Materials of Construction - Acid Resistant Linings - Installation Specification
November 8, 2002

Introduction Vessel Fabrication Surface Preparation Application of Pecora Mastic Application of PTFE Sheets Application of Rubber Lining Installation of Brick Lining Handling and Storage of Materials Standards

Associated Links Acid Brick Pecora Mastic Rhepanol ORG

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Introduction

The proper installation of an acid resistant lining is important to ensure that the lining will provide trouble free service for the life of the equipment.   The following are points to be considered when designing, specifying and installing and acid resistant lining.

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Vessel Fabrication

• All welded joints shall be continuous and ground smooth to a minimum of 1/8" radius for convex corners and to a minimum of 1/4" radius for concave corners.

• All surfaces shall be free of weld splatter of foreign material.

• Voids, gaps, holes, pockets or undercut welds are not permitted.

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Surface Preparation

• Prior to applying the Pecora, the Contractor shall prepare the surface to be lined in accordance with SSPC-SP10, blast clean using silica to ensure that the surface is free of all rust and foreign matter.

• Following cleaning, all dust and silica shall be removed. The surfaces to be lined shall be dried.

• The Contractor must inspect the surfaces to be lined and confirm that after cleaning, they are acceptable for application of the lining.

• Immediately prior to applying the Pecora, the surface to be lined shall be free of all rust and foreign matter. Spot cleaning may be done by wire brushing followed by solvent cleaning.

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Application of Pecora Mastic

• Pecora must be applied before the steel surface develops a visible rust film.   Any rusted surfaces must be cleaned again.

• Pecora mastic shall be trowelled onto the surface to a thickness of 3 mm (1/8 inch).

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Application of PTFE Sheets

• PTFE film shall be applied over the Pecora mastic while the mastic is still tacky. The film shall be attached at the top of the sheet and rolled downwards to eliminate any air pockets.

• Application of PTFE sheets shall start at the lowest part of the vessel and progress upwards.  Successive sheets shall be applied above the first sheets such that there is an overlap of 200 mm (8 inches) onto the underlying sheet.

• A thin layer of mastic shall be used to seal the overlap to the underlying sheet. Any air pockets must be eliminated.

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Application of Rubber Lining

• After sandblasting the metal surface a suitable primer shall be applied.   After primer is dry, apply a coat of cold-set adhesive (i.e. rubber cement or as recommended by the rubber lining supplier) to the surface to be lined and to the rubber sheet.  Allow to adhesive to dry before applying th rubber sheet to the vessel wall.

• The rubber sheet stock is to be applied to the vessel by hand.  Each sheet is to be carefully laid and rolled into place to ensure all air is expelled between the sheet and metal surface.

• Edges of sheet are to skived and carefully rolled.  Adjoining sheets are to be overlapped 50 mm (2") minimum.  Seams are to rolled and stitched to ensure intimate contact.

• Lining is to be carried through all nozzles.  The nozzle lining is to overlap the lining on the vessel wall 25 mm (1") minimum.

• Upon completion of the lining operation, but prior to vulcanization, the lining shall be tested at 7500 volts with a "Violet Ray" tester.

• Any leaks detected shall be repaired by patching with unvulcanized material of the same compound as the original lining.

• Lining shall be cured in a steam atmosphere consistent with material being used.

• Upon completion of cure, the lining is to be spark tested and a check of the Durometer Hardness against the manufacturer's specification.

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Installation of Brick Lining

• The vessel must be protected from the influences of weather and temperature.  

• Cutting of bricks shall be done only outside of the vessel.  Cuts shall be smooth and straight and all residual water from the saw chall be wiped dry from the brick.

• Unless specified otherwise, mortar joints shall be 3 - 5 mm (1/8 - 3/16 inch) thick.

• Joints between adjacent courses of brick and between layers of brick shall be staggered by at least 20 mm (3/4 inch).

• In addition, brick layers on tower floors must be placed exactly as indicated on the detail drawings.

• The temperature of both the steel shell and inside of the vessel must be maintained at 10°C (50°F) minimum while the mortar is being applied.

• At all times, the temperature must be maintained at least 3°C (5°F) above the dewpoint of the ambient air.

• At all times, the relative humidity shall be no more than 80%.

• Where external heating is used, the shell and internal temperatures shall be monitored and recorded.

• Mortar which has started to set shall not be used.  In extremely hot weather, special cooling measures will be required to give a reasonable working time for the mortar.

• Mortar shall be allowed to cure for a minimum of five days (at 20°C, 68°F).   For lower temperatures, the minimum curing period shall be increased as per manufacturer's instructions.

• Any brickwork wetted prior to curing (directly or by condensation) must be replaced.

• After curing, the vessel interior shall be thoroughly cleaned.  Then the brick surfaces shall be washed with a 20% H2SO4 solution to protect against damage from moisture.

• Excess mortar shall be cleanly cut off and removed with a trowel.

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Handling and Storage of Materials

• The contents of damaged containers are to be discarded.

• All materials shall be shipped, handled and stored in accordance with manufacturer's instructions.

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Standards

The following standards are applicable to the installation of acid resistant linings:

DIN

28060    Bricklined Vessels and Apparatus; Design and Construction

28061    Bricklining of Vessels and Apparatus; Materials, Construction, Operation

ASTM

C397    Standard Practice for Use of Chemically Setting Chemical-Resistant Silicate and Silica Mortars

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