For pump station designers - things I now know that I wish I had learned earlier
This is basically a list of mistakes I have made in pump station design over the years that I plan never to repeat. I hope it helps you.
(This is a draft list - there are many more to add!)
Pipework
Adequate support, anchors
All bolts in wetwell should consider stainless steel
Backing rings stainless steel
Be careful with Denso on PE pipe can possibly soften
Care with solids velocity in vertical enlargers
Cast iron pipe maximum 1200 mm long (5.3 m DI)
Concrete blocks under valves
Counter-rotation in wetwell anticlockwise
Drop inlets
Flanges AS/NZS4087 (Class 14 usually)
Flap valve on overflow
Flexible joints on incoming lines
Flush valve
Freezing
Full face ABS flanges have no pressure rating.
Hazard zone NZS6101.1:1988
NPSH
Nylon coated valves and CI pipework
Pump drilling to match flanges
Removable pipework
Bubbles through flow meter
Flow meter flowing full
ABS plastic threaded fittings derated
ABS unions 100 mm class C only
ABS Victaulic shoulders maximum capacity 1400 kPa for 100 mm
ABS>150 mm Class D maximum
Screen or siphon on overflow
Seal around pipes
Stainless steel bolts lock up Molybond coat
Stub flanges fit in wall cast extra concrete, shear forces
Take off tee for pump out
Thermal expansion specification
Threaded fittings pressure limitations
Tideflex valves from tanks (specify pipe OD and if valves need to be eccentric) Also maximum backpressure, forward pressure and headloss
Valve and fittings support
Valve on incoming sewers
Vibration
Vortices
Wrap buried gibaults in Denso tape
Pump Well
1050 mm dia can be too narrow to work in without getting dirty for deep pump stations especially.
400 mm minimum ladder width OSH
Air entrainment cavitation at minimum water depth
Install air vent
All steelwork, brackets and pipe specials to be sandblasted and galvanised
Anchor blocks
Baffle to storage and overflow
Benching
Cabinets buildings etc keyed alike
Caisson scabbled and attached
Chains
Chamfer concrete edges
Ensure valve slamming noise doesn't irritate neighbours
Flood levels
Flotation
Flygt Tops bases should be considered
Fosroc Supercast SW as a waterstop where PE pipes pass through walls
Harness clips 15 kN
Head height for working (1.2-1.8 m minimum)
Hooks for chain, cable, floats
Inlet baffle water falls downwards from inlet pipe can miss baffle
Inlet splash air entrainment
Inlet spray onto ladder
Ladder away from inlet splash, near control cubicle
Ladder better than rungs
Ladder doesn't clash with pumps (really!)
Ladder on caisson step rungs obstruct clam-shell
Ladder or pole to grab above surface
Ladder top rung high, handles on getting out
Lid hole and pump location dimensioned
Location of existing pipes on existing pump stations
Manhole rungs should be on downstream side nearest road. (least chance of new incoming lines)
No surface water flowing into lid
Overflow from subsidiary manhole with valves to allow wetwell to be worked on
Overflow pipe diameter
Paint Devshield worth considering
PE rungs option in corrosive area
Pump labels
Pump spacing centres at least 2.1 x square root of flow in m³/s
Safety rungs (300 centres)
Schedule manhole water test
Site all-weather vehicle access
Stainless steel hold down bolts detail
Standard services disclaimer note
Tripod setup
Ultrasonic beam cone angle
Valve chamber ball valve on drain line
Valve chamber drain threaded plug, not under pipe, vertical pipe as handle
Valve chamber flotation
Valve chamber plug to prevent flooding with string
Vehicle access
Vehicle loadings
Water sprays for washdown
Water supply
Rising Main
Adequate cover to air valves label on long section
Adequate velocity (1-1.07 m/s for raw sewage) or check using tractive force method
Air bubble velocity rising main
Air inlet valves can cause water hammer as well
Air release valves odour, noise
Air release valves suck air in bubbles
Allow for build-up of deposits on pipe in treatment plant.
Anchor blocks
Can jet pipeline 160 m (250 m maximum)
Check for collapse under negative pressures
Class B uPVC can collapse under vacuum
Drain rising main
Locator tape (300 to 600 mm below surface)
Traceable marker tape for plastic pipe
No siphoning
Odour, retention time, sulphuric acid build-up
PE flanges, stainless steel, weld, smooth bore reducers 8° taper
Pipe collapse low pressure, external loads
Schedule destructive testing
Seepage cut-off collars
Specify source of water for testing.
Standard services disclaimer note
Water hammer including start-up