The challenge of safely and economically dealing with rainwater and petrochemical spills in ATEX Zone 0 areas is growing as more stringent monitoring controls come into place for Tank Storage Terminals, particularly in European countries. Certain ATEX Zone I areas within these terminals have been re-defined as ATEX Zone 0 areas, requiring a review of their risk assessment but also providing an opportunity for pump manufacturers

CRANE® Process Flow Technologies GmbH in Dusseldorf, Germany, are reporting an increasing number of enquiries for their DEPA® Air Operated Double Diaphragm (AODD) pumps which are certified for ATEX Zone 0 use by Physikalisch-Technische Bundesanstalt, Germany. The pumps, which can be air or nitrogen powered, eliminating the requirement for monitoring control systems, are proving particularly suitable for Tank Storage Terminals.

One of the main applications is their use on the “movable rooftops” of the huge gas tanks (See 1). The defined area above the rooftop is an ATEX Zone 0 area, as inflammable gases could occur. The self-priming AODD pump can evacuate the rainwater and any fluid spills very easily in a safe manner, as the pump has a Tx classification. The pumps are designed to deliver a 7 bar head pressure, and can handle running dry and with the 25 m continuously changing altitude as the tanks empty and are refilled.

Another recently identified area that requires ATEX Zone 0 certification is underneath tanks where a sump collects both rain water and any waste liquid from spills (See 2). With the possibility of inflammable gases occurring in both the sump and collecting vessel, both areas are designated ATEX Zone 0 with existing submersible centrifugal pumps shut down due to non-conformity to ATEX regulations.

DEPA engineers have recently demonstrated the range of AODD pumps which conformed to ATEX zone 0 regulations but, during technical discussions with one tank farm operator, it became apparent that the AODDs’ ability to self prime meant the pumps could be located in a more easily accessible location, adjacent to the tanks, but still in an ATEX zone 1 environment (See 3).

Thomas Walbroehl, Specialist Applications Engineer at DEPA, explained, “Because AODD pumps can self prime, it simply wasn’t necessary to locate them under the tanks in the Zone 0 environment, even though we have pumps for such applications. It made far more sense to locate them where they are easily accessible in the less stringent zone 1 environments. We were also able to offer a variety of housing materials including stainless steel, ductile iron and aluminium as they would be dealing with non-corrosive liquid, although, again, housings for corrosive liquids would not have presented a problem.”

“Previous tests had revealed that the old valves and impellers of EPDM (synthetic rubber) had failed due to oil content in the product. It was also, therefore, the inclusion of our nopped E4® diaphragms within the pumps that impressed the customer’s engineers as these offered a high chemical compatibility and provide an extended lifetime, thereby meeting ATEX requirements for a high safety level of the process. The purchase of the DEPA pumps has saved the customer about 25,000 Euros for each pump installation against the previously installed very expensive Zone 0 vertical centrifugal pumps.”

The terminal had been temporarily shut down last year because of safety issues in the EX-area but now fulfills all necessary ATEX requirements whilst also saving on running costs.

Colin Simpson, Sales Director of Crane's UK distributors, Tomlinson Hall Ltd, commented, "The DEPA® E4 Diaphragm is state-of-the-art technology which gives four primary benefits for end-users - increased life span, improved safety, increased efficiency, and an ultra clean working mechanism. Sales so far have exceeded our most optimistic forecasts and the feedback we are receiving from users is very positive with the diaphragms usually available for next day delivery throughout the UK."

CRANE ChemPharma and Energy, based in Düsseldorf, and a part of Crane Co., is a leading provider of highly engineered products for fluid handling applications worldwide. For more information please visit www.depapumps.co.uk or contact Tomlinson Hall on (01642) 379500.