CA1064779A - Coating of inorganic multicellular particles in bonding material on plastic pipe - Google Patents
Coating of inorganic multicellular particles in bonding material on plastic pipeInfo
- Publication number
- CA1064779A CA1064779A CA235,198A CA235198A CA1064779A CA 1064779 A CA1064779 A CA 1064779A CA 235198 A CA235198 A CA 235198A CA 1064779 A CA1064779 A CA 1064779A
- Authority
- CA
- Canada
- Prior art keywords
- pipe
- particles
- impact
- film
- bonding material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L57/00—Protection of pipes or objects of similar shape against external or internal damage or wear
- F16L57/06—Protection of pipes or objects of similar shape against external or internal damage or wear against wear
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L57/00—Protection of pipes or objects of similar shape against external or internal damage or wear
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Laminated Bodies (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
- Rigid Pipes And Flexible Pipes (AREA)
- Moulding By Coating Moulds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An energy-absorbing protective coating is bonded to the exterior of a plastic pipe. Preferably, the coating is a layer of low-cost, crushable, multicellular, inorganic particles, such as natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, slag, or furnace cinder, embedded in a thin film of plastic resin. the particles crush by breaking upon impact, which absorbs the energy of the impact and protects the pipe from damage.
An energy-absorbing protective coating is bonded to the exterior of a plastic pipe. Preferably, the coating is a layer of low-cost, crushable, multicellular, inorganic particles, such as natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, slag, or furnace cinder, embedded in a thin film of plastic resin. the particles crush by breaking upon impact, which absorbs the energy of the impact and protects the pipe from damage.
Description
-~L06477~31 COATING OF ~NORGANIC ~UhT~CELhU~AR PA~TIChE~
IN BOND'ING' MATER'I~L 'ON PhASTIC PI'PE
Back-g~o~nd -o'f t'he''I'n~'ent'i'on This invention relates to protecting plastic pipe ; 5 from impact damage and more particularly to a crushable, impact-protective coating applied to the exterior of plastic pipe.
Fiber-reinforced plastic pipe, particularly that made ; from khermosetting resin reinforced with glass fibers, is widely ùsed because of its resistance to corrosive liquids and its high strength. It is extensively used, for example, in the chemical, petroleum, and paper-making industries. In ~' these industries, the pipe is frequently installed above ground. In underground applications it is most commonly used to convey either water or sewege.
, .
~)647~
One of the disadvantages of plastic pipes made from thermosetting resins is that such pipes are brittle and therefore crack easily even when subjected to a relatively moderate blow. In many of the above applications, such plastic pipes are subjected to the risk of receiving impact damage during shipping or installation. For example, impact damage often occurs when the pipe is loaded or unloaded from trucks.
In above-ground installations, the pipe is commonly hoisted by cables, and can receive impact damage when striking a stationary object, such as a post. In underground installations, ~¦ impact damage usually comes from rocks which fall onto the pipe in a trench before the trench is back-filled.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an impact-protected pipe made from a pipe body of plastic material that is susceptible to cracking when subjecting 'I
it to an impact blow; a film of bond:ing material coated onto the pipe body; and a surrounding layer oE protective particles bonded , by the film in which said particles are partially embedded, `~ 2Q unembedded portions of the particles projecting freely from the film and constituting the exterior of the pipe, the embedded part of the particulate layer being thinner than the unembedded part thereof, and the particles being of a crushable, multi-cellular inorganic material such that the particles in practice collapse progessively proportionately to the force of the blow, thereby to soften the blow, the particles having such compressive strength that they will commence to crush substantially to absorb impact energy when an impact approaches a level that would damage a similar but unprotected pipe.
Also in accordance with the invention there is provi~ed ~/ :
977~
an impact protected pipe comprising a pipe body having a film of bonding material thereon and a surrounding layer of protect-ive particles bonded ther~to by the film in which said particles are partially embedded, unembedded portions of ~he particles projecting freely from the film and constituting the exterior of the pipe and the embedded part of the particulate layer being thinner than the embedded part, the pipe body consisting of a plastic material which is susceptible to cracking when subjected to an impact ~low, the particles being of crushahle, multi-cellular material selected from the group consisting of ; natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, furnace cinder, or mixtures thereof, and thepipe being such that the particles will collapse pro-portionately to the force of an impact blow to reduce the 15 effect thereof below a level that would damage a similar but unprotected pipe.
Further in accordance with the invention there is provided a plastic pipe having a particulate inorganic multi-cellular crushable outer coating of particles selected Prom
IN BOND'ING' MATER'I~L 'ON PhASTIC PI'PE
Back-g~o~nd -o'f t'he''I'n~'ent'i'on This invention relates to protecting plastic pipe ; 5 from impact damage and more particularly to a crushable, impact-protective coating applied to the exterior of plastic pipe.
Fiber-reinforced plastic pipe, particularly that made ; from khermosetting resin reinforced with glass fibers, is widely ùsed because of its resistance to corrosive liquids and its high strength. It is extensively used, for example, in the chemical, petroleum, and paper-making industries. In ~' these industries, the pipe is frequently installed above ground. In underground applications it is most commonly used to convey either water or sewege.
, .
~)647~
One of the disadvantages of plastic pipes made from thermosetting resins is that such pipes are brittle and therefore crack easily even when subjected to a relatively moderate blow. In many of the above applications, such plastic pipes are subjected to the risk of receiving impact damage during shipping or installation. For example, impact damage often occurs when the pipe is loaded or unloaded from trucks.
In above-ground installations, the pipe is commonly hoisted by cables, and can receive impact damage when striking a stationary object, such as a post. In underground installations, ~¦ impact damage usually comes from rocks which fall onto the pipe in a trench before the trench is back-filled.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an impact-protected pipe made from a pipe body of plastic material that is susceptible to cracking when subjecting 'I
it to an impact blow; a film of bond:ing material coated onto the pipe body; and a surrounding layer oE protective particles bonded , by the film in which said particles are partially embedded, `~ 2Q unembedded portions of the particles projecting freely from the film and constituting the exterior of the pipe, the embedded part of the particulate layer being thinner than the unembedded part thereof, and the particles being of a crushable, multi-cellular inorganic material such that the particles in practice collapse progessively proportionately to the force of the blow, thereby to soften the blow, the particles having such compressive strength that they will commence to crush substantially to absorb impact energy when an impact approaches a level that would damage a similar but unprotected pipe.
Also in accordance with the invention there is provi~ed ~/ :
977~
an impact protected pipe comprising a pipe body having a film of bonding material thereon and a surrounding layer of protect-ive particles bonded ther~to by the film in which said particles are partially embedded, unembedded portions of ~he particles projecting freely from the film and constituting the exterior of the pipe and the embedded part of the particulate layer being thinner than the embedded part, the pipe body consisting of a plastic material which is susceptible to cracking when subjected to an impact ~low, the particles being of crushahle, multi-cellular material selected from the group consisting of ; natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, furnace cinder, or mixtures thereof, and thepipe being such that the particles will collapse pro-portionately to the force of an impact blow to reduce the 15 effect thereof below a level that would damage a similar but unprotected pipe.
Further in accordance with the invention there is provided a plastic pipe having a particulate inorganic multi-cellular crushable outer coating of particles selected Prom
2~ the group consisting of natural volcanic light weight .
1 ~ aggreg~te, expanded shale, expanded clay, ~ hee, slag, and furnace cinder, or mixtures thereof, embedded in a thin film : of bonding mate*ial covering the exterior surface of the pipe, the particles being of sufficient thickness that a major portion of the particles projects freely away from the film of bonding material to form an impact-protective outer layer which crushes by breaking apart to absorb energy upon impact and provide a level of impact protection for the pipe body.
Further in accordance with the invention there is 3Q provided the combination of a plastic pipe, a film of bonding ~ - 2a ..~ ~,.....
7~79 material on the pipe exterior surface, and an outer layer of crushable, multi-cellular inorganic particles selected from the group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, and furnace cinder, or mixtures thereof, embedded in the bonding material so as to cover the exterior surface of the pipe, the particles being of substantially greater thickness than the film of bonding material so that the unembedded portions of the particles project away from the pipe body to provide a multi-cellular inorganic coating which crushes by breaking to absorb energy upon impact and provides a level of impact-protection for the pipe body.
The energy-absorbing coating for plastics of the invention preferably comprises a crushable, energy-absorbing, layer of multi-cellular inorganic particles bonded to the exterior of the pipe. The compressive characteristics of the multi-cellular particles are such that they tend to crush prcgressively upom impact rather than shattering. Such a protective pipe coating absorbs impact energy, and spreads the impact over a broader area by crushing to fit the shape of the impacting object. Multi-cellular inorganic particles such as natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, slag, or furnace cinder, are especially suitable coating materials because they have the desired energy-absorbing characteristics and they are very low in cost. Bestprotection is provided if the compressive strength of the particles is such that they do not crush substantially unless an impact approaches the level that would damage an unprotected pipe.
- 2b j,, 1 9~IEF D~:SCRIPTION OE' T~IE DRAWINGS
_ ,, " _ , These and other a~pects o~ the invention will be more fully understood by re~erring to the following detailed descriptio~ and the accompanying drawings in which:
FIG. 1 is a schematic elevation view showing a preferred method of applying a layer of bonding material to the exterior of a section of plastic pipe;
FIG. 2 is a schematic elevation view taken on line 2-2 of FIG. l;
FIG. 3 is a schematic elevation view showing a preferred method of applying a layer of impact-protective particles to the bonding material layer shown in FIG. l; and FIG. 4 is an enlarged fragmentary sectional elevation view of an impact-protective coating applied to a plastic pipe~
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 through 3 show a preferred method o~ coating a section of plastic pipe 10. The coating to be described ~0 below i8 particularly u~eful for protecting relatively ~hin-walled plastic pip~s made from fiber-rein~orced thermosetting resins~ Such pipes are usually brittle and therefore crack rela~ively easily when receiving a blow fxom an impacking obj~ctO
2 During coating, pipe section 10 is rotated in the direction indicated by the arrow 12 shown in FIG. 1. As the pipe section is rotated, a thin film 14 of fluid bonding material 16 is spread onto the outer surface o~ the pipe.
~he bonding material, preferably a thi~otropic plastic resin
1 ~ aggreg~te, expanded shale, expanded clay, ~ hee, slag, and furnace cinder, or mixtures thereof, embedded in a thin film : of bonding mate*ial covering the exterior surface of the pipe, the particles being of sufficient thickness that a major portion of the particles projects freely away from the film of bonding material to form an impact-protective outer layer which crushes by breaking apart to absorb energy upon impact and provide a level of impact protection for the pipe body.
Further in accordance with the invention there is 3Q provided the combination of a plastic pipe, a film of bonding ~ - 2a ..~ ~,.....
7~79 material on the pipe exterior surface, and an outer layer of crushable, multi-cellular inorganic particles selected from the group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, and furnace cinder, or mixtures thereof, embedded in the bonding material so as to cover the exterior surface of the pipe, the particles being of substantially greater thickness than the film of bonding material so that the unembedded portions of the particles project away from the pipe body to provide a multi-cellular inorganic coating which crushes by breaking to absorb energy upon impact and provides a level of impact-protection for the pipe body.
The energy-absorbing coating for plastics of the invention preferably comprises a crushable, energy-absorbing, layer of multi-cellular inorganic particles bonded to the exterior of the pipe. The compressive characteristics of the multi-cellular particles are such that they tend to crush prcgressively upom impact rather than shattering. Such a protective pipe coating absorbs impact energy, and spreads the impact over a broader area by crushing to fit the shape of the impacting object. Multi-cellular inorganic particles such as natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, slag, or furnace cinder, are especially suitable coating materials because they have the desired energy-absorbing characteristics and they are very low in cost. Bestprotection is provided if the compressive strength of the particles is such that they do not crush substantially unless an impact approaches the level that would damage an unprotected pipe.
- 2b j,, 1 9~IEF D~:SCRIPTION OE' T~IE DRAWINGS
_ ,, " _ , These and other a~pects o~ the invention will be more fully understood by re~erring to the following detailed descriptio~ and the accompanying drawings in which:
FIG. 1 is a schematic elevation view showing a preferred method of applying a layer of bonding material to the exterior of a section of plastic pipe;
FIG. 2 is a schematic elevation view taken on line 2-2 of FIG. l;
FIG. 3 is a schematic elevation view showing a preferred method of applying a layer of impact-protective particles to the bonding material layer shown in FIG. l; and FIG. 4 is an enlarged fragmentary sectional elevation view of an impact-protective coating applied to a plastic pipe~
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIGS. 1 through 3 show a preferred method o~ coating a section of plastic pipe 10. The coating to be described ~0 below i8 particularly u~eful for protecting relatively ~hin-walled plastic pip~s made from fiber-rein~orced thermosetting resins~ Such pipes are usually brittle and therefore crack rela~ively easily when receiving a blow fxom an impacking obj~ctO
2 During coating, pipe section 10 is rotated in the direction indicated by the arrow 12 shown in FIG. 1. As the pipe section is rotated, a thin film 14 of fluid bonding material 16 is spread onto the outer surface o~ the pipe.
~he bonding material, preferably a thi~otropic plastic resin
3 . .
~6~77~
1 is applied to the pipe exterior. in the thlnnest practical layer to minimize material costs. A typical thic~ness for the film layer is about 0.015 inch for a Z-i~ch diameter pipe, and about 0;025 inch for 24-inch diameter pipe.
S FIGS. 1 and 2 show the preferred method of accurately controlling the thickness of the resin lay~r. A movable, : T-shaped distribution head 18 located above pipe 10 spxeads the resin onto the pipe. The distribution head comprises a substantially upright, elongated tubular feed conduit 20 through which the resin passes, and an elongated perforated distribution tube 22 at the lower end;of the feed conduit for receiving the supply of resin and distributing it across the rotating pipe. The dis~ribution head moves slowly in the direction of the arrow 24 in FIG. 2 as it distributes the resin.
A brush 26 adjacent the distribution head has sof t bristles 28 held in contact with the resin film to spread it substantially uniormly across the outer surface of the plp~. .
If ~he resin does not ~ontain excessively abrasive fillers or pigments, it can be applied in the desired thickness by airless spray. If severe abrasives are present, or if the resin pot life is short,.the preferred method of applying the resin is by the method shown in FIGS. l and 2.
- 25 Upon completion of the win~ing process during the manu-facture of filament-wound pipe! the pipe typically has an excess o~ liquid resin on its surfaceO Thus, a suitably constructed wiper lnot shown) can be used to remove only ~1064~79 1 part of the resin and leave a thln f$1m having the desired thickness described above. However, in the pxeferred method the excess resin remaining upon completion of wind ing is completely removed from the pipe surface, and resin film 14 is applied thereafter. This metho~ permits selection of the resin and additives which provide best performance in . the coating, without being limited to the use of the specific resin used during winding of the filament layer.
After the entire outer surface of the pipe is coated with the resin film, crushable, multicellular par~icles 30 are applied to the resin, preferably;in accordance with the method shown in FIG. 3. An inclined, elongated chute 32 adjacent the pipe channels particles 30 under gravity onto the pipe so the particles adhere to the resin film which permanently bonds the particles to the pipe exterior. The particles tend to accumulate at the end of the chute, which presses the particles down through the resin film into firm contact with the pipe. ~hus, the particles are embedded in the resi~ film which strongly bonds the particles to the pipe. As ~he particles are being applied, the pipe is rotated slowly in the direction o~ the arrow 34 shown in FIG. 3.
Excess particles 30 which do not adhere to the resin film fall under gravity in the direction of the arrow 36 in FIG.
3 for collection and reuse.
Thus, the particles are closely packed together in a substantially single layer, and are pressed down firmly into the resin film to provide a strong bond. This coating is illustrated best in FIG. 4, in which the particles are extremely exaggerated in size for clarity.
1~64'779 1 The crushable particles 30 are bonded to the ou$er surface of the pipe so that a major portion of the resulting ~ellular particle layer projects away from the pipe in order that the projecting portions of the particles can b~ crushed by breaking to absorb energy upon impact. The preferred particle material is a low-cost, multicellular substance with a sufficient compressive strength that allows the particles to absorb a useful a~ount of energy during impact. This allows the particles to crush progressively upon impact, rather than shattering. In use~
when a missile strikes the protective coa~ing, the particles crush progressively in an amoun~ proportional to the force of the blow, which softens or absorbs the blow. The indenta-tion of the broken particles in the protective layer conforms to the shape of ~he impacting ob~ect, which spreads the impact over a larger area of the pipe. This progressive crushing of the particles protects the underlying pipe structure by preventing a damaging amount of impact energy contained in the missile from being transferred to the pipe.
The crushable particles 30 bond so strongly to the pipe that abrasions and minor impacts remove only the outer portion of some particles and leave a substantial remainder.
Major impacts crush a larger number of particles, which absorbs a larger portion of the shock. A portion of the ~5 crushed particles remain embedded in the resin film to provide some pro~ection against subsequen~ impacts.
1(:1~;47~9 1 The crushable coating preferably is of particles of fairly uniform size because they provide a unifor~ coating and better appearance of the final product. As shown best in FI~. 4, the crushable particles are of suc~ a size that they project a substantial distance away from the resin film, which enables them to receive the energy from the impacting object and crush by breaking without immediately transmitting the energy to the plastic pipe. Good results are obtained when the particle size is in the range of about 1/16 inch to about 1/4 inch. Generally, the larger particles give better protection, but the dynamic response of impacted pipe is such that smaller particles can give adequate protection for smaller pipe.
Preferably, the particles 30 are inorganic, multicelIular particles selected from the c!lass of materials which includes natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, and c~llular, crushable ~ypes of slag and furnace cinder, and mixtures thereof, although other inorganic~ multicellular,crushable materials having good energy-absorbing characteristics also can be used. The use of the class of inorganic particles described above provides an extremely low-cost coating for plastic pipe. At the present time, the inorganic, multicellular, crushable particles contemplated by this invention cost about $0.005 per pound. In contrast, a protective pipe coating made from particles of polystyrene foam, or any other expanded polymeric material, are tremendously more expensive. For example, polystyrene foam beads at the present time cost about $0.30 per pound. If polystyrene ~oam ~eads having a very low 1~64~79 1 density and compressive strength are used in a prote~tive pipe coating, they are generally incapable of absorbing the amount of energy necessary to protect the plastic pipe from impact damage. On the other hand~ if an acceptable impact-protective coating for plastic pipe is made from expandedpolymeric matexial, it would necessitate resorting to plastic foam particles of relatively high strength and density to achieve the compressive strength necessary to provide the required amount of energy absorption. However, such high density plastic foam particles are tremendously more expensive than the crushable, mult;~ellular, inorgan.ic particles con-templated by the present invention, and instead of using such costly plastic particles, it would be nearl~ as economical to . ~imply increase the wall thickness of the plastic pipe to . 15 achieve the desired impac~ resistance. The present invention avolds ~his problem by providing a protective layer which is . of such low cost that it can be applied to the outex surface : of the pipe:without the necessity of adding more costly resinous and reinforcing materials to the pipe to increa9e its wall thickness in order to obtain the desired impact resistance~
In one test on a 14-inch diameter experimental filament-wound, fiber-reinforced plastic pipe, the threshhold of damage to the pipe waæ kested ~y impacting the pipe with a
~6~77~
1 is applied to the pipe exterior. in the thlnnest practical layer to minimize material costs. A typical thic~ness for the film layer is about 0.015 inch for a Z-i~ch diameter pipe, and about 0;025 inch for 24-inch diameter pipe.
S FIGS. 1 and 2 show the preferred method of accurately controlling the thickness of the resin lay~r. A movable, : T-shaped distribution head 18 located above pipe 10 spxeads the resin onto the pipe. The distribution head comprises a substantially upright, elongated tubular feed conduit 20 through which the resin passes, and an elongated perforated distribution tube 22 at the lower end;of the feed conduit for receiving the supply of resin and distributing it across the rotating pipe. The dis~ribution head moves slowly in the direction of the arrow 24 in FIG. 2 as it distributes the resin.
A brush 26 adjacent the distribution head has sof t bristles 28 held in contact with the resin film to spread it substantially uniormly across the outer surface of the plp~. .
If ~he resin does not ~ontain excessively abrasive fillers or pigments, it can be applied in the desired thickness by airless spray. If severe abrasives are present, or if the resin pot life is short,.the preferred method of applying the resin is by the method shown in FIGS. l and 2.
- 25 Upon completion of the win~ing process during the manu-facture of filament-wound pipe! the pipe typically has an excess o~ liquid resin on its surfaceO Thus, a suitably constructed wiper lnot shown) can be used to remove only ~1064~79 1 part of the resin and leave a thln f$1m having the desired thickness described above. However, in the pxeferred method the excess resin remaining upon completion of wind ing is completely removed from the pipe surface, and resin film 14 is applied thereafter. This metho~ permits selection of the resin and additives which provide best performance in . the coating, without being limited to the use of the specific resin used during winding of the filament layer.
After the entire outer surface of the pipe is coated with the resin film, crushable, multicellular par~icles 30 are applied to the resin, preferably;in accordance with the method shown in FIG. 3. An inclined, elongated chute 32 adjacent the pipe channels particles 30 under gravity onto the pipe so the particles adhere to the resin film which permanently bonds the particles to the pipe exterior. The particles tend to accumulate at the end of the chute, which presses the particles down through the resin film into firm contact with the pipe. ~hus, the particles are embedded in the resi~ film which strongly bonds the particles to the pipe. As ~he particles are being applied, the pipe is rotated slowly in the direction o~ the arrow 34 shown in FIG. 3.
Excess particles 30 which do not adhere to the resin film fall under gravity in the direction of the arrow 36 in FIG.
3 for collection and reuse.
Thus, the particles are closely packed together in a substantially single layer, and are pressed down firmly into the resin film to provide a strong bond. This coating is illustrated best in FIG. 4, in which the particles are extremely exaggerated in size for clarity.
1~64'779 1 The crushable particles 30 are bonded to the ou$er surface of the pipe so that a major portion of the resulting ~ellular particle layer projects away from the pipe in order that the projecting portions of the particles can b~ crushed by breaking to absorb energy upon impact. The preferred particle material is a low-cost, multicellular substance with a sufficient compressive strength that allows the particles to absorb a useful a~ount of energy during impact. This allows the particles to crush progressively upon impact, rather than shattering. In use~
when a missile strikes the protective coa~ing, the particles crush progressively in an amoun~ proportional to the force of the blow, which softens or absorbs the blow. The indenta-tion of the broken particles in the protective layer conforms to the shape of ~he impacting ob~ect, which spreads the impact over a larger area of the pipe. This progressive crushing of the particles protects the underlying pipe structure by preventing a damaging amount of impact energy contained in the missile from being transferred to the pipe.
The crushable particles 30 bond so strongly to the pipe that abrasions and minor impacts remove only the outer portion of some particles and leave a substantial remainder.
Major impacts crush a larger number of particles, which absorbs a larger portion of the shock. A portion of the ~5 crushed particles remain embedded in the resin film to provide some pro~ection against subsequen~ impacts.
1(:1~;47~9 1 The crushable coating preferably is of particles of fairly uniform size because they provide a unifor~ coating and better appearance of the final product. As shown best in FI~. 4, the crushable particles are of suc~ a size that they project a substantial distance away from the resin film, which enables them to receive the energy from the impacting object and crush by breaking without immediately transmitting the energy to the plastic pipe. Good results are obtained when the particle size is in the range of about 1/16 inch to about 1/4 inch. Generally, the larger particles give better protection, but the dynamic response of impacted pipe is such that smaller particles can give adequate protection for smaller pipe.
Preferably, the particles 30 are inorganic, multicelIular particles selected from the c!lass of materials which includes natural volcanic lightweight aggregate, expanded shale, expanded clay, pumice, and c~llular, crushable ~ypes of slag and furnace cinder, and mixtures thereof, although other inorganic~ multicellular,crushable materials having good energy-absorbing characteristics also can be used. The use of the class of inorganic particles described above provides an extremely low-cost coating for plastic pipe. At the present time, the inorganic, multicellular, crushable particles contemplated by this invention cost about $0.005 per pound. In contrast, a protective pipe coating made from particles of polystyrene foam, or any other expanded polymeric material, are tremendously more expensive. For example, polystyrene foam beads at the present time cost about $0.30 per pound. If polystyrene ~oam ~eads having a very low 1~64~79 1 density and compressive strength are used in a prote~tive pipe coating, they are generally incapable of absorbing the amount of energy necessary to protect the plastic pipe from impact damage. On the other hand~ if an acceptable impact-protective coating for plastic pipe is made from expandedpolymeric matexial, it would necessitate resorting to plastic foam particles of relatively high strength and density to achieve the compressive strength necessary to provide the required amount of energy absorption. However, such high density plastic foam particles are tremendously more expensive than the crushable, mult;~ellular, inorgan.ic particles con-templated by the present invention, and instead of using such costly plastic particles, it would be nearl~ as economical to . ~imply increase the wall thickness of the plastic pipe to . 15 achieve the desired impac~ resistance. The present invention avolds ~his problem by providing a protective layer which is . of such low cost that it can be applied to the outex surface : of the pipe:without the necessity of adding more costly resinous and reinforcing materials to the pipe to increa9e its wall thickness in order to obtain the desired impact resistance~
In one test on a 14-inch diameter experimental filament-wound, fiber-reinforced plastic pipe, the threshhold of damage to the pipe waæ kested ~y impacting the pipe with a
4 pound steel ball dropped on the pipe. The test results showed ~hat the drop height xequixed to cause damage was : increased by a factor of 2 to 3 with a coating o~ 1/8-inch expanded shale particles.
~064779 1 Thus, a low-cost,impact-protective, crushable pipe coating is provided which protects thin-walled plastic pipe from impact damage coming from handling, loading, unloading, or installing the pipe.
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~064779 1 Thus, a low-cost,impact-protective, crushable pipe coating is provided which protects thin-walled plastic pipe from impact damage coming from handling, loading, unloading, or installing the pipe.
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Claims (12)
1. An impact-protected pipe made from a pipe body of plastic material that is susceptible to cracking when subjecting it to an impact blow; a film of bonding material coated onto the pipe body; and a surrounding layer of protective particles bonded by the film in which said particles are partially embedded, unembedded portions of the particles projecting freely from the film and constituting the exterior of the pipe, the embedded part of the particulate layer being thinner than the unembedded part thereof, and the particles being of a crushable, multi-cellular inorganic material such that the particles in practice collapse progressively oroportionately to the force of the blow, thereby to soften the blow, the particles having such compressive strength that they will commence to crush substantially to absorb impact energy when an impact approaches a level that would damage a similar but unprotected pipe.
2. The pipe according to claim l in which the pipe body is made from a thermosetting resinous material.
3. The pipe according to claim 1 in which the particles are distributed uniformly about the entire periphery of the pipe body in a substantially single layer.
4. The pipe according to claim l in which the particles are so distributed about the pipe body that there are open spaces between the projecting unembedded portions of the particles.
5. The pipe according to any of claims 1, 3 or 4 in which the film of bonding material is from 0Ø5 to 0.025 inch thick, and the particles are in the range of 1/16 to l/4-inch in size.
6. The pipe according to claim 1, in which the particles are of such compressive strength that the projecting unembedded portions thereof are able to absorb sufficient impact energy by crushing to increase by a factor of at least about 2 the drop height of an impacting object required to cause damage to the pipe when compared with an unprotected pipe body.
7. The pipe according to any of claims 1, 4 or 6 in which the particles are selected from a group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, furnace cinder or mixtures thereof.
8. An impact protected pipe comprising a pipe body having a film of bonding material thereon and a surrounding layer of protective particles bonded thereto by the film in which said particles are partially embedded, unembedded portions of the particles projecting freely from the film and constituting the exterior of the pipe and the embedded part of the particulate layer being thinner than the embedded part, the pipe body consisting of a plastic material which is susceptible to cracking when subjected to an impact blow, the particles being of crushable, multi-cullular material selected from the group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, furnace cinder, or mixtures thereof, and the pipe being such that the particles will collapse proportionately to the force of an impact blow to reduce the effect thereof below a level that would damage a similar but unprotected pipe.
9. The pipe according to claim 9, in which the film of bonding material is about 0.015 to 0.025 inch thick, and the outer layer of particles is between about 1/16 to about 1/4-inch in thickness.
10. The pipe according to claim 8 or 9 in which the particles are distributed uniformly about the pipe surface in a single layer which covers substantially the entire exterior surface of the pipe.
11. A plastic pipe having a particulate inorganic multi-cellular crushable outer coating of particles selected from the group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, and furnace cinder, or mixtures thereof, embedded in a thin film of bonding material covering the exterior surface of the pipe, the particle being of sufficient thickness that a major portion of the particles projects freely away from the film of bonding material to form an impact-protective outer layer which crushes by breaking apart to absorb-energy upon impact and provide a level of impact protection for the pipe body.
12. The combination of a plastic pipe, a film of bonding material on the pipe exterior surface, and an outer layer of crushable, multi-cellular inorganic particles selected from the group consisting of natural volcanic light weight aggregate, expanded shale, expanded clay, pumice, slag, and furnace cinder, or mixtures thereof, embedded in the bonding material so as to cover the exterior surface of the pipe, the particles being of substantially greater thickness than the film of bonding material so that the unembedded portions of the particles project away from the pipe body to provide a multi-cellular inorganic coating which crushes by breaking to absorb energy upon impact and provides a level of impact-protection for the pipe body.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/506,609 US3948294A (en) | 1972-03-01 | 1974-09-16 | Impact-protective coating for plastic pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1064779A true CA1064779A (en) | 1979-10-23 |
Family
ID=24015296
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA235,198A Expired CA1064779A (en) | 1974-09-16 | 1975-09-10 | Coating of inorganic multicellular particles in bonding material on plastic pipe |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5156016A (en) |
| CA (1) | CA1064779A (en) |
| DE (1) | DE2540748C2 (en) |
| NL (1) | NL7510356A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9752235B2 (en) | 2011-07-29 | 2017-09-05 | Fachhochschule Muenster | Workpiece comprising a laminate to protect against an impact stress |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3214319C1 (en) * | 1982-04-19 | 1984-03-29 | Hoesch Werke Ag, 4600 Dortmund | Metal tube with corrosion and stone protection coating made of plastic |
| DE102004056192B4 (en) * | 2004-11-20 | 2007-06-28 | Knoch, Kern & Co. | Plastic pipe |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3304219A (en) * | 1962-05-02 | 1967-02-14 | Little Inc A | Energy absorbing materials |
| US3396641A (en) * | 1964-12-16 | 1968-08-13 | Welty | Fabrication of slag surfaces and structures |
-
1975
- 1975-09-02 NL NL7510356A patent/NL7510356A/en not_active Application Discontinuation
- 1975-09-10 CA CA235,198A patent/CA1064779A/en not_active Expired
- 1975-09-12 DE DE19752540748 patent/DE2540748C2/en not_active Expired
- 1975-09-16 JP JP50112034A patent/JPS5156016A/ja active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9752235B2 (en) | 2011-07-29 | 2017-09-05 | Fachhochschule Muenster | Workpiece comprising a laminate to protect against an impact stress |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5156016A (en) | 1976-05-17 |
| DE2540748C2 (en) | 1984-08-09 |
| NL7510356A (en) | 1976-03-18 |
| DE2540748A1 (en) | 1976-04-01 |
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