Improve Sewer Hydraulics With HOBAS Sliplining

Hydraulics is typically an important consideration when planning pipeline rehabilitation. When sliplining is the chosen method, a slight diameter decrease will result. However, because of the much better flow characteristics of HOBAS liner pipe, normally the rehabilitated line's hydraulics are improved relative to its existing condition.

Parameters

The parameters that effect the changed hydraulics are the host and liner pipes' Manning's "n", diameter, and slope. Since the slope is unchanged, the relative flow capacity is computed as follows:

(Q_HOBAS / Q_Existing) = (n_Existing / n_HOBAS) (D_HOBAS / D_Existing)^{(8
/ 3)}

Characteristics

The n value of existing sewers varies widely, perhaps from 0.013 to 0.024 or higher. Due to corrosion, off-set joints, sliming, and other deterioration, a likely value for aged sewers is at least 0.018. The n value for new HOBAS pipes has been measured at 0.009. After several years of service (sliming, etc.), one agency determined an n value of 0.011.

Chart

The chart below shows the ratios of flow capacity of the HOBAS liner (Q HOBAS) to the host pipe (Q Existing) for various diameter combinations and ranges of Manning's "n". A ratio of greater than one indicates improved flow capacity after lining with HOBAS, while a value below one means a reduced flow capacity after the rehabilitation. A 1.1 ratio is a 10% flow capacity increase. A 0.9 ratio is a 10% flow capacity decrease.

Host Pipe Existing Flow Coefficient, n
		0.013	0.014	0.015	0.016	0.017	0.018	0.019	0.020	0.021	0.022	0.023	0.024
20" into 24"	0.009	0.961	1.035	1.109	1.183	1.257	1.331	1.405	1.479	1.553	1.627	1.700	1.774	20" into 24"
	0.010	0.865	0.932	0.998	1.065	1.131	1.198	1.264	1.331	1.397	1.464	1.530	1.597
	0.011	0.786	0.847	0.907	0.968	1.028	1.089	1.149	1.210	1.270	1.331	1.391	1.452
24" into 30"	0.009	0.851	0.916	0.982	1.047	1.113	1.178	1.244	1.309	1.375	1.440	1.505	1.571	24" into 30"
	0.010	0.766	0.825	0.884	0.943	1.001	1.060	1.119	1.178	1.237	1.296	1.355	1.414
	0.011	0.696	0.750	0.803	0.857	0.910	0.964	1.017	1.071	1.125	1.178	1.232	1.285
30" into 36"	0.009	0.936	1008	1.081	1.153	1.225	1.297	1.369	1.441	1.513	1.585	1.657	1.729	30" into 36"
	0.010	0.843	0.908	0.972	1.037	1.102	1.167	1.232	1.297	1.361	1.426	1.491	1.556
	0.011	0.766	0.825	0.884	0.943	1.002	1.061	1.120	1.179	1.238	1.297	1.356	1.414
36" into 42"	0.009	1.001	1.078	1.155	1.232	1.309	1.386	1.463	1.540	1.617	1.694	1.771	1.848	36" into 42"
	0.010	0.901	0.970	1.039	1.109	1.178	1.247	1.316	1.386	1.455	1.524	1.593	1.663
	0.011	0.819	0.882	0.945	1.008	1.071	1.134	1.197	1.260	1.323	1.386	1.449	1.512
42" into 48"	0.009	1.051	1.132	1.212	1.293	1.374	1.455	1.536	1.616	1.697	1.778	1.859	1.940	42" into 48"
	0.010	0.946	1.018	1.091	1.164	1.237	1.309	1.382	1.455	1.528	1.600	1.673	1.746
	0.011	0.860	0.926	0.992	1.058	1.124	1.190	1.256	1.323	1.389	1.455	1.521	1.587
48" into 54"	0.009	1.097	1.181	1.265	1.350	1.434	1.518	1.603	1.687	1.771	1.856	1.940	2.025	48" into 54"
	0.010	0.987	1.063	1.139	1.215	1.291	1.367	1.442	1.518	1.594	1.670	1.746	1.822
	0.011	0.897	0.966	1.035	1.104	1.173	1.242	1.311	1.380	1.449	1.518	1.587	1.656
54" into 60"	0.009	1.129	1.216	1.302	1.389	1.476	1.563	1.650	1.737	1.823	1.910	1.997	2.084	54" into 60"
	0.010	1.016	1.094	1.172	1.250	1.328	1.407	1.485	1.563	1.641	1.719	1.797	1.875
	0.011	0.924	0.995	1.066	1.137	1.208	1.279	1.350	1.421	1.492	1.563	1.634	1.705
60" into 66"	0.009	1.135	1.223	1.310	1.397	1.485	1.572	1.659	1.747	1.834	1.921	2.009	2.096	60" into 66"
	0.010	1.022	1.100	1.179	1.258	1.336	1.415	1.493	1.572	1.650	1.729	1.808	1.886
	0.011	0.929	1.000	1.072	1.143	1.215	1.286	1.358	1.429	1.500	1.572	1.643	1.715
66" into 72"	0.009	1.164	1.253	1.343	1.433	1.522	1.612	1.701	1.791	1.880	1.970	2.059	2.149	66" into 72"
	0.010	1.048	1.128	1.209	1.289	1.370	1.450	1.531	1.612	1.692	1.773	1.853	1.934
	0.011	0.952	1.026	1.099	1.172	1.245	1.319	1.392	1.465	1.538	1.612	1.685	1.758
72" into 78"	0.009	1.184	1.275	1.366	1.457	1.549	1.640	1.731	1.822	1.913	2.004	2.095	2.186	72" into 78"
	0.010	1.066	1.148	1.230	1.312	1.394	1.476	1.558	1.640	1.722	1.804	1.886	1.968
	0.011	0.969	1.043	1.118	1.192	1.267	1.342	1.416	1.491	1.565	1.640	1.714	1.789
72" into 84"	0.009	0.972	1.047	1.121	1.196	1.271	1.346	1.420	1.495	1.570	1.645	1.719	1.794	72" into 84"
	0.010	0.875	0.942	1.009	1.076	1.144	1.211	1.278	1.346	1.413	1.480	1.547	1.615
	0.011	0.795	0.856	0.917	0.979	1.040	1.101	1.162	1.223	1.284	1.346	1.407	1.468
84"FL into 90"	0.009	1.183	1.274	1.365	1.456	1.547	1.638	1.729	1.820	1.911	2.002	2.093	2.183	84"FL into 90"
	0.010	1.064	1.146	1.228	1.310	1.392	1.474	1.556	1.638	1.720	1.801	1.883	1.965
	0.011	0.968	1.042	1.117	1.191	1.265	1.340	1.414	1.489	1.563	1.638	1.712	1.768
84" into 96"	0.009	0.996	1.072	1.149	1.226	1.302	1.379	1.455	1.532	1.608	1.685	1.762	1.838	84" into 96"
	0.010	0.896	0.965	1.034	1.103	1.172	1.241	1.310	1.379	1.448	1.517	1.586	1.654
	0.011	0.815	0.877	0.940	1.003	1.065	1.128	1.191	1.253	1.316	1.379	1.441	1.504
96" into 102"	0.009	1.215	1.309	1.402	1.496	1.589	1.683	1.776	1.870	1.963	2.057	2.150	2.243	96" into 102"
	0.010	1.094	1.178	1.262	1.346	1.430	1514	1.598	1.683	1.767	1.851	1.935	2.019
	0.011	0.994	1.071	1.147	1.224	1.300	1.377	1.453	1.530	1.606	1.683	1.759	1.836
96" into 108"	0.009	1.043	1.124	1.204	1.284	1.364	1.445	1.525	1.605	1.686	1.766	1.846	1.926	96" into 108"
	0.010	0.939	1.011	1.084	1.156	1.228	1.300	1.372	1.445	1.517	1.589	1.661	1.734
	0.011	0.854	0.919	0.985	1.051	1.116	1.182	1.248	1.313	1.379	1.445	1.510	1.576

HOBAS Diameters are nominal for 36 psi pipe stiffness
Existing Sewer assumed full sized, Nominal diameter = ID
FL = Flush Joint. In tight fit cases, it may be required to utilize a flush joint. The ID's of the flush joint are nominal for the typical minimum flush joint pipes.
HOBAS 84" nominal size is based on the 87.0 OD mold.

Benefits

Sliplining rehabilitation of sewers with HOBAS pipes provides many benefits. Not only is the flow capacity frequently increased, but the host pipe is structurally reinforced, corrosion is stopped, and leakage is eliminated.