Fixture units at 100% certainly of occurrance?

[Camell]

I am designing an "outfall sewer" for a new mine. The main source of wastewater is the change house with a total no of fixture units of 484 (29 WC-pans, 52 WHB's, 36 Urinals, 49 Shower, 10 Wash machine, 8 Wash Trough)

The way I understand the fixture unit design method is that it is based on probability theory: i.e. the probability of certains fixtures discharging simultaneously, each with their own discharge rate, duration and interval.

I am concerned that at the end of a shift, practically all the fixtures will be in use at the same time. In this case, I am not sure that the fixture units method holds true. If not, how do I go about estimating the design discharge for the outfall?

Can anyone supply me with a bit more background to the method. I need details regarding the accepted individual fixture unit's discharge, duration and interval. I am looking to adapt the theory to account for the 100% certainty of simultaneous dischage, but dont have access to the basic data from which to work

 

[LHA]

The surest method I can imagine, and maybe the quickest for your design, would be to rent a flowmeter, and go to the site. Get permission, then open all fixtures, and write down the flow.

If you can't operate the fixtures, survey all the fixtures. Toilets and urinals usually have per flush flows printed right on the unit, shower heads often do. I would imagine a washing machine might have the inflow capacity on the back label. Spigots probably do not, but a measurement of system pressure and a simple Bernoulli's analysis of the diameter at the spigot will give you flow.

For any fixtures you can't solve this way, write down the model and manu., and jump on the web and/or phone to procure the rest.

Is there facilities or maintenance manager at the mine? He might know these flows too.

Engineering is the practice of the art of science - Steve

 

[bimr]

Most plumbin books have a discussion of fixture units.

Try the Piping Handbook by Nayyar, McGraw Hill. This book has a flow chart showing diameter of pipe capacity versus fixture units and slope.

Try Environmental Engineering and Sanitation by Salvato as well.

 

[eddieng27]

Camell,
What about the supply side? Does the mine's water supply have a meter that records flows at a interval that would/ might give you insight into the maximum demand flows? If not, you might be able to rent a flow meter, temporarily install it, and record flows over a representative period to gather the data you're looking for.