H.W Coefficient
This is the Hazen-Williams roughness coefficient used in calculating the friction loss in a pipe. The following are clean and typical design values:
| Hazen-Williams Coefficient | |||
|---|---|---|---|
| Clean* | Suggested design values | Source | |
| Bitumen lined concrete | 145-140 | 140 | (AS2118) |
| Spun bitumen-lined steel | 150-145 | 140 | (AS2118) |
| Cement lined iron or steel | 150-140 | 140 | (AS2118 & NFPA) |
| Cast iron (uncoated) | 140-125 | 100 | (AS2118, NFPA & NZ4541) |
| Cast iron (coated) | 145-130 | 115 | (unknown) |
| Ductile Iron | 100 | (NZ4541) | |
| Concrete | 150-140 | 110 | (unknown) |
| Copper | 160-155 | 150 | (AS2118 & NFPA) |
| Copper, MPVC, UPVC & PE | 140 | (NZ4541) | |
| Stainless Steel Tubing | 160-155 | 150 | (NFPA & NZ4541) |
| Stainless Steel Pipe | 140-130 | 130 | ((AS2118) |
| Stainless Steel Pipe | 140-130 | 140 | (NFPA750) |
| Welded & seamless steel (wet) | 150-140 | 120 | (AS2118, NFPA & NZ4541) |
| Welded & seamless steel (dry) | 150-140 | 100 | (NFPA) |
| Galvanised Gteel (wet) | 150-140 | 120 | (AS2118, NFPA & NZ4541) |
| Galvanised Steel (dry) | 100 | (NFPA) | |
| Steel galvanised after fabrication | 110 | (NZ4541) | |
| Steel, spun concrete lined | 130 | (NZ4541) | |
| CPVC | 150 | (NFPA) | |
| CPVC | 140 | (NZ4541) | |
| Polyethylene | 160-155 | 150 | (AS2118) |
| U.P.V.C. (Hose reel pipe) | 160-155 | 150 | (AS2118) |
| Fire hose (non-percolating) | 140 | (unknown) | |
| Fire hose (unlined or percolating) | 100 | (unknown) |
- Clean values are for concentrically joined and clean pipes. Values except for welded and seamless steel are from Australian Standard 2200-1978.
| Default values for Hazen Williams Coefficient used by HYENA | ||||||
|---|---|---|---|---|---|---|
| AS2118 | NFPA, SSCP52 & GB50084 | NZ4541 | ||||
| HW Co | Source | HW Co | Source | HW Co | Source | |
| Cement Lined C.I. | 140 | AS2118 | 140 | NFPA | 140 | AS2118 |
| Unlined Cast Iron | 100 | AS2118 | 100 | NFPA | 100 | NZ4541 |
| Copper | 150 | AS2118 | 150 | NFPA | 140 | NZ4541 |
| Stainless Steel Pipe | 130 | AS4587 | 140 | NFPA750 | 130 | AS4587 |
| Steel | 120 | AS2118 | 120 | NFPA | 120 | NZ4541 |
| PVC & CPCV | 150 | NFPA | 150 | NFPA | 140 | NZ4541 |
| HDPE | 150 | AS2118 | 150 | AS2118 | 140 | NZ4541 |
| HOSR | 150 | AS2118 | 150 | AS2118 | 140 | NZ4541 |
| HOSC | 140 | Unknown | 140 | Unknown | 140 | Unknown |
For HW coefficient used with AS4587 and NFPA750 see Surf Roughness - Mist Systems
The Hazen-Williams Coefficient may be entered in a number of places:
a default can be set under Set Defaults accessed from Configuration on the Menu Bar of the Main Screen. This value will be the default on opening a new project.
a default value may be entered above the H.W.Coefficient heading on the Pipes Tab Page and on the GRID Main Pipes Tab Page. Pipes with the H.W.Coefficient left blank in the column below these defaults will assume the default value.
For an individual pipe in the H.W.Coefficient. column on the Pipes Tab Page.
For the individual main or rising main pipes in a GRID on the Main Pipes Tab Page.
For the individual range or tree pipes in a GRID on the Ranges and Trees Pipes Tab Page.