Turnaround BP Workbook

TurnAround Best Practices Energy Services Division

Table Table of Contents Introduction Introduction – T/A Best Practices .............................................. ..........................................................3 ............3 Planning the T/A ............................................. ...................................................................... .......................................4 ..............4 Communicating Communicating the Best Practice T/A Plans .........................................5 .........................................5 System Lay-Up....................... Lay-Up ............................................... ................................................. .......................................7 ..............7 System Lay-up Best Practices................................... Practices............................................................ ............................9 ...9 a.

#1 Best Practice for Lay-up: “Keep the Water Recirculating” Recirculating” ...................... ...................... 9

b.

#2 Best Practice for Lay-up: Wet Lay-up............................................. Lay-up................................................... ...... 10

c.

#2A Best Practice for Lay-up: Drain, Dry and Purge ................................. ................................. 10

d.

#3 Best Practice for Lay-up: Drain and Dry......................... Dry ............................................... ...................... 11

Passivation Procedures......................... Procedures.................................................. ..............................................12 .....................12 a.

Chart – Passivation Passivation Options Review ................................................ .......................................................... .......... 12

b.

Pre- T/A – Wet Storage Lay Up...................................................... Up.................................................................. ............ 13

c.

Post T/A – Molybdate Molybdate / PSO Passivation Passivation ................................................. ................................................... .. 20

d.

Post T/A - Nitrite/PSO Passivation Passivation Procedure......................... Procedure............................................ ................... 27

e.

New System Passivation.......................................... Passivation.................................................................... .................................. ........ 33

f.

Emergency / Hurricane Wet Lay Up Passivation.............................. Passivation........................................ .......... 39

Exchanger Inspections ............................................... ....................................................................... .........................50 .50 Exchanger Inspection Form....................................... Form................................................................ ..........................51 .51 Post T/A Start-up........................ Start-up ................................................ ................................................. .................................53 ........53 Post T/A Reporting ................................................. ......................................................................... .............................54 .....54

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Table Table of Contents Introduction Introduction – T/A Best Practices .............................................. ..........................................................3 ............3 Planning the T/A ............................................. ...................................................................... .......................................4 ..............4 Communicating Communicating the Best Practice T/A Plans .........................................5 .........................................5 System Lay-Up....................... Lay-Up ............................................... ................................................. .......................................7 ..............7 System Lay-up Best Practices................................... Practices............................................................ ............................9 ...9 a.

#1 Best Practice for Lay-up: “Keep the Water Recirculating” Recirculating” ...................... ...................... 9

b.

#2 Best Practice for Lay-up: Wet Lay-up............................................. Lay-up................................................... ...... 10

c.

#2A Best Practice for Lay-up: Drain, Dry and Purge ................................. ................................. 10

d.

#3 Best Practice for Lay-up: Drain and Dry......................... Dry ............................................... ...................... 11

Passivation Procedures......................... Procedures.................................................. ..............................................12 .....................12 a.

Chart – Passivation Passivation Options Review ................................................ .......................................................... .......... 12

b.

Pre- T/A – Wet Storage Lay Up...................................................... Up.................................................................. ............ 13

c.

Post T/A – Molybdate Molybdate / PSO Passivation Passivation ................................................. ................................................... .. 20

d.

Post T/A - Nitrite/PSO Passivation Passivation Procedure......................... Procedure............................................ ................... 27

e.

New System Passivation.......................................... Passivation.................................................................... .................................. ........ 33

f.

Emergency / Hurricane Wet Lay Up Passivation.............................. Passivation........................................ .......... 39

Exchanger Inspections ............................................... ....................................................................... .........................50 .50 Exchanger Inspection Form....................................... Form................................................................ ..........................51 .51 Post T/A Start-up........................ Start-up ................................................ ................................................. .................................53 ........53 Post T/A Reporting ................................................. ......................................................................... .............................54 .....54

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Introdu ctio n – T/A T/A Best Practices Practices Turn Arounds (T/As) are consistently the one time period where all cooling water treatment companies are judged. This is the customer’s one chance to inspect the equipment and directly evaluate the performance of the cooling water treatment. You know that a successful cooling water treatment program is based on a large number of variables. These include the Mechanical, Operational and Chemical control of the cooling water system. Fair or not, when an exchanger is opened, its condition is attributed directly to the water treatment company’s performance. How Nalco personnel handle themselves before, during and after a T/A can often be the difference between maintaining, winning or losing an account. Professionally handling all aspects of a T/A will ensure that we are delivering value to our customers. It will lead to improved reliability and decreased maintenance costs. It will help determine where the customer should utilize their resources during and after the T/A. Our customers are looking to you as the Nalco representatives to bring to their site Best Practices. The term “Best Practices” refers to Nalco’s best technology, products, equipment and processes. The following is designed to help identify the items that likely will be required at your site. These lists should help provide an outline of the steps necessary to properly plan for any cooling water system T/A. This document is designed to help you get fully integrated into your customer’s T/A process. You will need to identify where the site currently operates and how this differs from Nalco’s Best Practices. You will need to present these gaps to the Customer management and outline how these gaps can impact their plans for their unit’s safe and reliable operation. Once you have agreement on implementation of Best Practices, allow your customer management to direct your efforts in moving this forward. In order to engrain these Best Practices into the customer’s T/A plans and culture, the site management will have to communicate their importance to the T/A planning organization. Then work with these customers to initiate these recommendations into their normal T/A plans. From that point it will be about execution of these plans. If you are successful convincing the site management on the gap between current and Best Practices, you have the opportunity to become a part of the customer’s T/A culture.

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Planni Planni ng the T/A T/A A large amount of planning planning goes into a T/A. Likewise, you need to plan, communicate and get agreement on Nalco’s involvement in your customer’s T/A plans. Although it is quite possible to never start too early, begin your planning at least 18 months in advance. This “lead time” will vary by site and by the complexity of the T/A plans. Planning your involvement well in advance will ensure you are included in all T/A plans and procedures. If Nalco has not been an integral part of your sites T/A planning activities, you will need to back up and do an assessment of what your customer does at a T/A with respect to the cooling water system. Then assess how these activities relate to Nalco’s T/A Best Practices. This gap analysis will help determine what is needed and what will or won’t be allowed by the customer. In order to engrain these Best Practices into the customer’s T/A plans and culture, you will have to communicate with the site management to get agreement on your recommendations. They will then help you get these implemented by communicating these recommendations to the customer’s T/A planning organization. Work with these professionals to institute these recommendations into their normal T/A plans. From that point it will be about execution of these plans. If you perform this initial planning step with the site management successfully, you will only have to convince the site of these Best Practices and their value once. Establis Establis h T/A T/A Best Practices with Custom er for sit e Determine Current T/A Practices at Site Identify Gaps between current site practices and Recommended Best Practices – Utilize recommendations from the Best Practice Gap Analysis report or the most recent MOC audit. Meet with Customer Management to review Gaps and present Recommendations to move to Best Practices Get Agreement and set Path-Forward to Implement Best Practices for all future T/As Have Customer Management set up involvement with T/A Planning Team to Integrate Best Practices into Formal T/A Plan (Understand Scheduling, Timing, Equipment Plans, etc.) • •

•

•

•

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Communi cating the Best Practice T/A T/A Plans •

•

Communicate Best Practice T/A Plans to T/A Team, Operations, other necessary customer groups Shut Down / System Lay-up o Equipment Inspections o Cooling Tower Basin Cleaning o Exchanger Repair / Replacement Plans o Exchanger Cleaning Plans o Exchanger Hydrotesting Procedures o Cooling Tower Repairs o Recirculation Pump or Screen Repairs o Individual Exchanger Repassivation Plans o System Return to Service Plans, Timing o Start-up CW Recirculation Procedures o Exchanger Back flushing and return to service o System Repassivation o Transition back to Base Treatment Program o

Acti Ac ti on Items Item s to t o Acc A ccom om plis pl is h – Near Term Ter m T/A Planni Plan ning ng Determine Cooling System Volume (needed for accurate passivation o estimates on required treatment volumes and resulting economics Determine passivation program – Type and amount of products o needed to ensure sufficient product inventory to complete entire repassivation Communicate costs to appropriate budgetary personnel o Place chemical product orders to ensure products are on-site well o ahead of scheduled outage Determine T/A equipment needs (feed systems, inspection o equipment, safety equipment, PPE, camera and camera supplies, etc.) Place orders well in advance of T/A to ensure all necessary equipment is on-site before it is needed Completion of all associated MOC – chemical treatment, exchanger o cleaning, exchanger photography, etc. Plan Nalco manpower schedules to ensure 100% coverage o throughout the T/A Understand all customer paperwork requirements (safety, PPE, o MOC, permits, etc.) o Coordinate all customer-supplied resources (forklifts, cranes, etc. prior to T/A to ensure timely availability Determine schedule of process/water shutdown paying particular o attention to staggered shutdown of multiple units or unit components, as this will possibly require multiple lay-up applications 5


•

Acti on Items to Accom plis h – Long Term T/A Planning Exchangers Examples of Exchanger Design Changes o Hot Process By-pass to eliminate throttling of cooling water flow to o exchanger Installation of sacrificial anodes on all dissimilar metallurgy conditions o Upgrade of exchanger metallurgy – tubes or entire exchanger o Design improvements to meet current operational conditions – o change in # passes, tube size, installing macro-filters on water inlet, etc. Installation of back flush or air-rumble connections o Installation of strainer and/or diagonal screens for debris control o Installation of water sample points on the inlet and outlet of o exchangers Installation of taps for local temperature or pressure indicators o Installation of temperature indicators to run signal into DCS (either o process or water) Installation of block valves to allow isolation/by-pass of exchanger o Cooling Tower Issues with cooling tower (basin, tower fill, return line distribution o valves on top of deck, distribution nozzles, etc.) Identified issues with existing cooling water or make-up water piping o (size or location changes) o Repair of make up water or basin level control system Repair / calibration of flow meter in supply header o Pumps, Piping Installation of Cooling Water Return Line “Gas Hat” for monitoring o and sampling for presence of light hydrocarbons Installation of valves to isolate or back flush sections of recirculating o water piping Installation or repair of blowdown piping on return header piping o Chemical Feed, Storage, Monitoring and Control Installation of analyzer repairs / upgrades while system is out of o service (pH / acid feed system, conductivity control of blowdown, oxidizing biocide control, etc.) Chemical Storage Tank Upgrades – repair or replace tanks while o system is down to minimize potential impact on system performance

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System Lay-Up A critical step to protecting the cooling water system during the T/A is how the system lay-up is planned and executed. Prevention of corrosion, minimizing microbiological growth and minimizing the amount of foulants and chip scale are the primary focus of a good lay-up program. In order to fully understand the Best Practice recommendations that we make, we need to fully understand the mechanisms at work with respect to corrosion and corrosion inhibition.

Low Flow and Corrosion Inhibition Corrosion and corrosion control occur at the metal surface. Corrosive species and corrosion inhibitors move to the metal surface and corrosion products move away from the metal surface. In the corrosion/corrosion inhibition process the flow of water across the metal surface has a direct effect on the movement of corrosion inhibitors to the metal surface and the removal of corrosion products from the surface. The flowing water is broken into two parts, a thin diffusion boundary layer at the metal surface and the bulk solution. The thin diffusion layer’s thickness varies with flow rate. As flow increases the diffusion boundary layer’s thickness decreases and when flow rates decrease, the diffusion boundary layer’s thickness increases. Since the thin diffusion boundary is at the metal interface its thickness greatly influences the corrosion control process. Optimum flow velocities for mild steel exchangers in cooling service are generally set at 3-6 ft/sec. As the velocities increases over 6 ft./sec. the effects of erosion/corrosion become more pronounced. High velocity erosion/corrosion has a substantial increase in metal loss because the turbulent water has enough energy to destroy the protective corrosion films. When these films are destroyed the metal’s corrosion increases substantially. When flow velocities for mild steel exchangers decrease below 3ft/sec. corrosion rates also begin to increase. As flow decreases below 1 ft./sec. the corrosion rates become extremely high. This increase in corrosion is due to an increase in the thickness of the diffusion boundary layer and its relationship to mass transfer. Mass Transfer defines the transport of chemical species to the metal surface (corrosion inhibitors) and from the metal surface (corrosion products). Mass transfer brings the corrosion inhibitors through the diffusion boundary layer to the metal surface. Why does this flow/ boundary layer process become so important for corrosion control? It becomes important because the boundary layer thickness regulates the 7


amount of corrosion inhibitor that reaches the metal surface. As the boundary layer becomes thicker the concentration of corrosion inhibitor at the metal surface decreases. These mass transport values can be quantified by using Fick’s diffusion law treatments and Nernst’s diffusion layer treatments but for the application of corrosion inhibitors in cooling water treatments it simply means that as flow decreases below 3 ft/sec. the corrosion inhibitor concentration decreases at the metal surface. The metal surface in effect is “under-treated”. At flows < 1 ft./sec this under-treatment is extreme and corrosion rates are very high. Iron tuberculation is also very severe in low flow because the corrosion products cannot be transported from the metal surface, so they just deposit. Modern cooling water chemistry corrosion inhibition chemicals are used in cycled cooling water environments where there are high degrees of super-saturation, microbiological contamination and foulants. This high degree of super-saturation prevents most corrosion inhibitors from being increased to levels that would be high enough to be effective at the metal surface. In addition, microbiological and fouling control issues present additional difficulty. The “best treatment” for low flow corrosion is to take a mechanical approach and get velocities increased to the recommended 3-6 ft./sec. Mass Transfer Through Diffu sion Layer

N a lc o C h e m ic a l C o m p a n y

Note that the concentration of C obulk (bulk water corrosion inhibitor concentration) decreases to C osurface (corrosion inhibitor concentration at metal surface) Solid line - Fick’s treatment Dash Dotted line – Nernst treatment

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* More in depth reading on these treatments can be found in the Metals Handbook, Volume 13 Corrosion, Kinetics of Aqueous Corrosion.

System Lay-up Best Practices a. #1 Best Practice for Lay-up: “ Keep the Water Recircu lating” The absolute best method of Lay-up available is to not take a system out of service. This means keeping the cooling water recirculating with its normal velocity and normal treatment program. If only a small portion of a system will have to come down for a T/A, only remove from cooling water service the minimum amount of the system required to perform maintenance. By maintaining recirculating cooling water to the rest of the system, you remove the two most damaging mechanisms that can adversely impact the system. The first is stagnant water. In order for most of the normal chemical treatment programs to perform, a vital component is the water’s velocity. The graph below illustrates the relationship between water velocity and corrosion.

N alco Chemical C ompan y Nalco Com pany

In the graph, the flat “bottom of the horseshoe” is the 3-6 ft/sec (0.305 m/s) velocity range, ideal for minimal corrosion rates. Also note that as the flow 9


increases above the 6-ft./sec. corrosion increases due to erosion corrosion. As flow decreases below the 3-ft/sec. corrosion decreases due to diffusion layer issues (under treatment). In order to fully protect a system when the water recirculation is stopped, the system must be treated one of two ways. Choosing which method is largely based on the primary problem issues associated with that system.

b. #2 Best Practice for Lay-up: Wet Lay-up If the system suffers from fouling and chip scale issues, especially after previous outages, this is the method your customer should use. It is also a preferred method when there are sections of piping that cannot be fully drained (esp. underground piping) or if your system is greater than 15 years old. An internal, visual inspection of the recirculation piping is seldom, if ever performed by the customer. The old saying “out of sight, out of mind” is extremely accurate. Since this equipment is seldom visually inspected, our customers often don’t think of protecting this piping. After all, this pipe is usually as old as the unit itself. We have to discuss with the customer the corrosive damage that can be done with stagnant water. Also as discussed previously, any water that remains stagnant in the cooling water system will become very corrosive if left untreated. The normal chemical treatment program will not provide corrosion inhibition during periods of stagnant water flow. The only way to minimize corrosion during stagnant water situations is to treat the systems with very high dosages of specific chemistries. We also have to discuss the increased potential for fouling when a system is allowed to sit dry for weeks at a time. What occurs is a drying out of the existing deposits on the piping. As these become dry and brittle, they crack and easily separate from the piping surface. These deposit pieces will become system foulants if not removed from the system. The proper Wet Lay-up procedure for ensuring corrosion inhibition during a system outage is found in the Passivation Procedures Section.

c. #2A Best Practi ce for Lay-up: Drain, Dry and Purge The “other” Best Practice for proper lay up of a cooling water system prior to an outage is the Drain, Dry and Purge. This method is designed to prevent corrosion by assuring the system is free of any water. This is the preferred method where the system is young (< 15 years old) or if the primary issue at the unit is corrosion. 10


Younger systems will likely not have had sufficient time for the cooling water recirculation lines to have experienced significant corrosion, deposition and fouling. Due to these lines being relatively “clean” of these potential foulants, these recirculation lines are not likely to be a possible source for post-T/A chip scale and other foulants at start-up. It is also important that the system have not had any significant problems with corrosion. This will also ensure “clean” piping that will not be a source for post-T/A chip scale. These criteria are inplace to prevent start-up issues with fouling at the cooling water exchangers. If the Drain, Dry, Purge method is used on systems that do not fit these criteria, there is an increased potential for exchanger fouling during and after startup. When the system is allowed to dry out and sit stagnant for a period of time, the existing metal surface will dry and become less adherent to the metal surface. All deposits, corrosion tubercles or cracks in the piping surface will provide the source for later foulants. When the system’s recirculation water is restarted, these deposits and weaknesses in the piping surface will allow this material to be dislodged from its source location. When this happens, the material becomes migratory chip scale and will deposit and settle out in an area of low flow. Often, this is in the first pass of a cooling water exchanger. These migratory foulants will deposit in the low flows of the channel head, on the tube sheet and inside the tubes. This can obstruct or completely block the water flow through the tube, leading to future problems with heat transfer, fouling and corrosion. The capability to dry and purge a cooling water system is extremely sitespecific. Procedures to accomplish this will have to be developed specifically for each cooling water system. By performing a Drain, Dry and Purge procedure, you are protecting the metal surfaces by keeping moisture out of the equipment. Purging the system with either nitrogen or plant air will help ensure the equipment remains free of moisture. It should be noted that there is often resistance to the use of nitrogen due to the hazards associated with the use of this gas. These should be fully discussed with the customer to ensure it is the best method for that site and that all proper steps are taken to ensure personnel safety. The use of plant air can also perform well if the air is also free of moisture.

d. #3 Best Practice for Lay-up: Drain and Dry This is the least preferred lay-up method, yet most commonly employed due to its ease of implementation. Often the customer either does not want to deal with the time and effort of purging the system, or they are not adequately equipped to perform a purge on the system.

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If the customer cannot perform a system purge and is not willing to perform a wet lay-up, then this is the last available method to minimize system corrosion. The key to this procedure is to ensure, check and recheck that all of the system is drained and dried. Any remaining water in the system will cause localized corrosion. If the customer wants to perform a Drain and Dry Lay-up but you are aware of sections of the cooling water system that can not be drained (i.e., underground piping), then you should discuss the potential impacts on these areas and what options are available to minimize or remove this risk. It will also be important to ensure the customer understands the impact drying the system will have on the post-T/A start up. Ensuring that procedures are inplace to minimize the impact of the chip scale that will be generated is key to avoiding future problems. These post-T/A start-up procedures are included in the later section of this workbook (page 51).

Passiv ation Procedures a. Chart – Passi vation Options Review

Nalco Pretreatment Options Pretreatment

pH Range Program Requirements / Conditions

MoO4/PSO based

#1 Best

MoO4

100 ppm

PSO

50 ppm

Polymer

21 ppm

Azol e

15ppm

7.8-8.5

Best program overcomes issues operating with heat load and MB Time frame ~48 - 72 hours control options (can use either bleach No Calcium Required or gas Cl2). Can operate over longer Can operate with a heat load time frames with good iron Can initiate regular tr eatment prog ram at management . MoO4 can deactivat e any time during passivation Pits. Compatible with all treatment programs.

7.8-8.5

Good program overcomes issues with Time frame ~48 - 72 hours heat load, Operating over 48 hours No Calcium Required increases microbial growth concerns, Can operate with a heat load need non-oxidizing biocide feed Can initiate regular tr eatment prog ram at during passivation, cannot u se gas any time during passivation Cl2 during passivation. Compatible with all treatment programs.

NO2/PSO based #2 Very Good

NO2

1000 ppm

PSO

50 ppm

Polymer

21 ppm

Azol e

15ppm

Nalprep III - 2500 ppm

#3 Good

PolyPO4

500 ppm

TT

30 ppm

Polymer

46 ppm

Surfactant

40 ppm

Comments

6.5-7.5

Time frame 24-48 hours Requires 100 ppm Ca as CaO3 minimum No heat load, Acid Feed Need to blowdow n to <10 ppm PO4 prior to start of heat load

NO HEAT Load!! Operating over 48 hours increases Polyphosphate reversion and precipitation of calcium or iron phosphates (Fe Limit <3.0 ppm), not suitable for long-term operation. Not compatible with treatment programs. Only use for individual exchanger passivations.

Notes 1) All pretreatment procedures require flushing of the system to m inimize iron levels prior to addition of passivation products 2) Iron management controls the ability to cycle the system. The goal is to maintain less than 3.0 ppm during passivation stage 3) MoO4/PSO and NO2/PSO are compatible with all treatment programs and no need to blowdown prior to start of maintenance program. 4) Refer to Nalco documents on correct overall procedures, dosages and testing methods

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PSO Dosage Chart

Inhib itor (MoO4 and PSO) Dosage Chart

PH

Hottest Water Temperature

Ca as CaCO3

7.0

7.5

8.0

8.5

Inhibitor level ppm <75

75-100

100-120

>120

<50

100

100

80

80

MoO4/PSO

125/60

150/75

200/100

50-100

100

80

50

50

100-200

80

60

50

50

>200

80

60

50

50

100/50

PSO as Active PolyPO4 Dosage Guide (for Nalprep III) PH Ca as CaCO3

7.0

7.5

8.0

8.5

<50

N/A

N/A

N/A

N/A

50-100

N/A

N/A

N/A

N/A

100-200

500

500

400

300

>200 400 400 Off-Line application only, no heat load

300

250

b. Pre- T/A – Wet Storage Lay Up Open Recircu lating Cooling Systems Significant attention is routinely given to treatment and control of operating cooling water systems. Often, however, less focus is provided to systems once they come down for turnaround (T/A). Unfortunately, system reliability can be substantially compromised during these periods. Some of the related concerns include: • • • • • •

Stagnant water corrosion Flash (atmospheric) corrosion Aerobic (slime-forming) bacteria infection Anaerobic (corrosive) bacteria infection Drying/cracking of piping corrosion products – chip scale Iron buildup and deposit formation

The damage resulting in such situations can be very significant affecting the long-term equipment life as well as premature heat transfer problems. The purpose of this document is to provide Best-in-Class procedures for proper layup of cooling water during T/A downtime. Wet lay-up of system piping is preferred to “dry lay-up” where water is evacuated from the piping. The primary reason for this is drying and subsequent cracking of piping tuberculation which can often lead to chip-scale fouling of exchangers upon start-up. Further, it is more difficult to protect “moist” metal from corrosion during the lay-up period. If “dry lay-up” is required, see Best-in-Class recommendations on this subject. 13


Passiv ation Product Selection When performing the various passivation procedures, there are a large number of products that can be used to deliver the various chemical components. This includes both single function products and blended, multi-functional products. Be sure you understand the products, their components and their percent actives. This is critically important to ensure the correct dosages and economics are calculated. Also remember that while blended products may offer the advantage of fewer products to handle, they offer less treatment flexibility and will likely be more expensive. Listed below are some general product names that are commonly used around the world. Some regions use different product names, so please consult your region’s select product list. If you have any questions or concerns, please consult the CPP or contact your regional ITC or marketing personnel for assistance. Single Function Products Molybdate – 7357 PSO – 3DT180 (untraced), 3DT179 (traced) TSHP – 3DT190 Azole – 3DT198, 1336, 73181 (TT); 3DT199, 73199 – BZT; 3DT197 (new azole) Microbio Dispersants / Detergents – 73550, 7348 Non-oxidizing Biocides – 7338 (gluteraldehyde), 7330 (isothiazoline) • • • •

• •

Blended, Multi -Functi on Product Moly, PSO, TT, HSP, Surfactant - 3DT701 •

Step 1 – System Preparation Before high-level corrosion inhibitors and biocide are added to the open recirculating cooling system it must have its microbiological and Total Dissolved Solids (TDS) levels lowered as much as possible. Microbiological levels need to be at a minimum to reduce the demand on the wet storage biocide (nonoxidizing biocides have maximum application limits in open recirculating cooling systems) and reduce the source for biological inoculation during TAR. The minimal TDS levels are needed to lower the corrosion potential of the water and also allow the system’s blowdown to be minimized or blocked prior to shutdown (maintains the inhibitors at their applied level). 5 Days prior to shu t down: 1. Begin addition of biodispersant @ 10-20 ppm (N-73550) – Slug feed if not set up for continuous injection of the biodispersant. Note: If biodispersant is included in the routine treatment program continue the program but adjust feed for decreased cycles and the increased 20 ppm feed level. Caution – remember the N-73550 can foam if overdosed, slowly increase the feed rate 14


2.

3.

4.

5.

6.

to 20 ppm or until an acceptable level of foam is generated. Increase the free chlorine levels to 0.5 –1.0 ppm for 12-24 hours. After the high level chlorine, begin increased blowdown to lower the cooling tower cycles to 2 cycles or as close to 2 as possible (if makeup restricted). Add 250* ppm of Nalco 7338 (Glutaraldehyde) . The goal is to maximize deposition prior to the N-7338 addition to minimize the initial demand for the biocide so it can maintain activity longer in the system. * The maximum N7338 dose permitted by the label is 250 ppm. Maintain routine treatment dosages during the blowdown period to and reduce free chlorine @ 0.3-0.6 ppm. Once at 2 cycles, increase product dosages by 50%. Additionally, it is critical to maintain oxidizing biocide control (no loss of feed) to keep the system’s microbiological activity at a minimum prior to system shutdown. Systems that don’t used chlorine as their primary biocide need to deploy their biocide program in a manner that will have the system prepared for wet lay-up. Systems that use stabilized halogens and/or non-oxidizing biocides should apply non-oxidizing biocide to the system on a daily basis. Biocide levels going to the waste plant need to be calculated. As an example, if there are a few small cooling systems discharging into a large waste facility the additional biocide will not present an impact. A fast killing, rapid hydrolyzing (detoxify) non-oxidizing biocide (DBNPA) can be used during this system preparation phase if the normally applied biocide or Glutaraldehyde presents a problem. All biocides, oxidizing and non-oxidizing, can be deactivated by sodium bisulfite if needed. Dosages can be calculated for the stream going to waste along with biocide residual testing. N-7408 (uncatalyzed sodium bisulfite) is applied based on ppm/ppm of biocide to be deactivated. The reaction(s) are extremely fast. It is recommended that the deactivation take place as close to the waste inlet as possible. This allows maximum deactivation of the biocides through natural degradation prior to the point of injection. There are many locations upon which have multiple processing units tied to one cooling tower that do not go into Turn Around at the same time. The cooling tower does not shut down but the units are down. In these cases, the unit going into T/A still needs to go into a low corrosive condition by lowering cycles of concentration to minimize the level of Chloride and Sulfate in the water, increase the pH to at least 8.0 and with increased inhibitor dosages. The ortho PO 4 level may not be able to be increased due to potential scaling conditions in the other operating units. However, the use of PSO and MoO 4 will not precipitate in the hot systems and should be used. Other inhibitors are not recommended (i.e. like Nitrite due to MB concerns in the other operating units or PO 4 due to scale formation). At least 50 ppm of MoO 4 and 100 ppm of PSO should be slugged to the system and adequately mixed to provide corrosion protection. Prior to lowering the cycles of concentration, a high level shock of Cl 2 with subsequent follow up with a non oxidizing biocide is required. 15


Step 2 – System Lay-up Procedur e After system preparation, the microbiological activity and TDS concentration will be at a minimum and the system will then be ready for wet lay-up. Once the lay-up is started, the system blowdown will be blocked in to prevent accidental draining of the basin. Cooling water TDS levels will begin to cycle up based on the heat load. This is normal and expected. Conductivity should be run every six hours, if the system doesn’t have continuous conductivity monitoring, to plot the increase rate in TDS. If delays are experience in the shutdown process (>24 hours) a small amount of blowdown may be needed if the system is still under full heat load. Additional biocide feed will be required if delay is > 3 days. If there is no heat load (or negligible load) during a delay, blowdown will not be needed. 24 hours prior to anticipated system shutdown 1.

Block in all sources of “controllable” blowdown

2.

Stop Biodispersant feed

3.

Stop normal phosphate inhibitor chemical feed

4.

Stop Chlorine feed

5.

Set pH control for 8.0-8.5 range

6.

Add 400 ppm of Nalco 7338 (Glutaraldehyde)

7.

Add 800 ppm of Nalco 7357 (216 ppm MoO 4)

8.

Add 350 ppm of Nalco 3DT-180 (105 ppm PSO)

9.

Add 50 ppm of Nalco 3DT198 (25 ppm Na-TT) or 3DT199 (20 ppm NaBZT)

10. Continue cooling system circulation with inhibitors (minimum time 12 hours) 11. Open any dead legs or blocked-in lines just enough to displace existing water with “lay-up” water. DO NOT ALOOW EXCESS WATER LOSS AS THIS WILL DIMINISH CHEMICAL CONCENTRATIONS! 12. Stop normal cooling water dispersant chemical just before system shutdown 13. Test all inhibitor chemical levels and non-oxidizing biocide levels and adjust as needed. 14. Stop recirculation and block in cooling system 15. Loss of cooling system water must be minimized especially in exchangers. 16. Preserve treatment inhibitor concentration. 17. Prevent corrosion at the air–water interface if down for extended periods. 16


Addi ti onal Cons ideratio ns 1. If the unit to be in T/A is part of a large cooling water system that will still be in operation for other processing units, it is imperative that only the MoO4 and PSO be dosed to the cooling water prior to shut down. While the entire loop will see the high treatment levels, it will only add to the current corrosion program and not produce any adverse effects. High levels of phosphate will not be as protective as the Molybdate and PSO and may cause an issue with fouling if added to the cooling water system after the T/A is over. Nitrite is not as option due to the potential for the cooling water to leak into the unit in T/A and cause increased MB growth, especially if the unit is not clean to begin with. The addition of nitrite to the operating cooling water system may increase MB formation if biocide control is poor. 2. If system is to be down for >2 months, supplemental or interim steps may be required to insure long-term protection. The nature of this supplement will depend on the length of down-time, ability to “bump circulation, etc. Advise your Nalco representative if an expended down-time is anticipated. 3. If sections of the system are to be blocked-in before water flow is terminated, notify your Nalco representative. Preemptive treatment prior to the scheduling above may be required to protect these parts of the system. 4. If parts of the system are to be drained during the T/A, contact your Nalco representative. These parts will become subject to “atmospheric” corrosion if not addressed. Remedies may include desiccation, nitrogen blanketing, or other protective steps. Step 3 – System Restart A. Clean calibrate all control probes, detectors, i.e. pH, Trasar, Conductivity, etc. B. The start-up water chemistry tests prior to recirculation. a. Molybdate - Hach Method 8036 (Mercaptoacetic Acid Method 0.3-40 ppm) b. Azole c. pH d. Total microbiological count e. Sulfate reducer counts f. Active Glutaraldehyde level - (GLUTATECT – WT by Alden Scientific) g. Conductivity h. Active polymer i. Total iron (digested) j. Total copper (digested) k. PSO (Hach method 8007 – UV Light method or Method 8190 acid per sulfate digestion). C.

Active Glutaraldehyde Level (prior to recirculation once recirculation is established) 17


a. If the active level is below the maximum established level for discharge to waste treatment then sulfite neutralization will not be needed. b. If the active level is > than level for discharge then N-7408 (uncatalyzed sodium bisulfite solution) should be added at 10ppm/ppm active Glutaraldehyde. This will deactivate the Glutaraldehyde to < 2 ppm. c. Glutaraldehyde level should be tested prior to the waste plant and as close as possible to waste plant inlet. This sample point monitors the amount that would enter the waste plant, allowing for maximum uptake prior to the waste facility D.

Total Microbiological counts (prior to recirculation and once recirculation is established) collect sample for MB testing then add 200 ppm of N-7338 during start up, then follow the recommended treatment protocol depending upon the results of the MB testing. a. < 1000 – resume normal chlorine treatment with biodispersant b. 10,000 – resume normal chlorine treatment with biodispersant + application of 200 ppm Nalco 7338 biocide c. 100,000 – resume normal chlorine treatment with biodispersant + application of 200 ppm Nalco 7338 biocide. Retest in 24 hours and reapply if > 10,000 counts.

E.

Sulfate Reducers – Positive detection = application of 200 ppm Nalco 7338 biocide. Retest in 24 hours and reapply Nalco 7338 with positive detection. F. Begin Plant cooling system startup procedures, backflush exchangers, blowdown for iron control, etc. G. Plan to test water chemistry routinely until equipment is back in service. H. Begin Nalco All Soluble Startup Passivation procedure. Note: If the unit is equipped with steam driven pumps, use these first (prior to electric driven pumps). These pumps should be capable of ramping up to speed in a more controlled manor than electric driven pumps. This will minimize any shock conveyed to the system pimping that might dislodge any chip scale or other debris that can plug the exchangers.

18

TurnAround Best Practices Energy Services Division Lay-Up/Start-Up Log Sheet Plant: System: Date

-5

-4

-3

-2

-1

TAR TAR TAR TAR TAR TAR TAR

+1

+2

+3

+4

+5

Preparation Phase Biodispersant Feed (gals) Nalco 7338 Feed (gals) Free Chlorine Residual (ppm) Cycles of Concentration Feed (gals/day) Feed (gals/day) Feed (gals/day) Lay-Up Phase Water Loss Blocked In Biodispersant Feed Discontinued Phosphate Feed Discontinued Chlorine Feed Discontinued pH Level N-7338 Feed (gals) N-7357Feed (gals) 3DT-180 Feed (gals) N-73181 Feed (gals) Dead Legs Flushed Water Circulation for 12 hrs min Dispersant Feed Discontinued Chemical Tests (ppm) Glutaraldehyde MoO4 PSO Azole Product Feed Adjustments N-7338 Feed (gals) N-7357Feed (gals) 3DT-180 Feed (gals) N-73181 Feed (gals) Circulation Stopped Start-Up Phase Circulation Started Chemical Tests (ppm) Glutaraldehyde MoO4 PSO Azole Active Polymer Total Bacteria Count Anaerobic Bacteria Count pH Conductivity Total Iron Total Copper N-7338 Feed (gals) Blowdown Rate (gp m) Exchangers Backwashed Corrator Reading Coupons Installed

19


c.

Post T/A – Molybd ate / PSO Passi vatio n After a chemical or mechanical cleaning, turnaround, or emergency or longterm lay-up, it is important to pre-treat or passivate carbon steel heat exchangers and supply piping to minimize flash corrosion and/or deposit formation. Corrosion under deposits can lead to the development of localized corrosion cells or pitting. There are 3 major areas of concern after cleanings, lay-ups or turnarounds: • • •

Control of debris that can block cooling water flow Minimization of deposition and localized corrosion Minimization of microbiological fouling.

Careful attention to the procedures described below will help minimize these problems. Phase 1 Back fl ushin g and high-level blowdow n Precautions must be taken after a cleaning, turnaround or lay-up event to effectively flush accumulated debris, mud, silt, etc. from the cooling system. This will minimize the potential for exchanger fouling and plugging as a result of chip scale and other debris being transported throughout the system piping. The object of the back flushing and blowdown is to ensure plant reliability by minimizing cooling water corrosion and fouling during start-up. In many systems, chip scale and iron deposition pose the greatest threat to tube and tube sheet plugging during start-ups. The best method for dealing with this issue is to use either a strainer on the inlet side of the exchangers and/or insure each exchanger that is on the primary cooling water circuit has the capability to be back flushed. This is particularly important for those exchangers that sit at the end of the cooling water supply piping that can accumulate trash. Suggested back flushi ng and blowdow n procedure 1. When the make-up line is put back into service, the initial slug of water may contain high levels of chip scale, mud and iron. This initial slug should be diverted from the tower basin. If after the initial slug, any mud or high iron levels are introduced into the basin, the basin can be overflowed to wash that out before recirculation begins. 2. If the unit is equipped with steam driven pumps, use these first (prior to electric driven pumps). These pumps should be capable of ramping up to speed in a more controlled manor than electric driven pumps. This will minimize any shock conveyed to the system piping that might dislodge any chip scale. 20


3. As circulation begins, the water flow should be directed to exchangers that are equipped with strainers to filter out any chip scale. If possible exchangers should be blocked in and the flow of cooling water should be directed through the system supply piping and flushed prior to opening any of the blocked-in exchangers. 4. Back flush all exchangers that were exposed to the initial flow of water vigorously for 20-30 minutes, and continue back flushing until all evidence of chip scale has subsided. 5. The remaining exchangers (those without strainers on the primary cooling water service) should be put into service on a staggered basis. Close the outlet side valve. Open the back flush nozzle to allow flushing of the lines up to the exchangers. When that runs, clear back flush the exchangers. When the water runs clear, close the back flush valve and open the inlet valve. If possible, install inlet and outlet pressure gauges to monitor pressure drop. After all the exchangers have been put into circulation and the back flush is complete, begin the microbial cleaning and passivation procedures. • •

• •

•

•

Phase 2 Application of t he 3DTRASAR all-solubl e inhibi tor p rogram The goal of the PSO/molybdate based passivation program is to apply a high level of inhibitor to the metal surface to inhibit flash corrosion and minimize deposition. Deposits on new heat exchange bundles can lead to localized corrosion and significantly shorten bundle life. Both Molybdate and PSO are highly soluble and will not precipitate with iron-based deposits. The use of tagged high stress polymer (THSP) will help control iron based deposits and a high level of azole will help passivate admiralty or other copper alloy tube bundles and chelate soluble copper in the water as the system is returned to operational status. Passivation Product Selection When performing the various passivation procedures, there are a large number of products that can be used to deliver the various chemical components. This includes both single function products and blended, multifunctional products. Be sure you understand the products, their components and their percent actives. This is critically important to ensure the correct dosages and economics are calculated. Also remember that while blended products may offer the advantage of fewer products to handle, they offer less treatment flexibility and will likely be more expensive. 21


Listed below are some general product names that are commonly used around the world. Some regions use different product names, so please consult your region’s select product list. If you have any questions or concerns, please consult the CPP or contact your regional ITC or marketing personnel for assistance. Single Function Products Molybdate – 7357 PSO – 3DT180 (untraced), 3DT179 (traced) TSHP – 3DT190 Azole – 3DT198, 1336, 73181 (TT); 3DT199, 73199 – BZT; 3DT197 (new azole) Microbio Dispersants / Detergents – 73550, 7348 Non-oxidizing Biocides – 7338 (gluteraldehyde), 7330 (isothiazoline) Blended, Multi-Function Product s Moly, PSO, TT, HSP, Surfactant - 3DT701 The passivation pro cess should pr oceed as follows 1.

Recalibrate all 3DTRASAR)

analyzers

(pH,

conductivity,

ORP,

TRASAR

and

2.

Collect a cooling water sample. Analyze for pH, iron, copper, total hardness/calcium, and microbiological control with Easi-cults or equivalent.

3.

Begin circulating the water to the main lines only, and adjust the pH within a range of 7.5 - 8.5. (In general operating at the higher end of the pH range will help minimize corrosion and aid the passivation process).

4.

Maintain free halogen residual levels with a bromine or chlorine based chemistry at 0.2- 0.4 ppm TRO and/or use a non-oxidizing chemistry such as 7338 at 200 ppm. If the system has been stagnant for an extended period of time, you may need to complete a microbiological cleanup prior to beginning the passivation procedure.

5.

Dose the system with 200 ppm of N-7338 and 10 ppm of N-73550. Monitor the N-7338 actives with the GlutatTect WT test kit, looking for a minimum of 70 ppm active and checking on the consumption compared to what was fed. A minimum of 48 hours with 70 ppm active should be maintained. Chlorine should be maintained at 0.2 – 0.6 ppm free after the initial 48 hours. Confirm both general microbiological activity is minimal and SRB activity is nonexistent.

6.

As in all pre-treatment work, addition of the passivation chemicals must be accomplished as soon as possible after heat exchangers have been cleaned to minimize flash corrosion. 22


7.

Once the system has been pH adjusted, begin adding the chemicals specified in Table 1 to the pump basin. Watch for foaming when adding the 73550. You may want to have anti-foam on site. If the system is small, you may consider using Nalco 3DT701, which is a single, drum blend of all the chemicals given in Table 1. Feed 1250 ppm of Nalco 3DT701.

8.

The initial PSO level will be measured as organic phosphate and should be about ~15- 18 ppm (higher levels will not cause problem).

9.

Open all exchangers and circulate the passivation chemicals. Maintain a circulation velocity of at least 3 feet/sec through the heat exchangers.

10. After this treatment has been in operation, typically for 3-5 days, clean all strainers/filters that may be in-line with the heat exchangers. 11. Resume all chemical treatments at dosages shown in Table 2 and initiate the normal treatment program and control ranges (pH, Conductivity, etc) When using Nalco 3DT701, the system is usually returned to normal cooling system operation after 24-48 hours of circulation. Table 2 dosages are not used. 12. Continue this treatment regime typically for 2 to 4 weeks, shorter times may be used. This treatment approach is compatible with all 3D TRASAR® programs. The normal 3D TRASAR program should be started during this period with the resumption of the heat load to the tower. 13. Perform daily testing of the pH, iron, copper, active polymer, TRASAR, molybdate, azole, conductivity, total/calcium hardness and microbio activity 14. Blowdown should be adjusted to maintain iron (Fe) levels less than 2.03.0 ppm while maintaining the dosages given in Table 2. This is necessary to minimize the potential for iron fouling in the system. 15. After 2 to 4 weeks, turn off the passivation chemicals and maintain the normal cooling tower treatment program after iron levels drop below 2 ppm. The system does not need to be drained or flushed to rid the system of the pretreatment chemical program.

23


Table 1. Passivation Chemicals--start up dosages Description Product Dosage Product 7357 Molybdate 364 ppm 3DT190 Tagged HSP 60 ppm 3DT199 Sodium BZT 40 ppm 73550 Surfactant 10 ppm 3DT180 PSO 160 3DT701 Blend of above non 1250 ppm biocide components TRO or 7338 biocide 0.2-0.4 TRO or 200 ppm

Table 2. Passi vation Chemicals--dosages after start-up Product Description Product Dosage 7357 Molybdate 182 ppm 3DT190 Tagged HSP 50 ppm 3DT199 Sodium BZT 40 73550 surfactant 10 ppm TRO or 7338 biocide 0.2-0.4 TRO or 100 ppm 3DT180 PSO 160

Control Parameter 100 ppm as MoO 4 21 ppm active polymer 13.4 ppm as azole 5 ppm as active 50 ppm as PSO Active Maintain for 24-48 hours 90 ppm active

Control Parameter 50 ppm as MoO 4 * 18 ppm active polymer 13.4 ppm as azole 5 ppm as active 45 ppm active 50 ppm as PSO Active*

* Molybdate interferes with the certain iron tests. The following interference levels for various Hach iron tests are given below. Hach FerroVer (Method 8008) no interference at <80 ppm MoO 4 (range 0.02 –3.0 ppm Fe) Hach TPTZ (Method 8112) MoO4 at 5 ppm interferes (Range 0.012 – 1.8 ppm Fe) Hach FerroMo (Method 8365) eliminates high MoO4 interference (Range 0.01 – 1.8 ppm Fe) Hach 1,10-Phenanthroline (Unicells) MoO4 not listed as an interference (Range 0.1 – 5.0 ppm Fe)

Phase 3 Transiti on t o on-goin g 3DTRASAR coolin g water pro gram 1. After the high-level passivation program is complete, adjust system pH to normal operating level with return of heat load. 2. Balance the blowdown rate to keep the iron level less than 1-2 ppm . 3. If the cooling water treatment program uses orthophosphate, do not raise the orthophosphate level up to the normal operating target until the iron level decreases below 1-2 ppm. 4. Once the iron level is below 1 ppm, increase cycles at equal increments to return to normal dosage levels. 5. Monitor corrosion rates on NCM during the return to heat load.

24


Literature is available from the CPP on 3DT701 and on the 3D TRASAR Passivation Program (PR 272). Passivation Program Contingency Guide Good control of every cooling water treatment program is necessary to achieve desired results. Problems, however, can arise with even the best control. The contingency guide shown in Table 3 will assist you in correcting problems should they occur. It should also be used in outlining what actions your customers should take when control testing indicates a problem with the pretreatment program.

Table 3. Problem Contingency Guide Problem Result pH rises above 8.5 Potential for increased iron deposition or Ca 3(PO4)2 formation exists if back to normal treatment levels Initial slug of treatment Insufficient chemical to too low effectively complete passivation. Excessive foam Pump cavitation; possible (this is an unlikely aesthetic problem in plant problem) or community. Temporary system Stagnant treatment; shutdown due to settling of suspended mechanical problems. debris. Overfeed of sulfuric pH goes below 6.5 acid.

Corrective Actio n Add sulfuric acid to reduce pH to 7.5 to 8.5 or normal operating levels

Add additional

Add small increments of NALCO 71D5plus or similar antifoam until foam height reaches an acceptable level. Debris will be resuspended on system start-up. Increase blowdown if there is highly turbid water If the problem is caught quickly, add soda ash to elevate pH. If the problem was not noticed soon (which should not be the case during the pretreatment), blowdown the tower heavily, and add make-up to regain pH. Re-establish highlevel passivation chemistry.

Words of Caution In the long term, successful system operation will be largely determined by your attention to in-plant training. Properly trained plant personnel will insure that Nalco recommended chemical/mechanical treatment programs are being operated as prescribed. Listed below are a few areas where additional attention is warranted. 1. Iron Levels at Start Up It is important to note that iron will be “picked up” into the re-circulating water at startup. The “normal” level seen at startup are usually less than 10 25


ppm. The iron is removed from the system through blowdown. Systems with iron levels > 6 ppm will need to operate at low cycles to quickly remove the iron from the system. Systems with heavy iron contamination will consume more products because of the high blowdown. The product calculations should be done assuming the system will operate @ 2 cycles during the initial 48 hour period. 2. Highly Stressed Conditions Some systems being returned to service may be classified as a “ high stressed” startup. A “high stressed” system is one that: 1. 2. 3.

experienced a severe acid excursion prior to shutdown contains equipment that has been sitting for long periods in the yard (no pre-cleaning or pre-treating) has contained standing water (stagnant) in system piping for greater than 3 weeks

Greater levels of iron “pickup” (~60-100 ppm) will be expected from these “high stressed” situations. These systems should have product consumption calculated for 5 days operating @ 2 cycles. 3. Ensure Suffic ient Passivation Chemicals Inventory A frequently encountered problem during passivation is having insufficient chemical inventory to properly complete the process. This compromises the effectiveness. Prior to start up ensure adequate inventor y of chemical treatment prod ucts are located on-sit e. 4. Do Not Overfeed Dispersant to Sup ply Targeted PSO Do not substitute the use of 3DT191 or 3DT192 as the sole source of PSO for the pretreatment program. This causes an over-feed of polymer which can be corrosive to both carbon steel and admiralty brass metallurgy. If you want to use a THSP/PSO blended product, use it to supply the targeted level of dispersant. Supplement the treatment with a PSO-only product (3DT180) to get the PSO dosage to the targeted level. 5. When in doubt, Ask for Help! There is no substitute for experience. When planning these system repassivations, discuss with more experienced Nalco personnel, your District Manager, Regional marketing or ITC personnel. They can offer you advice and suggestions on what to watch and how to react to unexpected events.

26


d.

Post T/A - Nitri te/PSO Passi vation Procedure Phase 1 Backflushing and High Level Blowdown to Control Debris Fouling Precautions must be taken after a Turn Around or lay up event to effectively flush accumulated debris, chip scale, mud, silt, etc. from the cooling system. This will minimize the potential for exchanger fouling and plugging debris that will be transported throughout the system piping. The object is to ensure plant reliability by minimizing cooling water corrosion and fouling during start-ups. In many system, chip scale and iron deposition pose the greatest threat to tube and tube sheet plugging during start-ups. The best methods for dealing with this issue is to use either strainers on the inlet side of the exchangers and/or ensure each exchanger that is on the primary cooling water circuit have the capability to be back flushed to remove any debris on the inlet tubesheet. This is particularly important for those exchangers that sit at the end of the cooling water supply piping that can accumulate trash, chip scale, mud and silt, etc. Procedure 1. When the make up line is put back into service, the initial slug of water may contain high levels of chip scale, mud and iron. If possible, this initial slug should be diverted from the tower basin. If even after the initial slug, any mud or high iron levels introduced into the basin, the basin may be overflowed to wash that out before recirculation begins. 2. If the unit is equipped with steam driven pumps, use these first (prior to electric driven pumps). These pumps should be capable of ramping up to speed in a more controlled manor than electric driven pumps. This will minimize any shock conveyed to the system pimping that might dislodge any chip scale or other debris that can plug the exchangers. 3. As circulation begins, the water flow should be directed to exchangers that are equipped with strainers or traps to filter out any chip scale. If possible, exchangers should be blocked in and the flow of cooling water should be directed through the system supply piping and flushed prior to opening any of the blocked in exchangers. This is of particular importance for those exchangers that are positioned at the end of the supply piping. 4. Backflush all exchangers vigorously for a minimum of 20-30 minutes that were exposed to the initial flow of water and continue backflushing until all evidence of chip scale has subsided. 5. The remaining exchangers (those without strainers on the primary cooling water service) should be put into service on a staggered basis. Close the outlet side valve. Open the backflush nozzle to allow flushing of the lines up to the exchangers. When that runs clear back flush the exchangers. When the water runs clear, close the back flush valve and open the inlet valve. If possible install inlet and outlet pressure gauges to monitor 27


pressure drop across exchangers as they are put into service. If backflush valving does not exist, open to drain the CW supply piping for 15 minutes before establishing flow to those exchangers. 6. Very good microbial control is needed during the passivation with Nitrite. Stagnant water, during the TAR, can rapidly allow MB growth, and a microbiological cleanup prior to beginning the passivation procedure is needed. a. Re-establish Chlorine feed and maintained at 0.5 – 1.0 ppm free for the initial 24-48 hours of flushing. Confirm both general MB activity is minimal and SRB activity is non-existent. To aid in MB control add 510 ppm of N-73550. (Note- The addition of N-73550 may generate some foam so dose the system slowly). b. With the use of gas chlorination in this water it will be important to initiate pH control maintaining a pH >7.8. 7. After all the exchangers have been put into circulation and the backflush is complete, check the iron levels in the water, as the chlorination step is likely to cause an increase in iron and begin heavy blowdown until iron levels are less than 3 ppm. Prior to the addition of the Pretreatment products, stop the chlorination and dose the system with 200 ppm of N-7338 and 10 ppm of N73550. Monitor the N-7338 actives with the GlutatTect WT test kit, looking for a minimum of 70 ppm active and checking on the consumption compared to what was fed. A minimum of 48 hours with 70 ppm active should be maintained. Phase 2 System Repassiv ation The goal of the PSO/Nitrite based passivation program is to apply a high level of inhibitor the metal surface to inhibit flash corrosion and minimize deposition. Deposits on new bundles can lead to localized corrosion and significantly shorten bundle life. Both Nitrite and PSO are highly soluble and will not precipitate with iron-based deposits. The use of HSP will help control iron based deposits and a high level of azole will help passivate Admiralty bundles and chelate soluble copper in the water as the system is returned to operational status. The passivation pro cess proceeds as foll ows: 1. Clean and Recalibrate all analyzers (pH, conductivity, ORP, TRASAR, 3D TRASAR, etc.) 2. Collect a cooling water sample. Analyze for pH, iron, copper, total hardness/calcium, and microbiological control with Easi-cults or equivalent and field SRB test vials. If solids were seen in the water or any sludge was removed from the system, SRB testing is needed. 3. While circulating the water adjust the pH to 8.0. This will aid in the repassivation and help minimize the corrosion potential of the MU water. 28


4. As in all pre-treatment work, addition of the passivation chemicals must be accomplished as soon as possible after heat exchangers have been cleaned and back-flushed to minimize flash corrosion. Once the system has been pH adjusted, begin adding the chemicals specified in Table 1 to the pump basin. 5. The initial PSO level will be measured as organic phosphate (method AP-25 or AP-70). Target maintaining 160 ppm of product (50 ppm as PSO). The Nitrite level should be 1000 ppm as NO 2. 6. Maintain a circulation velocity at a minimum of 3 feet/sec through all the heat exchangers during the passivation. 7. After 24 hours with the passivation chemistry in the system, collect water samples and check all water chemistry parameters: pH, Ca hardness, Total hardness, alkalinity, iron (filtered and unfiltered), NO 2, ortho phosphate (filtered and unfiltered), organic phosphate, active polymer, conductivity, free chlorine, copper and azole. Recheck the calibration of the 3D Trasar controller and cell fouling 8. After this treatment has been in operation, 2 days, clean all strainers/filters that may be in-line with the heat exchangers. Resume the flow and initiate the high-level regular treatment program. 9. If the heat load has been started on the tower, monitor iron levels closely and maintain a maximum of 3 cycles of concentration.

Phase 3 Transition to 3D Trasar Cooling Water Program 1. Recalibrate all analyzers (pH, conductivity, ORP/Chlorine, 3D Trasar, etc.) 2. Initiate pH and halogen control at normal levels. 3. Continue feed of the passivation product, do not blowdown the nitrite from the system, it is compatible with the base program. Start feed of the base program products at elevated dosages per the passivation dosage chart 2. DO NOT slug the ortho phosphate product (feed should be restarted via the injection pump). Transition each week to the next lower level of passivation dosages. 4. Perform daily water testing during the entire 2 week period on the following: pH, iron, copper, active polymer, NO 2, azole, conductivity, total and calcium hardness, M-alkalinity, SRB and Total Bacteria Dipslides. 5. Operate at cycles to maintain iron levels less than ~2 ppm. If the iron rises above 2 ppm, increase blowdown rate while maintaining dosages given in Table 2. This is necessary to minimize the potential for iron fouling in the system. 6. Return to the normal program dosages and control ranges after 1 week. Passivation Products When performing the various passivation procedures, there are a large number of products that can be used to deliver the various chemical components. This includes both single function products and blended, multi-functional products. 29


Be sure you understand the products, their components and their percent actives. This is critically important to ensure the correct dosages and economics are calculated. Also remember that while blended products may offer the advantage of fewer products to handle, they offer less treatment flexibility and will likely be more expensive.

Table 1. Passivation Chemicals--start up dosages Passivation & Start Up Chemical Program Passivation Dosages Suggested Product Product Actives, % Product Dosages, ppm Control Target, ppm Actives

Tagged HSP 3DT190 35% 60 20

pH Control Cycles of concentration

PSO 3DT180 31% 160 50

NO2 73310 25% 4000 1000

TT 3DT198 42.0% 36 15

MB Disp. 73550 50% 15 8

N.O.biocide 7338 45% 200 70

8.0 – 8.5 2-3

Table 2 Post Passivation Chemicals--Contin uous dosages Post TAR - Repassivation & Start Up Chemical Program Repassivation Dosages Suggested Product Product Actives, % Product Dosages, ppm Control Target, ppm Actives 3DTrasar Program StartUp Post-passivation, Week 1 Actives Post-passivation, Week 2 Actives Post-passivation, Week 3 Actives

Tagged HSP 3DT190 35% 60 21

PSO 3DT180 31% 160 50

NO2 73310 25% 4000 1000

15 12

30 15

600

Scale Inhibition

TT 3DT198 42.0% 36 15

Traced O-PO4 ** 3DT-184 34.7% Don't use if Fe > 3 ppm

4 18 3 12 Normal Program Dosage Range Corrosion Inhibition

MB Disp. 73550 50% 10 5

N.O.biocide 7338

5 5

NA NA

200 70

Microbio Control

** Do Not Slug Feed O-PO4

PROGRAM CONTINGENCY GUIDE Good control of every cooling water treatment program is necessary to achieve desired results. Problems, however, can arise with even the best control. This contingency guide (See Table 3) will assist you in correcting problems should they occur. It should also be used in outlining what actions your customers should take when control testing indicates a problem with the pre-treatment program.

30


Table 3 Problem Contin gency Guide Problem Result pH rises above 8.5 Potential for increased iron deposition or Ca3(PO4)2 formation exists if back to normal treatment levels Initial slug of Insufficient chemical treatment too low to effectively complete passivation. Excessive foam Recirculation Pump (this is an unlikely cavitation; possible problem) aesthetic problem in plant or community. Temporary system Stagnant treatment; shutdown due to settling of suspended mechanical debris. problems. Overfeed of sulfuric pH goes below 6.5 acid.

Corrective Actio n Add sulfuric acid to reduce pH to 7.8 to 8.5 or normal operating levels. Increase Active polymer residual to 20 ppm.

Add additional chemical to meet target dosage requirement Add small increments of NALCO 71D5 Plus or similar antifoam until foam height reaches an acceptable level. Debris will be resuspended on system start-up. Increase blowdown if there is highly turbid water If the problem is caught quickly, add soda ash to elevate pH. If the problem was not noticed soon (which should not be the case during the pre-treatment), blowdown the tower heavily, and add make-up to regain pH. Re-establish high-level passivation chemistry. Determine the root cause of the low pH, check for draining of diked areas into the cooling tower, acid pump operation, proper pH measurement, refilling of acid tank, etc.

Overall Control In the long term, successful system operation will be largely determined by your attention to in-plant training. Properly trained plant personnel will insure that Nalco recommended chemical/mechanical treatment programs as being operated as prescribed. It is important to note that iron will be “ picked up” into the re-circulating water at s tartup . The “normal” level seen at startup are ~ <10 ppm. The iron is removed from the system through blowdown. Systems with iron levels > 6 ppm will need to operate at low cycles to quickly remove the iron from the system. Systems with heavy iron contamination will consume more products because of the high blowdown. The product calculations should be done assuming the system will operate @ 2 cycles during the initial 48 hour period. 31


Some systems being returned to service may be classified as a “high stressed” startup. A “high stressed” system will be one that has 1) experienced a severe acid excursion prior to shutdown, 2) addition of equipment that has been sitting for long periods in the yard (>3 weeks), exposed to the elements and not receiving any pre-cleaning or pre-treating or 3) greater than 3 weeks of standing water (stagnant) in system piping. Greater levels of iron “pickup” (~60-100 ppm) will be expected from these “high stressed” situations. These systems should have product consumption calculated for 5-15 days operating @ 2 cycles. A frequently encount ered pr oblem duri ng passi vatio n is havin g insufficient chemical inventory to properly complete the process. This compr omises the effectiveness. Prior to start up ensure adequate inventory inhibitors. Do not substitute the use of 3DT191 or 3DT192 as the source of PSO for the pretreatment program. This will result in overfeed of polymer and be corrosive to both carbon steel and Admiralty brass metallurgy. For example, to achieve a 50 ppm (active) dosage of PSO using 3DT191, 100 ppm of active polymer will be fed into the system. This level of active polymer is likely to cause increased carbon steel and yellow metal corrosion. Caution : The use of the Nitri te based passivation progr am can cause a rapid increase in Microbial growth in the system. Microbial deposits can lead to localized corro sion cells and fouling of exchangers. The use of bleach and high levels of n on-oxidizing b iocid es is required. Recommended Iron Test Procedures (due to Mo interference): Hach FerroMo (Method 8365) eliminates high MoO 4 interference (Range 0.01 – 1.8 ppm Fe) •

Other Possible Iron Test Procedures: Hach FerroVer (Method 8008) –Test Range 0.02 –3.0 ppm Fe. No interference at <80 ppm MoO 4, no Nitrite interference Hach (1,10 Phenanthroline) (Method 8146 and Unicells) -Test range 0.01 – 5.00 ppm as Fe. MoO 4 and NO2 not listed as interfering with test results. Hach FerroZine (Method 8147) –Test Range 0.009 –1.400 ppm Fe. MoO4, and Nitrite not listed as interfering with test results. •

•

•

When using Nitrite, it is best to avoid systems with gas chlorination and the chlorinators are driven by tower drive water. The combination of low pH and high halogen levels will destroy the nitrite.

32


The use of bleach has not been seen to cause rapid degradation of nitrite especially at pH levels >7.8. A combination of low level halogen and non-oxidizer should control denitrifier activity level. Additionally, denitrifying bacteria are anaerobic.

e. New System Passivatio n 3D TRASAR Passivatio n Procedure fo r New Cooling Systems—prior to normal cooling operation When a new recirculating cooling water systems is constructed, the piping, exchangers, and tower basin may be flushed and hydrotested with water to remove any debris, loose rust, and to ensure the systems joints don’t leak, etc. after fabrication. The water flushing is an attempt to remove these extraneous materials from the system prior to commissioning. No other steps are usually employed to prepare the metal surfaces prior to applying the protective film. Acid cleaning of new equipment has been used to remove mill scale and rust; however, this method does not remove oils, greases and other miscellaneous materials. Usually, after water flushing, hydrotesting or acid cleaning operations, very little is done in the way of protecting the metal surfaces until the entire system is put into operation. Since protection is not available during this time, considerable corrosion may occur due to either stagnant wet conditions or circulation of untreated water on the metal components. Often flash corrosion is started due to residual acid left from acid cleaning. This condition may exist for weeks before application of a protective corrosive inhibiting film and produces a corroded surface with considerable corrosion products (iron and copper oxides) on the metal even before the inhibitor is applied. The corrosion products will deposit on the exchanger surfaces setting up under-deposit corrosion cells initiating localized corrosion. During the start-up or first few months of operation new cooling systems, considerable tuberculation and corrosion in the system may occur if the system is not properly treated. Normal maintenance level dosages may not effectively film even clean surfaces due to high initial demand for inhibitor to fill the metal surfaces. High levels of corrosion inhibitors may be more effective in establishing protection to metal surfaces. All metal surfaces will benefit from pre-treatment, but they must be clean for optimum formation of a protective film. If no attempt is made to prepare the metal surfaces for effective film formation, the corrosion inhibitor cannot properly react with the metal surfaces to form a protective film. The presence of rust, oils, organic films, etc. resulting from 33


manufacture or storage or the metal prior to use prevent effective film formation. Corrosion progresses unchecked under these foreign materials due to the formation of localized corrosion cells similar in effect to metal surfaces prior to painting or applying protecting coatings. We cannot emphasize too strongly the importance of surface preparation prior to applying the protective films or in the use of any barrier type corrosion prevention program. Phase 1 Back fl ushin g and high-level blowdow n to r emove chip scale and debris Suggested back flushing and blowdown procedure: 1. When the make-up line is put back into service, the initial slug of water may contain high levels of chip scale, mud and iron. This initial slug should be diverted from the tower basin. If even after the initial slug, any mud or high iron levels are introduced into the basin, the basin can be overflowed to wash that out before recirculation begins. 2. If the unit is equipped with steam driven pumps, use these first (prior to electric driven pumps). These pumps should be capable of ramping up to speed in a more controlled manor than electric driven pumps. This will minimize any shock conveyed to the system pimping that might dislodge any chip scale. 3. As circulation begins, the water flow should be directed to exchangers that are equipped with strainers to filter out any chip scale. If possible exchangers should be blocked in and the flow of cooling water should be directed through the system supply piping and flushed prior to opening any of the blocked-in exchangers. 4. Back flush all exchangers that were exposed to the initial flow of water vigorously for 20-30 minutes, and continue back flushing until all evidence of chip scale has subsided. 5. The remaining exchangers (those without strainers on the primary cooling water service) should be put into service on a staggered basis. Close the outlet side valve. Open the backflush nozzle to allow flushing of the lines up to the exchangers. When that runs, clear back flush the exchangers. When the water runs clear, close the back flush valve and open the inlet valve. If possible, install inlet and outlet pressure gauges to monitor pressure drop. After all the exchangers have been put into circulation and the backflush is complete, begin the cleaning and passivation procedures • •

• •

•

•

34


Phase 2 Application of t he 3DTRASAR all-solubl e inhibit or pr ogram The goal of the PSO/molybdate based passivation program is to apply a high level of inhibitor to the metal surface to inhibit flash corrosion and minimize deposition. Deposits on new heat exchange bundles can lead to localized corrosion and significantly shorten bundle life. Both Molybdate and PSO are highly soluble and will not precipitate with iron-based deposits. The use of tagged high stress polymer (THSP) will help control iron based deposits and a high level of azole will help passivate admiralty or other copper alloy tube bundles and chelate soluble copper in the water as the system is returned to operational status. The passivation pro cess should pr oceed as follows: 1. Recalibrate all analyzers (pH, conductivity, ORP, TRASAR and 3D TRASAR) 2. Collect a cooling water sample. Analyze for pH, iron, copper, total hardness/calcium, and microbiological control with Easi-cults or equivalent. 3. Begin circulating the water to the main lines only, and adjust the pH within a range of 7.5 - 8.5. (In general operating at the higher end of the pH range will help minimize corrosion and aid the passivation process). 4. Maintain free halogen residual levels with a bromine or chlorine based chemistry at 0.2- 0.4 ppm TRO and/or use a non-oxidizing chemistry such as 7338 at 200 ppm. If the system has been stagnant for an extended period of time, you may need to complete a microbiological cleanup prior to beginning the passivation procedure. 5. Dose the system with 200 ppm of N-7338 and 10 ppm of N-73550. Monitor the N-7338 actives with the GlutatTect WT test kit, looking for a minimum of 70 ppm active and checking on the consumption compared to what was fed. A minimum of 48 hours with 70 ppm active should be maintained. Chlorine should be maintained at 0.2 – 0.6 ppm free after the initial 48 hours. Confirm both general microbiological activity is minimal and SRB activity is nonexistent. 6. As in all pre-treatment work, addition of the passivation chemicals must be accomplished as soon as possible after heat exchangers have been cleaned to minimize flash corrosion. 7. Once the system has been pH adjusted, begin adding the chemicals specified in Table 1 to the pump basin. Watch for foaming when adding the 73550. You may want to have an anti-foam on site. If the system is small, you may consider using Nalco 3DT701---a single drum blend of all the chemicals given in Table 1. Feed Nalco 3DT701 at 1250 ppm. 8. The initial PSO level will be measured as organic phosphate and should be about ~15- 18 ppm (higher levels will not cause problem). 9. Open all exchangers and circulate the passivation chemicals. Maintain a circulation velocity of at least 3 feet/sec through the heat exchangers. 10. After this treatment has been in operation, typically for 3-5 days, clean all strainers/filters that may be in-line with the heat exchangers. 35


11. Resume all chemical treatments at dosages shown in Table 2 and initiate the normal treatment program and control ranges (pH, Conductivity, etc). When using Nalco 3DT701, the system is usually returned to normal cooling system operation after 24-48 hours of circulation. Table 2 dosages are not used. 12. This treatment regime is typically continued for 2 to 4 weeks, shorter times may be used. This treatment approach is compatible with all 3D TRASAR programs. The normal 3D TRASAR program should be started during this period with the resumption of the heat load to the tower. 13. Perform daily testing of the pH, iron, copper, active polymer, TRASAR, molybdate, azole, conductivity, total/calcium hardness and microbio activity 14. Blowdown should be adjusted to maintain iron (Fe) levels less than 2.0-3.0 ppm while maintaining dosages given in Table 2. This is necessary to minimize the potential for iron fouling in the system. 15. After 2 to 4 weeks, turn off the passivation chemicals and maintain the normal cooling tower treatment program after iron levels drop below 2 ppm. The system does not need to be drained or flushed to rid the system of the pretreatment chemical program. Table 1. Passivation Chemicals--start up dosages Product Description Product Dosage 7357 Molybdate 364 ppm 3DT190 Tagged HSP 60 ppm 3DT199 Sodium BZT 40 ppm 73550 Surfactant 10 ppm 3DT180 PSO 160 3DT701 Blend of above non 1250 ppm biocide components TRO or 7338 biocide 0.2-0.4 TRO or 200 ppm Table 2. Passi vation Chemicals--dosages after start-up Product Description Product Dosage 7357 Molybdate 182 ppm 3DT190 Tagged HSP 50 ppm 3DT199 Sodium BZT 40 ppm 73550 Surfactant 10 ppm TRO or 7338 biocide 0.2-0.4TRO or 100 ppm 3DT180 PSO 160

Control Parameter 100 ppm as MoO 4 21 ppm active polymer 13.4 ppm as azole 5 ppm as active 50 ppm as PSO Active* Maintain for 24 to 48 hours 90 ppm as active

Control Parameter 50 ppm as MoO4 * 18 ppm active polymer 13.4 ppm as azole 5 ppm as active 45 ppm as active 50 ppm as PSO Active*

* Molybdate interferes with the certain iron tests. The following interference levels for various Hach iron tests are given below. Hach FerroVer (Method 8008) no interference at <80 ppm MoO4 (range 0.02 –3.0 ppm Fe) Hach TPTZ (Method 8112) MoO4 at 5 ppm interferes (Range 0.012 – 1.8 ppm Fe) Hach FerroMo (Method 8365) eliminates high MoO4 interference (Range 0.01 – 1.8 ppm Fe) Hach 1,10-Phenanthroline (Unicells) MoO4 not listed as an interference (Range 0.1 – 5.0 ppm Fe)

36


Phase 3 Transiti on t o on -going 3D TRASAR cooling water pr ogram 1. After the high-level passivation program is complete, adjust system pH to normal operating level with return of heat load. 2. Balance the blowdown rate to keep the iron level less than 1-2 ppm . 3. If the cooling water treatment program uses orthophosphate, do not raise the orthophosphate level up to the normal operating target until the iron level decreases below 1-2 ppm. 4. Once the iron level is below 1 ppm, increase cycles at equal increments to return to normal dosage levels. 5. Monitor corrosion rates on NCM (Nalco Corrosion Monitor) during the return to heat load. 3D TRASAR Passivation Program Contingency Guide Good control of every cooling water treatment program is necessary to achieve desired results. Problems, however, can arise with even the best control. The contingency guide shown in Table 3 will assist you in correcting problems should they occur. It should also be used in outlining what actions your customers should take when control testing indicates a problem with the pretreatment program. Table 3. Problem Contingency Guide Problem Result Corrective Actio n pH rises above 8.5 Potential for increased iron Add sulfuric acid to reduce pH to 7.5 to deposition or Ca 3(PO4)2 formation 8.5 or normal operating levels exists if back to normal treatment levels Initial slug of Insufficient chemical to effectively Add additional treatment too low complete passivation. Excessive foam Pump cavitation; possible aesthetic Add small increments of NALCO (this is an unlikely problem in plant or community. 71D5plus or similar antifoam until foam problem) height reaches an acceptable level. Temporary system Stagnant treatment; settling of Debris will be resuspended on system shutdown due to suspended debris. start-up. Increase blowdown if there is mechanical highly turbid water problems. Overfeed of pH goes below 6.5 If the problem is caught quickly, add sulfuric acid. soda ash to elevate pH. If the problem was not noticed soon (which should not be the case during the pre-treatment), blowdown the tower heavily, and add make-up to regain pH. Re-establish high-level passivation chemistry.

37


Words of Caution In the long term, successful system operation will be largely determined by your attention to in-plant training. Properly trained plant personnel will insure that Nalco recommended chemical/mechanical treatment programs are being operated as prescribed. It is important to note that iron wi ll be “ picked up” into the re-circulating water at startup . The “normal” level seen at startup are usually less than 10 ppm. The iron is removed from the system through blowdown. Systems with iron levels > 6 ppm will need to operate at low cycles to quickly remove the iron from the system. Systems with heavy iron contamination will consume more products because of the high blowdown. The product calculations should be done assuming the system will operate @ 2 cycles during the initial 48 hour period. Some systems being returned to service may be classified as a “high stressed” startup. A “high stressed” system is one that: 1. experienced a severe acid excursion prior to shutdown 2. contains equipment that has been sitting for long periods in the yard (no pre-cleaning or pre-treating) 3. has contained standing water (stagnant) in system piping for greater than 3 weeks Greater levels of iron “pickup” (~60-100 ppm) will be expected from these “high stressed” situations. These systems should have product consumption calculated for 5 days operating @ 2 cycles. A frequently encountered problem during passivation is having insufficient chemical inventory to properly complete the process. This compromises the effectiveness. Prior to start up , ensure adequate inventory of all inh ibit ors. Also do not substitute the use of 3DT191 or 3DT192 as the source of PSO for the pretreatment program. This causes an overfeed of polymer and be corrosive to both carbon steel and admiralty brass metallurgy. Available Literature Confidential Product Profile 3DT701 PR-272 3DTRASAR Passivation Program

38


f. Emergency / Hurricane Wet Lay Up Passi vation Open Recircu lating Cooling Systems Open recirculating cooling systems must often be shut down very quickly during hurricane season. Most often there is not enough time bring the system down, as it would be for a scheduled turnaround. This puts the unit into a situation where stagnant and/or untreated water will be extremely corrosive to the system’s metallurgy. The Emergency Wet Storage Procedure is designed to minimize the corrosion that occurs during these stagnant conditions.

Passiv ation Product Selection When performing the various passivation procedures, there are a large number of products that can be used to deliver the various chemical components. This includes both single function products and blended, multi-functional products. Be sure you understand the products, their components and their percent actives. This is critically important to ensure the correct dosages and economics are calculated. Also remember that while blended products may offer the advantage of fewer products to handle, they offer less treatment flexibility and will likely be more expensive. Listed below are some general product names that are commonly used around the world. Some regions use different product names, so please consult your region’s select product list. If you have any questions or concerns, please consult the CPP or contact your regional ITC or marketing personnel for assistance. Single Function Products Molybdate – 7357 PSO – 3DT180 (untraced), 3DT179 (traced) TSHP – 3DT190 Azole – 3DT198, 1336, 73181 (TT); 3DT199, 73199 – BZT; 3DT197 (new azole) Nitrite - 73310 Microbio Dispersants / Detergents – 73550, 7348 Non-oxidizing Biocides – 7338 (gluteraldehyde), 7330 (isothiazoline) • • • •

• • •

Blended, Multi -Functi on Products Moly, PSO, TT, HSP, Surfactant - 3DT701 Nitrite, TT, HSP - 8349 • •

Step 1 – System Preparation Before high level corrosion inhibitors and biocide are added to the open recirculating cooling system it must have its microbiological and Total Dissolved Solids (TDS) levels lower as much as possible. Microbiological levels need to 39


be at a minimum to reduce the demand on the wet storage biocide (nonoxidizing biocides have maximum application limits in open recirculating cooling systems). The minimal TDS levels are needed to lower the corrosion potential of the water and also allow the system’s blowdown to be minimized or block prior to shutdown (maintains the inhibitors at their applied level). 5 Days prior t o anticipated hurric ane strik e 1. Begin addition of biodispersant @ 20 ppm (Nalco 7348 Plus or Nalco 73550) Note: If biodispersant is included in the routine treatment program continue the program but adjust feed for decreased cycles and 20 ppm feed level. 2. Begin increased blowdown to lower the cooling tower cycles to 2 cycles or as close to 2 as possible (if makeup restricted). 3. Maintain routine treatment (at reduced cycles) and maintain free chlorine @ 0.3-0.6 ppm. It is critical to maintain oxidizing biocide control (no loss of feed) to keep the system’s microbiological activity at a minimum prior to system shutdown. 4. Systems that don’t used chlorine as their primary biocide need to deploy their biocide program in a manner that will have the system prepared for wet lay-up. Systems that use stabilized halogens and/or non-oxidizing biocides should apply non-oxidizing biocide to the system on a daily basis. Biocide levels going to the waste plant need to be calculated. As an example, if there are a few small cooling systems discharging into a large waste facility the additional biocide will not present an impact. A fast killing, rapid hydrolyzing (detoxify) non-oxidizing biocide (DBNPA) can be used during this system preparation phase if the normally applied biocide or Glutaraldehyde presents a problem. 5. All biocides, oxidizing and non-oxidizing, can be deactivated by sodium bisulfite if needed. Dosages can be calculated for the stream going to waste along with biocide residual testing. Nalco 7408 (uncatalyzed sodium bisulfite) is applied based on ppm/ppm of biocide to be deactivated. The reaction(s) are extremely fast. It is recommended that the deactivation take place as close to the waste inlet as possible. This allows maximum deactivation of the biocides through natural degradation prior to the point of injection. Step 2 – System Lay-up Procedur e After system preparation, the microbiological activity and TDS concentration will be at a minimum and the system will then be ready for wet lay-up. Once the lay-up is started, the system blowdown will be blocked in. Cooling water TDS levels will begin to cycle up based on the heat load. This is normal and expected. Conductivity should be run every six hours, if the system doesn’t have continuous conductivity monitoring, to plot the increase rate in TDS. If delays are experience in the shutdown process (>24 hours) a small amount of 40


blowdown may be needed if the system is still under full heat load. If there is no heat load (or negligible load) during a delay, blowdown will not be needed. 24 hours prior to anticipated system shutdown 1.

Block in all sources of “controllable” blowdown

2. Stop Biodispersant feed 3. Stop normal phosphate inhibitor chemical feed 4. Stop Chlorine feed 5. Set pH control for 8.0-8.5 range 6. Add 400 ppm of Nalco 7338 (Glutaraldehyde) 7. Add 800 ppm of Nalco 7357 (216 ppm MoO 4) 8. Add 350 ppm of Nalco 3DT-180 (105 ppm PSO) 9. Add 50 ppm of Nalco 1336(21 ppm Na-TT) or Nalco 73199 (20 ppm NaBZT) 10. Continue cooling system circulation with inhibitors (minimum time 12 hours) 11. Stop normal cooling water dispersant chemical just before system shutdown 12. Test all inhibitor chemical levels and non-oxidizing biocide levels. Pull 2 retain samples. Send one to the Naperville lab for total cation and anion, filtered and unfiltered testing. Have the proper sample containers for collection and shipment on site. 13. Stop recirculation and block in cooling system 14. Loss of cooling system water must be minimized as much as possible prior to restart a. Preserve treatment inhibitor concentration. b. Prevent corrosion at the air – water interface if down for extended periods of time. Step 3 – System Restart 1. The start-up water chemistry tests prior to recirculation. a. Molybdate - Hach Method 8036 (Mercaptoacetic Acid Method 0.3-40 ppm) b. Azole c. pH d. Total microbiological count e. Sulfate reducer counts f. Active Glutaraldehyde level - (GLUTATECT – WT by Alden Scientific) g. Conductivity h. Active polymer i. Total iron (digested or ICP) 41


j. Total copper (digested or ICP) k. PSO (need to be sent to Naperville Analytical) l. Send a sample to Naperville lab for total cation and anion, filtered and unfiltered testing. Have the proper sample containers for collection and shipment on site. 2. Active Glutaraldehyde Level (prior to recirculation once recirculation is established) a. If the active level is below the maximum established level for discharge to waste treatment then sulfite neutralization will not be needed. b. If the active level is > than level for discharge then Nalco 7408 (uncatalyzed sodium bisulfite solution) should be added at 10ppm/ppm active Glutaraldehyde. This will deactivate the Glutaraldehyde to < 2 ppm. c. Glutaraldehyde level should be tested prior to the waste plant and as close as possible to waste plant inlet. This sample point monitors the amount that would enter the waste plant, allowing for maximum uptake prior to the waste facility 3. Total Microbiological counts (prior to recirculation and once recirculation is established) a. < 1000 – resume normal chlorine treatment with biodispersant b. 10,000 - resume normal chlorine treatment with biodispersant + application of 200 ppm Nalco 7338 biocide c. 100,000 – resume normal chlorine treatment with biodispersant + application of 200 ppm Nalco 7338 biocide. Retest in 24 hours and reapply if > 10,000 counts. 4.

Sulfate Reducers – Positive detection = application of 200 ppm Nalco 7338 biocide. Retest in 24 hours and reapply Nalco 7338 with positive detection.

5.

Begin Plant cooling system startup procedures (See attachment)

6.

Plan to test water chemistry routinely until equipment is back in service.

7.

Begin Nalco attachments)

8.

When Nalco All Soluble Startup Passivation is completed return to normal treatment

All

Soluble

Startup

Passivation

procedure

(See

42


g. Off-Line, Single Exchanger Passivation Typical chemical treatment of operating cooling water generally includes corrosion inhibitors for carbon steel metal surfaces. However, this chemistry and the component doses are designed to “repair” breaks in already passivated metal. For surfaces were passivation has not been established, these programs can take weeks or months install a complete inhibitor “film”. During this period, rapid corrosion is experienced. In addition to the interim damage experienced, the areas where corrosion sites have developed will be resistant to corrosion inhibitor protection afforded by the ongoing treatment program. Additional corrosion at these sites will continue – generally resulting deep pitting and premature tube failure. For this reason, it is necessary that all new or freshly cleaned exchanger tubes be exposed for a short period upon start-up to chemical inhibitors designed to provide very rapid metal passivation. Documented benefits from this procedure include a 20-50% extension in tube life as well as reduction in heat transfer problems related to tuberculation. The two methods of passivation are on-line and off-line. Off-line passivation is the much-preferred method as it allows the use of high levels of inhibitors designed specifically to promote a rapid protective film without any risk to the bulk cooling water and other operating equipment. This procedure requires that the exchanger remain off-line and blocked-in for the period of the passivation. Procedure Prior to installation and passivation, the exchanger should be inspected for cleanliness. For new exchangers, confirm that no “flash rust” is present due to atmospheric corrosion during storage on a ‘pad’ or in a ‘yard’. New exchangers need to be protected from the elements to minimize/eliminate flash rust from forming on the carbon steel exchanger tubing. For exchangers recently cleaned, insure that the cleaning was effective removing all scale and tuberculation. If not found satisfactory, the exchanger should be re-cleaned. Remember, the passivation only works on bare metal and will not protect surfaces covered by scale or corrosion products! Upon installation, immediately perform passivation. If exchanger is left over 23 days before passivation, interim corrosion becomes a concern . This procedure is designed for passivation of in-place exchangers that allow effective flow of water through the exchanger. Typically the reservoir for the passivation solution is from a vacuum truck or tank that can be heated and pumped through the exchanger.

43


Recommended Procedure: 1. After the cleaning, ensure the exchanger has been flushed with high quality water a. Best - condensate or BFW with soda ash to a pH>9.5 b. Good- Clean service water with soda ash to a pH >9.5, turbidity <5 NTU c. Acceptable- clean service water, turbidity <5 NTU d. Unacceptable – untreated fire water, untreated/untested service water 2.

Fill the passivation solution tank with high quality water typically condensate or BFW with soda ash to a pH>9.5. The use of cycled cooling tower water or high hardness (>50 ppm TH) is not recommended as the high temperature of the procedure can cause scale formation and reduce the effectiveness of the passivation.

3.

Heat the solution to 150F, the N-73310 to obtain 5000 ppm of NO 2 (as NO2). This is equal to 15.4 lbs of N-73310 per 100 gallons of water. Add soda ash to raise the pH to 9-10. Use either 3DT191 or 3DT192 to provide 15 ppm active HSP and 7.5 ppm PSO into the system

4.

Circulate the solution for 2-4 hours at 150F. The circulation rate should be adjusted to maintain a flow velocity of 3-6 fps. For best results, heated passivation is strongly recommended. However, if this is not possible, the circulation time must be increased to 8-12 hours.

5.

One the passivation is complete, the solution should be evacuated and disposed of and the exchanger purged dry under a N 2 blanket. Maintain a 3-5-psig N 2 blanket until put into service. The option to lay up the exchanger wet, with the passivation solution, exists but should be done for no more than 7 days. However, ensure the exchanger is fully flooded with solution and no air pockets exist or corrosion at the water line will occur. This passivation solution can be flushed straight into the cooling system when the exchanger is to be placed in service.

Addi ti onal Cons ideratio ns Ensure the pH of the passivation solution is 9-10, a low pH water < 4.5 will decompose the NO 2 to a toxic N xOy gas. It will also increase the inherent corrosivity of the solution. 1. A surfactant like N-7308 (50-100 ppm) can be added to solution if oils are present on the surface of the exchanger to be passivated 2. Very large exchangers may require an additional 1-2 hours of circulation time. 44


Passiv ation Product Selection When performing the various passivation procedures, there are a large number of products that can be used to deliver the various chemical components. This includes both single function products and blended, multi-functional products. Be sure you understand the products, their components and their percent actives. This is critically important to ensure the correct dosages and economics are calculated. Also remember that while blended products may offer the advantage of fewer products to handle, they offer less treatment flexibility and will likely be more expensive. Listed below are some general product names that are commonly used around the world. Some regions use different product names, so please consult your region’s select product list. If you have any questions or concerns, please consult the CPP or contact your regional ITC or marketing personnel for assistance. Single Function Products Molybdate – 7357 PSO – 3DT180 (untraced), 3DT179 (traced) TSHP – 3DT190 Azole – 3DT198, 1336, 73181 (TT); 3DT199, 73199 (BZT); 3DT197 (new azole) Nitrite - 73310 Microbio Dispersants / Detergents – 73550, 7348 Non-oxidizing Biocides – 7338 (gluteraldehyde), 7330 (isothiazoline) • • • •

• • •

Blended, Multi -Functi on Products Moly, PSO, TT, HSP, Surfactant - 3DT701 Nitrite, TT, HSP - 8349 • •

h. Off-Line, NALPREP III Passivati on Attached below is the CPP pre-section detailing the procedure for using NALPREP III. Although this chemistry can be used successfully, there are many drawbacks with the use of this product. It CANNOT be used with a heat load. Elevated soluble iron levels will cause potential for iron phosphate precipitation. Also there are environmental disposal issues due to the extremely high levels of phosphate in the discharge. It is highly recommended that NALPREP III only be used for individual exchanger passivations. Please review all of these issues carefully with your customer prior to use.

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NALPREP III PROCEDURES NALPREP III is uniquely designed to pre-treat both new and older systems that have been chemically or mechanically cleaned. It must be applied when no heat load is present while the system is on-line or they may be applied when the system is off-line. NALPREP III is a liquid blends of several materials including inorganic phosphate for mild steel corrosion protection, an organic corrosion inhibitor for yellow metals corrosion inhibition, a polymeric dispersant to disperse foulants, and a surfactant type oil emulsifier to remove oil and grease. It prepares metal surfaces in the system (including supply and return lines if done in a noheat load, on-line application) for long-term corrosion protection. They initially remove oil and grease from the metal surfaces to permit uniform layering of the passivating film, and aid in the prevention of flash corrosion when the system is most vulnerable to corrosive attack. If the customer has not been using pre-treatment programs, you must emphasize the importance of pre-treatment. 1. DOSAGE REQUIREMENTS On-Line pr e-treatment of new plants (witho ut Heat Load) 1. The first step in using NALPREP III in new plant start-ups (without heat load) is to determine the condition of the cooling tower. If the cooling tower is new, water in the system that was used to wet the tower lumber during construction must be removed, given the probable existence of copper, arsenic, and chromium in the water. These elements, added as wood preservatives, are easily leached from wood. Research has shown the application of NALPREP III in such a leachate produces a non-protective spongy deposit and not the adherent passivating film that is desired. 2. After blowing down the system, the tower should then be filled with a volume of water sufficient to flush main lines and laterals. All exchangers should be blocked in so that flush water and construction debris are not permitted entry. As a preferred practice, the flush water should be dosed with NALPREP III at 2700 ppm product based on the total flush water volume. Once flushing is complete, drain the tower and clean out the basin of all debris. 3. Next, refill the basin with water to a level sufficient to fill piping, heat exchangers, and provide sufficient head to the recirculating pumps. Begin circulating the water to the main lines only, and adjust the pH within a range of 6.5 - 7.5. Once the system has been pH adjusted, start adding NALPREP III to the pump basin. The calcium level in the system must be at least 100 ppm. 46


4. The initial total inorganic phosphate level (TIP) at its maximum should be about 470 ppm. Ideal water temperatures are from 90-100 oF [32-38oC], although slightly lower or higher temperatures pose no problems. As the passivating film starts to form, the phosphate level will decrease. Phosphate uptake within the system will approximate 25-75% of total inorganic phosphate within 24 hours. 5. Open all exchangers and circulate the NALPREP III for 24-48 hours. (24 hours is minimum; 48 hours is a recommended maximum, although going beyond 48 hours poses no problem). After the proper circulation time, begin tower blowdown. 6. The phosphate level must be decreased via blowdown to 10-20 ppm before the regular corrosion program is started (failure to do this could result in precipitation of calcium phosphate). The phosphate level should never be allowed to reach zero before beginning the normal high-level corrosion inhibitor program. 7. Once the correct phosphate level has been reached, the designated start-up program for corrosion control may begin. Consult the appropriate product CPP for start-up procedures.

2. DOSAGE REQUIREMENTS On-Line pre-treatment of Exist ing Systems (witho ut Heat Load) NALPREP III may be used to pre-treat existing systems where the entire system has been brought down for cleaning and repairs. Product is applied at 2700 ppm product based on the water volume in the system. Procedures are identical to those for new plants with the following exceptions: •

The initial water rinse step for removal of copper, arsenic, and chromium leachate is not necessary.

•

The flushing step to rid the system of construction debris is not necessary.

As in all pre-treatment work, addition of NALPREP III must be accomplished as soon as possible after heat exchangers have been cleaned to minimize flash corrosion. A minimum of 100 ppm of calcium is needed to form the calcium polyphosphate complex.

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3. DOSAGE REQUIREMENTS Off-line pre-treatment of a Single or Bank of Exchangers Effective off-line passivation of a single exchanger or a bank of exchangers can be accomplished at 150 oF [65oC] with 5000 ppm NALPREP III or at 130 oF [54oC] with 10,000 ppm NALPREP III in two hours. Calcium must be added if using condensate. This off-line procedure can be done in two ways: •

•

With the exchanger in place, and off-line, NALPREP III is applied to established equipment that has been thoroughly degreased. By pulling the bundle and immersing in a vat of heated NALPREP III.

Passivating solutions may be replenished no more than two times with NALPREP III to reestablish a total phosphate level of 470 ppm. Thereafter, old passivating solutions should be disposed of and fresh material used. Pretreatment of new equipment, which will have oil and grease on the surface, should utilize fresh NALPREP III each time.

4. PROGRAM CONTROL Table 1- NALPREP III. Control Guidelines

5. PROGRAM CONTINGENCY GUIDE Good control of every cooling water treatment program is necessary to achieve desired results. Problems, however, can arise with even the best control. This contingency guide (See Table 2) will assist you in correcting problems should they occur. It should also be used in outlining what actions your customers should take when control testing indicates a problem with the pre-treatment program.

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Table 2 Problem Contingency Guide for NALPREP III.

6. DISPOSAL PROCEDURES Some plants may be able to use the phosphate in the cooling tower blowdown as a nutrient source in their waste treatment process. However, if phosphate removal from the blowdown is necessary, the general procedure outlined below may be used. Two chemicals are used to remove phosphate from the blowdown: a solution of ferric chloride (FeCl3) and 50% sodium hydroxide. 1. Pump the phosphate containing blowdown to suitable ponds or tanks as quickly as line limitations permit. Establish a constant flow rate of the blowdown to aid in optimum chemical treatment dosages. 2. As the phosphate bearing blowdown reaches the treatment site, begin adding ferric chloride and caustic. Note that the order of addition of FeCl3 first and NaOH second is very important for optimum phosphate removal. These two chemicals should be added at two points at least 4-5 feet [1.2-1.5 meters] apart. 3. Add 3.5 gallons [13 liters] of a 39% FeCl3 solution to every 1000 gallons [3785 liters] of blowdown (solutions of different strengths will require a volume that is proportional to the strength). 4. Then add 1.4 gallons [5 liters] of 50% sodium hydroxide per 1000 gallons [3785 liters] of blowdown. NaOH addition should generate a pH at the NaOH mixing point of 6.0. 49


5. Samples should be taken several feet [1 meter] from the final mixing point and at a more remote point in the waste treatment system to assess successful phosphate removal. Feed of FeCl3 or NaOH should be adjusted as necessary to effect adequate phosphate removal. Sampling to determine phosphate levels should occur hourly during the blowdown process. 6. For systems where the blowdown line enters a retention pond directly, a temporary mixing baffle constructed of plywood will aid the mixing and phosphate removal process.

Exchanger Inspections Once the unit has come down and exchangers are being opened for inspection and maintenance, it is time to begin to inspect the equipment. It is very important to inspect every cooling water exchanger that is opened. As soon as these exchangers are opened and inspected by the customer, they will usually either clean in-place or pull the bundle and transport to a location where they are cleaned. Time is money during the T/A - they will not wait on you if you are not present to inspect an exchanger when opened. To make sure you do not miss any inspections, you will need to get a copy of the T/A exchanger schedule from the T/A group. It is also important to identify the individual(s) who will be managing the exchanger scheduling during the T/A. Since the planned schedule will often change, keeping in close touch with them will help ensure you do not miss any equipment openings. Another area that is important is ensuring you have the needed inspection equipment supplies ready to go once they start opening exchangers. This would include sample deposit / whirl pack bags, tools for the inspection (camera, flashlight, magnet, knife, screwdriver, etc). Be sure to understand the permit requirements for using a camera on-site and make arrangements to have the necessary permit in advance of the exchangers’ openings. The final item of need is a pad of Nalco exchanger inspection forms. These are available from the literature forms directory in KM as Form 968, Exchanger Inspection Form. This form is on the following pages and should be used for all inspections. It is important to be thorough in each inspection. Take deposit samples and send in for analysis to Naperville. Take multiple photos that detail the condition of the exchanger. Be sure to have the exchanger’s name with each picture. A 3”x5” note card & marker can allow you to make a small label for the photo. Also be sure to take detailed notes and fill out the entire inspection form attached below for each exchanger.

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Exchanger Inspection Form

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Post T/A Start-up Precautions must be taken after a Turn Around or lay up event to effectively flush accumulated debris, chip scale, mud, silt, etc. from the cooling system. This will minimize the potential for exchanger fouling and plugging debris that will be transported throughout the system piping. The object is to ensure plant reliability by minimizing cooling water corrosion and fouling during start-ups. In many system, chip scale and iron deposition pose the greatest threat to tube and tube sheet plugging during start-ups. The best methods for dealing with this issue is to use either strainers on the inlet side of the exchangers and/or ensure each exchanger that is on the primary cooling water circuit have the capability to be back flushed to remove any debris on the inlet tube sheet. This is particularly important for those exchangers that sit at the end of the cooling water supply piping that can accumulate trash, chip scale, mud and silt, etc. Procedure 1. When the make up line is put back into service, the initial slug of water may contain high levels of chip scale, mud and iron. If possible, this initial slug should be diverted from the tower basin. If even after the initial slug, any mud or high iron levels introduced into the basin, the basin may be overflowed to wash that out before recirculation begins. 2. If the unit is equipped with steam driven pumps, use these first (prior to electric driven pumps). These pumps should be capable of ramping up to speed in a more controlled manor than electric driven pumps. This will minimize any shock conveyed to the cooling water piping that might dislodge any chip scale or other debris that can plug the exchangers. 3. As circulation begins, the water flow should be directed to exchangers that are equipped with strainers or traps to filter out any chip scale. If possible, exchangers should be blocked in and the flow of cooling water should be directed through the system supply piping and flushed prior to opening any of the blocked in exchangers. This is of particular importance for those exchangers that are positioned at the end of the supply piping. 4. Back flush all exchangers vigorously for a minimum of 20-30 minutes that were exposed to the initial flow of water and continue back flushing until all evidence of chip scale has subsided. 5. The remaining exchangers (those without strainers on the primary cooling water service) should be put into service on a staggered basis. Close the outlet side valve. Open the back flush nozzle to allow flushing of the lines up to the exchangers. • •

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Turnaround BP Workbook

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