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Air Entrapment Tees

Technical Background

In rising mains (especially sizes >DN350) 'Air Entrapment Tees' are typically installed, instead of air valves mounted directly on the pipeline. Air Entrapment Tees comprises of a PE tee piece (typically an Equal tee or one size smaller) installed in the pipeline and fitted with a 316 stainless steel flanged blanking plate. This blanking plate includes a threaded or flanged SS fitting welded to the blanking plate to plumb the takeoff using PE to another location for remote air management.  

The three main reasons an Air Entrapment Tee is used:

1. Insufficient cover – as the pipe size gets larger, the height from the top of the pipe to the top of the air valve increases because the components get larger. Therefore the pipeline must be buried deeper (have more cover) to accommodate the increasing air valve height inside the chamber. (The cost of burying a pipe deeper is incredibly more expensive than simply installing air valves above ground in a remote chamber away from the pipe)

2. Air valve size – Typical air valves are DN 50, 80, 100, sizes greater than this are available, but are costly and not commonly available. So in larger pipelines, where large volumes of air are released when filling the pipeline, or air let in when draining the pipeline, a manifold of smaller valves is typically used. 

2. Capturing air bubbles – in order to De-gas a pumped rising main effectively, you need to capture small air bubbles that are created by changes in pressure and pumping which are carried along inside the pipe. Where sewer velocities are high (>1.0m/s), especially in larger pipes, these bubbles rush past off takes quickly so are not expelled. Air Entrapment tees provide a circular 'catchment area' above the flow path to maximise capture of air bubbles created through pumping operations or changes in pressure where velocities are relatively high.

Air Entrapment Tee / Moulded / PN16 / SDR11 / PN16 EN1092 FBE Flanged Offtake

Fully pressure rated PE100+ fabricated assembly with long spigot ends for electrofusion on-site. Matched with a FBE steel flanged blanking plate and a flanged or threaded reducing outlet for connection to the PE assembly with an O-Ring NBR seal. This fitting can be used for the direct connection of a sewer air valve onto the pipeline or attached to PE flange adaptor and 90º bend, allowing one or more air valves to be located in an alternate location on an air release/intake manifold. 

The flange offtake size is configurable in various combinations to suit the application - Refer to the flange blanking plate table below.

P5826.A6.250250 250 250 FL 250 PN16 535 130 266 8-12 weeks
P5826.A6.315300 315 315 FL 300 PN16 650 150 317 8-12 weeks
For smaller sizes: use EF tee and LS flange assembly.
Product Code dn1 dn2 L le Z2 Availability in Hong Kong

Air Entrapment Tee / Fabricated / PN16 EN1092 316SS Flanged Offtake

As above using fabricated PE tees offering PN16 pressure ratings in larger sizes.

PN10 SDR17 PN16 SDR11 dn1 dn2 L le Z1 Z2 Availability in Hong Kong
P5314.61.355350 P5316.61.355350 355 355 FL 350 PN16 1045 300 523 374 8-12 weeks
P5314.61.450450 P5316.61.450450 450 450 FL 450 PN16 1160 300 580 448 8-12 weeks
P5314.61.500500 P5316.61.500500 500 500 FL 500 PN16 1310 350 655 489 8-12 weeks
P5314.61.560500 P5316.61.560500 560 560 FL 500 PN16 1380 350 690 532 8-12 weeks
P5314.61.630600 P5316.61.630600 630 630 FL 600 PN16 1450 350 725 601 8-12 weeks
P5314.61.710700 P5316.61.710700 710 710 FL 700 PN16 1530 350 765 695 8-12 weeks
P5314.61.800800 P5316.61.800800 800 800 FL 800 PN16 1660 350 830 773 8-12 weeks
P5314.61.900900 P5316.61.900900 900 900 FL 900 PN16 1860 400 930 855 8-12 weeks
P5314.61.10001000 P5316.61.10001000 1000 1000 FL 1000 PN16 1960 400 980 936 8-12 weeks

Air Entrapment Blanking Flange with Offtake / PN16 EN1092 316SS

Both flanges are BS EN 1092-1 rated and drilled PN16 unless indicated as a 'BSP' threaded SS socket for DN 50 offtakes. Larger sized flanges supplied with SS lifting hooks blind threaded into the flange.

Product Code DN1 DN2 Z3 Availability in Hong Kong
P09S6.557.10088 100 50 BSP 102 8-12 weeks
P09S6.G6.100080 100 80 107 8-12 weeks
P09S6.557.15088 150 50 BSP 104 8-12 weeks
P09S6.G6.150080 150 80 109 8-12 weeks
P09S6.G6.150100 150 100 121 8-12 weeks
P09S6.557.20088 200 50 BSP 106 8-12 weeks
P09S6.G6.200080 200 80 111 8-12 weeks
P09S6.G6.200100 200 100 123 8-12 weeks
P09S6.557.25088 250 50 BSP 109 8-12 weeks
P09S6.G6.250080 250 80 114 8-12 weeks
P09S6.G6.250100 250 100 126 8-12 weeks
P09S6.557.30088 300 50 BSP 112 8-12 weeks
P09S6.G6.300080 300 80 117 8-12 weeks
P09S6.G6.300100 300 100 129 8-12 weeks
P09S6.557.35088 350 50 BSP 115 8-12 weeks
P09S6.G6.350080 350 80 120 8-12 weeks
P09S6.G6.350100 350 100 132 8-12 weeks
P09S6.557.40088 400 50 BSP 120 8-12 weeks
P09S6.G6.400080 400 80 125 8-12 weeks
P09S6.G6.400100 400 100 137 8-12 weeks
P09S6.557.45088 450 50 BSP 122 8-12 weeks
P09S6.G6.450080 450 80 127 8-12 weeks
P09S6.G6.450100 450 100 139 8-12 weeks
P09S6.557.50088 500 50 BSP 126 8-12 weeks
P09S6.G6.500080 500 80 131 8-12 weeks
P09S6.G6.500100 500 100 143 8-12 weeks
P09S6.G6.600080 600 80 140 8-12 weeks
P09S6.G6.600100 600 100 152 8-12 weeks
P09S6.G6.710080 710 80 148 8-12 weeks
P09S6.G6.710100 710 100 160 8-12 weeks
P09S6.G6.710150 710 150 187 8-12 weeks
P09S6.G6.800080 800 80 159 8-12 weeks
P09S6.G6.800100 800 100 171 8-12 weeks
P09S6.G6.800150 800 150 198 8-12 weeks
P09S6.G6.900080 900 80 167 8-12 weeks
P09S6.G6.900100 900 100 179 8-12 weeks
P09S6.G6.900150 900 150 206 8-12 weeks
P09S6.G6.1000080 1000 80 175 8-12 weeks
P09S6.G6.1000100 1000 100 187 8-12 weeks
P09S6.G6.1000150 1000 150 214 8-12 weeks