Pump Cabinets: Control the Heat!

by Rand Weyler

Vacuum Pump CabinetFire_in_Hand_cropped
Design Considerations

Vacuum pumps suck, and that suction power can produce significant heat! When a pump is trapped in an enclosed and acoustically-insulated vacuum pump cabinet, the air temperature can quickly rise beyond the operating range of the pump. This common oversight can be quite frustrating upon completion of the lab project. The users move in and their vacuum pumps immediately begin to overheat. To protect the pumps, they leave the pump cabinet doors open, or the pumps are pulled out and put on the floor until the problem can be resolved.

How can we avoid this? Vacuum pump cabinets are designed for basic smaller pumps but can be configured for larger pumps or even multiple smaller pump units. A bit of simple design preplanning on vacuum pump cabinets is essential to a successful project. And it’s not just the heat output that is important; it’s the noise level, the weight of the vacuum pump, the size of the pump, and how the pump is serviced that also need to be addressed. In this blog post we will discuss all of these considerations.

HEAT – In order to have enough air to keep the pump cool in an enclosed vacuum pump cabinet, we will likely need a motorized fan to bring in room air and remove heated air. Because hot air rises, I would recommend that the fan be located high inside the cabinet and blowing out, while the air inlets are kept low to bring the coolest room air in. The more heat the vacuum pump produces, the more air we will need to exchange. Considerations on where to locate the fan exhaust should also be made. Typically the heated exhaust air should be blowing away from the user or any nearby obstructions.

DanaFarber-005c_v2BLOGPICThe fan’s airflow requirement can be determined using the vacuum pump’s heat in BTUs per hour or Watts. Also needed is the expected ambient (room) temperature and the pump’s recommended operational temperature range. For example, let’s use a vacuum pump that produces 2500 BTUs per hour in a 75° F room. The safe operational range of this pump goes up to 95° F. If the fan’s airflow is 150 Cubic Feet of air per Minute (CFM) the temperature within the vacuum pump cabinet will rise 15.4° F. With an internal temperature rising to 90.4° F, the heated air is approximately 5° F lower than the maximum allowable temperature to operate the vacuum pump. Since there is static pressure within the closed cabinet we would recommend that the 150 CFM be about 75% of the fan’s rated flow, so a fan rated at 200 CFM should be used. For assistance in calculating the fan requirements of your vacuum pumps, chillers or other heat producing equipment, contact our Technical Services Manager now! (That's me!)

NOISE LEVEL – The vacuum pump cabinet is usually insulated for sound reduction. Unfortunately some air openings in the insulation are necessary to cool the pump. Often louvers are used, but however the openings for cool air are provided, they should be the same total size as the open area of the fan or fans. A 6” diameter fan has an open area of about 28 square inches. To get a 28 square inch grill, we need a quantity of 113 (at) ½” x ½” square holes, or 144 (at) ½” diameter (round) holes somewhere on the lower portion of the vacuum pump cabinet. When using two fans, we need to double this. The more openings we have, the more noise we will hear. Fortunately the sound can be kept farther from our ears when we keep the open areas down low on the cabinet to bring in the cooler air.

Look for vacuum pump cabinets that use a 1” thick sound deadening foam that is not adhered to the cabinet interior. Insulation that is held in place by a metal frame is easily replaceable when it gets dirty or worn, where the glued-on version just becomes a big sticky mess.4

WEIGHT – SIZE – SERVICE – These three usually go hand in hand. Typical vacuum pumps sit on the bottom of the cabinet. To make it easier to access and service the pump, they can be placed on a pullout shelf. This shelf is often a containment pan to catch accidental oil spills. The size of the vacuum pump needs to fit in the pan, so providing the size of the pump to the cabinet manufacturer is important. Also, because the pan is on drawer runners, the runners need to support the weight of the vacuum pump. Standard drawer runners are rated at 100 lbs but 200lb drawer slides are also available. The runners allow the pump to be pulled out of the cabinet for service, such as changing the oil.

In cases where the pump is bigger or heavier than what the pullout shelf can handle, a vacuum pump cabinet can be made without a bottom. In this scenario, the cabinet toe kick opens with the door and the vacuum pump can either sit directly (in a pan) on the floor, or can pull out for service if it sits in an independent cart. The cart is a 4 wheel dolly that also has a containment pan for spilled oil. The three sided cabinet should be reinforced at the floor for strength, and ideally has a smooth surface on the lower interior so that the cart does not catch on a leveler leg or other cabinet structure. The toe kick should be height adjustable so it can be raised if the floors are not level or if a comfort mat is on the floor in front of the cabinet. When sizing the pump cart, remember that the toe kick on the door is 3" deep, so the cabinet door needs to open beyond 90° in order to have the full opening for the cart. This is illustrated in the image below.pump_cabinet_comparison_images

With New England Lab, YOU can control the heat and any other aspect of your vacuum pump cabinet design! We specialize in solutions that meet your needs, and we are set up to work with you through the budgeting and design process. Please contact our Technical Services Manager to help you with your new vacuum pump cabinet design today!