With the collaboration of independent ATEX specialist 123ATEX, Dutch cargo pump manufacturer MarFlex has carried out an analysis of its deepwell pumps and subjected them to various ATEX tests
For owners and operators of inland waterway tankers and barges on the European waterway system, the last few years have been challenging. The industry has been plagued by low water levels in the river Rhine since 2018 and in 2019, the inland waterway system was brought into line with regulations on the international carriage of dangerous goods. The aim of the regulation is to promote safety and protect the environment.
A large number of changes were introduced with the international carriage of dangerous goods regulation, one being to harmonise with the ATmosphéres EXplosibles (ATEX) directive for explosive atmospheres. IMO has designated cargo tanks on inland waterway vessels as ATEX zone 0 – the highest risk of explosion. This requires that the cargo pumps must be constructed to operate normally in ATEX zone 0, and within parameters of malfunction without creating an ignition. This requires carefully chosen materials for the pumps.
MarFlex technics and QHSE manager Peter Raaijmakers said “I was impressed about the large amount of severe testing and design verifications that had to be done to prove that our products comply with Annex II of the Directive 2014/34/EU. After passing all tests we all were very pleased.”
In a risk analysis, the construction was assessed for the correct use of materials and the correct tolerances. In addition, any potential ignition sources were identified to ensure the appropriate control measures were in place. For example, the oil contained in a bearing pipe is critical to provide lubrication for the bearings, which in turn prevents them from becoming too hot. But if the temperature on the outside of the bearing pipe becomes too high due to a lack of oil, then that can result in ignition. Checking the oil level, by means of a certified switch, is therefore an ATEX requirement.
To investigate the strength of a construction, the pumps were pressure tested and impact tested. The impact test consisted of a calibrated hardened steel weight, with a ball at the bottom, released from a height onto the part being tested. In addition, the pump was tested for the highest measured temperature, as well as stabilisation of the temperature under unusual conditions, such as an empty tank or a constant minimum tank level. In this test, the pump is operated until the temperature does not rise by more than 2°C per hour. The maximum temperature reached is then regarded as the ‘hottest spot’.
The MarFlex ATEX pumps conform with the requirement through a number of special features. These include the top cover of the deepwell pump being equipped with an oil-level sensor so that the pump stops automatically when the oil level in the top cover is too low. This prevents the bearings in the pump head and in the pipe stack from rotating and overheating without lubrication.
The ATEX certification takes into account that T4-level chemicals ignite at temperatures above 135°C. For safety reasons, the standard states that the temperature must not exceed 80% of this value, ie a temperature of 108°C. The dry run after discharging is set at a maximum of eight minutes. Tests have shown that safe discharging is still possible after 16 minutes, provided the outside air or cargo temperature does not exceed 45°C. However, to eliminate the human factor during a dry run, extra protection must be built in.
ATEX requires reduction or elimination or static electricity to minimise the chance of ignition. In the MarFlex deepwell pump, the piston rod of the draining pump is completely insulated (by non-conductive seals), but there is a possibility that static electricity can be stored up, which can lead to sparking. To prevent the build-up of this static electricity, the piston rod must be constantly connected to earth. In the ATEX version, a carbon brush is installed for this purpose, which can be easily checked and/or replaced.
Finally, MarFlex complies with Annex IV of the Directive, which means the entire organisation had to fulfil stringent requirements that not only assure all supplied products are built exactly like the tested product, but also that training and procedures are in place to monitor for possible risks and improvements. Mr Raaijmakers said “Being able to comply with this proves our level and focus on quality. Worldwide, only 200 companies have achieved such status. We are very proud to be one of them”.
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