Mueller Multiple Effect Stills and Pure Steam Generators come in a variety of sizes to ensure that one is available as close as possible to the size you need. However, often, the design capacity is not the maximum capacity of the unit. This means you may have “free” capacity available on your existing unit! Here are the steps to determining what “free” capacity you have available.

1. Measure current capacity, if different from design capacity, and calculate maximum available capacity. You can use the charts and graphs in Mueller's clean utility literature to determine an approximate max capacity, and Mueller engineers can help perform calculations on your exact unit. In order to calculate maximum capacity, you will need to know the plant steam pressure available to the unit, and for PSGs, the pure steam pressure required from the unit.
   
   
2. Determine what system changes are needed to reach the maximum capacity. Often, the capacity can be increased by changing the size of the orifice disks, and for an MES, changing the first effect setpoint and the feedwater pressure regulator setting. However, a Mueller engineer can help you determine if more extensive changes are needed. They will analyze your control valve sizing, degasser spray tube pattern (if equipped), pump sizing (if equipped), and utility requirements. There may also be multiple capacity upgrades available depending on how many items you want to modify.
3. Make the changes. Some changes, such as swapping orifice disks, can be completed by qualified maintenance staff, however, Mueller service technicians are available to make all required changes, whether large or small. Additionally, whether the changes are made by site personnel or Mueller technicians, Mueller recommends that you have a Mueller service technician startup the equipment after the modifications. They will ensure that the unit is operating at the optimum setpoints and that all mechanical components, such as the feedwater pressure regulator on an MES, are set correctly to balance the operation of the unit.
   
   
4. Verify the system capacity. With the proper setup, the pure steam or distillate capacity can be directly measured. However, if this is not possible on your site, a Mueller engineer can help to approximate it. The Mueller engineer will need to know the plant steam control valve Cv and % open, the plant steam pressure, the evaporator pressure, and the first effect (or separator) temperature setpoint.
   
   

What can you do if these steps don’t work for you? What if you are already producing at the maximum capacity for your unit?

• For an MES - Make sure you are using your control logic and water effectively. Each time the unit starts up from standby, it goes through a purge cycle that sends water to drain for approximately 15 minutes. If your unit is starting and stopping often, you could be sending a lot of water to drain. Since the MES is usually signaled to generate WFI after the tank level drops below a certain point, determine if you could have your MES startup at a lower tank level and run all the way to 100% full on your tank. The advantage of this practice is that it allows the MES the longest run possible and minimizes the number of purge cycles that your unit goes through.
  
  
• For a PSG - Determine the lowest pure steam pressure that you can accept. Mueller PSGs can produce more pounds per hour of steam if that steam is produced at a lower pressure. If your current production is at or above 45 psig, you can likely increase production by lowering your pure steam temperature setpoint. Additionally, you can determine if the unit you have is capable of an evaporator upsize. For the Mueller 7000 series, units that end in “zero” generally have a larger evaporator that could be substituted into your existing unit. Additional changes may be necessary to make this new evaporator work. A Mueller engineer can help you with the calculations for either of these potential changes.
  
  
• For both MESs and PSGs - Determine if you can increase your available plant steam pressure. Mueller MESs and PSGs are typically rated to accept plant steam up to 125 or 150 psig. If you are supplying plant steam at a lower pressure, see if you can increase it.
  
  

Finally, if all these steps don’t give you the capacity you need, contact a Mueller Regional Sales Manager for information about a new, larger MES or PSG. Even if you have tight corridors, small doors, or an elevator to get into your facility, Mueller can work with you to find a solution that will work for you.

If you have additional questions or are in need of service support, you can also reach out directly to our service team at 1-888-281-5800.