GENERAL REQUIREMENTS FOR CONCRETE VIBRATORS, SCREED BOARD TYPE

GENERAL REQUIREMENTS FOR
CONCRETE VIBRATORS, SCREED BOARD TYPE

SCOPE


This standard lays down the requirements for materials, sizes,
construction, assembly and performance of screed board concrete vibrators,
screed board vibrators operated by pneumatic power are not
covered in this standard.


TERMINOLOGY

For the purpose of this standard, the following definitions shall apply.

Amplitude of Vibration - Maximum displacement of a vibrating.
body from its mean position during vibration. It is usually expressed
as half of its total displacement.

Eccentric Shaft ( Rotor ) - The rotating shaft of the vibrating unit
designed to produce the required frequency and amplitude of vibration.

Anchor - The arrangement provided to give a support to the screed
board when desired.

Frequency of Vibration - Number of complete cycles of vibrations
per minute.

Screed Board ( Tamping Beam or Vibrating Beam ) - The beam to
which the vibrating unit is affixed and which compacts the concrete due
to its vibration.
Tube (Casing ) - Fitting whieh encases the eccentric shaft.
2.7 Vibrating Units - The complete assembly of tube, the eccentric
shaft and its bearings, affixed to the screed board to impart vibrations
to it.

Vibration of Acceleration - The maximum acceleration per cycle of
vibration. It is usually expressed as a multiple of g, the acceleration
due to gravity.

MATERIALS


The eccentric shaft shall be made of carbon steel of Grade 35C8 of
IS : 1570 ( Part 2 )-1979” and shall be tempered and polished

The tube or casing of the vibrating unit and other parts shall
conform to IS : 226 - 19757

The rivet bars shall conform to IS : 1148 - 1982$ or IS : 226- 1975t.
3.4 Spring shall be manufactured from suitable grade of wire conforming
to IS : 4454 ( Part 1 )-19813.

All other materials to be used in construction of the screed board
vibrator shall conform to the relevant Indian Standards.

SIZES
Size Designation - The size of the vibrator is designated by the
*overall length of the screed board expressed in metres. Common sizes
of the vibrators are 3, 4 and 5 m.


The vibrating unit or units shall be rigidly affixed to the screed
‘board so that there is no relative : movement between the vibrating beam
and th-e vibrating unit, during operation. Suitable arrangements shall be
provided- to allow for easy fixing and removal of the vibrating unit from
the screed board. Suitable arrangement shall also be provided for occasional
tightening of the fixing joint between the vibrating unit and~the
screed board which may become necessary during operation.

vibrations of vibrating unit or the vibrating beam are not transferred to
it thereby affecting its life and performance; and the efficiency of the
drive shall be such that there is no significant slippage under full operating
loads. In case of belt drives, multiplev-belt drives should preferably
be used, tensioning device shall be provided to keep the transmitting
medium adequately tensioned during operation.

The vibrating unit or units shall be suitably positioned, generally,
symmetrically with respect to the centre of length of the screed board,
to ensure that the amplitude ,and frequency of the screed board are as
far as possible uniform all along its length.
The vibrating beam shall be rigid enough and vibrating units and
the beam supports shall be so placed as to prevent excessive vibration
( whipping ) of the beam between the positions of vibrating units. The,
weight of the beam and the elasticity of the supports shall be so
proportioned that the vibrations are not damped aut by the supports.

Vibrating Unit - The vibrating unit shall be of totally enclosed
construction and shall be filled with correct amount of lubricant and
properly sealed to protect against the entry of dust and moisture.

The tube or casing of the vibrating unit shall be seamless in
construction and shall be of material as specified in 3.2. The minimum
finished wall thickness of the tube anywhere in its length including the
thickness on the bearing seating shall not be less than 4 mm.

The bearings and the eccentric shaft shall be-so assembled as
to enable the easy removal of the shaft for repairs and replacements.
Suitable arrangements shall be provided for adequate lubrication of
bearings so as to prevent them from being heated excessively-in actual
operations. Such a provision also should take care of prevention of
entry of moisture or cement slurry by providing a one way entry for the
lubricant with the help of valve.

Screed Board - The screed board shall generally be of well-seasoned

hard wood timber of cross-section not less than 75 X 150 mm or any
other suitable material. The width of the screed board in any case
shall not be less than 75 mm. If made of hard wood the screed
board shall be shown with steel plate not less than 1’6 mm thick. The
screed board should be checked periodically against bending of board so
that the vibrated surface does not result in a curve.

Handles - The vibrator shall be provided with two handles, each
suitably mounted on either end of the screed board. Each handle shall
be provided with suitable anti-vibration packings or springs so as to
protect it from direct vibrations of the screed board. The handles and

Anchor - An anchor of suitable design shall be provided at one
end of the screed board, preferably mounted on the handle so as to give
support to the entire unit when required. The anchor shall be designed
to dig into ordinary ground without much difficulty.

PERFORMANCE REQUIREMENTS


Operation Characteristics - The vibrators shall be so designed that
when tested for operational characteristics
provisions given in 6.1.1.
shall comply with the
The requirements given in 6.1.1 shall be
checked on selected samples on the basis of suitable sampling scheme.

Frequency of Vibration                                                                     Minimum Amplitude
Vibrations/minute                                                                                          mm
3 000 to 3 200 for thickness of                                                                        1.5
concrete up to 15 cm
3 000 to 3 200 for thickness of                                                                         2.0
concrete from 15 to 25 cm
3 500 to 3 700                                                                                                   1.5

NOTE - In no case frequency less than 3 000 shall be accepted.

Mechanical Efficiency - After continuous running of vibration for
more than 4 hours, the rotor temperature shall not be more than 70°C
and shall be tested in accordance with IS : 6923 - 1973*

Endurance Test - The endurance test shall be in accordance with
IS : 6923 - 1973*.

INSTRUCTION SHEET

An instruction sheet containing instructions relating to installation,
maintenance and lubrication of the vibrator and the prime mover shall
be given.

MARKING

8.1 Each vibrator shall have firmly attached to it a mark plate ‘bearing the
following information:
a) Manufacturer’s name or trade-mark:
bj Vibrator reference number;
cl Type and rating of the power unit to be used;
d Year of manufacture; and
e) Frequency and amplitude.

e) Frequency and amplitude.


Comments

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Testing method

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