INTERNAL PIPE COATING – POLYGLASS/CORROGLASS PS1
Valid from: 23 October 1996
Last reviewed: August 2020
- Flange faces are to be rebated in order that the coating can be carried from the pipe bore out across the inner part of the flange face. This procedure will afford protection of the weld seam and prevent crevice attack between flange joints. Where possible, flange rebates are to be machined prior to fabrication and in accordance with Figures 2, 3 and 4.
- All welds are to be reasonably smooth and should be slag and spatter free.
- Accessible sharp edges in areas to be coated shall be ground to a minimum radius of 1.5mm.
- Pipe spools should be flanged at both ends and at any branch connections where field fit welds are to be carried out after coating. Refer to Spec PS2 for further information.
- In order to prevent damage to the coating through the fitting of threaded plugs etc., this type of arrangement should be avoided wherever possible. Where tapped bosses and saddle connections are fitted these should be manufactured from a non-corrodible metal for the service environment; the coating will then be terminated overlapping the non-corrodible insert.
- The maximum fabrication lengths that can be economically accommodated are detailed in Figure 1. Wherever possible sizes should be kept within these confines.
- NOTE: Lengths ‘L’ quoted are for straight pipes only using pipe rolling application techniques. For pipe sizes above 3″ nominal bore, bends are not acceptable when attached to lengths greater than 2 metres unless otherwise agreed with Corrocoat, as this is the practical limit for hand application techniques. For diameters of 8″ and above where the Corrocoat pipe blaster and pipe sprayer are to be used, length ‘L’ may exceed those quoted above for both straight pipe and pipes with bends. Please consult Corrocoat for further information.
- Surfaces requiring coating, including machined rebates, are to be grit blasted using copper slag or other Corrocoat approved abrasive, to ISO Standard 8501-1 Sa2½ (minimum). A minimum blast profile of 50 microns should be aimed for, however, in small bore pipe this is not always attainable, particularly on the inner radius of long bends. Therefore, provided white metal cleanliness is achieved no profile conditions will be enforced on pipe below 150mm diameter.
- Blast residues are to be removed from pipe internals by vacuuming or blowing surface with dry oil-free compressed air.
- Polyglass/Corroglass shall be applied as soon as is practically possible. The coating may be applied as a single coat, but in most applications it is preferable to apply the required film thickness in two or three coats, dependent upon application method.
- Finished coating thickness shall be in the range of 750 microns to 3mm dependent upon service duty and environment.
- After coating, material in flange rebates shall be levelled with the existing flange face by rubbing with a suitable rubbing block and checking for squareness with a straight edge.
- Wherever possible, testing for coating integrity shall be carried out using a high frequency spark tester in accordance with Corrocoat data sheet 7/30 and a suitable extension probe. Thickness checks should be carried out using an inductance type instrument to ensure minimum total film thickness is achieved.
This information is given in good faith without guarantee or liability.