Most engineers know that pockets of air in pipelines create problems such as
- Accelerated corrosion.
- Magnified pressure spikes from water hammer events.
- Unsteady pipeline operation.
- Reduced capacity.
Reduced capacity is often the most urgent of these. Renewing or replacing pipelines to meet increased demand is both expensive and disruptive.
Much work has already been done to reduce demand by minimising leaks and educating consumers. Further opportunities lie in increasing capacity of existing pipelines by removing air pockets.
This approach was chosen in Nairobi, Kenya where current water demand has grown to 740 000m3/day against the supply of 550 000m3/day.
A.R.I. air valves were installed on a 7km 450mm dia. gravity main with the aim of evaluating improvements in pipeline efficiency from modern air valves.
A.R.I. air valves were chosen because of their reliability. They are guaranteed for 10 years against seal leakage – a common problem in most air valves.
A 19% increase in flow rate was measured after half of the A.R.I. air valves had been installed. We expect further gains as the project progresses.
A full case study by Eng Nahason M. Muguna Technical Director Nairobi City Water & Sewage Company is available here: