Ovoid Pipes

Milton offers a range of concrete ovoid pipes including a flexible joint seal for use with both foul and surface water applications.

The ovoid concrete pipe is produced and tested in accordance with the relevant provisions of BS EN1916:2002/BS5911-1:2002 including dimensional tolerances, crushing, hydrostatic, water absorption and joint tests.

The ovoid pipe has better velocity characteristics at low flows than equivalent circular pipes, which provides:

  • Lower operating costs, where some sewers may be laid without the need for pumping.
  • Better self cleansing and therefore less risk of siltation and blockage.
  • Reduced costs of trench excavation resulting from shallower gradients.

Pipe weights and dimensions                                                                 BS 5911-1:2002 class 150

Nominal internal size Effective length Width of base Approx. external dimensions over socket Approx weight Joint type
width A height B E Width C Height D
mm mm m mm mm mm kg  
600 900 2.50 375 900 1210 2170 Lamell
800 1200 2.50 490 1100 1545 3300 Lamell
400 600 1.25 See www.cpm-group.com/drainage/ovoidpipes 910 'G' Ring
  • The 600x900 and 800x1200 ovoid pipes are supplied with two lift anchors cast in the top for use with 'Flexilift' lifting/jointing system.
  • 'C' hook available for lifting/jointing 400x600 ovoids.
  • Lifting/jointing equipment can be supplied on request
  • Short lengths of either spigot/socket butt pipes can be supplied for building into the manhole wall for the 600x900 and 800x1200 ovoids, and are 1.25m long and 0.625m long for the 400x600 pipe.
  • Junctions can be fitted and can be made from drainage material other than concrete

Cross section of ovoid pipe 600 x 900 and 800 x1200

Installation of ovoid pipe with flexible joint seal

Cross section of ovoid pipe (400x600)

External dimensions - barrel 770 socket 840

Ovoid pipe 400x600

Standard form 1 ovoid

(400mm x 600mm R= 200mm)

(600mm x 900mm R=300mm)

(800mm x 1200mm R=400mm)

'C' hook for lifting/jointing

Tables of capacities and velocities for ovoid pipes

Slope
400 x 600
Ks 0.3 Ks 0.6 Ks 1.5
Qm3/s V m/s Qm3/s V m/s Qm3/s V m/s
Area 0.18m2
Size of circular pipe with nearest area is 450mm/525mm diameter
0.0001
0.0002
0.0005
0.0010
0.0020
0.0050
0.0100
0.0200
0.0500
0.1000
0.038
0.055
0.089
0.126
0.182
0.290
0.412
0.586
0.930
1.317
0.206
0.299
0.484
0.685
0.989
1.580
2.239
3.185
5.054
7.158
0.036
0.052
0.083
0.118
0.169
0.269
0.382
0.544
0.857
1.214
0.196
0.283
0.451
0.641
0.918
1.462
2.076
2.956
4.658
6.598
0.033
0.047
0.074
0.106
0.151
0.240
0.339
0.480
0.760
1.074
0.179
0.255
0.402
0.576
0.821
1.304
1.842
2.609
4.130
5.837
600 x 900 Area 0.4134m2
Size of circular pipe with nearest area is 750mm
0.0001
0.0002
0.0005
0.0010
0.0020
0.0050
0.0100
0.0200
0.0500
0.1000
0.111
0.160
0.258
0.368
0.525
0.837
1.189
1.686
2.674
3.786
0.268
0.387
0.624
0.890
1.270
2.024
2.876
4.078
6.467
9.157
0.106
0.151
0.242
0.345
0.490
0.778
1.103
1.563
2.474
3.502
0.256
0.365
0.585
0.834
1.185
1.882
2.668
3.780
5.984
8.470
0.096
0.137
0.218
0.310
0.439
0.696
0.985
1.395
2.207
3.122
0.232
0.331
0.527
0.750
1.062
1.683
2.382
3.374
5.338
7.551
800 x 1200 Area 0.73504m2
Size of circular pipe with nearest area is 975mm
0.0001
0.0002
0.0005
0.0010
0.0020
0.0050
0.0100
0.0200
0.0500
0.1000
0.237
0.341
0.549
0.784
1.116
1.777
2.522
3.576
5.667
8.024
0.322
0.464
0.747
1.067
1.518
2.418
3.431
4.865
7.710
10.916
0.226
0.323
0.516
0.734
1.042
1.654
2.344
3.320
5.256
7.439
0.307
0.439
0.702
0.999
1.418
2.250
3.189
4.517
7.151
10.121
0.206
0.293
0.466
0.662
0.937
1.485
2.102
2.974
4.706
6.657
0.280
0.399
0.634
0.901
1.275
2.020
2.860
4.046
6.402
9.057

Source of data: Capacities calculated by Wallrus Simulation Part 1. Velocities calculated from areas derived from Crimp and Bruges tables. The equivalent circular sizes shown have approximately the same flows and velocities for given roughness and gradients as the ovoid pipes. The capacities of ovoid pipes are 1.6 times the capacities of circular pipes of the same width, whereas the velocities are similar.

Hydraulic calculations

Design of sewers using ovoid pipes

CPM ovoid pipes are a form 1 ovoid section for which approximate full and part full velocities and discharges can be readily determined using the following procedure.

An equivalent circular pipe diameter is calculated by using Da = 0.773y where y is depth of ovoid.

This is a circle with the same hydraulic radius as a form 1 ovoid.

The actual equivalent diameter then has to be corrected to the nearest nominal metric pipe size to utilise hydraulic flow charts. All values are for pipes flowing full.

Where:

Qa = Equivalent circular diameter discharge (m3/s)

Qn = Nominal diameter discharge from charts (m3/s)

Va = Equivalent circular diameter velocity (m/s)

Vn = Nominal diameter velocity from charts (m/s)

Da = Equivalent circular pipe diameter (m)

Dn = Nominal circular pipe diameter (m)

X = The value is dependant on the Reynolds Number, however an average of 2.675 can be assumed.

Qovoid = Ovoid full pipe discharge (m3/s)

The following can be established.

Pipe - full velocities

Read directly from charts for nominal circular pipe diameter (Vn) and apply Interpolation expressions to calculate Va.

Pipe - full discharges

Read directly from charts for nominal circular pipe diameter (Qn) and apply Interpolation expressions to give actual pipe discharge (Qa). Multiply Qa by a shape factor of 1.089 for a form 1 ovoid. Hence discharge in ovoid pipe is then given by

Qovoid = Qa x 1.089

Part - full velocities and discharges

Determine pipe full values and apply proportional flow information given for part-full ovoid pipes. For more detailed information reference should be made to Hydraulics Research document "Charts for the design of channels and pipes" or calculation by Wallrus Simulation Part 1.

Example:

Given a foul sewer is to be laid using WN 800 x HN 1200 ovoid pipes at a gradient of 0.005 (1 in 200) with an assumed Ks = 1.5mm.

1. Calculate the full bore discharge.

Equivalent circular pipe diameter Da = 0.773y
Da = 0.773 x 1.2 = 0.928m
Nearest nominal pipe size is DN 900
From hydraulic chart Qn at 0.005 gradient is 1.26m3/s

Interpolating Qa = (1.26 x(0.928)2.675)/0.900 = 1.37m3/s

Final shape correction gives

Qovoid = 1.37 x 1.089 = 1.49m3/s

2. Calculate discharge when depth of flow is 0.3m.

Proportional depth = 0.3 / 1.2 = 1.37m3/s

From (1) Qovoid = 1.49m3/s

From proportional flow table, proportional discharge is 0.113.

Hence discharge at a flow depth of 0.3m is 0.113 x 1.49 = 0.17m3/s

3. Calculate velocity when minimum flow is 0.1m3/s.

From (1) Qovoid = 1.49m3/s

Proportional discharge = 0.1 / 1.49 = 0.067

By interpolating proportional flow table, proportional area is 0.108

ence from Q = VA

Where:

Q = Discharge m3/s

A = Area of Ovoid (0.73504m2 for WN 800 x HN 1200)

V = Velocity m/s

V = 0.1 / (0.108 x 0.735) = 1.26m/s

WN400 x HN600 - Ovoid y = 600 - Area = 0.18m2

WN600 x HN900 - Ovoid y = 900 - Area = 0.41346m2

WN800 x HN1200 - Ovoid y = 1200 - Area = 0.73504m2

Tel: (01795) 425191
Fax: (01795) 420360
E-Mail: sales@miltonprecast.com

Milton Pipes Limited, Milton Regis, Sittingbourne, Kent. ME10 2QF