PE Pipes for Aquaculture - System Group Marine Division

HDPE pipes are usually classified based on minimum resistance required for operating pressure at 20 °C for 50 years, such as PE80 or PE100. However, the working pressure of the pipes is not a relevant feature in the construction of floating cages, as are the intrinsic characteristics of the material, thickness, weight, resilience, strength and flexibility.

SDR dimensional ratio is commonly used for the choice of a pipes for aquaculture. This parameter represents the ratio between diameter and thickness of the pipe. High values of the SDR ratio correspond to thinner pipe thicknesses.

When pipes are used to build circular cages, a fundamental factor is the torsion capability and the flexural elastic modulus. The first factor influences the minimum bend radius for the pipe, while the second factor influences the effort necessary to obtain a given curvature.

SDR dimensional ratio	Bending radius
9	20 x OD
11	23 x OD
13,6	25 x OD
17	26 x OD
21	27 x OD
26	30 x OD

Below are shown the values of thickness (T) and buoyancy force (B) in fresh water per meter of pipe, considering only the empty volume, given the fact that HDPE has a specific weight slightly lower than water.

OD	SDR26		SDR17		SDR13,6		SDR11		SDR9		SDR7,4
OD	T	B	T	B	T	B	T	B	T	B	T	B
mm	mm	kg/m	mm	kg/m	mm	kg/m	mm	kg/m	mm	kg/m	mm	kg/m
50	2,0	1,66	3,0	1,52	3,7	1,43	4,6	1,31	5,6	1,18	6,9	1,03
63	2,5	2,64	3,8	2,41	4,7	2,26	5,8	2,07	7,1	1,87	8,6	1,65
75	2,9	3,76	4,5	3,42	5,6	3,20	6,8	2,96	8,4	2,66	10,3	2,32
90	3,5	5,41	5,4	4,93	6,7	4,61	8,2	4,25	10,1	3,83	12,3	3,36
110	4,2	8,11	6,6	7,36	8,1	6,91	10,0	6,36	12,3	5,73	15,1	5,00
125	4,8	10,46	7,4	9,54	9,2	8,92	11,4	8,20	14,0	7,39	17,1	6,48
140	5,4	13,11	8,3	11,96	10,3	11,20	12,7	10,31	15,7	9,26	19,2	8,11
160	6,2	17,11	9,5	15,61	11,8	14,61	14,6	13,44	17,9	12,12	21,9	10,60
180	6,9	21,69	10,7	19,76	13,3	18,48	16,4	17,02	20,1	15,35	24,6	13,44
200	7,7	26,76	11,9	24,38	14,7	22,86	18,2	21,02	22,4	18,92	27,4	16,56
225	8,6	33,91	13,4	30,85	16,6	28,89	20,5	26,59	25,2	23,94	30,8	20,97
250	9,6	41,84	14,8	38,15	18,4	35,70	22,7	32,88	27,9	29,62	34,2	25,90
280	10,7	52,52	16,6	47,84	20,6	44,79	25,4	41,26	31,3	37,12	38,3	32,49
315	12,0	66,51	18,7	60,52	23,2	56,66	28,6	52,20	35,2	46,99	43,1	41,12
355	13,6	84,39	21,1	76,85	26,1	72,01	32,2	66,33	39,7	59,66	48,5	52,28
400	15,3	107,17	23,7	97,65	29,4	91,43	36,3	84,19	44,7	75,77	54,7	66,33
450	17,2	135,66	26,7	123,54	33,1	115,69	40,9	106,48	50,3	95,88	61,5	83,98
500	19,1	167,49	29,7	152,47	36,8	142,80	45,4	131,51	55,8	118,48	–	–

Characteristics of Centraltubi pipes for floating cages:

Dimensional characteristics	The fundamental requirement for floating pipes is to comply with the dimensional characteristics so that the polystyrene filling elements and all the cage accessories can be safely applied. All the pipes are tested according to regulation EN ISO 3126.
Resistance to UV rays	The pipes are tested according to regulation ISO 6964 to ensure a carbon black percentage higher than 2%, to significantly increase the resistance of polyethylene from the damage induced by UV radiation. The dispersion of the pigment is tested according to regulation ISO 18553.
Impact Resistance	The pipes are tested to impacts after stay in a chill room to simulate the most severe working conditions according to regulation EN 744.
Flexibility	Flexibility is verified during tensile tests, with a flexible flexural modulus guaranteed less than 1200 MPa.
Solder compatibility	The resistance of butt welding is tested according to regulation ISO 13953.
Abrasion resistance	Pipes are tested according to regulation EN 295-3 in order to ensure the best performance in terms of resistance to the abrasive effect of the sand.
Chemical compatibility	Polyethylene is inert to sea water, acids and strong bases according to regulation ISO TR 10358.
Resistance to cleaning	Pipes are tested to resist cleaning processes with pressure jets up to 120 bar.
Resistance to traction	Pipes are tested according to regulation ISO 6259 to withstand traction stresses above 19 MPa.
Environmental Compatibility	Pipes in HDPE are totally recyclable and do not release harmful compounds.
Traceability	Centraltubi ensure the total traceability of its products guaranteed by a quality management system certified according to regulation ISO9001
Labelling	Centraltubi can label the pipes according to customer specifications with a large number of possible customizations.

RAW MATERIAL CHARACTERISTIC

Density	g/cm3	0,955 – 0,965	ISO 1183
Fluidity index 5 kg 190°C	g/10min	0,4 – 0,7	EN ISO 1133
Moisture content	mg/kg	< 300	EN ISO 15512
Carbon black content	%	2 – 2,5	ISO 6964

Characteristics of Centraltubi pipes for Sinker Tube:

Dimensional characteristics	Sinker tubes are produced according to dimensional specifications, verified according to regulation EN ISO 3126.
Resistance to UV rays	Raw material is tested according to regulation ISO 6964 in order to ensure a carbon black percentage between 2% and 2.5%.
Solder compatibility	The resistance of butt welding is tested according to regulation ISO 13953.
Abrasion resistance	Pipes are tested according to regulation EN 295-3 to ensure the best performance in terms of resistance to the sand carried by the wind.
Chemical compatibility	Polyethylene is inert to sea water, acids and strong bases according to regulation ISO TR 10358.
Environmental Compatibility	Pipes in HDPE are totally recyclable and do not release harmful compounds.
Traceability	Centraltubi ensure the total traceability of its products guaranteed by a quality management system certified according to regulation ISO9001.
Labelling	Centraltubi can label the pipes according to customer specifications with a large number of possible customizations.

RAW MATERIAL CHARACTERISTIC

Density	g/cm3	0,952 – 0,965	ISO 1183
Fluidity index 5 kg 190°C	g/10min	0,35 – 0,75	EN ISO 1133
Carbon black content	%	2 – 2,5	ISO 6964