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LINDE AGProcess Engineering and

Contracting Division

Engineering

Chemical Cleaning

Work Instruction

QPB 09.02(English)

Sheet 1 of 9 Sheets

02 20.04.98 CBA/Bairlein DQ-H/Dr.Heucke D / Wege QSU-Supplementation01 12.94 CBA/Bairlein CB / Mündel D / Dr.Belloni

Issue: Date: Prepared: Reviewed: Approved: Remarks: Intellectual property rights reserved.

QM-template: QMRICHTE.DOT/Rev. Jun 95 <: Y:\DQ\QSU-MANAGEMENT-SYSTEM\QPB-QSE\0902E.DOC

Table of Contents

Sheet

1 Scope of Validity..........................................................22 Purpose .......................................................................23 Definitions....................................................................24 Responsibilities, Procedure .........................................24.1 Extent of cleaning ........................................................34.2 Alkaline cleaning (boiling)............................................44.3 Pickling ........................................................................64.4 Passivation ..................................................................74.5 Checking the system once cleaned.............................74.6 Preservation ................................................................74.7 Protective coating process ..........................................74.8 Suction pipes from piston compressor and

expansion turbines ......................................................84.9 Disposing of rinsing media and solutions ....................85 Other Applicable Documents and Notes .....................86 Documentation, QSE-Records ....................................87 Amendments ...............................................................88 Distribution...................................................................9

Attachment: QPB 09.02.01 Alkaline Boiling Process

Supplementation Issue 02:Definition of the responsibility of theCommissioning ManagerQSE-SupplementationInclusion of the draft QPB 04.14 forCompressor Suction Lines in para 4.1 e

Sheet 2 QPB 09.02 Issue 02 LINDE AG Process Engineering and Contracting Division

<: Y:\DQ\QSU-MANAGEMENT-SYSTEM\QPB-QSE\0902E.DOC QM-template: QMRICHTE.DOT/Rev. Jun 95

1 Scope of Validity

This work instruction applies to all sections responsible for commissioning of plants except themanufacturing sections.

2 Purpose

This work instruction describes the chemical cleaning process for plant components. It alsodescribes the extent of cleaning, i.e. which parts of a plant have to be cleaned and the possibleways of doing this. This work instruction is a guideline for those responsible for commissioning theplants.The operating instructions issued by the plant component manufacturer have priority.A contractor usually performs chemical cleaning. Therefore his process description and cleaningprogram must be checked, including the special risks refering to safety, health and environmentwhen handling chemicals - see also para 4.9.

3 Definitions

Alkaline Cleaning Process (Boiling)

Boiling describes the process of cleaning the system using alkaline agents, preferably withchanging pressure. In conjunction with the system’s “breathing” (pressure changes), the chemicalsused remove loose iron oxide coatings, bring dust particles into suspension and emulsify oil andgrease.

Rinse Cleaning

Rinse cleaning refers to rinsing the system out using boiler feed water.

Pickling

The system is cleaned using a pickling solution.

Passivation

A passivation solution is used to passivate the bare internal pipe surfaces.

Protective Coating (of steam systems)

During the protective coating process, a thin magnetite layer builds up on the inside of the pipe.This magnetite coating protects against surface corrosion.

4 Responsibilities, Procedure

In case Linde has the contractual responsibilities for precommissioning, Linde's commissioningmanager is obliged to perform and check/proof the chemical cleaning activities according to thefollowing instruction.If commissioning is within Client's scope under Linde's supervision, this instruction should bebrought to client's attention.

To ensure that the systems work properly, the high pressure steam and feed water systems and thesuction lines from the piston compressor and expansion turbine must be cleaned thoroughly beforecommissioning.Begin by rinsing the systems thoroughly to remove loose dirt, rust, scale and foreign particles.Rinsing is followed by alkaline de-greasing or pickling.

LINDE AG Process Engineering and Contracting Division Issue 02 QPB 09.02 Sheet 3


If you do not rinse the systems or rinse them insufficiently, damage and blockages are likely tooccur despite thorough boiling and pickling. The formation of the magnetite protective layer isslowed down, and the steam will fail to meet purity standards for an extended period of time.

4.1 Extent of cleaning

Existing condensate lines can be used to circulate the cleaning solutions. Otherwise, temporarylines must be used.Basically, the following plant parts have to be cleaned chemically:

a) Boiler feed water high pressure system (HP-BFW)

- The boiler feed water system includes deaerator, up to the cracking furnace steamdrums and steam boilers, the boiler feed water control stations and the feed lines tothe high pressure steam desuperheaters, but does not include the boiler feed waterpumps (suction and discharge lines only).

- Boiler feed water lines to the steam let-down stations.

b) High pressure steam systems of cracking furnaces

- Pipes from the boiler feed water control station to the entrance of the feed waterpreheater.

- Transfer line exchanger and steam drums including risers and downcomers.- Feed water preheater and high pressure steam superheater.- High pressure steam pipes up to the high pressure steam shut-off valves.

c) Steam boiler high pressure systems

- Steam boiler comprising of feed water preheater, steam generator (diaphragm walls),superheater and steam drum including downcomers and risers.

- Pipes from the boiler feed water control station to the boiler feed water preheaterentrance(s).

- Pipes from the end superheater to the high pressure steam shut-off valves.

d) High pressure steam system

- High pressure steam shut-off valves at the cracking furnace steam drums and steamboilers, with connections to the high pressure steam line including start-up lineoutlets.

- High pressure steam lines up to turbines.- High pressure steam line up to the let-down station for high to medium pressure

steam.

e) Suction lines from piston compressors and expansion turbines

The Machine Department specifies the scope of delivery of reciprocating compressor units andexpansion turbines as follows:

Pulsation dampeners and prefabricated gas-lines are to be pickled, neutralized and suitablyprotected before shipment to site. The machine manufacturer specified the applicable picklingprocess and protection.Machine pipes leading process gas in Linde’s scope of supply and pipes which cannot beprefabricated completely in the machine manufacturer’s shop are to be pickled or cleanedmechanically after being welded on site. The Machine Department identifies these pipes in the PI-diagrams with regard to the scope of pickling and gives these to the Department Flow Diagramsand Operation for inclusion in the Linde construction and operation manual of the plant.



Construction and Commissioning Supervision on site inspects the pickled pipes before assemblyand connection to vessels (pulsation dampeners, heat exchangers, etc.) Additional measures are tobe taken if the systems are not clean.The scope of pickling in the case of very long pipes (> 100m) and large vessels (> 5m³) upstreamof reciprocating compressors, it is advisable to install a vessel type filter on the suction side. Theinstallation of such a filter is to be determined by the Machine Department in agreement with theDepartment Flow Diagrams and Operation. This will be shown in the PI-diagram.

The exact cleaning programme is drawn up by the contracted cleaning company, taking thesupplier’s guidelines into account.You will only achieve a good cleaning effect if the following points are adhered to:- Plan and prepare for pickling far enough in advance.- Define the extent of pickling.- Define the pickling process and the pickling agent.- Define the materials which should not be allowed to come into contact with the pickling

solution.- Remove these parts or take preventative measures.- Provide cleaning nozzles correctly and in sufficient quantity.

The cleaning program should include the following points:- Circulatory systems employed.- Information on the chemicals and utilities (see relevant accident prevention regulation and

hazardous material data sheets).- PI-diagram of circulation station and provisional lines.- List of piping parts to be removed.- Information on treatment/disposal of cleaning chemicals, etc.

4.2 Alkaline cleaning (boiling)

An alkaline solution is used for boiling. It consists of:- 1 kg solid sodium hydroxide or 1.3 l hydrated caustic soda (50%) per m³ water.- 1 kg trisodium phosphate in flake form with approximately 20% P205 per m³ water.

In the case of rusty surfaces, a good method of treatment is adding an oxygen binding agent suchas 0.2 l hydrazine 15 or 100 g sodium sulphite per m³ water.Boiling can be performed in two ways:A) System breathing

The system pressure is increased to approximately 50% of the nominal pressure and thetemperature to approximately 250 °C. This pressure is maintained for 2 - 4 hours, and thendecreased to about 25% of nominal pressure. Following de-pressurisation, the system iscooled to approximately 120 °C. This procedure is repeated 2 or 3 times.

B) System circulation:The boiling solution is circulated in the system using temporarily installed pipes and pumps.The system pressure is increased to around 50 - 60% of nominal pressure, and kept at thatpressure and increased temperature (see QPB 09.02.01) for approximately 50 hours. Amagnetite coating forms during this type of boiling.

ProcedureBefore boiling or pickling can begin, the systems must be checked for leaks, pressure tested,rinsed and de-greased with alkaline.Pre-rinse the systems using boiler feed water with a flow of 1 - 1.5 m/s using temporarycentrifugal pumps. Debris is discharged at intermediate discharge points. The turbidity(extinction) of the rinsing water is photometrically measured at each of these intermediatedischarge points. Once the turbidity value is satisfactory you can move on to the next rinsingsection. Pre-rinsing is complete when the turbidity at the end of the system is almost exactlythe same as the turbidity of the water entering the system.



The subsequent de-greasing process is performed using an alkaline de-greasing agent.Attempt to achieve a water flow of 0.2 - 0.5 m/s when circulating the alkaline solution. Thetreatment temperature should be around 90 °C. See the operating instructions of themanufacturer or the chemical cleaning contractor for exact details on how to prepare thealkaline feed water.During de-greasing, the phosphate content, pH value and conductivity are measured atdefined intervals. Circulation is stopped when phosphate is no longer being used up and thecirculation solution is optically clean. The alkaline solution is then removed from the system.In the case of steam drums and evaporators this is done by draining it off, and in the case ofpipes and heating surfaces it is done by flooding with boiler feed water.For system components that are not going to be boiled or pickled subsequently, the alkalinede-greasing treatment should be repeated one or two more times (e.g. high pressure steamand condensate lines).The remaining alkaline solution that accumulates should be collected and neutralised usinghydrochloric or sulphuric acid.

Boiling out boilers and furnace steam drumsBefore beginning the procedure on a plant component you must make sure that the partconcerned (boiler, furnace) is prepared for burner ignition, i.e. the ready-for-operationprotocol has been issued.Isolate the system to be boiled from the rest of the plant. The boiling procedure shouldcorrespond to the manufacturer’s instructions, which should specify the maximum operatingpressure and temperature, the duration of boiling and the concentration of the boilingchemicals.Fill the boiler or furnace steam drum to a visible water level with boiler feed water from thedeairator, then add the chemicals at a suitable place using a pump. Continue by filling thesteam drum to the normal level, and then close off the boiler feed water filling line.The pressure in the system is produced by igniting the burners (existing heat source), andincreased as described in the manufacturer’s instructions.

Important:When commissioning, the furnace and/or boiler lining are normally dried out as part of theboiling procedure. If this is being done, ensure that the heating curve with the lowesttemperature increase rate is applied (drying curve for lining or heating curve for alkalineboiling process).Annex QPB 09.02.01 contains a diagram showing the alkaline boiling process for the transferline exchanger / steam drum unit. A boiling time of at least 48 hours is necessary, and thefirst blowdown should take place after about 6 hours of boiling at 4 bar.Heating causes the drum water level to rise.The blowdown process is performed using pre-defined pressure stages and outlets. Theboiling procedure is monitored by conducting analyses; the phosphate content of the boilerwater, the p- value, the conductivity and the turbidity of the water are all measured at definedintervals. If the phosphate level drops to below half, phosphate can be added using theinstalled pump.The pressure should not be increased during the blowdown process. The boiling procedure,pressure increase rates, dwell times, blowdown times and maximum permissible pressure forblowdown should be specified by the manufacturer. The boiling process can be stopped oncethe phosphate level has been constant for several hours and the boiling solution is opticallyclean.After boiling, the entire contents of the transfer line exchanger must be drained off and thesystem rinsed at least 4-5 times with boiler feed water. The rinsing process can be stoppedas soon as the water drained off reaches 0.1 mval/l caustic, or as soon as the pH value andconductivity of the water drained off are approximately the same as those of the fresh rinsingwater. The water drained off should also be optically clean.Continue by opening the steam boiler drum and removing any dirt found inside. Check thefittings inside the drum. If the system has become very dirty after a long period of disuse ortransport, you will have to repeat the boiling procedure described above several times.The hot caustic solution drained off during and after boiling, which has a pH value of 12-14,must be cooled down and neutralised with acid before being disposed of in a biologicaltreatment plant. The system operator should take the steps necessary for this beforebeginning the boiling procedure.



If the system is not going to be used immediately after boiling, it must be preserved asspecified by the manufacturer. Upon inspection of the steam drum you will see that amagnetite layer has formed (black to blue-black). This layer will become thicker duringsubsequent operation. If the boiling procedure has been deemed successful, the boiler orfurnace can be put into operation, provided the furnace/boiler lining has dried out completely.

4.3 Pickling

Pickling is another method of preparing the high pressure steam and boiler feed water systems foroperation. Pickling is performed using weak acids (e.g. citric acid) at a temperature ofapproximately 90 °C.Like boiling, pickling must always be preceded by rinsing. Following pickling, the system must bepassivated and, if necessary, preserved.Pickling offers the following advantages:- The firing and heating gas systems do not have to be ready for operation.- As the system is cleaned out more thoroughly, commissioning will normally be quicker.- As pickling creates bare metallic surfaces, a homogeneous magnetite coating can

subsequently build up on these surfaces.

Disadvantage of pickling:- It is usually difficult to dispose of pickling solution.

Pickling of boiler and cracking furnaceIf pickling is to be used instead of boiling, it must be remembered that pickling involves anumber of technical and chemical problems. Accordingly, pickling should only ever be carriedout by a specialist firm. This firm must have several years of experience with the picklingprocesses, pickling agents and additives used. Because of this, these instructions contain nomore than a description of the various stages involved in pickling.Before beginning pickling, the pickling company must make sure that all flange connections,glands, etc. do not leak, and that the pickling solution is not going to damage anything. Thesurface being pickled should be checked thoroughly, and the nature of the scale coating andits solubility should be assessed.The high pressure valves should be kept open so that foreign particles cannot damage theseat surfaces and so that the gland packing is protected against the pickling fluid. If some ofthe valves are to be closed during pickling, the seats should be removed and cleaned and thepacking replaced.

The pickling process can be divided up into 11 stages:1. Rinse with water to remove loose dirt.2. Alkaline de-greasing at approximately 80 - 90 °C; duration 8 hours.3. Emptying and neutralisation.4. Rinsing of system.5. System pickled at approximately 85 - 90 °C; duration 15 - 18 hours.

The pickling solution should remove iron oxide among other things, so that the surface endsup clean and shiny in appearance. Adding suitable inhibitors limits the acid’s corrosive effecton the metal itself (maximum material loss: < 20 g iron/m² = < 0.0025 mm).The pickling process is complete when the iron content in the pickling solution is seen tochange by no more than + 0.2 g Fe/l over a period of 2 hours.

6. Emptying and neutralisation. (e.g. with ammonia solution)7. Rinsing with boiler feed water.8. Secondary pickling at approximately 60 °C; duration approximately 8 hours.

One of the purposes of this step is to remove rust that has formed in steps 6 and 7. To avoidfurther corrosion, steps 8 to 11 should be carried out without interruption. Secondary picklingis complete when the iron content in the pickling solution is almost constant and does notexceed 0.5 g Fe/l. After pickling, all of the surfaces that have been pickled should be cleanand free of rust and loose magnetite. The material loss as a result of pickling should notexceed 20 g/m². This can be checked by installing a representative piece of iron in thesystem before pickling.

9. Adjust the pickling solution’s pH value to approximately 10 by adding a solution such as 25%ammonia. Temperature approximately 50 °C.



10. Passivate the surfaces by circulating an alkaline solution.Duration: approximately 12 hours of circulation at about 80 °C. The pH value should remainbetween 9.5 and 10.

11. Empty the system and neutralise the passivation solution. Finish by rinsing the systemthoroughly with boiler feed water.

Following complete emptying, the system should be brought into operation immediately orpreserved as described by the manufacturer (e.g. dry preservation using nitrogen).

4.4 Passivation

Fill the system with boiler feed water of the specified quality, adding Levoxin (activated hydrazinehydrate) to a concentration of 0.1% and ammonia to a concentration of 0.2%. The temperature ofthe passivation solution should be around 95 °C. The passivation solution, whose pH value shouldbe 9.5 to 10, is then pumped in the system for 12 hours at normal system pressure as produced bythe auxiliary pumps.Empty the passivation solution out of the drums and piping systems using pressurised nitrogen, andcool the solution to 50 °C before emptying it into the wastewater system. Dry the system out bypurging with nitrogen.

4.5 Checking the system once cleaned

Before beginning the checking procedure, use air (100% free of oil and water; instrument air) toremove the nitrogen put into the system during passivation.Perform random sampling checks.Checking the low-points in the piping: experience has shown that deposits collect at these pointsand in the valves. These deposits must be removed completely. In the region of the waste heatblock you will need to cut out test sections to check the surface condition. The inspection nozzleson the distributors and headers are suitable for this purpose.Re-welding and 100% x-ray are the responsibility of the installation company and must be includedin their contract accordingly.

4.6 Preservation

We differentiate between wet and dry preservation. In the case of dry preservation(< 30% relativeair humidity), the system is filled with nitrogen. To do this, the system must be completely dry andpure nitrogen must be used.In the case of wet preservation, the system is filled with degassed boiler feed water. An oxygenbinding agent (e.g. hydrazine (100-300 mg/l)) is also added to the feed water.

4.7 Protective coating process

After the circulatory system has been cleaned, a thin protective magnetite coating is applied to theinternal surfaces of the pipes by heating the system to above 500°C. The oxygen needed forforming Fe3O4 comes from the water, leaving hydrogen whose concentration in steam normallydrops to around 5 to 10 µg/l of condensate after 2 days. The iron and iron oxide brought into thesystem in the feed water (along with some iron from the pipe wall) continues to be converted intomagnetite during operation; the extent of this depends a lot on the way the plant is run. Thehydrogen level of approximately 5 µg/l corresponds to iron conversion of 100 µg/l in Fe3O4.Note:If passivation is done using NaNO2 or KNO2 (more expensive), a magnetite coating will begin toform during passivation. An additional protective coating process is not required.



4.8 Suction pipes from piston compressor and expansion turbines

If the internal diameters are small, the best approach is to remove the suction pipes, clean themmechanically and de-grease them, and place them in a pickling bath.The working procedure for this is described in section 4.3.If internal diameters are large, isolate the pipes you want to clean from the rest of the system usingblind flanges before starting work.The pipes are then mechanically cleaned, de-greased, and pickled as described in section 4.3.

4.9 Disposing of rinsing media and solutions

As already mentioned, all rinsing media and solutions must be collected and neutralised beforebeing fed into the operator’s wastewater treatment system.It is important that the operator, Linde and the cleaning company work together to make thenecessary arrangements well in advance.The alkaline and acid resistant condensate treatment tank is suitable for collecting solutions;sometimes rainwater catch tanks and ballast water tanks are suitable for this purpose as well.The local rules and regulations concerning safety, health and environmental protection (disposal)are to be followed.

5 Other Applicable Documents and Notes

- P&I Diagrams- Operating manual- Data sheets- Transfer report for mechanical completion- Manufacturer’s operating instructions- Contracted cleaning company’s cleaning programme- Technical specifications for chemical cleaning of high pressure steam and feed water

systems- Relevant protection and safety measures when handling the chemicals used (accident

prevention regulations, information sheets on hazardous materials)- Ready-for-operation report for furnaces and boilers including a list of commissioning

preparation work already done (only required for boiling)

6 Documentation, QSE-Records

This Work Instruction is administered and archived by the Department Flow Sheets andCommissioning of Chemical and Gas Plants.

The chemical cleaning performed must be recorded in a protocol by the contractor who carries outthe cleaning.The protocol must contain all important information and data such as dwell times, pressures,analysis values, etc.One copy of the protocol goes to the customer, one to the project manager, and one to thecommissioning department for administration and their archives.

Archiving period is stipulted in QPA 05.03

7 Amendments

Amendment proposals to this Work Instruction can be submitted informally to the Department FlowSheets and Commissioning Chemical and Gas Plants.



8 Distribution

This Work Instruction is distributed by the QSE-Management.