QMS360P Vol 4.6 Rev 1 - Drying of Process Equipment

Sasol Technology Commissioning ManualLead and Enable to Direct Deliver Deliver Measure, Analyse and Improve Drying of process equipment QMS / 360P Volume 4.6, Rev 1 Issued by: Commissioning Engineering Applicable to: Internal and external to Sasol Technology Document Control Status: Approved Process Type: Mandatory Key Words: Drying of Process Equipment 1 Purpose (of this document) The purpose of this mandatory procedure is to describe the techniques and procedures to dry process equipment during the initial operations of a plant. 2 Scope This procedure is applicable to: general piping; reaction sections; refrigeration sections; refractory sections; and cold sections. Proposed by : Dirk Bosch Approved by : Richard Brink Validity : This document is only valid for 14 days after 11 May 2015, if printed Copyright : This document is protected by copyright and is the sole property of Sasol Technology. The information is proprietary to Sasol Technology and any unauthorised use, disclosure or copying or any other means of duplication or reproduction is prohibited. Copyright © 2009. Sasol Technology. All rights reserved Page 1 of 11 Copyright © 2009. Rev 1 3 Revision Description This has been re-written in the new format with a new number. 4 Approvals Proposed : SIGNED 21/09/2009 Dirk Bosch Date Principal Commissioning Engineer Recommended: SIGNED 21/09/2009 Andrew Oosthuizen Date Chief Commissioning Engineer Approved : SIGNED 21/09/2009 Richard Brink Approved and Effective Date Manager Commissioning Engineering Any comments and proposals for revisions or additions to be directed in writing to: MANAGEMENT SYSTEMS Management.Drying of process equipment QMS/360P Volume 4.6. Sasol Technology. if printed Copyright : This document is protected by copyright and is the sole property of Sasol Technology. The information is proprietary to Sasol Technology and any unauthorised use. All rights reserved Page 2 of 11 . disclosure or copying or any other means of duplication or reproduction is prohibited.local IB 4687 Proposed by : Dirk Bosch Approved by : Richard Brink Validity : This document is only valid for 14 days after 11 May 2015.Systems@Sasol. ... 6 8............................................................................................... 5 7.....................2 5 INTRODUCTION................... 5 7...............................5 8 7........................................... 7 8...............................................4 6 PURPOSE OF DRY-OUT......2 HAND DRYING.....4 DRY AIR SWEEPING...................................................................4 7 EQUIPMENT REQUIRING DRY OUT................ Sasol Technology.......10 10 REVIEW CYCLE............................................8 8................................................8 PRESERVATION..........................................................................................................................................................................................2 REFRACTORY DRY-OUT......................1 3 REVISION DESCRIPTION.6 8....Drying of process equipment QMS/360P Volume 4........................ if printed Copyright © : 2009......2 4 APPROVALS............................... 6 METHODS OF DRY OUT..........................5 NITROGEN OR INERT GAS SWEEPING.............3 PIGGING............................................................................................................................................................................................ All rights reserved Page 3 of 11 : Richard Brink ....................................................6. 7 8..................................................................................................................3 COLD SECTIONS DRY-OUT..........1 PIPELINES...............8 8.............11 Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015......................................................................................7 THE VACUUM DRY-OUT METHOD......................................................................................... 10 9 ACKNOWLEDGEMENTS........................................................6 DRYING-OUT BY LOOP CIRCULATION................... 7 8..................................9 8..........................................................................................................................................................................................................................1 DRAINING.....................................................................................................................................................................1 2 SCOPE. Rev 1 Table of contents PAGE 1 PURPOSE (OF THIS DOCUMENT)..................... 2 a the procedure of hydro testing equipment. Sasol Technology. construction and pre-commissioning of equipment. if printed Copyright © : 2009. All rights reserved Page 4 of 11 : Richard Brink .3 As the presence of water in liquid or vapour can cause serious complication during start-up and operation. Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015.1 Water will always be present in equipment after construction due to: 6. 5. water becomes entrained inside the plant in various forms. ii) hydro pigging. Rev 1 5 Introduction 5. 5.Drying of process equipment QMS/360P Volume 4. Excess moisture in systems can be prevented by: a following the basic guidelines to clean construction. system exposure to atmospheric conditions. 5.4 Several methods exist for the drying of equipment and need to be used in conjunction with each other and correctly to provide the required result.6. and iii) flushing. b cleaning procedures of systems including: c i) chemical cleaning.5 These methods include the following: a Draining b Pigging c Dry air sweeping d Nitrogen sweeping e Loop circulation with dryers f Vacuum dry-out 6 Purpose of dry-out 6. and b using pneumatic pressure testing techniques on critical systems.2 The water need to be removed to a predetermined level prior to commissioning.1 During manufacturing. 5. etc.5 Dry-out procedures should always be witnessed by the vendor as well as the client and temperatures continuously logged as well as any deviations i.4 Water remains in low points. if printed Copyright © : 2009.5 Even in relatively short-length gas pipelines a considerable amount of free water will therefore remain.1. 7.1 An internal lining is fitted to all fired heaters.1.2. 7.2.3 7. Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015. generally 60-100 g/m2 7.4 The main types of heater lining are as follows: a Refractory brickwork b Refractory lining c Castings d Ceramic fibres They all necessitate a drying-out operation achieved by progressively heating the lining with the heater burners.2 Before being brought into service. either gas or electrically powered.2. Sasol Technology.1 Pipelines 7. some reactors and incinerators. on the wall of the pipe as a film of water and typically have a film thickness of 50 to 100 microns depending upon the pipe wall roughness. 7. valve bodies.1. 7. and more importantly. it is required to expel any moisture from the lining.1.1.6.2 Refractory dry-out 7. trips logged during the process.1 Pipelines are generally handed over full of water following the hydrostatic test which takes place after construction. in accordance with dry-out temperature curves.e. sufficient water will remain in the pipeline to cause problems in the process.3 After the hydrostatic test water has been expelled. the main purpose of which is to avoid heat loss through the casing. with the possible exception of surface run lines. in order to prevent cracking and failure during normal operation.Drying of process equipment QMS/360P Volume 4. 7. All rights reserved Page 5 of 11 : Richard Brink . 7. 7. Rev 1 7 Equipment requiring dry out 7.2.2.2 Normally pipeline draining is not feasible. Liquefied Natural gas or Ethylene plants can be as low as -60 oC to – 160oC and as high as 40 to 50 bar.7 As the drying is of primary importance to the quality of the performance and of the life time of the heater.8 It is advised that where refractory dry out is required. It must be taken into account that most refractory system also comprises of some kind of waste heat boiler or scrubbing system that require to be fully operational during the dry-out in order to remove the latent heat generated during the dry-out process. utilities and gas feed lines to the specific system.1 Draining 8. 7. if printed Copyright © : 2009. Sasol Technology. 7.6 The dry-out procedure will always be provided by the heater manufactured.Drying of process equipment QMS/360P Volume 4.3. as will the dry-out temperature curves. Rev 1 7. refrigeration systems. Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015.2.2. 8 Methods of dry out The various methods used for drying-out process equipment are as follows: 8. All rights reserved Page 6 of 11 : Richard Brink .2. in order to allow enough time for proper dry out of the refractory.2 At these conditions it is absolutely essential that all sections are completely dry to prevent freezing up of the system.6. 7. the manufacturer’s procedure and vendor representative's recommendations will be exactly followed.3.1 Draining is the fist step in any drying exercise and is used to remove all “free” water from the system before commencing with more efficient drying methods.3 Generally a water content of 20ppm or -62oC dew point is acceptable for most systems. 7.3.2. 7.9 This also applies to the control systems. but for system at very low temperature a dew point of up to -80 oC will be required.1 The operating conditions of cold sections.3 Cold sections dry-out 7. that the plant layout is planned in such a way that owner access and handover of the specific area achieved early in the project. such as used in. 7.1. absorb more water until saturation. 8. 8. the air is said to be saturated with water.3 Pigging 8.2 Dry air does not mean that there is no water in the air. more water is "picked up" and removed.3. 8.4 Dry air sweeping 8. Rev 1 8. thus the system is progressively dried.4 When dry air is swept through the equipment involved. 8. if printed Copyright © : 2009. 8.4.4.1 When the quantity of water in the air reaches its maximum.2 Drain points should be provided on all low point and systems sloped towards these low points.1.3 Therefore saturated air is at its water dew point limit.1 Areas which can be reached should be dried using a cloth or sponge. 8. Sasol Technology. All rights reserved Page 7 of 11 : Richard Brink . These include: a sponge pigs. 8.4. vessels and tanks. and c squeegee pigs.4. Typical equipment which this method can used is distillation column (trays and down comers).1 Pigging can be used to remove water from low points on long pipelines for example underground sections and culverts.4.4. 8.6 Generally the following conditions should apply: Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015. the dry air becomes saturated with water and is exhausted to atmosphere. but generally that the ambient air has been dried by some means and is far below saturation.3. pumps.Drying of process equipment QMS/360P Volume 4.2.6. 8. Non-saturated air will.3. 8. in the presence of water.5 As more and more air is swept through the equipment. b rubber bellow pigs.3 Several pigging systems can be used for drying a pipe from “Free” water.2 Pigging is an expensive exercise and often required temporary modifications and should be avoided through the design of the system.2 Hand drying 8. 5.2 The water is removed in the dryers that will be alternatively in service and in regeneration.4.1 Drying-out operations carried out by sweeping with nitrogen or inert gas are identical to sweeping with air.2 However.6. Some water may be drained at the suction drum (depending on the after cooler temperature).5.4.5. 8. 8. 8.6 Drying-out by loop circulation 8.6.5 PS! Nitrogen blowing is not allowed as a pre-commissioning activity.Drying of process equipment QMS/360P Volume 4. 8.5.6.6 Special precautions and approval is required to introduce nitrogen into a plant while the plant is under construction or during pre-commissioning activities.5.4 Similar principals apply to that of air sweeping.3 Using pure nitrogen it is possible to reach -80°C dew point. suction drum and back to the compressor suction.3 This drying method whose principle is similar to air or nitrogen sweeping is very efficient and dew points as low as -100°C can be reached (depending on the dryer performance). With a standard inert gas generator it is possible to obtain water dew points of -30°C. c The pressure of air used should be as low as possible. 8. Start drying the system by venting air from the closest point to the source or connection point. through vents and drain until the air exits within specification. some inert gas generators can deliver inert gas with a water dew point < -60°C and therefore better performances can be obtained. 8. 8. Rev 1 8. Sasol Technology.7 a The air used for drying should be as dry as possible. b The system being dried should be as warm as possible. 8. if printed Copyright © : 2009.9 This will ensure that the air velocity is kept high.4.6.5 Nitrogen or inert gas sweeping 8. 8. d The flow of air should be as high as possible. 8.5. All rights reserved Page 8 of 11 : Richard Brink .1 The basic principle is to circulate the drying fluid with a compressor first through dryers.8 Then progress along the route by closing the specific venting point and venting further away from the source through the next vent or drain. cooler exchangers. 8. then through the system to be dried out. Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015. 8.6. 8. Sasol Technology.6.4 The water vapour is then withdrawn to atmosphere.7 The vacuum dry-out method 8.2 The system pressure is reduced to below atmospheric pressure and a vacuum is created.4 As this procedure is used in ethylene purification systems and as it is part of every start-up operation. hence even at ambient temperatures the water boils.7. All rights reserved Page 9 of 11 : Richard Brink . 8.6 The method can also be used in other process systems provided the necessary equipment is available.3 This reduction in pressure reduces the boiling point of water. Figure 1 Principle of loop circulation drying 8.5 Various methods can be used to create a vacuum but generally the following is used: Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015.1 This method is most frequently employed in processing units which comprise refrigeration or cryogenic processes. Rev 1 8.7.7. it will be described in detail in the operating manual.6.Drying of process equipment QMS/360P Volume 4. 8.5 Commissioning teams having to perform this type of operation will therefore comply with the procedure given in the operating manual.7. if printed Copyright © : 2009. 8.6. 8. and sometimes for pipeline drying-out.7. 8.1 It is important to note that all systems dried should be preserved in such a way to ensure that moist atmospheric air does not enter the system again.2 It will be sufficient to keep the system at 0.7 It is extremely important that the design pressures of the equipment to be vacuumed dried be verified as fit for the vacuum pressure to be pulled on the equipment. 8.8.Drying of process equipment QMS/360P Volume 4. Sasol Technology.5 bar above atmospheric pressure with a suitable medium at the correct moisture content 9 Acknowledgements The following persons / departments contributed to the development of this document: Brian Knott Andrew Oosthuizen Dirk Bosch Management Systems 10 Review Cycle This document to be reviewed within: 6 months Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015. The system is the filled with dry air from a dedicated external source.8. this should be held until all the water has evaporated. if printed Copyright © : 2009. All rights reserved Page 10 of 11 : Richard Brink . 8.6. Rev 1 8.7.7.6 a Vacuum pumps b Vacuum ejectors Firstly a vacuum should be pulled on the system.8 Preservation 8. All rights reserved Page 11 of 11 : Richard Brink .6.Drying of process equipment QMS/360P Volume 4. if printed Copyright © : 2009. Sasol Technology. Rev 1 1 year ü 2 years 3 years Proposed by : Dirk Bosch Approved by Validity : This document is only valid for 14 days after 11 May 2015.