Technical Committee Fuel Oils

Influence of Tank Inspections on the Quality of Heating Oil

In the past, a break down of heating systems was sporadically observed after tank cleaning. It was quite often impossible to find out the cause for such a break down. Sometimes, this led to irritations and arguments among the participating businesses (mineral oil traders, builders of heating systems, tank cleaning companies) and the customer.

A joint project was initiated in the fall of 2003 with partners from the mineral oil trade, tank protection companies and tank builders, in order to better understand the causes and interrelationships and to clarify the influence of tank cleaning on the quality of heating oil in the tanks of the customer. The objective of this project was to systematically document tank cleaning procedures, including an analysis of heating oils before and after tank cleaning. These investigations were coordinated by the Institut für wirtschaftliche Oelheizung e.V.

Samples were taken during tank cleaning operations from a total of 30 heating systems in 2004 – 2005. All prevalent types of tanks were included, such as battery of plastic tanks, underground storage tanks and tailor-made tanks, assembled on-site. 25 customer tanks were prophylactically cleaned. The investigation included samples of five customer tanks, where complaints had occurred in connection with tank cleaning.

Samples were taken from the middle of the fill level and 5 cm above tank bottom, before and after tank cleaning. In 2005, samples from the tank bottom were also included in the investigations.

All samples were analysed for total contamination, water content, copper content, particle number and particle size distribution.
The results for total contamination and water content were compared to the limit values for light heating oil as defined by DIN standard 51603, part 1.

Special attention was given to total contamination and water content of heating oil after tank cleaning with sampling 5 cm above tank bottom. These results are documented for every facility on a separate sheet in the appendix to this report.

This report describes the sampling and tank cleaning procedures, contains the analytical results and the conclusions and provides a perspective for still unresolved problems.