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by hand or by very light tapping. A tight or driving fit can
<br />damage a bearing, and may cause internal blower damage
<br />by forcing the impeller out of its normal operating position.
<br />A loose fit or wobbly sheave will cause vibration, and may
<br />result in shaft breakage.
<br />The driver sheave should also be mounted as close to its
<br />bearing as possible, and again should fit the shaft correct-
<br />ly. Position the driver on its adjustable base so the % of the
<br />total movement is available in the direction away from the
<br />blower, and mount the assembly so that the face of the
<br />sheave is accurately in line with the blower sheave. This
<br />position minimizes belt wear, and allows sufficient adjust-
<br />ment for both installing and tightening the belts. After belts
<br />are installed, adjust their tension in accordance with the
<br />manufacturer's instructions. However, only enough tension
<br />should be applied to prevent slippage when the blower is
<br />operating under load. Excessive tightening can lead to early
<br />bearing failures.
<br />In the absence of belt manufacturer's instructions for ten-
<br />sioning, the following procedure may be used.
<br />1. With the belts loose, pull the slack on all of them to the
<br />bottom side of the drive.
<br />2. Adjust motor position to tighten belts until they appear
<br />to be seating in the sheave grooves.
<br />S. Thump the belts with your fist. If they feel dead, tighten
<br />them more until they vibrate and feel springy when
<br />struck.
<br />4. Run-in the drive for a short period, after preparing the
<br />blgwer ps instructed in a following paragraph. While run-
<br />ning adjilst until only a very slight bow appears in the
<br />slack side�of the belts.
<br />5. Stop the motor apd compare the tensions of the in,
<br />belts by pressing down firmly with one hand
<br />on the top surface. It should be possible to deflect each
<br />belt only to the point where its top surface is even with
<br />the bottom of the other undeflected blets.
<br />6. A new set of belts should be first tensioned about
<br />greater than normal to allow for stretch and wear -in.
<br />Before putting the drive into normal operation, increase
<br />the tension as obtained above by a small amount. recheck
<br />after each 8 hour operating period during the first 50
<br />hours and, adjust as necessary.
<br />Before operating the drive under power to check initial
<br />belt tension, first remove covers from the blower connec-
<br />tions. Make sure the interior is still clean, then rotate the
<br />shaft by hand. Place a coarse screen over the inlet connec-
<br />tion to prevent anything tieing suehed into the blower while
<br />it is operating, and avoid standing in line with the discharge
<br />opening. Put oil in the sumps per instructions under
<br />LUBRICATION.
<br />Before connecting PIPING, remove any itemaining anti -
<br />rust compound from blower connections. Pipe used should
<br />be no smaller than these connections, and clean, new pip-
<br />ing throughout is strongly recommended. In addition, make
<br />sure it is free of dirt, scale, cuttings, weld beads, or foreign
<br />materials of any kind.'To further guard against damage to
<br />the blower, expecially when an inlet filter is not used, in-
<br />stall a substantial screen of 16 mesh backed with hardware
<br />cloth at or near the inlet connections. Make provisions to
<br />clean this screen of collected debris after a few hours' opera-
<br />tion. It should be removed when its usefulness had ended,
<br />as the wire will eventually deteriorate and small pieces go-
<br />ing into the blower may cause serious damage.
<br />Pipe flanges or male threads must meet the blower con-
<br />nections accurately and squarely. DO NOT attempt to cor-
<br />rect misalignment by springing or cramping the pipe. In
<br />most cases this will distort the blower casing and cause im-
<br />peller rubbing. In severe cases it can prevent operation or
<br />result in a broken drive shaft. For similar,reasons, piping
<br />should be supported .near the blower to eliminate dead
<br />weight strains. Also, if pipe expansion is likely to occur from
<br />temperature change, installation of flexible connectors or
<br />expansion joints is advisable.
<br />Figure 2 represents in diagram form a blower installa-
<br />tion with all accessory items that might be required under
<br />various operating conditions. Inlet piping should be com-
<br />pletely free of valves or restrictions. When a shut-off valve
<br />(not shown) cannot be avoided, make sure a full size vacuum
<br />relief is installed near the blower inlet. This will protect
<br />against blower overload caused by accidental closing.
<br />-BACK-PRESSURE SILENCERS MUST BE MOUNTED
<br />REGULAT0R OR WIIHIN ONE PIPE DIAMETER
<br />PRESSURE RELIEF OF BLOWER FIANCE,
<br />VALVE INLET 71L7ER�
<br />e -MANUAL UNLOADING VALVE
<br />CHECK
<br />VALVE
<br />INLET SILENCER
<br />THERMOMETERS F
<br />PRESSURE GAUGES
<br />D
<br />DISCHARGE
<br />SILENCERTEMPORARY ��
<br />EN
<br />ZPANSION ��IXPANSION
<br />JOINT JOINT
<br />WITH CONTROi UNiI
<br />Fgwe 2 — lnalell dm With Ameaemies
<br />Need for an inlet silencer will depend on blower speed
<br />and pressure, as well as sound -level requirements in the
<br />general surroundings. An inlet filter is normally recom-
<br />mended, especially in dusty or sandy locations, for blower
<br />protection. A discharge silencer is also normally suggested
<br />Specific recommendations on silencing can be obtained from
<br />the nearest Sales Office.
<br />Discharge piping requires, a pressure relief valve, and
<br />should include a manual unloading valve to permit starting
<br />the blower under no-load conditions. Reliable pressure/vacuum
<br />gauges and good thermometers at both inlet and discharge
<br />are recommended to allow making the important checks on
<br />blower operating conditions. The back -pressure regulator
<br />shown in Figure 2 is useful mainly when volume demands
<br />vary while the blower operates at constant output. If de-
<br />mand is constant, but somewhat lower than the blower out-
<br />put, excess may be blown off through the manual unloading
<br />valve.
<br />In multiple blower installations where two or more units
<br />operate with a common header, use of check valves is
<br />necessary. These should be of a direct acting or free swing-
<br />ing type, with one valve located in each line between the
<br />blower and header. Properly installed, they will protect
<br />against damage from reverse rotation caused by air and
<br />material back -flow through an idle blower.
<br />After piping is completed, and before applying power,
<br />rotate the drive shaft by hand again. If it does not move
<br />with uniform freedom, look for uneven mounting, piping
<br />strain, excessive belt tension or coupling misalignment. DO
<br />NOT operate the blower at this time unless it has been
<br />lubricated per instructions. Read LUBRICATION section.
<br />41
<br />4'1�
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