Man Hole Covers



GUIDELINES FOR FACTORY INSPECTION OF PRECAST

MANHOLE COVERS AND FRAMES (As per IS 12529:2002):

1) MarkingP-

Following information shall be clearly and permanently marked on top of each manhole cover and frame:

a) Identification of the source of manufacture;

b) Grade designation denoted by LD-2.5/MD-10/HD-20/EHD-35

c) Any identification mark as required by the purchaser; and

d) Year and month of manufacture of the manhole cover and frame marked at any appropriate location.

Manhole covers and frames shall be of the following four grades and types:

Grade Designation Type/Shape of Cover
 Light Duty LD-2.5 Rectangular, Square, Circular
Medium Duty MD-IO Rectangular, Square, Circular
Heavy Duty HD-20 Rectangular (Scrapper Manhole), Square, Circular and Lamp hole
Extra Heavy Duty EHD-35 ectangular (Scrapper Manhole), Square and Circular

2) Sampling:-

The number of covers and frames to be selected from the lot shall depend on the size of the lot and     shall be according to table given below:

No. of Covers or frames in the Lot

 Dimensional Requirements

No. of samples for Load test on Cover only

Sample size

Acceptance Number

 Up to 100

10

1

2

101 to 200

15

1

3

201 to 300

20

2

4

301 to 500

30

3

5

3) Physical MeasurementsNote :- If  the number of covers in the lot is 20 or less, the number of samples for the load test shall be decided by mutual agreement between the purchaser and the manufacturer.

The top and inside surface of frames shall be smooth. To prevent the top outer edge from possible damages, it shall be protected by 25 mm x 3 mm mild steel flat as part of the frame. Sufficient number of steel connectors shall be welded to the inner surface of the mild steel flat so as to connect it with the frame reinforcement and these shall be embedded in the concrete during casting.

Dimensions of Frame

Grade Designation

Description

Clear Opening in frame,

A

Step Height

B

Sitting ring height

C

Sitting ring width

D

Outer ring width

min

 Top Dia of cover F 

nominal

LD-2.5

Light duty

Rectangular

450 x 600

50

50

50

50

559 x 708

LD-2.5

Light Duty

Square

400 x400

450 x 450

50

50

50

50

50

50

50

50

508 x 50

558 x 558

LD-2.5

Light Duty

Circular

370

450

500

560

50

50

50

50

50

50

50

50

50

50

50

50

50

50

50

50

478

558

608

668

MD-10

Medium Duty

Rectangular

450 x 600

70

50

50

50

560 x 710

MD-10

Medium Duty

Square

450 x 450

600 x 600

70

70

50

50

50

50

50

50

560 x 560

710 x 710

MD-10

Medium Duty

Circular

450

500

560

600

70

70

70

70

50

50

50

50

50

50

50

50

50

50

50

50

560

610

670

710

HD-20

Heavy Duty

Rectangular

(Scrapper)

900 x 450

90

75

75

75

1060x610

HD-20

Heavy Duty

Square

560 x 560

90

75

75

75

720 x 720

HD-20

Heavy Duty

Circular

450

500

560

600

90

90

90

90

75

75

75

75

75

75

75

75

75

75

75

75

610

660

720

760

HD-20

Heavy Duty

lamp hole

350

90

75

75

75

510

EHD-35

Extra Heavy Duty

Rectangular

900 x 560

100

75

75

75

1060x720

EHD-35

Extra Heavy Duty

Square

560 x 560

100

75

75

75

720 x 720

EHD-35

Extra Heavy Duty

Circular

450

500

560

600

100

100

100

100

75

75

75

75

75

75

75

75

75

75

75

75

610

660

720

760

NOTES:
 1) Tolerance on C shall be ±5 mm, tolerance on ..4, B, D and E shall be  +5 ,0 mm.

2) For facility of removing the manhole cover suitable upward taper not more than 5 deg  may be provided to  Inner periphery of the frame.

3) If required for the removal of the moulds suitable taper not more than 5 deg can be given at the lower inner periphery of the frame.

4) The dimension F for frame is indicative only and has been arrived at based on the nominal values of dimensions A,B and D and a maximum taper of 5 deg on the inner periphery of the frame.  

- The maximum clearance at top between the frame and the cover all round the periphery is not more than 5 mm and the top surface of the frame and cover is in level within a tolerance of ± 5mm.

- The minimum diameter of mild steel rod use for lifting device shall be10 for light, 12 mm for medium duty covers and 16 mm for Heavy and Extra heavy duty covers.

- Clear cover to reinforcement shall be not less than 15 mm.

4) Load Test:

Procedure

1) The specified load as given below shall be applied without shock through the medium of a bearing block faced with hard rubber or other resilient material.

2) The bearing block shall be of the size specified in Table given below and shall bear centrally on the cover.

Grade of cover

Type

Load

KN

Dia of block

mm

LD-2.5

Rectangular, Square or Circular

25

300

MD-10

Rectangular, Square or Circular

100

300

HD-20

Rectangular, Square or Circular

200

300

EHD-35

Rectangular, Square or Circular

350

300

 4)All covers shall be submitted to the following tests:3)The block shall be sufficiently rigid to ensure that the load on the cover is uniformly distributed over the full area of the block.

a) Measurement of the permanent set of the cover after the application of 2/3 of the test load.

 b) Application of test load.

4.a)Measurement of Permanent Set of the Cover After the Application of 2/3 of the Test Load:

- Before the load is applied take an initial reading at the geometric centre of the cover.

- The load shall be applied at the rate of approximately 0.6±0.4 N/mm/s up to 2/3 of the test load. The load on the test specimen is then released.

- This procedure shall be carried out five times. Then take reading at the geometric centre.

- The permanent set shall then be determined on the difference of the measured readings before the first and the fifth loading.

-The permanent set shall not exceed the following values:

For LD- 2.5 and MD-10 – 1/100time the diameter of the largest circle that can be inscribed in the clear area of the frame

For HD-20 and EHD-35 – 1/300 time the diameter of the largest circle that can be inscribed in the clear area of the frame

4.b)Application of the Test Load

- Immediately after the test according to 4.a, the test load shall be applied at the same rate given in 4.a, the till the full test load is achieved.

- The test load to be maintained for 30±2 s. Cover shall not show cracks in the course of the test.

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