What are the energy and water usage impacts of these systems?
by Jason Ferris

Plans 21 & 23
API Plan 21 is another single seal plan (see Figure 3) that can consume large amounts of thermal energy because of the once-through flow of the process fluid within the heat exchanger. Commonly, larger heat exchangers are required by these plans to handle the high thermal load needed to cool the process temperature to a suitable level for the seal. This thermal load for Plan 21 doubles for cases in which the process temperature must be maintained, as in heat transfer applications, because the cooled fluid is reheated as it is recirculated into the process. API Plan 23 provides a good alternative to Plan 21, because the recirculation of fluid within the seal chamber cavity allows for smaller heat loads and corresponding exchanger sizes. In a direct comparison case study of these options prepared by FSA, an API Plan 21 configuration in a heat transfer oil application consumes 42 kilowatts (57 horsepower), compared to 5.8 kilowatts (7.8 horsepower) for Plan 23 in the same application.

Figure 3. API Plan 21

Plans 53 & 54
API Plan 54 is a dual seal plan (see Figure 4) that can consume relatively significant water or electrical energy depending on the application requirements and system design. In its simplest form, Plan 54 consists of a pressurized water source that runs once through the seal and is then sent to effluent treatment, which can result in extremely high water usage.

Figure 4. API Plan 54

More advanced systems consist of a closed-loop system with a dedicated circulator, requiring electrical energy for that circulator, and possibly cooling water, depending on the heat load placed on the system.

In some cases, energy and water usage can be reduced by changing to more advanced technology seals, such as flushless single slurry seals for abrasive services, or dual pressurized gas seals for hazardous services.

In other situations, a dual seal must be maintained because of application considerations—including the prevention of hazardous fluid leakage, seal face lubrication requirements or several other factors.

In these situations, Plan 53 offers lower energy consumption through the elimination of closed-loop Plan 54 circulation pumps. For open-loop Plan 54 systems, conversion to a closed-loop system will significantly reduce water and energy use costs. Alternately, flow and pressure regulation devices may be employed to reduce energy usage on open-loop systems. 

Conclusion
The selection and design of the sealing system can have a significant impact on energy and water use of the entire pumping system. The new ISO standard 14414 Annex will provide a simple selection guide for determining which options can minimize this impact, and the FSA/ESA Life Cycle Cost Estimator Tool can be used to further analyze the potential savings. In many cases, significant overall energy savings can be achieved by changing from less efficient to more efficient sealing system designs.

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