You’re part of a team involved in developing a new machine, and among your jobs is designing the onboard compressed air or vacuum system. You’ve read up on the various air moving technologies, plugged in your flow and pressure/vacuum requirements – maybe even checked out a few readily available standard pumps, just to get in the ballpark.
But now you’re ready to take the next step: looking into a custom-made pump that will be just right for your application. So, how do you begin? Even more, how do you work with your chosen supplier to be sure the pump you get is the ideal combination of performance and price?
Here’s a step-by-step guide, including some real-life “Field Notebook” anecdotes.
Analyze and Document
The first step is entirely yours – carefully defining the application requirements. Answer these questions to begin the dialog. If your suppliers need additional information or details, they’ll ask.
Air flow and pressure/vacuum. Define the maximum airflow and maximum vacuum or pressure requirement. Performance curves showing pressures or vacuum that can be delivered at various flows are available from many pump manufacturers.
Power source. If direct current (dc), specify the voltage; if alternating current (ac) define the voltage as well as the frequency (generally 60 Hz in North America and 50 Hz in Europe and many other places in the world). List any power consumption and current draw limitations, and whether thermal overload protection is required. Finally, determine the duty cycle of the application. Define as either “continuous” or, if intermittent, indicate a pattern of “minutes on, minutes off.”
Envelope. List height, width, and length maximums. Also, determine how much free air space will exist around the unit. This will help the pump manufacturer know whether additional fans or other cooling mechanisms will be required.
Service-free lifecycle. Custom pumps may be designed for as little as 500 service hours, for more than 30,000 hours of service-free life, or anywhere in between. In addition to your expectations for service-free pump life, be sure to let your pump manufacturer know if serviceability is required so that the pump can be chosen or designed accordingly.
Environment. Typical ambient temperatures for pumps are from 50-104ºF (10-40ºC). However, special designs can operate in temperatures as low as 40ºF or as high as +212ºF (40ºC to +100ºC). Also describe the air surrounding the pump – clean, dusty, gaseous, etc – and determine the relative humidity.
Sound and vibration. Be sure to describe any concerns or requirements that could affect the pump type and mounting recommended.
Certifications. Make sure your supplier is aware of all the agency requirements (UL, CSA, TUV, FDA, ISO, etc) for your application.
Altitude. Height above sea level is a critical factor in pump performance, especially at higher pressures or vacuums. Make sure that the application specialist is aware of any requirement to work at varying altitudes so that the pump can be properly selected or designed to meet the application requirements.
Cost. Sometimes the role of cost is secondary, sometimes primary – but it’s always present and should be one of the key factors considered. When analyzing cost, consider all elements – including first-cost, lifecycle operating and maintenance cost, cost of a unit failure, and so on. Let your manufacturer know which of these elements is your top priority.
Get a Sense of Technologies
No single air pressure or vacuum technology is best across the board, so it’s smart to look to a broad-line supplier familiar with the various technologies. Here’s a quick look at the most common types and key characteristics:
Wobble piston: High pressure and vacuum capabilities relative to the compact size and light weight of the unit. Moderate to high air flows. Very efficient, relatively quiet and easily serviceable. Dry-running (oilless) design for very clean output. Not suitable for full-pressure restarts.
Rotary vane: Highest air flow relative to physical size, but not applicable to high-pressure applications. Free of pulsation. Simple design contributes to long life. Less efficient than piston or diaphragm pumps. Characteristic “whine,” especially in smaller sizes. Not suitable for full-pressure restarts.
Articulated piston: Generally chosen for heavy industrial applications requiring longest life, especially where full-pressure restart is required. High pressure and vacuum with high flows. Noise can be an issue. Relatively heavy and higher priced.
Diaphragm: Best for lower pressure or moderate vacuum at lower air flows. Tolerant of aggressive media, including liquids. Quiet, low pulsation. Can be designed for full-pressure restarts.
Linear: Limited to moderate flow with low pressure or vacuum. Extremely low power consumption. Low pulsation.
Look to the Experts
You’re the expert on the products you design and manufacture. But let’s face it, you’ll never know as much about pressure and vacuum pumps as the company that makes them. So don’t underestimate the value that a top-quality pump supplier can bring to the application table. Share the information you’ve collected, then challenge your supplier to propose the highest-value pressure or vacuum solution.
And be open to ideas. With healthy give-and-take and open communications, the result is likely to be the perfect pump at the lowest possible cost.
FIELD NOTEBOOK
System Perspective Delivers Maximum Value
During a visit to check on a sample compressor provided to an Italian maker of food dispensing equipment, a Thomas engineer had the opportunity to carefully study the unit’s entire air system. Based on his analysis, he proposed a system redesign that resulted in saving the customer over $50 in cost for tubing and valves, an equal amount in assembly labor, and delivered increased efficiency and reliability. The savings easily exceeded the additional cost required to modify the WOB-L piston compressor to work with the new design.
The Importance of Open-Mindedness
A large biomedical equipment company was in the midst of redesigning a longtime product that used regenerative blower technology from another vendor and opened the project up for proposals. Thomas was already an approved vendor, having supplied peristaltic pumps for another application.
Rather than simply offering to replace the existing regenerative blower, Thomas began by looking at the function the blower provided and determined that the blower could be replaced by a WOB-L piston pump and an integrated small pressure tank – at a substantial cost savings.
Rapid Prototyping Meets Regulatory Deadline
A U.S. supplier of systems to the automotive and off-road equipment industries faced a government-mandated deadline to deliver emission control systems to a large customer. When it was clear, just six months from the delivery deadline, that a standard compressor was not making the grade, the company found expert help in Thomas.
Quick-turnaround plaster-cast prototypes of a modified Thomas WOB-L piston compressor verified fit concerns, then sand-cast prototypes completed the qualification process as well as serving as a limited production bridge until longer-run die-cast tooling could be completed.
Roll-Up-Your-Sleeves Philosophy
Technical support concerns caused a British manufacturer of beverage dispensers to consider alternatives to its current vendor. Thomas marshaled engineering support immediately and, suspecting a less-than-ideal compressor match to the application, approached the customer by suggesting a careful analysis of system requirements before any product proposal.
A collaboration among the customer’s engineering teams and Thomas experts in England and the U.S. resulted in a hybrid WOB-L piston compressor ideal for the application, and at a substantial cost savings.
An International 11th Hour Success
Facing serious performance problems with a pump, a medical products manufacturer in Scandinavia turned to Thomas. The customer sent a system to Thomas’s Sheboygan engineering center for analysis, and development work on a better solution began immediately. After a period of time, the customer arranged to visit Thomas for final prototype approval. While the customer was en route to the U.S. from Sweden, final tests by Thomas raised concerns about the accuracy of some specifications the customer had provided.
Once the customer arrived, the specifications were clarified and corrected, re-engineering work began that afternoon, and a new prototype was built overnight and approved by the customer the next morning.
Standard Pump Platforms Jump-Start Development
A maker of commercial inkjet printers needed a quick-turnaround single-source solution for both liquid pumps and printer-head cleaning pumps, which had previously been supplied by two different companies. Thomas responded with diaphragm compressors made in the United States and linear liquid pumps made in Germany – supported by Thomas teams in the U.S., Germany, and the U.K.
A very fast 5-month concept-to-completion cycle was made possible using standard pump platforms from the broad Thomas line as the basis for the ultimate custom pumps.