Fluid network solutions: Eurospacer spacers

 
 

Eurospacer project validation


 

MAIN "EUROSPACER" PRODUCTS REQUIREMENTS


FRICTION FACTOR

Insulating spacers must have a very low friction factor to get an easy insertion of the carrier pipe into the casing (steel, concrete, fiber-glass reinforced pipes).


WEAR RESISTANCE

With the new no-dig drilling technologies, crossings of 500 m (1640 ft.) (microtunneling by pushing) and 2000 m (6562 ft.) (microtunneling by pulling) can be easily achieved.

Wear resistance of insulating spacers must be higher to face such long crossings, without damages or breakings.


COMPRESSIVE STRENGTH

Insulating spacers must have a carrying capacity (also with fluid) for its operating lifetime, also preventing any contact between carrier and casing.


ELECTRIC SPECIFICATIONS

Of course, insulating spacers must have a high electrical resistance and dieletric strength.


METAL FREE

The insulating spacers must be assembled and wrapped on the pipe without any metallic parts (bolts, nuts, fasteners).


MODULARITY

Insulating spacers project must cover a wide diameter range from DN15 (1/2") to more than DN1200 (48") with a modular approach. Modular elements must be designed to be easily assembled in order to form the expected spacer diameter, with marks which speed up the manual procedure. No specific tools have to used for tightening the insulating spacers on the carrier pipe.


NUMBER OF MODULES

The number of modules which cover the pipe diameters range from DN15 (1/2") to more than DN1200 (48"), must be minimized in order to reduce inventory levels both for contractors and wholesalers. Final design requires only 6 elements to fullfill the entire diameters range.


MODULES LENGHT

Insulating spacers design must maximize the module lenght to reduce number of modules needed to form a spacer, in order to attain better stability and stiffness.


BAND FLEXIBILITY

Spacer band, supporting spacing blocks, must be flexible enough (see picture) to be easily and firmly tightened to the carrier pipe, despite any uneveness, and dirtiness of the pipe surface.

Elements, with premoulded bending and rigid band due to unfit thickness, are not allowed because each element, for the modular approach, has to match with a wide range of pipe diameters.

In the case of premoulded bending or rigid band, the result is a low contact area, between elements and pipe surface.

In the worst case, when elements bending is less than the carrier pipe bending, wear of  carrier lining (if any) can break, due to elements edge tripping.


FIRM CLAMPING

The insulating spacer elements design must provide a firm clamping, either during assembling and thightening (vibration effects) operations and during carrier insertion into the casing (temperature effects).

Further no radial shifting of grip wedges/register is allowed.

Thightening must result from a continuous and progressive action while the whole insulating spacer is settled on the carrier pipe.


GAP BETWEEN SPACING BLOCKS

The design must minimize the gap between spacing blocks on each spacer, in order to have many blocks under load while supporting the carrier pipe.

This feature claims for an increased torsional strength of the insulating spacers and an improved wear resistance.

Final design results are:

  • Magnum Eurospacer : 60-70 mm (2,4"- 2,7")
  • Midi Eurospacer : 50 mm (2") 
  • Mini Eurospacer : 35 mm (1,4")
  • Fast Eurospacer : 21 mm (0,8") (see News)

PROJECT CHOICES

"Eurospacer" project has tracked two main aspects, related with the module shape design and the selection of the synthetic resin to be used. The aims of these aspects are to fullfill all project requirements, in order to get a firm clamping by a continuous and progressive action.


MODULE SHAPE DESIGN

Each module shape option has been 3D modelled and investigated by stress analysis (FEM, ADAMS) and by flow analysis (Mouldflow).

Fatigue behaviour was simulated by means of I-Deas and FE Fatigue codes.

This  model approach allowed a lot of alternatives to be investigated, as well as geometric details (radius, thikness gradient, holding projection, convexity).

Simulations showed that these parameters are quite relevant for the spacers behaviour under casual stressing.

SYNTHETIC RESIN SELECTION

Main feature of the selected resin are:

  • electrical resistivity
  • dielectric strength
  • compressive strength and creep
  • friction coefficent
  • collision strength

First, we considered the technical features of the selected resin for injection moulding and, secondary, reasonable production costs.

Accordingly to our experience and technical sheets, we selected three types of resins for deeper investigations:

  • high density polyethylene 
  • polyamide
  • polypropylene 

A first test, runned on injection moulded specimens, showed that the polypropylene has aptitude to splinter when bumping projections simulating  enevenness on casing internal surface: moreover it becomes brittle at low temperature.

Thus polypropilene was given up as a possible material for "Eurospacer" insulating spacers.

Compression tests and sliding test (concrete pipe as casing) with carrier pipe  wrapped with HDPE and polyamide insulating spacers showed no relevant differences, referring to pull/push force (friction coefficent), in wear and  behaviour under load.

For more information on testing procedures, please Contact us.

Final decision is to market HDPE (specific formulation) insulating spacers. For special applications (hot temperature like in district heating distribution) "Eurospacer" insulating spacers can be supplied, on demand, also in polyamide or other synthetic resins. "Eurospacer" products are white, the natural colour of the plastic resin:

  • an intrinsic quality mark

  • no additive are used to avoid any degradation of resin characteristics

  • at-sight highlights of any surface change (dirtness, wear, damages)

Black colour was left out for the related degradation in electrical features.


EXPERIMENTAL RESULTS

WEAR RESISTANCE

The results of sliding tests (according to Sliding test STD 9.02.02) with spacers (1,6") height , on welded steel pipes (carrier: pipe diameter :48"; casing: 60"), and crossing length increased from 120 m (390 ft) to 300 m (980 ft), are:

  • no spacing block has a wear higher than 1 mm (height reduction less than 2,5%)  (see picture)

  • tender specifications usually allow a 10% as height reduction, over a crossing length of only 120 m.


COMPRESSION STRENGHT

The results of the compression test (STD 9.0201) are as follow:
  • no permanent deformation of spacing blocks (under compression load of 15.000N - 3.300 lb)
  • permanent deformation of spacing blocks (mushroom shape, see pictures) without any breaking or cracking (under compression load of 250.000 N - 55.500 lb)

For details of test results see:

DIELETRIC STRENGHT 

Electrical tests on "Eurospacer" insulating spacers show that the injection moulding process does not affect any degradation of the HDPE resin which has a dielectric strength up to 150 Kv/mm (DIN 53481).


FINAL CONSIDERATIONS

"Eurospacer" insulating spacers fullfill all specifications required by demanding customers and qualified tenders, i.e.:

  • wear resistance
  • compressive strength
  • dielectric strength
  • corrosion prevention

"Eurospacer" products are a smart and innovative solution, with balanced features like flexibility and strength of the band supporting spacing blocks



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