In light of the operational concerns reviewed in Part 1, this chemical recycling firm decided to evaluate different pump technologies. Fortunately, recent advances in vacuum pump technology make dry-running pumps a viable option for many of those currently using liquid ring pumps. Dry pump technologies like chemical-resistant diaphragm pumps can be considered as a viable alternative to liquid ring pumps in many cases, and completely eliminate the water consumption of a liquid ring pump. Dry pumps do present higher upfront (capital) costs than liquid ring pumps. However, the corresponding savings on operating costs and improved throughput more than justify the incremental capital costs, as we will see in the present example of the chemical recycling firm from New Jersey.
Chemical-resistant diaphragm pumps, such as those offered by VACUUBRAND, use a layer of overmolded fluoropolymers on all wetted parts, and operate at relatively lower temperatures. This allows for corrosive chemical vapors to pass through the pump without causing damage. It also allows for chemical-resistant diaphragm pumps to obtain hazardous location ratings (e.g., ATEX Internal Atmosphere rating) for use with potentially reactive gas mixtures. Diaphragm pumps can also use variable frequency drives (VFDs) or variable speed motors to precisely control the process vacuum level over the full pump operating range and to drastically reduce pump power consumption. This means that chemical-resistant diaphragm pumps are very well-suited to a variety of processes. For example, processes that involve aggressive chemicals, or situations where precise process control is particularly important, or in cases when operating costs must be minimized by eliminating the consumption of water and reducing power consumption, are all excellent candidates for the use of diaphragm vacuum pumps.
The customer faced a choice to replace their existing liquid ring pumps with the same or equivalent models, or to invest in chemical-resistant diaphragm pumps. Based on information provided by the customer, VACUUBRAND has calculated the economic return achieved by switching to chemical-resistant diaphragm pumps. This analysis is shown below as a real-world example of the financial return achievable by switching to dry vacuum pumps. Note that the productivity benefits associated with higher throughput were not readily quantifiable at the time of this writing, so the economic value of the higher throughput is not included in the figures below.
The cost of acquiring new liquid ring pumps was estimated by the customer at approximately $9,000, including both primary and back-up pumps. Using the published water, sewer, and electric rates and customer-provided data for the cost of pump maintenance, the liquid ring pumps are estimated to have operating costs of approximately $16,500 per year.
In contrast, the equivalent chemical-resistant diaphragm pump solution was estimated to have an upfront cost of $45,000. This figure is based upon using pumps from VACUUBRAND’s VAC 24seven process vacuum pump line. Using the same utility rate data, and based on VACUUBRAND’s published 15,000 operating hour service intervals suggests that operating costs of these pumps would be approximately $5,500 per year.
By plotting the total cost of ownership of both the liquid ring pumps and the VACUUBRAND VAC 24seven pumps, we can see that the payback period for switching to the chemical-resistant diaphragm pumps is approximately 3.4 years. Once payback is achieved, the customer enjoys annual operating cost savings of over $10,000. The financial return five years after making the switch to diaphragm pumps is estimated to be nearly 50%, or an annual compound return of 8%. After accounting for near-certain increases in water and sewer rates, the operating cost savings, and thus financial return, would be even higher. This is addition to the incremental revenue achieved through greater uptime and higher throughput rates.
