installed representative collection points on the equipment. Some premises are important:
- Drainage points drag waste that is deposited at the bottom of the crankcase and does not participate in lubrication;
- Collection in the reservoir provides information about the condition of the lubricant, but the information about wear is diluted throughout the volume of the crankcase;
- Collects after filters – wear particles are retained in the filter and not in the oil sample;
Considering that the collection of samples is intended to detect the condition of the lubricant, the presence of external contaminants, and the presence of wear, the best collection point is right after the lubrication point. However, you can choose to collect periodic samples at a point that aggregates all the lubrication information of the equipment, such as the return to the reservoir before the lubricant reaches the crankcase – summary point. At the moment that this sample identifies some deviation, additional samples are collected by lubricated part (points 01, 02, and 03) to identify where this deviation arose to take the necessary actions.
The drainage points are not the most suitable for the collection of samples, but, if there is no other point available, they can be used with some care. It is important to easily estimate the dead volume of lubricant between the bottom of the crankcase and the collection or drainage point. Before collecting the sample, this volume should be drained by the valve and discarded for monitoring.
Despite the planning of lubricant sampling, whenever there is any non-routine event, such as excessive noise, abnormal vibration, more demanding operation outside the indicated curve of equipment operation, lubricant temperature increase, etc., it is very important to consider an extra sample collection to assist in the evaluation of how much the non-routine event affected lubrication. Thus, it is possible to anticipate possible failures.
Collection procedure
The sampling procedure must be well documented and the persons responsible for this activity are properly trained. In addition, the material should be all clean and new; The reuse of bottles is very dangerous because it is a source of external contamination.
All material for sampling should be cleaned and dried. The sampling point should be thoroughly cleaned before the procedure. Sample bottles, sample labels, clean cloths, disposal container, gloves, and protective equipment as needed will likely be required.
When the sampling point is the crankcase drain point, the drainage container is critical to collect the dead volume of the pipe between the bottom of the reservoir and the collection point.
The collection pump shown in the previous figure allows the plastic tube to be dipped in the middle of the reservoir for representative sampling, despite the dilution of the wear information, as already mentioned. In some cases, the end of the pipe has a hitch that fits into the valve of the collection point.
If the sample bottle is open to the environment, it is very important to prevent the entry of external contaminants into the sample such as rainwater, dust, etc. When you want to perform the particle count test, this form of collection is not adequate.
After sampling it is important to note the appearance of the sample. For this reason, transparent bottles are more suitable. If free water is identified, it is not necessary to send this sample to the laboratory. This is already an indication that a major contamination has occurred and an immediate action of exchange or purification of cargo along with the identification of the origin of the contamination is urgent.
Sampling in engines should be done with the hot engines just turned off. Great care is essential because the lubricant will be at a high temperature and can damage the bottle and cause burns to the operator.
The bottle should be filled to about 75% of its volume. The volume of air is important so that the sample can be homogenized just before it is analyzed.
The identification of the sample shall contain the following information:
- TAG of the equipment;
- Collection point (crankcase, return, etc.);
- Date and time.
The laboratory that analyzes the samples has to receive, in addition to the previous information, the following data:
- Equipment time meter or mileage;
- Name of the lubricant in use;
- Date of last cargo exchange;
- Level replacements and maintenance procedures performed since the last lubricant collection.
Quanto mais informações o laboratório receber, melhor será a qualidade do laudo emitido.
Quando se empacota um conjunto de amostras para envio ao laboratório, é fundamental que cada amostra seja embalada separadamente. O vazamento de um frasco danificará a identificação de todos os outros frascos, desperdiçando todo o trabalho realizado.
Após uma coleta representativa de lubrificante em uso e do envio para o laboratório, é importante selecionar as análises que devem ser feitas. Este é o assunto do próximo artigo. Não perca!
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