GB1596305A - Internal lining of cylinders - Google Patents

Internal lining of cylinders Download PDF

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Publication number
GB1596305A
GB1596305A GB1795377A GB1795377A GB1596305A GB 1596305 A GB1596305 A GB 1596305A GB 1795377 A GB1795377 A GB 1795377A GB 1795377 A GB1795377 A GB 1795377A GB 1596305 A GB1596305 A GB 1596305A
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GB
United Kingdom
Prior art keywords
cylinder
straight cylinder
polymeric material
lining
liquid
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
Application number
GB1795377A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Worcester Valve Co Ltd
Original Assignee
Babcock Corrosion Control Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Babcock Corrosion Control Ltd filed Critical Babcock Corrosion Control Ltd
Priority to GB1795377A priority Critical patent/GB1596305A/en
Priority to AU35523/78A priority patent/AU522752B2/en
Publication of GB1596305A publication Critical patent/GB1596305A/en
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Moulding By Coating Moulds (AREA)

Description

(54) INTERNAL LINING OF CYLINDERS (71) We, BABCOCK COR ROSION CONTROL. LIMITED, a British company, of 119-120, High Street, Eton, Windsor, Berkshire, SL4 6AN, do hereby declare the invention, for which we pray that patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the internal lining of cylinders and, more particularly, relates to a method of depositing a protective layer of polymeric material internally of a straight cylinder, such as a pipe.
According to the present invention there is provided a method of depositing a lining of polymeric material internally of a straight cylinder including introducing into the cylinder a solidifiable liquid having a viscosity of less than 1000 centipoises at the time of introduction and which will set to a solid polymeric material; rotating the cylinder about the longitudinal axis thereof, which is positioned to extend horizontally, such that the material is distributed evenly over the interior of the cylinder before the material sets to a solid; and containing said solidifiable liquid within said straight cylinder during rotation thereof.
According to the invention there is also provided a straight cylinder having an internal lining of a polymeric material which is formed from a solidifiable liquid polyurethane having a viscosity of less than 1000 centipoises at the time of introduction into the cylinder.
In one embodiment of the invention a 15 cm (6") internal diameter mild steel straight cylindrical pipe having end flanges is to be lined. To ensure good adhesion of the lining to the pipe wall the pipe is internally shot blasted and then primed with a priming agent, heated to 90"C for one hour to de-gas and to thoroughly dry the pipe, and then allowed to cool to room temperature in a dry atmosphere. Centrally apertured, dished covers are then bolted to the circumferential edge of the pipe flanges, such that the outwardly directed faces of the flanges lie within the covers, thereby permitting flow of the lining material onto the said flange faces. The dished covers also contain the lining material within the pipe during rotation thereof.
The pipe is placed on horizontal rollers and raised to a uniform temperature in the range of 20 to 400C.
One material having the requisite properties enabling it to be used for the lining process is a polyurethane available from Bostik Limited and known under their trade description PM 801 which is supplied as a two component liquid mixture including a first liquid pre-polymer and a second liquid curing agent, both are liquid at a temperature of 18"C/64"F. At this temperature the viscosity of the mixed components is about 180 centipoises.
Sealed containers of the first and second liquid component are positioned adjacent the pipe and are gravity connected to a metering mixer pump, provision being made to restrict ingress of atmospheric moisture which is likely to affect the polyurethane precursors.
The pump discharges mixed components at a rate avoiding gelling and also avoiding -entraining air through a line provided with a nozzle which is positioned to extend through the central aperture of the cover plate some 8 cm into the rotating pipe whilst the pipe is rotated at about 600 r.p.m.
The centrifugal effect produced by rotating the pipe causes the liquid to form a uniform lining of the required thickness (say 6 mm) along the whole of the pipe and also fill the cylindrical gaps at the end flanges.
The speed of rotation of the pipe is such as to permit movement of any bubbles within the liquid lining to the radially inner surface and there escape. Within a few minutes the viscosity of the liquid begins to increase and continues to do so until the lining has set to a solid smooth surface with a substantially bubble free interior.
The temperature of the pipe is then increased progressively up to a maximum of 60"C (140cm). The rotation and heating are maintained for about 1+ hours.
The drive to the rotating rollers is then de-energised and the hot pipe is removed and placed in a curing chamber where it is further heated to 90"C (200"F) for 1 hour to complete the chemical curing of the polyurethane lining.
It should be noted that an alternative to providing centrally apertured dished covers to contain the solidifiable liquid during rotation of the cylinder is to provide the cylinder with regions having different internal diameters. For example, a straight cylinder having a central region oa relatively large internal diameter, which is to be lined, this region extending in a longitudinal manner into opposed regions of relatively small internal diameters.
Another alternative to providing covers to contain the solidifiable liquid is to attach a coaxial ring onto the exterior of the straight cylinder around an end portion thereof. The function of the coaxial ring being to prevent the flow of solidifying material emerging from the respective end of the straight cylinder during rotation thereof from propagating over regions of the exterior of the cylinder beyond the concentric ring.
Pipes having internal diameters of between 5 cm and 50 cm are readily treated in the foregoing manner and it will be appreciated that cylinders of larger diameter may also be treated.
A very important factor in the deposition method is the thickness of the layer of polymeric material required. When depositing a thin layer of material in the form of a surface coating, a liquid of low viscosity will tend to adhere to the cylinder to some extent by natural "wetting" or surface tension effects. Problems arise when depositing a relatively thick layer of material. In the trade, a distinction tends to be drawn between "coatings" which are surface coverings ranging from films of a few microns thickness up to layers of about 1 mm thickness, and "linings" which are relatively thick protective layers ranging from about 1 mm to several centimetres thickness depending on the bore of the cylinder.
When applying "linings" by the method of this invention the effect of the rotation of the cylinder becomes very important.
Because the solidifiable liquids have initially low viscosities there is a tendency for the liquid to shear or run back very readily and there is not only the tendency for the liquid to shear or slip against the wall of the cylinder but for flow to occur within the thickness of the layer. While the solidifiable liquid is setting to a solid the viscosity of the liquid is changing and hence the propensity to slip is changing. If there is any variation in the viscosity of the liquid axialIy along the cylinder at any moment during the setting then differential slip may occur between adjacent regions of liquid and this will tend to give rise to wrinkling in the lining.We have discovered that if the cylinder is rotated at a high speed so that the circumferential distribution of the liquid is uniform because of centrifugal forces acting on the liquid, and the temperature of the cylinder is controlled over fine limits so that it is substantially the same over the whole length of the cylinder and the speed of setting of the liquid is the same throughout the cylinder, then the setting of the liquid to a solid can occur without the problem of wrinkling occurring to a significant extent.
The speed of rotation necessary to achieve centrifugal action is either determined experimentally or calculated.
For "coatings" where all the particles within the layer can be considered as being at the same distance from the central axis and rotation, and ignoring the effect of slip so that one has a theoretically rigid system, and ignoring surface tension effects and the like so that particles within the coating can be considered as behaving independently of each other, the minimum contact pressure will occur at the top of the cylinder and to achieve centrifuging, the outward (and at that point upward) force must be greater than the downward effect of gravity, giving an equation wherein the minimum rotational speed is inversely related to the square root of the internal radius of the cylinder, namely:
where R is the speed of rotation in revolutions per minute, g is the acceleration due to gravity in cm/sec2, and r is the internal radius of the cylinder in centimetres.
However, with "linings" of low viscosity liquids there is a tendency for the liquid to slip back and the rotational speed of the cylinder has to be increased to take this into account.
It is found that when using liquids having a density of 1.0 to 1.5 g/cm3, a viscosity less than 400 centipoises (such as the material Bostik Limited PM 801 of viscosity 180 centipoises) and when producing linings of 0.5 to 1.25 cm thicknesses, the minimum satisfactory rotational speed has to be about 60% greater than the minimum speed calculated on the simplified formula quoted above.
The formula for calculating the speed appears to be a complicated one but a parameter (p) characterising the degree of slip-back is determined by the relationship 30 Rxd where 9 (eta) is the viscosity of the liquid in centipoises, x is the thickness of the lining in centimetres, d is the density of the liquid in g/cm3 and R is the rotational speed in revolutions per minute.
WHAT WE CLAIM IS: 1. A method of depositing a lining of polymeric material internally of a straight cylinder including introducing into the cylinder a solidifiable liquid having a viscosity of less than 1000 centipoises at the time of introduction, and which will set to a solid polymeric material, rotating the cylinder about the longitudinal axis thereof, which is positioned to extend horizontally, such that the material is distributed evenly over the interior of the cylinder before the material sets to a solid; and containing said solidifiable liquid within the straight cylinder during rotation thereof.
2. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claim 1 wherein the solidifiable liquid is a multi-component mixture of precursor for a solid polymeric material and wherein said components are mixed together immediately prior to depositing.
3. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claim 2 wherein the multi-component mixture consists of a two component mixture having as a first component a low viscosity liquid prepolymer, and as a second component a low viscosity liquid curing agent.
4. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 3 wherein the method further includes internally shot blasting said straight cylinder; priming said straight cylinder with a priming agent; heating said straight cylinder to a temperature of 900C for one hour to de-gas; drying said straight cylinder; and cooling said straight cylinder in a dry atmosphere prior to introduction of said polymeric material.
5. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 4 wherein said straight cylinder is maintained at a uniform temperature during introduction of said solidifiable liquid into said straight cylinder.
6. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 5 wherein said straight cylinder is rotated at a uniform angular velocity such that a circumferentially even distribution of the liquid is effected by centrifugal action, and wherein the rotation is maintained during the period of solidification of the solidifiable liquid from the liquid state to the solid state.
7. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 6 wherein the method further includes the step of curing said polymeric material in an oven after its introduction onto the internal surfaces of said straight cylinder.
8. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable liquid is contained within the cylinder during rotation by a centrally apertured cover attached to each end of said cylinder.
9. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable liquid is contained within the cylinder during rotation by providing the straight cylinder with regions of different internal diameter.
10. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable material is contained within the cylinder during rotation by attaching an external coaxial ring to an end portion of said cylinder.
11. A method of depositing a lining of a polymeric material internally of a straight cylinder substantially as hereinbefore described.
12. A straight cylinder having an internal lining of a polymeric material which is formed from a solidifiable liquid polyurethane having a viscosity of less than 1000 centipoises at the time of introduction into the cylinder.
13. A straight cylinder as claimed in Claim 12 wherein the polymeric material is introduced in a liquid state whilst the cylinder is being rotated about its longitudinal axis such that material is distributed evenly over the interior of the cylinder before the material sets to a solid.
14. A straight cylinder as claimed in Claim 12 and or Claim 13 wherein the cylinder is provided with flanged portions and wherein centrally apertured covers are secured to the circumferential edges of said cylinder such that on rotation of said cylinder, a lining of polymeric material is applied to outwardly directed faces of said flanged portions.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. The formula for calculating the speed appears to be a complicated one but a parameter (p) characterising the degree of slip-back is determined by the relationship 30 Rxd where 9 (eta) is the viscosity of the liquid in centipoises, x is the thickness of the lining in centimetres, d is the density of the liquid in g/cm3 and R is the rotational speed in revolutions per minute. WHAT WE CLAIM IS:
1. A method of depositing a lining of polymeric material internally of a straight cylinder including introducing into the cylinder a solidifiable liquid having a viscosity of less than 1000 centipoises at the time of introduction, and which will set to a solid polymeric material, rotating the cylinder about the longitudinal axis thereof, which is positioned to extend horizontally, such that the material is distributed evenly over the interior of the cylinder before the material sets to a solid; and containing said solidifiable liquid within the straight cylinder during rotation thereof.
2. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claim 1 wherein the solidifiable liquid is a multi-component mixture of precursor for a solid polymeric material and wherein said components are mixed together immediately prior to depositing.
3. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claim 2 wherein the multi-component mixture consists of a two component mixture having as a first component a low viscosity liquid prepolymer, and as a second component a low viscosity liquid curing agent.
4. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 3 wherein the method further includes internally shot blasting said straight cylinder; priming said straight cylinder with a priming agent; heating said straight cylinder to a temperature of 900C for one hour to de-gas; drying said straight cylinder; and cooling said straight cylinder in a dry atmosphere prior to introduction of said polymeric material.
5. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 4 wherein said straight cylinder is maintained at a uniform temperature during introduction of said solidifiable liquid into said straight cylinder.
6. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 5 wherein said straight cylinder is rotated at a uniform angular velocity such that a circumferentially even distribution of the liquid is effected by centrifugal action, and wherein the rotation is maintained during the period of solidification of the solidifiable liquid from the liquid state to the solid state.
7. A method of depositing a lining of polymeric material internally of a straight cylinder as claimed in Claims 1 to 6 wherein the method further includes the step of curing said polymeric material in an oven after its introduction onto the internal surfaces of said straight cylinder.
8. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable liquid is contained within the cylinder during rotation by a centrally apertured cover attached to each end of said cylinder.
9. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable liquid is contained within the cylinder during rotation by providing the straight cylinder with regions of different internal diameter.
10. A method of depositing a lining of a polymeric material internally of a straight cylinder as claimed in Claims 1 to 7 wherein the solidifiable material is contained within the cylinder during rotation by attaching an external coaxial ring to an end portion of said cylinder.
11. A method of depositing a lining of a polymeric material internally of a straight cylinder substantially as hereinbefore described.
12. A straight cylinder having an internal lining of a polymeric material which is formed from a solidifiable liquid polyurethane having a viscosity of less than 1000 centipoises at the time of introduction into the cylinder.
13. A straight cylinder as claimed in Claim 12 wherein the polymeric material is introduced in a liquid state whilst the cylinder is being rotated about its longitudinal axis such that material is distributed evenly over the interior of the cylinder before the material sets to a solid.
14. A straight cylinder as claimed in Claim 12 and or Claim 13 wherein the cylinder is provided with flanged portions and wherein centrally apertured covers are secured to the circumferential edges of said cylinder such that on rotation of said cylinder, a lining of polymeric material is applied to outwardly directed faces of said flanged portions.
15. A straight cylinder as claimed in
Claim 12 wherein the cylinder is provided with regions of different internal diameter.
16. A straight cylinder as claimed in Claim 13 wherein the cylinder is provided with an external coaxial ring attached to an end portion thereof.
17. A straight cylinder substantially as hereinbefore described.
GB1795377A 1977-04-29 1977-04-29 Internal lining of cylinders Expired GB1596305A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB1795377A GB1596305A (en) 1977-04-29 1977-04-29 Internal lining of cylinders
AU35523/78A AU522752B2 (en) 1977-04-29 1978-04-27 Method of internally coating a pipe

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1795377A GB1596305A (en) 1977-04-29 1977-04-29 Internal lining of cylinders

Publications (1)

Publication Number Publication Date
GB1596305A true GB1596305A (en) 1981-08-26

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Application Number Title Priority Date Filing Date
GB1795377A Expired GB1596305A (en) 1977-04-29 1977-04-29 Internal lining of cylinders

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AU (1) AU522752B2 (en)
GB (1) GB1596305A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012177144A1 (en) * 2011-06-23 2012-12-27 Pu Teknikk As Tubular body coated with an internal wear coating and method of manufacturing such a coating

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012177144A1 (en) * 2011-06-23 2012-12-27 Pu Teknikk As Tubular body coated with an internal wear coating and method of manufacturing such a coating

Also Published As

Publication number Publication date
AU3552378A (en) 1979-11-01
AU522752B2 (en) 1982-06-24

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PCNP Patent ceased through non-payment of renewal fee