Here is a question; what is an eductor? Eductors are also called ejectors, Venturi jets, aspirators, jet mixers, or jet pumps. Eductors use either compressed gas or liquid to generate a vacuum by a Venturi effect which is based on Bernoulli’s equation. (You can read more about the person here, “People of Interest: Giovanni Battista Venturi March 15, 1746 – April 24, 1822 By Tyler Daniel”.) They can be used for vessel evacuation, gas sampling, pump priming, venting, and blending. EXAIR Line Vacs work on this same principle in creating a Venturi vacuum by using compressed gas. In this blog, I will cover the design, verification, and testing that EXAIR provided for a customer’s special.
For this customer, the design was based around our 2” and 1” 316SS Line Vacs. They required ISO flanges on the vacuum and exhaust sides to match their piping connections for gas sampling. They would supply nitrogen to the inlet port as a carrier gas to generate the venturi and to mix with the sample gas. Since the accuracy of the test is dependent on the amount of each gas, we had to test the operations of the Line Vacs at different conditions.
First, EXAIR designed these special Line Vacs to get approval. Once the customer approved, EXAIR had to make a strong effort to meet the other criteria that was requested. Generally, with our standard Line Vacs, we use our test data with estimated conveyance rates, inlet flow rates, and vacuum pressures measured at 80 PSIG (5.5 bar). For these special Line Vacs, we had to do a bit more work because it was for gas sampling. This was not a problem for us. EXAIR has many calibrated instruments to accurately measure different conditions. For this customer, we had to measure the inlet flow, suction pressure, velocity, and maximum back pressure at different inlet pressures. We also had to create another chart showing the exhaust velocities with a back pressure present.
From these details, the customer could calculate the amount of nitrogen that would be introduced to the gas sample at different pressures and backpressures. And, as an added preference, they requested us to do a leak check after assembly. We were willing to buy the flange blanks and add this test procedure to the router. We looked for leaks between the cap and body of the special Line Vac, as well as the flanges to verify that gas was not escaping. EXAIR tries to support our customers to the best of our abilities. For this customer, we worked together to provide the needed information for their setup.
The reason that I wrote this blog was to show that EXAIR has the capabilities to make special items for specific applications. If we need to use different materials, design configurations, and even present test data, we can decide the best course of action. With special products, they are unique to customers in fit, form and function as a solution, whether for end-users or OEMs. For the special Line Vac above, we presented the data as related to an eductor for this customer’s decision to place the order. If you would like to see if EXAIR can make a special product for you, please do not hesitate in contacting an Application Engineer at EXAIR. We will be happy to work with you.