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Cleaning and Flushing Methods

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Cleaning and Flushing Methods

Cleaning and Flushing Methods
ROUGH COPY
© 1996 Bechtel Corp. Piping/Mechanical Handbook 13-1
Section 13
Cleaning and Flushing Methods
MAINTAINING CLEANLINESS DURING CONSTRUCTION
The following guidelines should be followed to maintain system cleanliness during fabrication,
installation, and rework operations:
 To keep a system clean, start with clean materials. During work operations, keep the
materials in a clean condition.
 Apply rust preventatives to the internal surfaces of carbon steel components. Preventatives
must normally be removed prior to turnover.
 Keep openings into components sealed when work is not actually in progress.
 Perform localized cleanup after completing work operations and prior to reclosing the system.
 Protect clean systems in the vicinity of foreign matter or dirt producing work operations. This
can be done by establishing clean areas and by using internal dams or external encapsulation
when systems are opened.
 Establish a foreign object and access control procedures for clean areas.
 Immediately remove all visible metal particles or chips after cutting.
 Do not use flame cutting in areas where slag may blow into inaccessible surfaces.
 Do not cut pipe in a vertical position if there is a possibility of cutting chips falling into
inaccessible areas.
 Clean grinding dust from a ground out area prior to breaking through the wall or root pass to
prevent the dust from entering the clean system.
 Use magnetic drill bits to drill holes in carbon or alloy steel pipe to minimize the entry of metal
particles. Frequently clean holes during the drill operation.
 Use hole saws when cutting chips cannot be easily removed form internal surfaces. Holes
should be cleaned just prior to breaking through and the plug should be immediately be
removed.
 Clean the ends of threaded pipe to remove lubricant and metal chips at the completion of
threading.
 Provide an oil-free air blow of all field fabricated piping assemblies, including valves, to
remove loose foreign material.
 Seal the openings in completed field fabricated piping assemblies until installed. Provide
desiccant on the inside of the completed pipe assembly if required by the project
specifications.
 Prior to fitting or bolting up flanged or other mechanical joints, clean flange faces of mill
varnish or other preservatives.
 Cover tack welded pipe joints to prevent the entry of dust until the joint is to be welded out.
 Follow access control and foreign object control procedures when working on clean systems.
Section 13 Cleaning and Flushing Methods
13-2 Piping/Mechanical Handbook 1996:Rev.2
Cutting Lubricants
Cutting lubricants can have a detrimental effect on a number of critical process systems including
vacuum, oxygen, and argon systems. Wherever possible, lubricants on critical systems should be
removed after the completion of cutting, threading, drilling, or hole sawing. If there is a possibility
that the lubricant will remain in the system, the type of lubricant used should be approved by the
engineer or the manufacturer of the affected equipment.
In general, lubricants used on stainless or carbon/alloy systems should meet the following criteria:
 Contain less than 1% by weight total organic and inorganic halogen (chloride, fluoride,
bromide, and iodine)
 Contain less than 200 ppm by weight of inorganic halogen
 Contain less than 1% by weight sulfur
 Contain less than 1000 ppm by weight low melting point metals (lead, bismuth, zinc, mercury,
antimony, and tin). No individual low melting point metal must exceed 200 ppm. Mercury
must not exceed 50 ppm.
Ordinary oil based cutting lubricants may be used on non-critical carbon and alloy steel systems.
The cutting lubricants used on lube oil and hydraulic systems must be compatible with the oils
normally used during system operation.
Desiccants
Desiccant bags are used to control the humidity level in enclosed systems. The bags are
normally placed in a perforated container attached to the pipe end cap. The container is not
normally allowed to come in contact with the interior surface of the pipe. Humidity indicating cards
should also be placed at an opening remote from the desiccant bag location. A transparent
plastic end cap is used to permit monitoring of the card. The location and number of desiccant
bags should be marked on the outside of the pipe or on the end cap.
The quantity of desiccant required may be computed as follows:
U = 1.2V
Where:
V = Volume of the interior system in cubic feet
U = Units of desiccant which is defined as the quantity of desiccant that will absorb 3.0
grams of moisture at 20% relative humidity with air temperature at 77 oF as stated
by the manufacturer.
The desiccant used should consist of nondeliquescent, nondusting, chemically inert, dehydrating
agents. Desiccants satisfying military specification MIL-D-3464, Type II satisfy this requirement.
The desiccant should be provided in bags and contain less than 0.25% halogen. The bags
should be puncture, tear, and burst resistant. If the dessicant bag is opened inside a piping
system, the system should be immediately cleaned to remove the dessicant material.
Cleaning and Flushing Methods Section 13
1996:Rev.2 Piping/Mechanical Handbook 13-3
Cleanliness Requirements for Field Purchased Materials
Stainless steel materials must be delivered to the site in a "metal clean" condition and the
surfaces must be free of particulate foreign material such as metal particles, chips, weld slag,
filings, grinding dust, or rust. Surfaces should also be free of organic films and foreign materials
such as oils, grease, paints, and nonsoluble preservatives or inhibitors.
Carbon steel and alloy steel materials should be free of particulate foreign materials (metal
particles, chips, weld slag, or filings). Thin, nonflaking, soft, scattered rust film is permissible,
however, hard rust, mill scale, or heavy rusting is not acceptable since it will be more difficult to
clean at the site and will increase construction costs. The pipe surfaces should also be free of
organic films and foreign materials such as oils, grease, and paints. A water soluble, inorganic
rust preventative coating (such as phosphate preservatives) should be applied to the interior pipe
surface after cleaning. Pickled piping should be coated with a light oil film or rust preventative.
Phosphate preservatives are composed of 0.5% by weight.
MECHANICAL CLEANING METHODS
The following is a summary of various mechanical methods used in cleaning piping and
components:
Handwiping
 Cloths or rags should be lint-free
 Water or solvent is typically used in conjunction with the handwipe cleaning process
Wire Brushing
 Either hand or power driven wire brushing is an effective method of cleaning small sections of
piping
 Use corrosion resistant brush material on stainless steel components and do not use the
same brushes on both stainless and carbon steel
Tube Cleaning Brushes
 Air, water, or electric powered expanding type power brushes that drive air or water through
the brush provides a method of power flushing the interior surfaces of piping
 The water used to flush the interior surfaces of the piping must be compatible with the piping
system cleanliness
 Do not use air driven brushes that require lubricated air if the motor air enters the pipe
 Do not use tube cleaning brushes through valves, strainers, flow orifices, or other sensitive
components
 Avoid using tube cleaning brushes through socket welded or short radius fittings
Section 13 Cleaning and Flushing Methods
13-4 Piping/Mechanical Handbook 1996:Rev.2
Grinding
 Grinding wheels and discs used for cleaning should only be vitrified or resinoid bonded
aluminum oxide or silicon carbide
 Aluminum oxide flapper wheels and buffing discs provide effective mechanical cleaning on
exterior surfaces
 Rotary files can be used for localized cleaning but should be faced with tungsten or titanium
carbide
Shot or Grit Blasting
 Blasting is typically performed to the Steel Structures Painting Council (SSPC) standards
 Do not blast through sensitive components
 Only use iron-free grit for blasting stainless steel surfaces
 Sand grit may be used on carbon steel buttwelded piping
 Do not blast areas requiring liquid penetrant examinations
 For 2 inch and smaller piping, a radial type blast nozzle may be inserted into the pipe to blast
the interior surface
Mechanical cleaning operations are usually followed by hand cleaning of accessible internal
surfaces and by air blow or water rinse of inaccessible internal surfaces. Air blowing is preferred
after a shot or grit blast.
VACUUM CLEANING
Vacuum cleaning can be used for the removal of metal chips and airborne foreign materials while
working or for local cleanup subsequent to work operations.
AIR BLOWING
Filtered, oil-free compressed air is used in the following applications to clean piping:
 Local cleanup of foreign material produced during erection or fabrication
 Drying of previously wetted systems
Care must be exercised to direct the air blow and particles away from internal surfaces of the
components being cleaned. Particles must also not be blown through or at sensitive components.
SOLVENT CLEANING
The following solvents are typically used to clean piping:
 Alcohol
 Ethyl alcohol (Ethanol)
 Methyl alcohol (Methanol) anhydrous
 Isopropyl alcohol
 Acetone
Cleaning and Flushing Methods Section 13
1996:Rev.2 Piping/Mechanical Handbook 13-5
 Toluene (Toluol) which is useful in removing silicone based lubricants
 Naphtha
 Distilled Petroleum Spirits or Mineral Spirits
NOTE: This solvent is preferred due to its low flammability potential.
It is important to note that alcohol, acetone, toluene, and naphtha are extremely hazardous and
flammable and must be dispensed in sealed containers and only used in well ventilated locations.
Refer to the manufacturer Material Data Safety Sheet (MSDS) for important information on how
to safety use these products. In general, prolonged exposure to the skin must be avoided.
For lined piping, solvents used for cleaning must be compatible with the lining material. When
bristle brushes are used in conjunction with solvent cleaning, they must be nonshedding.
WATER BLAST CLEANING
Water blast cleaning or hydrolasing consists of a high pressure (more than 1000 psig), low
volume (20 gpm or less) water jetting of the internal surfaces of the piping system to remove rust,
mill scale, oil, and other foreign materials. Radial type spray nozzles that drag the supply hose or
push type cleaning nozzles should be used. When cleaning carbon steel or alloy steel piping,
0.5% to 1% by weight of trisodium phosphate should be used.
Water quality must be compatible for use on the piping system being cleaned. The hydrolaser
water jet must not come in contact with valve seats, flow nozzles, or other sensitive components.
After cleaning carbon steel and alloy steel systems, the pipe must be dried by air blowing or other
methods.
SYSTEM FLUSHING METHODS
Several methods of system flushing are used to clean piping systems. In general, the water used
for flushing must be compatible with the system being cleaned. After the completion of the flush,
carbon steel and alloy steel systems must be air dried.
Recirculating Flush
This flushing method uses a single batch of water which is recirculated under pressure through
the piping system in a closed path at a prescribed velocity through strainers, filters, or
demineralizers to remove debris and water impurities.
Velocity Flush
A cleaning technique that utilizes the ability of the rapidly flowing liquid or air to scrub, sweep, and
scour foreign material from internal walls of the system. Particles picked up in the flush are sent
out as waste or trapped and collected on mesh screens or filters. The effective velocity should
exceed the design flow rate by two times through the system to perform as desired.
Section 13 Cleaning and Flushing Methods
13-6 Piping/Mechanical Handbook 1996:Rev.2
Soaking Method
This process is used when it is not possible to achieve flow by the recirculating method due to the
inlet connections or tube shapes for vessels. The disadvantage of this method is that it requires a
stronger solution to perform the cleaning and sampling is not as accurate.
Acid Cleaning
This process cleans the internal surfaces of water touched pressure parts to remove mill scale
and rust. The acid solution reacts with iron scale and forms ferric oxide.
Chemical Cleaning
This process uses the circulation of a hot alkaline water or citric acid solution through the pipe
systems to remove oil, grease, fitting lacquers, preservatives, inhibitors, and possible siliceous
materials from carbon steel piping and equipment. The hot alkaline water is followed by an acid
solution flush to remove iron oxide and mill scale. The acid solution flush liquid is neutralized and
flushed out of the piping system.
CLEANING ADDITIVES
Wetting Additives
Wetting agents are used to improve the contact of a cleaning solution with the pipe and
equipment. The additives reduce the surface tension of the cleaning solution and thereby
enhance the cleaning of the metal. Because they are detergent based, the wetting agents tend
to foam which may not be acceptable in all applications.
Anti-Foam Agent
These agents are sometimes used when detergents are added to chemical cleaning solutions.
Their use maintains a low foaming level during cleaning and discharging of the solution to the
waste collection system or tank.
Acid Inhibitors
When added to the cleaning solutions, these inhibitors allow higher cleaning temperatures and
slow the reaction between the cleaning solution and the piping or equipment base metal.
Chemical Cleaning Set-up
Temporary equipment is usually required to perform any on-site cleaning. A P&ID should be
marked up and reviewed showing:
 Scope of the cleaning
 Desired flow path
 All temporary piping and instruments
 Heating source for the operation
 Strainer and filter locations
This type of cleaning operation is best subcontracted to specialty subcontractors.
Cleaning and Flushing Methods Section 13
1996:Rev.2 Piping/Mechanical Handbook 13-7
Temporary Piping
All temporary pipe should adhere to the following:
 Pipe should be Schedule 40 minimum
 Welded joints should be used to prevent leaks
 Check gaskets to ensure they are compatible with the heat and chemicals being used
 Monitor the system to prevent over pressurization
Temporary Instruments
 Make sure temporary glass site gauges installed
 Provide differential pressure gauges across strainers to indicate fouling or flow reduction
 Install temperature indicators to monitor flushing temperatures
Solution Heating Equipment
There are two methods for heating chemical cleaning solutions.
 Direct contact method
 Steam supply heat exchanger
Flushing Safety
Safety measures such as warning signs, barriers, or temporary personnel insulation should be
considered. Review all chemical flushing with the Site Safety Representative before starting the
flush. Safety and OSHA regulations must be observed for proper protection of personnel and
equipment.
Chemical Cleaning Set-up
Mechanical cleaning (line-pig) can be used to knock loose dirt and sand particles and remove oil
and grease from the interior piping walls. Filtered well water, plant water, or city water is normally
used for line-pigging of the system. The drums and coolers required for the cleaning are normally
prepared by the vendors prior to the equipment arriving at the site.
Following the mechanical cleaning and field assembly of required temporary piping, the acid
solution is applied to remove scaling. Whenever possible, agitate the piping to shake any loose
materials free. After the acid cleaning, rinse the system with fresh water. When using citric acid,
a fresh water rinse is not normally performed.
The descaled pipe is then passivated to prevent further corrosion by applying a phosphate
coating. Any of three different solutions are typically used:
 Monosodium phosphate
 Disodium phosphate
 Sodium nitrate
Section 13 Cleaning and Flushing Methods
13-8 Piping/Mechanical Handbook 1996:Rev.2
Note: When using citric acid in the first step, raise the pH level to 9 or 10 with ammonia and then
add sodium nitrate.
After being passivated, the system is dried using dry nitrogen or filtered, dry compressed air. Do
not flush the passivated system with water. After drying, inspect the piping to be sure it is free
of rust, mill scale, or other foreign material and restore and close the system tightly. Blanket the
system with inert gas, apply a rust preventative, or fill the system with oil to minimize rusting in the
system. Finally, paint, varnish, or otherwise protect the exterior pipe and fitting surfaces.
For systems provided with an inert gas blanket, a periodic check of the system should be made to
ensure the gas blanket remains in the system.
Lube Oil Flushing
Prior to any lube oil flushing operation, it is important to check supplier, engineering, and client
requirements for the flushing operation to ensure that the criteria for the conduct and acceptance
of the flush is clearly understood. It is best to have a specific procedure or instruction defining the
flushing operation approved by all parties prior to the start of the work.
The first step in lube oil flushing is to chemically clean and passivate all associated piping, heat
exchangers and vessels. The following are the normal steps used in a lube oil flush:
 Prepare jumpers around seals and bearing housings as close as possible to the bearings.
 Charge the system with the specified oil. If this oil is not available, Turbine Oil 32 may be
substituted with supplier and/or engineering approval. The fill amount should give an
operating level near that for which the system was designed.
 Install 100 mesh screen in the return line to the reservoir.
 Circulate the flushing oil for a minimum of 4 hours at the maximum recommended temperature
while hammering the piping, switching valves, and cycling bearing and seal oil rundown tanks
(if so equipped). Clean the 100 mesh screen and circulate the flushing oil for 4 more hours
with continued hammering and cycling. Remove and inspect the 100 mesh screen again.
The screen should be essentially clean with no evidence of magnetic particles or dirt on the
screens. If not, repeat the flushing process in 4 hours increments until the screens are clean.
 When clean, remove all temporary jumpers, and reconnect all permanent piping. Install 100
mesh screens at the inlet to each bearing. Install blinds in the seal oil system, if so equipped,
so as not to flush through the seals. If the unit has a oil lube coupling, install 100 mesh
screen in the oil outlet line to the coupling.
 Unless otherwise specified by the supplier, continue to circulate the flushing oil in 4 hour
increments until all screens are clean.
 When clean, remove temporary jumpers, reconnect all permanent piping, remove screens,
replace filters and clean filter housings. Check pump inlet screens and clean if needed.
 Circulate oil for a minimum of 8 hours.
 Discard filters and clean the filter housings. The client may want to see the discarded screens
to verify the adequacy of the lube oil flush.
 Drain the flushing oil, inspect and clean reservoirs, replace filters, charge with service oil and
continue circulating until the system is turned over to startup or the client.
Cleaning and Flushing Methods Section 13
1996:Rev.2 Piping/Mechanical Handbook 13-9
Note: If service oil was used for flushing and the system is clean, there may not be a reason to
drain the flushing oil. The client should concur with this decision.
Plant Steam Start-up
The set-up to perform plant steam starting begins when the system is being placed in service.
Begin with a walkdown of the system looking for any discrepancies, checking the hydrotesting
restoration. The following steps represent one method to start-up for plant steam and are done
with concurrence and direction of Startup and/or Client representative:
 Check gaskets and valve line ups.
 Tag-out the system as needed
 Open drain valves
 Close all steam trap inlets to prevent clogging
 Start Boiler and open isolation valves
 As the system heats up let the condensate and steam run freely out the open drains. After the
condensate has slowed to a steady rate begin opening steam trap branches and closing the
drains.
 Replace or repair any steam trap not functioning properly.
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