Introduction
Every unit in the oil and petrochemical industry regularly requires a maintenance turnaround. At the start of a turnaround, the hydrocarbons are removed from the process equipment to allow maintenance engineers safe access. The cleaning process is defined in the decontamination procedure.
Over the years, vaporising has been the most frequently used way of removing hydrocarbons. Until recently, however, there was no method for monitoring the decontamination process. The duration of the vaporising procedure was based on past experience. But a steam monitoring method is now available. The progress of the vaporising procedure can be clearly visualised. It is possible to determine when vaporising can be stopped. More importantly, it is possible to intervene quickly in response to sudden measurements of higher hydrocarbon contents. The cause can be ascertained and the problem resolved. The advantage of measuring is that it makes the vaporising process easier to control, thus saving time. Altena has several field laboratory vans, equipped with measurement equipment, to perform fast local analyses in the vapour phase of the unit.
Execution
A sampling point is prepared at different places in the steam circuits so as to gather a quantity of steam condensation at regular intervals (every hour, every two hours). In the field laboratory, every condensation sample is prepared for analysis of the total hydrocarbon content, benzene, LEL and H2S. Other substances can be measured at the customer's request. The quality of the measurements is guaranteed by means of a fixed procedure for calibrating the test equipment at the start of every shift. Monitoring requires that every sample must be analysed within half an hour. Under these conditions, the unit’s owner can keep a sharp watch on the decontamination process.
Examples
We have supported various large customers in the vapour phase of the decontamination process. References for these projects are obtainable from us on request.
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