LOCAL HEAD LOSS IN PLASTIC PIPELINE JOINT WELDED BY ...

J. Melichar, J. Háková, J. Veselský, L. Michlík
306
ζ s (1)
0.8
0.6
0.4
0.2
5x10
Re (1)
4 5x105 105 0.0
Fig. 7. Values of basic local loss coefficient for the βPP-H tube joint ζ in dependence on Reynolds number.
Obr. 7. Hodnoty základního součinitele místní ztráty spoje βPP-H trub ζ v závislosti na Reynoldsově čísle.
Conclusions
The paper shows basic values of the local loss
coefficient for the βPP-H tube joints with butt
welds that were experimentally determined for turbulent
flow with Reynolds numbers within the
range of 60 000 < Re < 500 000. The local loss
basic coefficient at pipeline joints was for the
above-mentioned range of Reynolds numbers constant
with the average value of ζ = 0.6 . This value
was determined for PP tube diameter of 72.5 mm
and for the joint and diameter proportion
d0/d = 0.87 .
It is necessary to point out that in practice the local
loss value can be dependent on various butt
weld dimensions that depend on a technological
process of the assembly. However, taking into account
the exact size variability is practically impossible.
With regard to large pressure drops at buttwelded
PP tube joints that become significant in
particular for long pipelines it is possible to recommend
removing the butt welds projections
and/or using tube joint technology, which would
not result in this kind of local losses.
Acknowledgement. The authors are particularly
grateful to the companies FIS CZ s.r.o. Praha and
BHV sensory s.r.o. Praha. Thanks are expressed to
the Company FIS CZ for necessary material supply
and experimental pipeline assembly and to the
Company BHV for granting the techniques for experimental
measurements.
Received 15. December 2005
Review accepted 14. June 2006
List of symbols
b, b´ – width of inner butt weld projection at pipeline joint
[m], [mm],
c – mean flow velocity [m s -1 ],
d – inner pipeline diameter [m], [mm],
h – height of butt-welds projections [m], [mm],
I – electric current [A], [mA],
K – constant in Eq.(6),
k – hydraulic roughness of inner pipeline wall [mm], constant
in Eq.(9),
l – length of straight pipelines sections [m], [mm],
p – static pressure [Pa],
Q – flow rate [m 3 s -1 ],
Re – Reynolds number [–],
T – fluid temperature [ 0 C],
Y – specific fluid energy [J kg -1 ],
λ – friction factor [–],
ν – kinematic viscosity [m 2 s -1 ],
ρ – fluid density [kg m -3 ],
ζ – local loss coefficient [–],
∆ – difference.
Subscripts
e – equivalent,
f – frictional,
l – local loss,
s – pipeline joints,
z – loss-making,
0 – at pipe contraction,
12, 2S, S3 – at cross sections between marked locations,
eventually between pressure taps.
REFERENCES
HÁK V., 2002: Long force main projection speciality by pipeline
thermoplastic PE-HD application. (In Czech.) Heating,
ventilation, installation no. 4, p, 142–145.
IDELČIK I. E., 1960: Handbook of hydraulic. (In Russian.)
Moskva: Gosenergoizdat, p. 123.