Dresser RCS 사용 설명서 - 페이지 2

{카테고리_이름} Dresser RCS에 대한 사용 설명서을 온라인으로 검색하거나 PDF를 다운로드하세요. Dresser RCS 19 페이지. Rotary lobe blowers

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1. Maintenance/Replacements

OPERATING CHARACTERISTICS

Roots RCS blowers, as covered in this manual, are

available in basic frame size of 4Y2 inch gear diameter.

Within this frame size are two case lengths, selected to

produce reasonable steps in blower carJacity ratings. All

units are designated as air blowers, and may be used for

handling air in either pressure or vacuum service. They

are unsuitable for handling gases because shaft seals are

not designed to prevent leakage to atmosphere.

The basic Roots rotary lobe blower is a positive

displacement type unit, whose pumping capacity is deter-

mined by size, operating speed and pressure conditions. It

employs two double-lobe impellers mounted on parallel

shafts and rotating in opposite directions within a

cylinder closed at the ends by headplates. As the impellers

rotate, air is drawn into one side of the cylinder and forced

out the opposite side against the pressure existing there.

The pressure developed,

therefore, depends on the

resistance of the discharge system.

Effective sealing of the blower inlet area from the

discharge area is accomplished by use of very small

operating clearances. Resulting absence of moving con-

tacts eliminates the need for any internal lubrication.

Clearance between the impellers during rotation are main-

tained by a pair of accurately machined timing gears,

mounted on the two shafts extended outside the blower

casing.

Operation of the rotary lobe blower is illustrated in

FIGURE 1, where air flow is right to left from inlet to

discharge with the lower impeller rotating clockwise. In

Position 1 it is delivering a known volume (A) to the

discharge, while space (B) between the upper impeller and

cylinder wall is being filled. Counterclockwise rotation of

this impeller then traps equal volume (B) in Position 2,

and further rotation delivers it to the discharge in Posi-

tion 3. At the same time, another similar volume is form-

ing under the lower impeller, and will be discharged when

rotation reaches Position 1 again.

One complete revolution of the driving shaft alter-

nately traps four equal and known volumes of air (two by

each impeller) and pushes them through to the discharge.

The pumping capacity of a lobe blower operating at a con-

stant speed therefore remains relatively independent of

reasonable inlet or discharge pressure variations. To

change capacity, it is necessary either to change speed or

rotation or vent some of the air.

No attempt should ever be made to control capacity

by means of a throttle valve in the intake or discharge pip-

ing. This will not only increase the power load on the

driver, but can also overload and seriously damage the

blower. If a possibility does exist that flow to the blower

inlet may be cut off during normal operation of a process,

then an adequate vacuum relief valve must be installed

near the blower. A pressure type relief valve in the

discharge line near the blower is required for protection

against cut-off or blocking in this line. See Figure 2.

When a belt drive is employed, blower speed can

usually be adjusted to obtain desired capacity by dhang-

ing the diameter of one or both sheaves. In a direct

coupled arrangement a variable speed motor or transmis-

sion is required, or excess air may be blown off through a

manually controlled unloading valve and silencer. If

returned to the blower inlet, the air must be cooled to

100 OF (38°C) through a by-pass arrangement to maintain

acceptable blower temperatures.

Before making any change in blower capacity, or

operating conditions, contact the nearest Sales Office for

specific information applying to your particular blower.

In all cases, operating conditions must be maintained

within the approved range of pressures, temperatures and

speeds as stated under LIMITATIONS. Also, the blower

must not be used to handle air containing liquids or solids.

Serious damage to the rotating parts will result.

OPERATING LIMITATIONS

To permit continued satisfactory performance, a

Roots RCS blower must be operated within certain ap-

proved limiting conditions. The Manufacturer's warranty

is, of course, also contingent on such operation.

Maximum limits for pressure, temperatures and

speed are specified in Table 1 for RCS blowers. These

limits apply to all blowers of normal construction, having

operating clearances as listed in Table 5, when operated

•

POSITION 1

POSITION 2

POSITION 3

~207'J

Figure 1 :- Flow Through ReS Blower