CS220765B2 - Method of isolating the pipe - Google Patents

Abstract

Metal e.g. steel pipe insulated with foamed polyurethane plastic is made in a multi-stage continuous process in which an inner layer of polyurethane plastic is foamed on the pipe and at least partially cured to form low-density foam having high heat insulating capacity, and an outer layer of polyurethane plastic is foamed on the inner layer to provide a foam layer of higher density, the outer layer having a density at least 25% greater than that of the adjacent inner layer, the thickness of the outer layer being 5 to 30% of the total thickness of the foamed insulation. The inner layer may be subdivided into two or more layers having different physical properties. A common protective layer e.g. polythene/butyl adhesive tape, epoxy, heat actuated adhesive or asphalt may be first applied to the pipe. An outer protective layer of paper, butuminous inactive or plastic e.g. polythene, polypropylene or epoxy may be applied. The plastic may be heat shrinkable.

Description

(54) Pipe Insulation Method

For thermal insulation of a pipe, for example a metal pipe with a corrosion protective coating, at least one foamable plastic composition is applied to the pipe to form the first inner layer of low density insulation and hence high insulating ability, the composition is foamed in situ and onto the surface of the last of the applied inner layer, a foamable plastic composition is applied to form an outer layer of higher density insulation, wherein the outer layer has a density at least 25% higher than the density of any inner layer and a thickness of 5 to 30% of the total layer thickness.

The invention relates to a method of insulating a pipe. for example, metal pipes with an anticorrosive protective coating, at least one inner layer and one outer layer of foamed plastic insulation.

According to a known embodiment, it has been proposed to insulate a pipe by spraying one or more layers of foamed plastic, such as foamed polyurethane, the applied layer or layers being cured and provided with a layer of insulation or an envelope of insulating material that acts as a protective or barrier layer. This method describes e.g. Bauer et al., U.S. Pat. No. 3,480,493. The foam insulation layer resulting from this manufacturing process has a specific gravity corresponding to the properties resulting from the requirements of maximum thermal insulation and the requirements of maximum strength and damage and abrasion resistance. Also known is the method of Henderson et al., Described in U.S. Pat. No. 4,044,315, wherein a foamable liquid mixture is sprayed onto a pipe, the foam formed being wrapped with a protective material in the form of, for example, a foil, prior to this. until the foam has fully cured. This increases the specific gravity of the foam at the location of the outer surface. A major disadvantage of this process is that it is limited to a helically wound protective film to provide the insulation surface. This film is wound on tension to increase the specific weight on the outer surface of the foam layer. Such a manufacturing process is relatively difficult to control under normal manufacturing conditions. The degree of specific gravity and thickness of the higher specific gravity layer depend on various critical factors, such as the temperature of the foam plastic, the foaming speed of the plastic mixture, the curing of the plastic, the delay before application of the protective film and the tensile strength of the protective film. strained. All these factors affect the degree of curing of the foamed plastic prior to application of the protective film. In addition, the thickness of the layer of increased density depends on the thickness and compressibility of the low weight foam.

The above drawbacks are overcome by the method according to the invention, characterized in that at least one foamable plastic composition is applied to the pipe to form the first inner insulation layer, which composition is foamed in situ until a density of 0.024 to 0.096 g / cm ^{3 is} achieved. and on the surface of the last applied inner layer, a foamable plastic composition is applied to form the outer layer of insulation, the coating being applied before foaming or curing or after foaming or curing of the last applied inner layer of insulation; achieving a stiffness and density of at least 25% higher than that of any inner layer.

and thickness - 5 to 30% of the total layer thickness.

Said foamable plastic compositions are preferably polyurethane-containing compositions.

Since the thickness and weight of each layer is independent of each other and can be individually adjusted and controlled, the process of the present invention allows the use of an inner layer having a high thermal insulation capacity at low cost and applying an outer layer of higher strength and higher density. . These benefits are achieved at an overall lower cost of insulation. The two layers of insulation provide a combination of properties that are optimal for pipe insulation and protection at a minimum total cost.

The degree of specific gravity - between the inner and outer insulation layers required for optimum results depends on the pipe diameter, the relative thickness of the layers, the minimum strength required and the temperature difference between the pipe and its surroundings, as well as other less significant factors . Generally speaking, the density of the outer layer should be at least 25 percent greater than the inner layers. and the outer layer thickness should be from 5 to 30% of the total thickness of the foam insulation layers. If deemed appropriate, the inner layer may be subdivided into two or more successive layers, the physical properties of the layers being different.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in greater detail in the accompanying drawings, where Figure 1 is a sectional view showing one embodiment of the invention and Figure 2 is a sectional view showing another embodiment of the invention.

In the embodiment shown in FIG. 1, the metal tube 10 is provided with an inner layer 12 of foamable rigid insulation. . low density polyurethane of 0.032 to 0.096 g / cm ³ . This inner layer 12 of foamed plastic insulation has a thickness of about 2.5 to 15.5 cm and is surrounded by the outer layer 14 of foamed rigid polyurethane insulation with a density of at least 25% higher than the density of the inner layer 12. the outer insulation layer 14 'of a thickness of 5-30% of the total thickness of the inner layer 12' and the outer insulation layer 14.

According to a preferred embodiment of the invention, the inner layer 12 of the foamed insulation has differences from the outer layer 14 or more such layers which consist not only of lower specific weight and hence higher insulation capacity, but also of higher heat resistance, that is to say. the inner layer is thermally stable at higher temperatures, for example up to 177 ° C, whereas the outer layer or foamed insulation layers exhibit heat stability only up to, for example, 93.5 ° C.

A second embodiment of the invention is shown in Fig. 2. The tube 10 is intended here for conveying hot liquids at a temperature of 150 to 180 ° C. The tube 10 is provided with an inner insulation layer which is further divided into a first layer 20 is the insulation of foamed polyurethane, low density zvoleráho so, and ^would b ^yl stable at temperatures up to 180 ° C and the second layer 22, insulation of ^PE n ^{e d} it ^y PCL ^urethane on ^at approximately the same ^e m ^of whom was ^ters weight but zvotend it so that it is stable only up to temperatures around 100 ° C.

The high density polyurethane foam outer layer 24 has a density at least 25% greater than the layer 20 or 22, and has a thickness of 5 to 30% of the total thickness of the layers 0, 22, 24. In another embodiment of the invention wherein the tube 10 is intended for the distribution of cooling fluid under very low ^to ACTIVE te ^pl of ^T, the ^{order of} b ^s in an enlarged ^h at - ¹² 9 ° C, the layer 20 is formed so that it is semi-place rigid so as to avoid brittleness and ^{p at} pH adnému ^{p ka} ras in the ^p Růt> ^{E P} oužívání hu, and the layers 22, 24 are formed so as to be rigid.

When applying from^preindeer^pO^dle to^hoto vyn^andClimbing is a haunch that is typically made of steel^prve o^gamet^{á p}ro o ^ trans^dmoisture and is cleaned^pto remove dirt mesh^ujand rust. For this purpose, mo^hou^bý^tpoužit^y however you go^ofn^E of^preindeer no^ištěsuch as^je otr^ywith^toneither^Mrsor^toof time tteem okartá^C'ov^andn^and No^bO^podo^bn^E způso^by. If it is mercy^dcucí^, can go^použi^th dv^E not more such methods.

In some cases it may be desirable to provide the surface of the first pipe anti-corrosion ^and m ^p o ^l Akemi is ^{straight Ste} e ^d by applying a ^PE NB luminous plastic. However, this is not always necessary. Any anti-corrosion material or method can be applied as the corrosion coating. It can be wrapped with a polyethylene layer but ^{to ylk} AuCu ew ^ em adhesion of a tape-epoxy insulation, heat activated adhesive or bitumen. A foamable thermoplastic ^can be ^converted by Ola ^H applied to the tube or to the surface of any corrosion protective coating applied to it first ^s tru ^bk u. Usually produced, it is desirable that the temperature of the tube being higher than ^p o te ^pl ojová ^to OTA. Exact te ^pl OTA závmí on the nature and composition of the foamable plastic. Such plastic is usually applied in the form of a material sprayed by a spray nozzle onto a rotating tube that advances along several nozzles. . It can be used in various · zpěniteteých polyurethane composition ^pl Astute and složed depends on the characteristics of that is from the final ^é him ^to the genus ^{p p d} Oza Ovan. ZvMšf suitable composition of a liquid mixture of substances, which react to form a polyurethane containing a conventional foaming agent in an amount necessary ^p ro formation ^Walking n ^Y are ^as C. ^The desired density which may be about ^{0, 0 24-0, 09} 6 ^{g /} cm ³ . The first layer of ^PE alterable ^s kappa lazy allowed to froth foaming effect and act ^IDL. Loušť ^l'k and ^p r ^s VRST ^{yp y} en ·· may vary widely depending on the same factors that have been separated above in connection with differences in specific weight of iso ^{l I} C ^h AČN ^{layers MU} e vary depending on the diameter of tubes and ^ky le ^d after the temperature at which the pipe will be repaired inferred ^d ium ^copper. In general, the thickness of the ^p oh ^Yb ovata between about 2Д4 to ¹⁵ 4 cm ^2.

The outer layer 14 or 24 for a foaming plastic is then applied to the outer surface of ^PE previously ^é n ^E do not dip ^yp izotačrn layers ^and coatings, ^p rove ^d eného oOvyldým ^ em caused on the surface of the rotating tube and the forward pushing. The second layer may be first applied before or after curing the first layer and ^straight even before · tm not ^{from B-yl} accomplished by first foamed layer. In one embodiment, the second složern ^h of PLA ^with zpěniteteélro herein if the ^{d w} n ^{e d} by its složemm previously ^{é it,} except the amount of foaming agent. The formulation is adjusted so that the foamed insulation of plastics material having in its VRC ^h n ^e vrsteě ^currency rnou ^{h ENGINE} NCS ^ta At least a 2 ^5% higher-than M ^E R N, ^{and h} Weigth ^p RVE layer ^Y and tteusťto ^p r ^s vrdv ^y is 5 to 30 ° / ^s tloušťty on the total of the two layers. In another ^{MPLEMENTATION s p} o ^d e in ^{Y is N,} can climb MFT outer layer 14 or 24 from the lower heat than ^P or Interior layer or ^ETSI has th ^ or has these two different characteristics.

The total thickness of ^PE n ^{e d} zc ^{1 l ation} you ^{some j ja} ko thickness vniitřm layers ^i.e. About ^2.54 to ^15, 24 (эд ^from his e Lish RP ^and vitlctt on ^the difference te Lot ^{p y} content trub- ^alkyl and pipes ^for oM ^ ^p ccording further Rumer ^p ^ m ^of pipes ^ters hmoteo ^{TI-enoic s} and ^t he ^pl u ^p from.

^P ro temperature difference between ⁴¹ 5 to 1 ⁵⁰ ° C obv ^YKL e ^p osta ^whose thickness between the ^MOT · 2Д about ^{4-1 5.24} centtmetru. Generally Ric ^ in ^E that the network is the temperature difference between ^p abrasion ^{running in} the two countries ^ should be greater insulation thickness. In chladírens ^Ké m ^{p y} rum services to standards-not just ^{IVa p} ro larger ^'s temperature difference and thickness ^ ^ lyuretanové foam between 7.6 to 15.24 cm. For pipelines or ^{h to} give the usual characterized slug temperatures between ^55.5 to 89 ° C. For hot oil piping is normálrn thickness Izotec ^2, 54 and 6 ^M, 4 cm. The molten sulfur conveying pipe is provided with a foam insulation having a thickness of 6.3 to 7.65 cm, the inner layer 12 or 20 being selected to withstand high temperatures, i.e. to be stable at temperatures up to 149 ° C. Abortion ^{is running p} ro ^h or ^k y o ^{l EJ, C} o is ^the UD Dozen ^PU DE required under normal conditions the thickness of ^{PE-new and} from ^l ation 5Д cm ^b not less. Polyurethane foam has an extremely low value · · thermal transmissibility which Ra ^d s ^of about not less třitoát ^{ho p p} ELNA řestupnost foam glass.

The following is a suitable composition for producing a sufficiently rigid foam.

Component Weight parts Methylenediphenyldiisocyanate 115 Polyol 100 ALIGN! Silicone oil 1 Triethylenediamine 0.5 Dibutyl-Sn-dilaurate 0.1 Trichlormonofluormetan 35.0 Tris (2-chloroethyl) phosphate 10

All these components except the diisocyanate are premixed, the diisocyanate is mixed immediately prior to foaming and spraying with a conventional device to produce a rigid foam having a density of 0.029 g / cm ³ . A decrease in the proportion of trichloronofluoromethane results in an increase in specific gravity. Increasing the solids content of the above formula, as well as adding 30 parts of methylcellulose without increasing the addition of a foaming agent, also leads to an increase in specific gravity. Higher temperature resistance of the foamed plastic is achieved by conventional compounding techniques and by selecting components, such as by reacting aromatic amine-containing materials with the remaining components, as described, for example, in U.S. Patent 3,909,465.

«

Increased friability resistance, which is also desirable for the outer foam insulation layer, can also be achieved by selecting polyol admixtures, as described, for example, in U.S. Patent No. 3,928,257 or No. 3,928,258.

Any kind of coating may be applied to the outer layer of foam insulation. For example, it is possible to provide the outer surface of the Insulation by winding or extrusion, a layer having a protective character or acting as a moisture barrier, either of paper or plastic, for example of polyethylene or polypropylene. It is possible to make a coating or wraps of plastic having a shape memory and suitably shrunk to match the surface of the foam insulation, it is also possible to apply a liquid cured epoxy resin coating in place, or to use an asphalt mastic layer or any conventional protective material. Due to the good resistance of the applied foam insulation to dents and to abrasion damage, in particular the outer manufactured polyurethane foam plastic layer made in accordance with the present invention, an upper additional covering layer is only needed to achieve puncture resistance and to prevent moisture penetration.

Claims (2)

SUBJECT A method of insulating a pipe, for example a metal pipe with an anticorrosive protective coating, at least one inner layer and one outer layer of foamed plastic insulation, characterized in that at least one foamable plastic composition is applied to the pipe to form the first inner layer of insulation, foaming in situ until it reaches a specific gravity of 0.024 to 0.096 g / cm ³ , and a foamable plastic composition is applied to the surface of the last applied inner layer to form an outer layer of insulation, the coating being applied prior to foaming In or after curing, or after foaming or curing of the last applied inner layer of insulation, the applied composition is foamed in situ until the stiffness and specific gravity is at least 25 ° / higher than the density of any inner layer, and 5 to 30% of the total layer thickness. 2. A method according to claim 1, wherein the foamable plastic compositions are polyurethane-containing compositions.