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GBH Enterprises, Ltd.

Ammonia Plant Technology Pre-Commissioning Best Practices GBHE-APT-0101

Piping and Vessels Flushing and Cleaning Procedure

Process Information Disclaimer

Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the information for its own particular purpose. GBHE gives no warranty as to the fitness of this information for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.



Ammonia Plant Technology Pre-Commissioning Best Practices: Piping and Vessels Flushing and Cleaning Procedure CONTENTS 1 Scope 2 Aim/purpose 3 Responsibilities 4 Procedure 4.1 Main cleaning methods 4.1.1 Mechanical cleaning 4.1.2 Cleaning with air 4.1.3 Cleaning with steam (for steam networks only) 4.1.4 Cleaning with water 4.2 Choice of the cleaning method 4.3 Cleaning preparation 4.4 Protection of the devices included in the network 4.5 Protection of devices in the vicinity of the network 4.6 Water flushing procedure 4.6.1 Specific problems of water flushing 4.6.2 Preparation for water flushing 4.6.3 Performing a water flush 4.6.4 Cleanliness criteria 4.7 Air blowing procedure 4.7.1 Specific problems of air blowing 4.7.2 Preparation for air blowing 4.7.3 Performing air blowing 4.7.4 Cleanliness checks



4.8 Steam blowing procedure 4.8.1 Specific problems of steam blowing 4.8.2 Preparation for steam blowing 4.8.3 Performing steam blowing 4.8.4 Cleanliness checks 4.9 Chemical cleaning procedure 4.9.1 Specific problems of cleaning with a chemical solution 4.9.2 Preparation for chemical cleaning 4.9.3 Performing a chemical cleaning 4.9.4 Cleanliness criteria 4.10 Re-assembly - general guideline 4.11 Preservation of flushed piping



1.0 Scope This Process Engineering guide covers Best Practices in Ammonia Plant - Pre-commissioning; Piping and vessels flushing and cleaning procedures, and shall apply to all GBH Enterprises (GBHE) process engineers worldwide. 2.0 Aim/purpose This procedure applies generally to the cleaning and flushing of underground and above ground pipelines, tanks and vessels which shall be performed for process reasons during pre-commissioning. Special instructions for the system will be fixed by a detail procedure. The purpose of flushing and cleaning lines and vessels is to remove loose foreign matter, production residues and surface protection substances from the inside of line and vessels (welding rods, sand, earth, pebbles, nuts and bolts, tools, rags, oil and greasy films, etc.) in order to avoid line blockages, damage to sensitive components such as orifice plates, turbine, compressors, pumps impellers, valve seats and so on. 3.0 Responsibilities The responsibilities are given in the work instructions to the plant operator, standard engineering procedures preparation of commissioning, working step, network cleaning, flushing and purging. 4 Procedure 4.1 Main cleaning methods 4.1.1 Mechanical cleaning When a system, or part of a system, can be entered, it may be possible to carry out pipe wall or vessel wall cleaning manually using either rotary (i.e. air driven) or hand held steel wire brushes. Rust, scale, and dirt that are dislodged may be subsequently removed by the use of an industrial grade vacuum cleaner, by air blowing, or a combination of these two methods. In any event, stainless steel equipment is not likely to have significant deposits of surface dirt or oxide, i.e. mechanical cleaning is normally not applicable.



4.1.2 Cleaning with air Two main methods may be used: a) Continuous blowing of air Air is continuously blown from a source (directly from air compressor or via a large capacity vessel) at a high velocity through the lines (and vessels) to carry away the loose material. Due to the high velocity of the air, a light erosion of the walls generally occurs during the air blowing, which is beneficial with regards to cleaning. b) Quick decompression A network is filled with compressed air up to the setting pressure of a rupture disk. When the rupture disk blows out, the source of air is stopped and the pressure inside the network decreases quickly. This operation will preferably be done using a "quick opening valve" after having pressurized the network to the desired level of pressure. The existing valves of the network may not be used for this purpose, except for special cases. The quick decompression causes a high velocity of air in the pipes, thus removing loose material and performing a light erosion on the walls which eliminate rust and scale. During this operation the reaction forces affecting the piping shall be considered. 4.1.3 Cleaning with steam (for steam networks only) Whenever steam is available, an excellent cleaning fluid is provided. Steam can be used, like air, for continuous blowing, and preferably, for intermittent blowing. The advantage of the latter is that between two blowings the pipes (and possibly vessels) cool and contract causing millscale and rust deposits to crack. These deposits are then easily removed in subsequent blowings. Steam blowing shall be used only for steam networks.



4.1.4 Cleaning with water 4.1.4.1 Cleaning of piping by circulation of water Line flushing uses water from the normal supply network of the plant, if available. Water supply could conceivably be from other sources, i.e. city water lines, supply boat temporary pumps, etc. depending upon the ongoing situation. This type of flushing normally involves taking a section of piping and flushing it from a "start-point" to an open end. A high velocity flow should be achieved in order to be effective in removing loose debris and rust from piping (or vessel) walls. In some circumstances additional pumping capacity will be required. 4.1.4.2 Cleaning of piping by retro-jetting In case retro-jetting will be considered as cleaning method, a subcontracted specialist will be selected and all technical aspects will be reviewed and shall be accepted before starting the work. 4.1.4.3 Fill and dump water flushing Fill and dump flushing is often used for cleaning vessels. The method being quite simple, the adequately vented vessel is filled to the desired level with flush water and then dumped to grade, the flush water dislodges loose debris and rust and carries it out of the equipment. Note that some lines connected to the vessel can be flushed by dumping the water through them. One major problem with this method is the disposal of the large quantities of water involved which may overload the normal drain systems. 4.1.4.4 Cleaning of vessel or equipment by water spray or high pressure water If there is only dust on the walls of a large vessel, a water spray from a hose pipe might be sufficient. High pressure water may be used to remove solid particles or foreign matter from inside walls or inside parts of vessel or equipment, in particular where access is a problem.



Attention has to be given to the potential corrosiveness of water (chloride ions on stainless steel, sea water on carbon steel) and special water quality may be necessary (demineralized water or inhibited water). 4.1.4.5 Cleaning with a chemical solution Cleaning of piping and inside walls of vessels or equipment by circulation of a chemical solution is only used for removing production residues and surface protection substances (oil and greasy films, etc.) in case it should disturb commissioning or start-up of the plant. This type of cleaning is applicable subsequent to a.m. flushing methods. A chemical solution will be circulated by means of a pump and finally disposed to waste water treatment or special treatment. The cleaned piping, vessel or equipment to be flushed with fresh water or demineralized water to remove remaining chemical solution. 4.2 Choice of the cleaning method The choice of the cleaning method shall depend upon: a) The fluids available on the site: compressed air, steam, cooling water, service water, potable water, demineralized water and so on. b) The volume of the network: this determines the quantity of fluid to be used and the time needed to fill the network to the desired pressure (quick decompression method). c) The piping diameter:

• Circulation of water, is usually selected for diameters up to DN150, because of the large flow required.

• Water "retro-jetting" is effective up to large diameter lines but necessitates a specialized subcontractor.

• Air blowing is acceptable for small diameter lines to be calculated according to the possible air flow and an average speed of 40 m/s.

• Air quick decompression method can be used on any pipe diameter provided necessary precautions are taken (see paragraph 4.7).

• Mechanical cleaning shall be used for vessels (manual cleaning) but also for large diameter pipes (≥ DN 800) providing safety rules are respected (vessel entry).



d) The design conditions of the system: some large diameter piping used for gas service cannot withstand their own weight when they are full of water. Some piping cannot withstand the expansion caused by steam blowing. e) The material specification: for stainless piping, air blowing is better (if the other conditions allow it) than water cleaning, to avoid the possibility of corrosion by chloride ions. f) The process function of the system:

Water lines are usually flushed with water. Process gas lines, inert gas lines and air lines should be air blown.

Low operating temperature lines shall be air blown. Hydraulic pipelines shall be air blown.

4.3 Cleaning preparation The following principles shall apply:

• Whenever possible, the cleaning fluid shall flow from top to bottom. • The diameter of the outlet pipe may be at least two thirds of the

diameter of the line to be cleaned, and at least as large as the inlet pipe.

• Main headers shall be cleaned first (i.e., before their connecting lines). • Large diameter pipes shall be cleaned before small diameter ones. • Dead ends shall be avoided or, if not possible, cleaned separately. • Fragile devices included in the network (all flanged valves, turbine-type

flowmeters, orifice restrictions, etc.) shall be removed (see section 4.4).

• Protection of the devices in the vicinity of the network shall be carefully studied in particular near the water (or air) outlet in order not to damage electric motors or instruments with water or dirty air (see section 4.5).

• Existing block-valves on the lines to be cleaned shall not be used to control an air flow as they could be damaged by erosion (due to the high velocity of the fluid).

• A special care shall be taken for vessels designed only for an atmospheric pressure service, in order not to create, during washing, a high pressure due to a water head.



• Whenever a vessel full of water has to be emptied, a special note shall be issued to state that a vent will have to be opened previously in order not to create a vacuum in the vessel.

• The cleaning fluid shall not flow through a conventional exchanger unless the pipes upstream of the flushing flow have been cleaned (use the by-pass, if any, or "break" the line before the exchanger). It shall never be flown through a plate exchanger.

• The cleaning fluid shall never flow through pumps or compressors unless the upstream lines have been cleaned, the lines shall be disconnected before the equipment or a "jumper" shall be installed.

• For large diameter pipes, some temporary supports, hangers, pads, etc., may have to be added to withstand the weight when a line is disconnected

• During flushing, the spring supports, spring hangers, etc., shall be blocked according manufacturer’s instructions.

• When a couple of flanges has to be opened to allow the flow to flush out, distance between the two flanges shall be at least 1/6 of the pipe diameter.

4.4 Protection of the devices included in the network During the flushing or the blowing of a line, some particles such as sand, rust, etc. are carried away at high velocities and may either damage some devices when an impact occurs, or clog small diameter pipes. Accordingly, fragile devices have to be removed from the pipe before flushing/blowing. Are considered as fragile devices:

o Control valves and check valves o Safety valves o Calibrated orifices o Turbine type flowmeters o Pitot tube flowmeters o Venturies o Rotameters o In-line flowmeters except types without internals o Nozzles of ejectors o Traps o Bellow valves o Internals of filters and strainers

The list is not exhaustive and shall be revised according to local necessities.



• Process impulse lines for instruments shall be isolated by means of the block valve on the impulse pipe itself and, whenever possible, shall be disconnected. This operation shall be made by an instrument specialist

• Thermowells may remain installed. • When a couple of flanges has to be opened to allow the flow to flush

out, it shall be checked that this operation does not create any stress on a pump, turboexpander, compressor flange upstream or downstream.

• The flushing is generally not carried out through columns or drums. But if it is necessary to go through such equipment, or if the vessel is used as an air reservoir, the removable internals have to be dismantled prior to starting the flushing, in order not to damage them.

• Any column or drum to be used as an air reservoir must have its associated relief valve(s) in normal operation before pressurizing starts (except it is ensured that the source for pressurizing the column/ drum will not deliver a higher pressure than the design pressure of the equipment).

4.5 Protection of devices in the vicinity of the network During flushing and blowing operations, large quantities of dirty water and dirty air are spread out in the units. This water or air generally contains sand, particles of rust, etc., and might damage other equipment (for example: breaking the glass of a pressure gauge). Additionally, the water itself may damage the insulation materials, the electrical motors, etc. Accordingly, the following actions shall be taken where necessary:

• to put a tarpaulin on motors, insulation, instruments near the flow outlet.

• to direct the outlet flow towards a place where there is no (fragile) equipment.

• to change the direction of the flow by rotating an elbow. • to connect a hose pipe at the outlet to drive the flow to a desired

location (for water flushing only). • to add a dummy spool to extend the outlet further. • to install and fix properly, a sheet of metal (insulation cover sheet

for example) perpendicularly to the flow, in order to break the flow impact.

• drains, which are not designed for such large flows, should not be used to evacuate water, as they might be flooded.



4.6 Water flushing procedure 4.6.1 Specific problems of water flushing - Slow velocity: The water velocity through the pipe is normally only about 3 to 4 m/s, seldom higher, which is much lower than air blowing velocity. - Dirty water disposal: As the drains are generally not designed for high water flow rates, additional temporary piping and connection, might be required - Weight of water: For lines designed for gas service, the weight of pipes full of water may be too heavy for the hangers, supports (this has to be checked prior to any water flushing). - Corrosion factor: Water can cause corrosion due to its chloride content. - Carbon steel pipes and vessels: Cooling water, fire-fighting water and service water can be used for the first wash but the final rinsing may be carried out with inhibited water, if necessary. - Stainless alloy pipes or vessels: Demineralized water with a chloride content specified for hydrostatic pressure test may be used. However, in some cases deviations are possible if they are agreed with the department concerned. In any case the final rinsing must be carried out with low chloride containing water. 4.6.2 Preparation for water flushing Note: Before the detailed preparation work starts, a meeting shall organized with GBHE and the customer commissioning representatives to finalize the detailed procedures based on the present general procedures, taking into account the site restrictions and possibilities. Commissioning will advise the operators during the preparation.



4.6.2.1 Definition of the network to be cleaned A first selection shall be made according to construction progress and geographical or functional criteria (i.e. drains, hot oil network, etc.). Then it shall be adapted to suit the site requirements, the devices to be removed, the configuration of the lines (low points, high points, lengths, heights, etc.). 4.6.2.2 Calculation of the necessary flow During cleaning operation, the water velocity shall be as follows: - In liquid process lines and water lines, the velocity shall be the lowest figure between 3 to 4 m/s and the velocity obtained with 1.3 times the maximum process or water flow. The minimum velocity shall be 2 m/s. - Gas process lines are generally blown, if they have to be flushed, use 3 m/s, ensure that water filled lines are adequately supported. 4.6.2.3 Determination of the network pressure and maximum allowable pressure Estimate the maximum head loss. With the velocity calculated as above, estimate the head loss for a flow going through the principal piping and add the static head (if any). If the flow and the head loss are compatible with the pumps available on the site, go ahead, otherwise air blowing has to be considered. If several pumps are available, a combination of pumps in parallel or in series has to be studied to meet the flow or head loss requirements. The pressure shall be carefully studied and specified in order that the maximum allowable pressure in the system is never exceeded. 4.6.2.4 Sketch of the network to be cleaned A sketch of the network to be cleaned shall be specially drawn for the cleaning operation (P&ID’s will be used for this purpose).



The following color code may be used: - Blue: lines to be flushed - Green: items to be removed - Pink: flanges to be disconnected - Orange: items to be isolated Although blinds are seldom used for flushing operations, if they are necessary they will be indicated and numbered with a red color. Installation and removal of blinds shall be followed up by commissioning by the mean of a blind list. Installed blinds shall be tagged and equipped with a visible handle painted red. 4.6.2.5 Location of water inlets and outlets A site review shall be done to determine the possible water inlets and outlets, the water source, the pump(s) location, the additional pipes or hose pipes layout from the source to the network. The water disposal problem (flood risk) and the protection of the equipment and people nearly shall be carefully studied. 4.6.2.6 Additional material and pieces of equipment required The drawings for the additional pipes to be manufactured and erected may be drawn if required. The required material (pipes, valves, gaskets, etc.) and the means (monorails, cranes, pulleys blocks, etc.), tools, gaskets, grease for bolts, nuts, etc. required to carry out the removal and reassemble, the needs for the dummy spools (flanges, pipes, etc.) will be determined. 4.6.2.7 Fragile devices to be removed All "fragile" devices to be removed shall be identified. The removal possibilities shall be investigated on site. The required dummy spools to be fabricated shall be drawn on sketches. Attention shall be mainly paid to:

• heavy devices (control and block valves, check-valves), • supports, hangers, pads, spring supports, possible stresses on

pumps’ flanges.



4.6.2.8 Quality of water Whenever possible, good quality water shall be used from the beginning until the end. However, if the quantities involved are very large, and except for stainless steel materials, it is allowed to carry out the first flushing operations on a given network with raw water, and to perform the last one (rinsing) of the same network with a good quality water. The quality of the water shall comply with the specification for hydrostatic test and the design basis for the plant respectively. 4.6.2.9 Safety The safety rules and instructions must be strictly obeyed. The following particular precautions shall be taken for flushing operations: - Period of time for flushing: Generally water flushing will take place during normal working hours. - Restricted area: An area of at least 5 meters around the outlet points will be roped off during the release of water. - Work permit: Any water flushing operation shall be subject to specific work permits according to the safety procedure. - Space between flanges at the outlet: When a couple of flanges has to be opened to allow the flow to flush out, the distance between the two flanges shall be at least 1/6 of the pipe diameter. - Restraints: Wherever necessary, the pipes at the water outlets shall be rigidly fixed to avoid damage to the lines, equipment and people nearby. - Environment protection: Adequate protection of the devices in the vicinity of the water outlet has to be installed in order not to damage electric motors or instruments with water.



- Personal protection: Protection of personnel carrying out the operation must be ensured by suitable protective equipment, i.e. gloves, boots, coveralls, goggles, etc. 4.6.2.10 Preparation of documents and notice to commissioning - A work permit shall be issued for each flushing operation according to the safety procedures. - Notice to the commissioning team shall be sent together with colored P&ID(s). 4.6.3 Performing a water flush Once all preparation works are completed the commissioning engineer shall inspect the site and give the authorization to start the water flushing operation. To check the flow rate if no flowmeter is installed, a pressure gauge can be installed at the inlet of the network to be flushed (downstream of the inlet valve) and the flow then adjusted by acting on the inlet valve till the head loss equals that calculated for the required velocity. The flow / discharge pressure curve of the pump can also be used to check the flow rate (make sure the pump runs at its normal speed). When the main header of the network is deemed clean (see 4.6.4), stop the water flow and prepare the network to flush the connections and smaller diameter pipelines. When the complete network has been flushed satisfactorily, the circuit shall be rinsed if necessary. Then the removed devices shall be reassembled and, if necessary, fill up with inhibited water.



4.6.4 Cleanliness criteria The duration of the flushing is the time needed for the outlet water to be as clean as it is at the inlet (take two samples in glass bottles and compare), and shall also be sufficient to open all the vents, drains, impulse lines (when the instruments are disconnected) and to obtain clean water at each of these points. Commissioning engineer shall estimate when the cleanliness criterion has been reached and give authorization to stop the flushing operation. 4.7 Air blowing procedure 4.7.1 Specific problems of air blowing - Large volumes of air: If the quick decompression method is used, large volumes of air are required, and it may take a significant time to raise the pressure in the network up to the desired value. - Air blowing is a HAZARDOUS OPERATION: Very high forces are generated at the air outlet. Therefore, specific safety procedures must be closely adhered to; generally air blowing operations will be undertaken when all other works have been stopped on site. - Air quality: For some operations, especially instrument air system, oil free air and/or dry air might be needed (temporary drier and oil extractor may be necessary). 4.7.2 Preparation for air blowing Note: Before the detailed preparation work starts, a meeting shall be organized with GBHE and the customer commissioning representatives to finalize the detailed procedures based on the present general procedures, taking into account the site restrictions and possibilities. Commissioning will advise the operators during the preparation.



4.7.2.1 Definition of the network to be cleaned A first selection shall be made according to construction progress, and geographical or functional criteria (i.e. compressor suction line, main transfer line, air service system, etc.). Then, it shall be revised to suit the site requirements, depending in particular, of the facilities available on site, the devices to be removed, the configuration of the lines, etc.. 4.7.2.2 Calculation of the necessary flow During cleaning operation, the air velocity shall be as follows: - In the gas process lines, the velocity shall be the lowest figure between 60 m/s and the velocity obtained at 1.3 time the maximum process flow rate. The minimum velocity shall be 30 m/s. - In liquid process lines, a velocity between 30 m/s and 60 m/s shall be used. If the quick decompression method is used, the pressure in the network could be raised up to 6 bars. The total volume of the network shall be estimated and the time required to raise the pressure up to 6 bars with the compressor(s) shall be calculated. Mechanical design pressure limits are to be considered. 4.7.2.3 Determination of the network pressure and maximum allowable pressure If the quick decompression method is used, the air pressure in the network shall never exceed 6 bars. It should also be checked that all pipes and vessels of the network are designed to withstand a pressure of 6 bars. If the network cannot withstand a pressure of 6 bars, the pressure shall be carefully studied and specified in order that the maximum allowable pressure in the system is never exceeded. If a rupture disk is to be installed on a large diameter pipe, the set pressure of the disk shall be carefully calculated in order to limit the energy released when bursting occurs to an acceptable level (in particular with regard to recoil effect).



For pipes above DN 250 especially the first blowing will take place with the network pressurized at only 2-3 bars. 4.7.2.4 Sketch of the network to be cleaned Identical to 4.6.2.4 only the lines to be flushed will be colored yellow. 4.7.2.5 Location of air inlets and outlets A site review shall be made to determine the possible air inlets, the possible outlets, and the necessary temporary pipes (avoid hose pipes when possible). Detailed drawings shall be prepared if necessary, and the required equipment to be supplied and installed (pipes, valves, gaskets) shall be determined. 4.7.2.6 Opening means Where the quick decompression method has been selected, the pressure release can be obtained by: - a quick opening valve, - a rupture disk. In the first case, the flow rate may be roughly adjusted, if necessary, and the valve may be closed in case of emergency; in the second case, no control is possible. Due to the high velocity involved, the quick opening valve might be eroded if it is used in an intermediate state (i.e. not completely opened). Therefore, whenever possible, the valve shall be completely open. 4.7.2.7 Fragile devices to be removed Same as for water flushing (see item 4.4 und 4.6.2.7). Attention shall be paid to tray manholes and other internals of the vessels used as air capacities (quick decompression method). 4.7.2.8 Quality of air The quality of air shall comply with the design basis.



4.7.2.9 Safety The safety rules and instructions must be strictly obeyed. Due to the high forces generated at the air outlet, the following particular precautions shall be taken for blowing operations: - Period of time for blowing: Generally air blowing will take place after normal working hours. - Restricted area: An area of at least 30 meters around the outlet points will be roped off during the release of air. - Work permit: Any air blowing operation shall be subject to specific work permits according to the safety procedure. - Space between flanges at the outlet: To obtain the desired space without hammering, spacers (pieces of tube of a diameter slightly larger than the bolts), or pile of washers, may be installed on bolts fixed by two nuts between the two flanges in two holes diametrically opposed (see figure below). Other fixing systems are also possible.



- Restraints: The flanges(s) at the air outlet shall be fixed by means of shackles and cables or slings. For diameters larger than DN100, at least four cables shall be used. The second end of the cable shall be fixed rigidly to the structures (see figure below).



- Clamps, tie bars, rigid struts, shims, U-bolts, etc.: Wherever necessary, the pipes shall be rigidly fixed with clamps, tie bars, rigid struts, U-bolts, etc., to avoid damage to the lines, equipment, and people nearby.



- Blanks: Blanks shall be rigidly fixed to the flanges by bolts and nuts in order to prevent them flying off when opening the quick opening valve or when the rupture disk blows out. - Environment protection: The large quantities of dirty air released during the flushing carries particles of sand, rust. welding rods, .etc. which could damage nearby equipment. Therefore adequate protection has to be installed. - Personnel protection: Protection of personnel carrying out the operation must be ensured by suitable protective equipment, i.e. ear protection, gloves, coveralls, goggles as a minimum. 4.7.2.10 Preparation of documents and notice to commissioning Identical to 4.6.2.10. 4.7.3 Performing air blowing Once all preparation work is completed the commissioning engineer shall inspect, the site (and check specially that all protections are installed: pipe restraints, clamps, supports, protection of equipment in the vicinity of air jets) and obtain the clearance of the safety engineer. Once satisfied he shall give the authorization to start the air blowing operation. 4.7.3.1 Continuous blowing method - Start the compressor (see particular procedure and vendor requirements). - Open the valves on the main header to be air flushed. - Allow the air flow to enter the network up to the calculated flow rate (check by difference at the outlet of the compressor, before and after).



- If the valve between the compressor and the network to be flushed is a globe valve, and if the compressor allows for quick increases of flow rates, changes of flow rates in the line may be made, thus changing the velocity and removing more quickly the rust and scale encrusted on the surfaces (this method may be attempted if the amount of encrustation is large and / or if the pipe has to be very well cleaned). For normal dirtiness, a continuous blowing at a constant speed should be sufficient. Instead of a compressor a large capacity vessel (column or drum) can be pressurized by a smaller compressor (to approx. 6 bar, depending on the mechanical design pressure), then the content of this vessel can be depressurized into the system to be cleaned as described above. 4.7.3.2 Quick decompression method Check that the network is isolated. - If a quick opening valve is used, allow the air to enter the network and carefully check that pressure in the system never exceeds the maximum allowable pressure. When the required pressure is reached, check that all safety measures have been adhered to, and open the valve. If necessary, this operation shall be repeated several times (see cleanliness criteria in paragraph 4.7.4). - If a rupture disk is used, after having checked that safety measures have been taken, allow the air to enter the network; check continuously the pressure rise, and when the rupture disk blows out, stop the air inlet in the network. The operation shall be repeated several times (see cleanliness criteria in paragraph 4.7.4). 4.7.4 Cleanliness checks These depend upon the ongoing requirements. For instance a compressor suction line will need to be much more thoroughly cleaned than a drain line.



Principal checks are: - Color of the air at the exit point. This will roughly indicate whether or not rust and dirt remain in the piping. This is usually sufficient for the majority of process and utilities piping. - Inspection by having a close look at the line system. Commissioning engineer shall be responsible to estimate that the desired cleanliness has been reached and shall then give the authorization to stop the flushing operation. 4.8 Steam blowing procedure 4.8.1 Specific problems of steam blowing - The principle differences between air blowing and steam blowing are: a) the temperature, which creates dilation stresses. Therefore steam blowing shall be performed only for steam networks. b) the vacuum hazard created when steam condenses in a closed system. This can cause vessels and large diameter piping to collapse. - The main advantage of steam over air is the embrittlement of pipe wall deposits, especially millscale, caused by temperature changes between blowings and the subsequent contraction of the piping or equipment causing a cracking effect on pipe wall deposits. - Steam blowing is a HAZARDOUS OPERATION: Very high forces are generated at the steam outlet. Therefore, specific safety procedures must be closely adhered to; generally steam blowing operations shall be done when most of the other works in the area have been stopped, personnel which will stay in the area should be informed/warned before blowing, hearing protection is mandatory. 4.8.2 Preparation for steam blowing Note: Before the detailed preparation work starts, a meeting shall organized with GBHE and the customer commissioning representatives to



finalize the detailed procedures based on the present general procedures, taking into account the site restrictions and possibilities. Commissioning will advise the operators during the preparation. 4.8.2.1 Definition of the network to be cleaned A first selection shall be made according to construction progress, and geographical or functional criteria (i.e. steam inlet line, main transfer line, etc.). Then, it shall be revised to suit the site requirements, depending in particular, of the facilities available on site, the devices to be removed, the configuration of the lines, etc.. 4.8.2.2 Calculation of the necessary flow During cleaning operation, the steam velocity shall be the lowest figure between 60 m/s and the velocity obtained at 1.3 time the maximum process flow rate. The minimum velocity shall be 30 m/s. 4.8.2.3 Determination of the network pressure and maximum allowable pressure The pressure and temperature shall be carefully studied and specified in order that maximum allowable pressure and temperature in the system are never exceeded. For steam blowing the maximum working pressure shall be limited to 9 bar. 4.8.2.4 Sketch of the network to be cleaned Identical to 4.6.2.4 only the lines to be flushed will be colored red. 4.8.2.5 Location of steam outlets A site review shall be made to determine the possible steam outlets and the necessary temporary pipes and devices. Detailed drawings shall be prepared if necessary, and the required equipment to be supplied and installed (pipes, valves, gaskets) shall be determined.



4.8.2.6 Additional material and pieces of equipment required The drawings for the additional pipes to be manufactured and erected may be drawn if required. The required material (pipes, valves, gaskets, etc.) and the means (monorails, cranes, pulleys blocks, etc.), tools, gaskets, grease for bolts, nuts, etc. required to carry out the removal and reassemble, the needs for the dummy spools (flanges, pipes, etc.) will be determined. 4.8.2.7 Fragile devices to be removed Same as for water flushing (see 4.4 und 4.6.2.7). 4.8.2.8 Quality of steam The quality of steam shall comply with the design basis. 4.8.2.9 Safety The safety rules and instructions must be strictly obeyed. Steam is potentially very dangerous and can cause severe burns. About two thirds of the total heat in steam is taken up in the change of state from boiling water to steam, and hence when steam condenses, two thirds of its total heat is given up to the body on which it condenses. This is what makes steam such an effective heating fluid, and this is also what makes it very dangerous if it condenses on the human body. Hence to get a part of the body in a jet of steam is many times worse than in a corresponding flow of hot air at the same temperature . The following precautions should be observed: - When blowing steam lines make sure that everyone is clear of the area. - Follow the guidelines laid down for air blowing operations (see paragraph 4.7.2.9). - Personnel must always be adequately clothed when working in the proximity of steam lines. Shorts and tee-shirts are forbidden. - Close liaison with boiler house personnel is required. 4.8.2.10 Preparation of documents and notice to commissioning Identical to 4.6.2.10.



4.8.3 Performing steam blowing Pipe work systems are to be prepared for steam blowing operations in much the same way as for air blowing but it must be borne in mind that much higher pressures, line, and escape velocities may be involved. Obviously in these cases additional restraints and clamps will be required to overcome reactive forces and avoid damage. Special attention must be paid to system blinding and isolation. Once all preparation work is completed the commissioning engineer shall inspect, the site (and check specially that all protections are installed: pipe restraints, clamps, supports, protection of equipment in the vicinity of steam jets) and obtain the clearance of the safety engineer. Once satisfied he shall give the authorization to start the steam blowing operation. Initially steam should be slowly introduced into the system to allow a steady temperature rise in the piping or equipment. Condensate must be drained from all low points to avoid producing water slugs which could be propelled at high velocity through the piping causing hydraulic shock and possible damage. Following this warm-up period steam blowing may be started. In certain applications, such as steam turbine HP steam inlet line blowing it may not be possible to use a quick opening valve. In this case it is very important to use an intermediate block-valve for controlling the steam flow. Always avoid using a final stop valve in case its seat is damaged by erosion, this will cause future problems when the steam supply needs to be isolated. When steam blowing small diameter lines the normal block-valves may be used for a limited time and should not be liable to damage. When a steam blow has been completed, ensure the piping and equipment are adequately vented to avoid pulling a vacuum during the cool down period. If required, cool down can be accelerated by the injection of service air. 4.8.4 Cleanliness checks Cleanliness checks are to be carried out as explained in paragraph 4.7.4. Additionally, target plates may be used if the steam line will feed a steam turbine. - A polished aluminum or soft metal target plate is attached to the target plate carrier on the tailpipe end (see the following figure)



- There is little point in using a target plate during the initial steam blowings, these plates should be installed when the exhaust steam appears to be clean.



Proceed as follows: - If the exhaust steam appears to be clean install a target plate and steam blow the system. - Examine the plate at the end of the steam blowing. - If the plate has became eroded and pitted, easily seen by a matt gray appearance and surface pitting, continue steam blowing. - Mark each plate and store in a safe place for comparison. - The target plate surfaces will become brighter after each subsequent blowing. - When the plate surface remains bright it will be possible to count the number of impact pits per blow caused by large dirt or rust particles. - When the plate remains unmarked it may be assumed that the piping is clean. - If requested, submit the series of target plates to the equipment vendors representative for his scrutiny and final approval. - Ensure no dirt is re-introduced into piping during re-assembly following steam blowing. In the case that target plates will be used, note that wet steam may produce a "matting" effect on a polished target plate which can be misleading. In this case look for pitting marks as a general guideline. When the equipment is considered to be clean, and / or meets the equipment vendors representative requirements, etc., allow the piping to cool, drain condensate from low points and, if necessary, carry out a drying procedure. Reassemble the piping taking care not to reintroduce dirt into the equipment. Commissioning engineer shall assess if the desired cleanliness has been reached and give the authorization to stop the steam blowing operation.



4.9 Chemical cleaning procedure 4.9.1 Specific problems of cleaning with a chemical solution - Field of application: This procedure is applicable for removing production residues and surface protection substances, i.e. oil and greasy films, in case it should disturb commissioning or start-up of the plant. This procedure is not applicable for special surface treatment, i.e. "pickling and or passivation" - GBHE-APT-0102 - Degreasing: A grease layer may have formed during transport or storage of the equipment which may disturb further procedures. In this case, the surfaces shall be degreased by means of a special lye (components: carbonates, alkali-hydroxide phosphates and wetting agent). - Treatment: A pre-treatment of the system using a method acc. to paragraphs 4.6 and 4.7 is necessary. The treatment itself will be carried out by circulation of a chemical solution in a closed system. When the equipment is degreased the solution has to be removed and disposed to waste water treatment or special treatment. Finally the system will be rinsed with fresh water or demineralized water to remove the remaining chemical solution. After that the system may be dried out by air or inert gas if necessary. - Solution handling: A separate vessel or drum may be necessary for preparation of the chemical solution. Additional temporary pump, piping and connection might be required. Precautions by handling chemicals must be observed.



4.9.2 Preparation for chemical cleaning Note: Before the detailed preparation work starts, a meeting shall organized with Uhde and the customer commissioning representatives to define the systems to be treated and finalize the detailed procedures based on the present general procedures, taking into account the site restrictions and possibilities. Commissioning will advise the operators during the preparation. 4.9.2.1 Definition of the system to be cleaned A first selection shall be made according to process requirements for commissioning and start-up of the plant, construction progress and geographical or functional criteria (i.e. vessel, piping, etc.). Then it shall be adapted to suit the site requirements, the devices to be removed, the configuration of the lines (low points, high points, lengths, heights, etc.). 4.9.2.2 Calculation of the chemicals Estimate the volume of the system to be cleaned and of the auxiliary device. Determine the necessary chemicals for treatment and the required concentration. Generally a concentration of 3 to 5 wt-% (Na-OH or KOH or K2CO3 etc.) shall be used. Calculate the amount of chemicals and water for treatment and rinsing. Determine the air for drying out the system. During cleaning operation, the chemical solution velocity shall not reach the high figures as given in chapters 4.6 to 4.8 to avoid erosion. For chemical cleaning it is important that all surfaces to be cleaned are in good contact with the solution, the high velocities are here not so important as for mechanical cleaning. 4.9.2.3 Determination of the network pressure and maximum allowable pressure Estimate the maximum head loss. With the velocity actual, estimate the head loss for a flow going through the principal piping and add the static head (if any). If the flow and the head loss are compatible with the pumps available on the site, go ahead, otherwise reduced flow or external pump has to be considered.



The pressure shall be carefully studied and specified in order that the maximum allowable pressure in the system is never exceeded. 4.9.2.4 Sketch of the network to be cleaned A sketch of the network to be cleaned shall be specially drawn for the cleaning operation (P&ID’s will be used for this purpose). The following color code may be used: - Blue with flags: lines to be chemical cleaned - Green: items to be removed - Pink: flanges to be disconnected - Orange: items to be isolated Blinds used for chemical cleaning operations, if they are necessary they will be indicated and numbered with a red color. Installation and removal of blinds shall be followed up by commissioning by the mean of a blind list. Installed blinds shall be tagged and equipped with a visible handle painted red. 4.9.2.5 Location of inlets and outlets A site review shall be done to determine the possible solution and water inlets and outlets, the water source, the pump(s) location, the additional pipes or hose pipes layout from the source to the system. The water disposal problem and the protection of the equipment and people nearly shall be carefully studied. 4.9.2.6 Additional material and pieces of equipment required The drawings for the additional pipes to be manufactured and erected may be drawn if required. The required material (pipes, valves, gaskets, etc.) and the means (monorails, cranes, pulleys blocks, etc.), tools, gaskets, grease for bolts, nuts, etc. required to carry out the removal and reassemble, the needs for the dummy spools (flanges, pipes, etc.) will be determined.



4.9.2.7 Fragile devices to be removed All "fragile" devices to be removed shall be identified. The removal possibilities shall be investigated on site. The required dummy spools to be fabricated shall be drawn on sketches. Attention shall be mainly paid to: - heavy devices (control and block valves, check-valves), - supports, hangers, pads, spring supports, - possible stresses on pumps’ flanges. 4.9.2.8 Quality of water Good quality of fresh water and or demineralized water shall be used from the beginning until the end. The quality of the water shall comply with the specification for hydrostatic test and the design basis for the plant respectively. 4.9.2.9 Safety The safety rules and instructions must be strictly obeyed. The following particular precautions shall be taken for chemical cleaning operations: - Period of time for flushing: Generally chemical cleaning operations will take place during normal working hours. - Restricted area: An area of at least 5 meters around the system will be roped off or closed off during the cleaning operation. - Work permit: Any chemical cleaning operation shall be subject to specific work permits according to the safety procedure.



- Restraints: Wherever necessary, the pipes shall be rigidly fixed to avoid damage to the lines, equipment and people nearby. - Environment protection: Adequate protection of the devices in the vicinity of the system and water outlet has to be installed in order not to damage equipment, electric motors or instruments with chemical solution or water. - Personal protection: Protection of personnel carrying out the operation must be ensured by suitable protective equipment, i.e. gloves, boots, coveralls, goggles, etc.. 4.9.2.10 Preparation of documents and notice to commissioning - A work permit shall be issued for each cleaning operation according to the safety procedures. - Notice to the commissioning team shall be sent together with colored P&ID(s). 4.9.3 Performing a chemical cleaning Once all preparation works are completed the commissioning engineer shall inspect the site and give the authorization to start the chemical cleaning operation. Cleaning operation will be performed by circulating the chemical solution for a predestined time. To check the flow rate if no flowmeter is installed, a pressure gauge can be installed at the inlet of the system to be cleaned (downstream of the inlet valve) and the flow then adjusted by acting on the inlet valve till the head loss equals that calculated for the required velocity. The flow / discharge pressure curve of the pump can also be used to check the flow rate (make sure the pump runs at its normal speed). The temperature of the cleaning solution shall be approx. 50 to 70 °C. When the complete system has been cleaned satisfactorily, the circuit shall be emptied chemical solution.



After completion of chemical flushing the system shall be flushed with clean water (quality depending on the operating systems). This step is to remove the remaining chemicals from the system and may be repeated if required. Then the system may be dried out with air or inert gas, if necessary, and the removed devices shall be reassembled. 4.9.4 Cleanliness criteria The duration of the cleaning is the time needed for the reaction of the chemicals with the oil and greasy material in the whole system expressed as retention time plus an additional safety margin. Test on side may be carried out if necessary. Commissioning Engineer shall estimate when the cleanliness criterion has been reached and give authorization to stop the cleaning operation. 4.10 Re-assembly – general guideline After the cleaning operations, pipes, fragile devices, etc., have to be reassembled. Great care is necessary in this operation. The construction specifications have to be complied with, with particular emphasis on the following points: - Ring joints have to be carefully cleaned. - New gaskets must be used on flanges broken for flushing purpose. - Spring supports, sliding pads. etc., have to be installed according to the drawings and released when the reassemble is completed. - Threads shall be checked and wrapped with PTFE. - Stuffing boxes and packing of valves shall be checked and changed if necessary. - Absence of stresses on pump and compressor flanges has to be checked. - The orientation of check valves, globe valves, etc., shall be checked (according to their arrow) against the direction of flow.



- In-line instruments such as flow orifices, restriction orifices, rotameters, shall be installed by instrument specialists. - Expansion bellows shall be freed according to the vendor's instructions. - Temporary blinds installed for cleaning purposes shall be removed. 4.11 Preservation of flushed piping Following the flushing operations, if necessary, precautions for preservation of the equipment shall be carried out, i.e. subsequent commissioning is not practicable.

GBH Enterprises, Ltd.

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