HERMETIC offers a wide variety of mounting arrangements for its two distinct sealless pump models, the TCN and TCAM. Pumps are available with flow rates of up to 1,800m³/h and delivery heights of up to 1,000m, and canned motor powers are available with up to 448kW. For hazardous area applications, HERMETIC canned motor pumps are certified according to the EC type examination certificate under directive 94/9/EG ATEX.
Environmental awareness, which has increased over the past few years, has resulted in chemical and petrochemical plants being judged more severely in regard to health and safety regulations. Under the new EC directive 96/61/EC (the so-called IPPC directive) — which is reflected in the Federal Immission Protection Law and the TA-Luft — sealless pumps, particularly canned motor pumps, are increasingly being used as the best available technology (BAT) to prevent and reduce volatile emissions.
Thanks to the EC directive as well as the Federal Immission Protection Law and the TA-Luft, emissions from pumps have been severely restricted. Today, as a consequence of these restricted regulations in environmental protection for toxic, explosive and liquefied gases, there has been an increasing tendency not to provide vessels and vessel drains with a lateral outlet or bottom outlet, i.e. with a drain nozzle installed in the range of the bottom.
For such applications vertical submersible pumps are generally the preferred choice, alongside conventional submersible pumps with stuff box packing or single and double mechanical seals, and hermetically sealed pumps that do not have any shaft sealing and thus are completely leakage-free.
The sealing of the shaft passage at the pump housing is a critical point with conventional centrifugal pumps. Some system-related liquid can leak from the shaft seal, however, and this is not always visible. This problem can be resolved by a double mechanical seal. The immersion depth of the pump stipulates the number of the required medium lubricated guiding bearings. Depending on the pump size, one guide bearing per 1.2m to 1.6m is required.
The basic and outer construction of a conventional pump with mechanical seal can be compared with the design of a submersible pump with magnetic drive. The difference of sealing to the atmosphere is the containment shell of the magnetic coupling that is directly installed to the pump component. The containment shell ensures an absolutely leakage-free pump operation and can also be installed on the outside of the vessel. Because of that, the drive shaft of this construction type is not medium-lubricated but operates in a dry place. The bearings used are pre-lubricated roller bearings which are placed in a support tube under dry conditions.
Canned motor pumps have no shaft sealing and are therefore completely leakage-free. The compact design of the canned pump, with integral motor sharing a common shaft, results in a pump considerably shorter than either conventionally sealed or magnetic drive units. The length of the shaft is independent of immersion depth. Installation and removal of the pump can be completed more economically due to the individual design of the cable conduit and discharge pipe, which can be supplied with shorter flanged segments. The pump unit itself offers increased plant availability and reduced lifecycle costs through the proven ability to work with minimum maintenance.
