SITE INFORMATION AND CORRESPONDENCE

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Operating Characteristics No attempt should ever be made to control capacity by means of a throttle valve in the in- The M DPneumatics rotary lobe blower is a take or discharge piping. This will increase the positive displacement type unit, whose pump- power load on the drive system, increase � ing capacity is determined by size, operating operating temperatures, and can overload speed, and pressure conditions. It employs tri- and/or seriously damage the blower. Likewise, lobe or dual-lobe rotors rotating in opposite if a possibility exists that flow to the blower in- directions within a housing closed at the ends let may be cut off during normal operation of by end plates. a process, then an adequate vacuum relief valve Effective sealing of the blower inlet area to must be installed near the blower. A pressure the discharge area is accomplished by use of type relief valve in the discharge line near the very small operating clearances. Resulting blower is also strongly recommended for pro• absence of moving contacts eliminates the tection against cut-off.or blocking in this line need for any internal lubrication. Clearances Check valves should also be used on every between the rotors during rotation are maintain- blower when more than one blower is con. ed by a pair of accurately machined helical tim- nected to a discharge line. This is for both safe• ing gears, mounted on the two shafts extend- ty and operating conditions. ed outside the air chamber. The two in- When a belt drive is employed, blower speed, termeshing rotary lobes are designed to rotate if necessary, can usually be adjusted to obtain and trap air or gas between each rotor and the desired capacity by changing the diameter of housing. As the rotor lobes rotate past the edge one or both sheaves, or by using a vari-speed of the suction port, the trapped air or gas is motor pulley. In a direct coupled arrangement, essentially at suction pressure and temperature, a variable speed motor or transmission is re- since the blower is a constant volume device, the quired, or excess air or gas may be blown off trapped air remains at suction pressure until the through a manually controlled unloading valve leading rotor lobe opens into the discharge port. and silencer. Gas units can use bypasses, but Immediately, the high pressure air in the some application may require additional cool- discharge line compresses the low pressure air ing. If there is a large volume of high pressure to discharge pressure. The rotors continue to air or gas downstream of the blower, a check rotate and force the air from the blower into the valve in the piping downstream of the blower discharge line. will protect the blower from overspeeding It can be seen by the illustration that the air backwards on shutdown. moves not between the rotors but between the Consult your M D Pneumatics sales rotors and the side of the housings. Also, the representative if questions arise. rotation of the blower can make either side the inlet or discharge. INLET INLET INLET DISCHARGE DISCHARGE DISCHARGE FIGURE 1 2