When selecting a positive displacement blower for your home or office, you will want to know how it works. There are three main types: Rotary lobe, Rotary vane, and screw. Learn which one is best for your needs. Then decide what size you need based on these factors.
In this article, you will learn about the maintenance require to upkeep these machines, as well as what can go wrong.
Table of Contents
Positive displacement
A Positive Displacement Blower is a device that moves air from a positive pressure environment to a negative pressure environment. Click here for more information. It is typically used to transfer polymer powders and pellets. These devices are available in a variety of sizes, and are driven by direct-connected motors or a gearbox and belt arrangement.
These machines are typically oil splash-lubricated or can be equipped with forced-feed lubricants. They are often designed to respond to market demands, but traditional designs often prevail over innovation.
While this type of machine is capable of providing adequate air flow, they can be susceptible to starved inlet conditions. Starved inlets can cause the internal temperature of the blower to rise. When this happens, the parts may start to brown.
The yellowish rotor color indicates an internal temperature of around 430 degrees. However, in some cases, positive displacement blowers can reach temperatures of 640 degrees or more.
Rotary lobe
A rotary lobe blower works on the same principal as a rotary vane type. Its two impellers, each rotating in opposite directions, trap gas on the inlet side and exhaust it on the outlet side. Gas travels in cavities around the lobe chamber.
The rotors’ rotation speed and chamber size determine the volumetric flow of air. Despite the similarity, positive displacement blowers are different from their vane-based counterparts.
A positive displacement blower creates flow by filling and emptying two or more chambers. This process creates a flow independent of the operating pressure of the compressor.
There are several variations of positive displacement blowers, each using the same principle, but with slightly different designs. These include rotary lobe, rotary vane, and radial lobe.
Positive displacement blowers are generally equipped with a rotary lobe, which means that its rotors are arranged in a spiral pattern. This enables them to operate at constant speeds, even when the pressure of the system increases.
The device is suitable for a wide range of applications, including exhausting. The constant speed operating characteristics of these devices allow them to function as an exhauster or a compressor.
Limitations
Although a positive displacement blower can perform multiple functions, its operating range is limited by its high compression ratio.
While the ratio is largely governed by the operating temperature, the device may become damaged by high pressure or low vacuum. These conditions can lead to distorted impellers and casings. To extend the operating range of a positive displacement blower, oil lubrication is recommended. This lubricant will provide cooling for the blower’s components.
This device can be costly to operate and may cause costly downtime if a failure occurs. When the air inlet is inadequate, the machine will overheat and develop a yellow color, indicating an internal temperature of 430 degrees. It may even reach 640 degrees, meaning it is incapable of turning down to a lower speed.
To prevent this problem, it is advisable to check the device’s oil levels before running conveyors.
Maintenance
Performing routine maintenance is important to keep it working properly. Although small amounts of dirt and debris won’t affect it, larger particles can cause the impeller to become clogged and fail.
Cleaning and dislodging all particles is crucial for performance. If you hear unusual noises, vibrations, or excessive current, it may be time for maintenance. Here are some tips to help you with routine maintenance.
Always check the oil level. It’s important to check your machine’s oil level regularly and never run it when the filter is starved of oil. Otherwise, you’ll experience premature gear failure and end clearance changes, and your positive displacement blower will malfunction.
When this happens, replace the filter. It’s also essential to visually inspect the device for any debris. If the inlet filter is dirty, it’s too late. Replace it as soon as possible. Click the link: https://www.scdot.org/business/pdf/stormwater/SC-M-815-8.pdf for technical specifications about inlet filters.
A positive displacement blower has two or more rotating impellers in a central casing. The impellers spin in opposite directions to force air into the machine’s chamber. The air trapped between the impellers is at atmospheric pressure. The resulting circulation ensures that the airflow is unidirectional.
Because these machines have relatively few parts, they’re easy to maintain and operate. In general, positive displacement blowers don’t require routine maintenance, but they can experience a sudden failure and stop working. Be sure to follow these tips to be safe.
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