ashrae cooling towers standards

The following article was published in ASHRAE Journal, July 2007. ©Copyright 2007 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. It is presented for educational purposes only. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE.

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Things to Know About Cooling Water Treatment

By Bill Gaines, Martin R. Orban, and David R. Welch

A

n objective evaluation of competing cooling water proposals only can be made when they are uniform. An unambiguous

specification would seem ideal for this purpose. Yet each facility is unique and industry standards of quality and performance still leave open areas of interpretation due to those unique system characteristics. How can a facility manager know when a change in suppliers or chemical program is warranted? This article provides a practical guide to determine the value of a water treatment program and to perform a critical review of alternative programs. It is equally suitable when proposals are solicited or when an end-user wants to compare a new supplier to an existing program. In the auto industry, a “tight” part specification is a necessity. Components must meet rigid tolerances, be of high quality, perform to expected standards, and, 50

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of course, be economical and provide value to the customer. A cooling water treatment program must have the same qualities. Poorly specifying performance metrics is unwise and imprudent, yet writing entirely prescriptive requirements for a cooling water program is, at best, difficult and impermanent. Constantly changing regulations, variable manufacturing fluids/processes, and development of new treatment chemistries demand a s h r a e . oarsgh r a e . o r g

that a treatment program be flexible to reflect optimum conditions. A comprehensive system specification that rules out discovery, experience, and innovation minimizes the opportunity to use a supplier’s expertise. It also sets the stage to focus on the specification rather than actual system performance. Does this mean a well-defined performance specification isn’t necessary? Indeed not! The need for an explicit specification is critical to protect the integrity of process equipment. The individual elements of what must be included have been well documented in previous literature. 1,2 Unfortunately, industry standards of quality and performance still leave areas open to interpretation due to unique system requirements, and create significant variations between apparently similar proposals. Given this situation, About the Authors Bill Gaines is a principal engineer with Ford Motor Company in Dearborn, Mich. Martin R. Orban is a director of product management & technology at Mitco in Grand Rapids, Mich. David R. Welch is the Michigan district manager at Mitco.

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how can a facility manager know when a change in suppliers or chemical program is warranted?

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Five Front-End Elements to Establish

There is no single “right” solution to selecting a treatment regime. Even the “best” program involves tradeoffs between cost and effectiveness. However, certain elements always improve the likelihood of success: 1. System Characterization

Nothing is more important than an accurate system characterization -- it is the foundation upon which all other decisions are made, and provides the basis for proposals that optimize cost and performance. Even greater benefit is gained when suppliers are offered the opportunity to survey the system to gain additional information. Essential system characteristics include: • The volume of water used in the previous year (if unknown, start measuring it); • The number of operating days and seasonal variation; • The total system volume (easy to determine); • A complete makeup water analysis (if you don’t have one, get one); • The recirculation rate (if unknown, pump horsepower or tons of cooling capacity can be used to estimate it until it is measured); • Present cycles of concentration (CoC); and • A list of the materials of construction for all wetted parts within the system. Water usage is a source of difficulty in bid preparation and evaluation. Left to their own, suppliers who may have to estimate makeup and blowdown will skew cost estimates. In the absence of reliable metered water usage, it is essential that annual water usage be defined in the specifications.

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Test procedures, interpretation of results, and corrective actions; Product bulletins and material safety data sheets (MSDSs); and Routine service reports.

4. “Face Time”

Treatment programs are provided on either a full service or limited (namely, advisory) basis. Under a full-service agreement, the supplier provides total management of the program. Under a limited agreement, the supplier recommends a program, provides chemicals and offers consulting to the site. Facility personnel maintain the equipment, administer the chemicals, and monitor water quality, operational characteristics, and program performance. The primary responsibility of a water treatment supplier is to manage the water treatment program. The supplier should ensure the completeness of analytical tests, know how to interpret them and foresee potential problem areas. “Face time” is the frequency and duration of “service” provided by the supplier. In many cases, this is the most costly of all the program components. Therefore, interview the representative as if you were hiring a full-time employee. Realize that when you specify service frequency, you are directly impacting the program cost and inviting a cost that may not connect to your desired program value. The experience of the representative plays a critical role in program success and cost. Although dollars spent divided by hours of service may be a helpful calculation, it is the quality of service that determines the largest portion of program value. Alternatively, one must ask “What are the components of the present service program? What actually happened in the hour of service that I received and how much am I willing to do in support of the program that I specify?” Many high-performing programs are 90% self-managed.

2. Restrictions

Any restrictions due to discharge requirements or corporate policies must be communicated (e.g., zinc and/or molybdate not allowed). Equally important is when there is a bias toward a particular program (e.g., halogen). In this case, the active chemical and its control range must be defined, while still allowing voluntary alternate programs that use supplier experience. 3. Performance Metrics

The current metrics (if satisfactory) or expectations (if unsatisfactory) must be communicated. Remember that high demands escalate costs and may promote future dissatisfaction. The best method for determining performance metrics is to combine information garnered during the bidding process with knowledge from the vendor, end-user and industry organizations. High performance cannot be sustained without proper training. Vendors need to provide a manual to administer the program safely and as designed. Such a manual needs to include at a minimum: • Emergency contact information; • Chemical treatment programs and control limits; July 2007

5. Deliverables

Operator logs and vendor service reports provide valuable data that in conjunction with water, deposit, and other analyses, measure progress against defined performance metrics. Regular reviews of the program cover performance, costs, problem areas and corrective action plans. Therefore, it is common to request a copy of a review authored by the representative you are considering. Also, a water treatment company’s corporate support structure impacts its pricing. Be aware of the type and amount of additional support that you most likely will need. Five Elements to Establish During the Selection Process

Uniformity among the various proposals is crucial to allow objective evaluation. Seeking an apples-to-apples comparison works well for apples, but not always for water treatment programs. Each facility is unique and industry standards of quality and performance still leave many areas open to interpretation based upon those unique system characteristics. Once proposals are received, the process of evaluating them can be quite challenging. Five areas requiring evaluation are: ASHRAE Journal

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1. Product Evaluation

2. Method of Application

MSDSs don’t provide sufficient information to compare products. End-users usually address this is by requiring full disclosure with submittals. Full disclosure allows the end-user to examine programs in terms of suitability, health and safety, and material compatibility. Once the proposals and product information are in hand, one can compare them to the previous years’ total pounds of each chemical used, cost per pound, total program cost, and the number of hours that the supplier spent on site. One must consider the product recommendation and its impact on CoC. The product concentration (dilution) accounts for wide variations in unit pricing, making it impossible to compare usage and cost. Therefore, respondents must also provide annual use rates. Maximum cycles also vary depending on the treatment chemistry. Similar programs from different vendors ought to yield similar CoC. If a program has greater cost but higher CoC, then the evaluation should reflect the reduced makeup. An insightful metric is total annual cost divided by million pounds of blowdown. Ideally, deviations are addressed during the pre-bid meeting and walk-through. But if a reasonable irregularity surfaces after the fact, then bidders need to be offered an opportunity to make appropriate revisions. However, they should not be allowed license for changes outside the irregularity identified.

Just as the choice of chemistry must be appropriate to the individual system, so too must be the method of addition. Proposals must address: a. Control Method: Is the feed and monitoring equipment appropriate for the chemical program? Will it be on a continuous or intermittent basis, or a combination of both? If additional equipment is required, several options are available: • Direct Purchase: End-user purchases and installs required equipment; • Lease-to-Own: A third-party lease agreement; • Added to Price of Chemical: This is popular when capital budgets are limited. However, both parties must understand the term and/or volume limits for which the adder is applied (a depreciation schedule is advantageous if there is a need to change vendors before satisfying the terms of the agreement); and • Vendor Supplied: The vendor retains ownership and maintenance and folds the cost into the chemical price. This method is gaining in popularity as more end-users view this as an opportunity to keep up with advances in control technology. b. Inventory Management: Proposals must be consistent with the end-user inventory needs and storage of each product appropriate for its usage. They must also demonstrate that adequate

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but not excessive inventory levels will be provided. Many companies do not want to dispose of containers when drums are used, and some vendors have responded with “drumless” programs. c. Ordering/Shipping: While most endusers specify FOB delivered, this is often not the most economical choice. Overall charges are cheaper when higher volumes

are shipped, but some vendors apply a higher freight charge in case only a few drums are ordered. Usually it’s better to specify prepay and add. This way, the end-user enjoys the quantity freight discounts for large orders, as well as, lower charges when only a few containers are shipped. Alternatively, it’s often advantageous to ship on a consignment basis if

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the end-user has storage space and the parties agree on invoicing methods. The vendor minimizes cost by shipping larger truckloads less frequently and passes the savings on to the end-user. 3. Who Do You (And Who Do You Not) See?

Proposals must identify resources that will be made available when the primary representative is unavailable. They must include names and biographical information for the primary and backup support personnel, as well as, the key corporate support personnel to be assigned under such conditions. Thoroughly check all references! Evaluation of services cannot be made by a predetermined formula that applies to all cases. However, certain questions aid in the review: • Does the service representative have the skill to identify and correct problem areas as they arise? • Does the proposal consider plant procedures, safety training and lockout procedures? • What is supplier turnover rate, and how long have the personnel been assigned to the local area? • Is there an allowance for emergency service? If so, are separate charges clearly delineated? • Is periodic (typically annual) indepth equipment inspection provided? Proposals should describe how this will be done and what inspection equipment is to be used. 4. Corrective Measures for Routine ‘Out of Control’ Parameters

Given the highly dynamic nature of plant systems, an unexpected event will occur. When the program is collaborative, service is proactive, and standard operating procedures have been written; then personnel follow uniform methods to “act and correct” following an upset. The answer to a water treatment problem is not always the application or increased usage of a chemical. The representative must always be cognizant of physical or operational changes, as well as, chemical upsets. It has been reasonably stated that “…80% of chemical problems are mechanical.” Above all we must try to 54

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remember that, in the real world, change is sometimes necessary. When this occurs, the method of change should be thoroughly considered, rather than a knee-jerk reaction. The management of change is best achieved when a systematic approach is applied to each process and subprocess.

Five Ongoing Elements

improve results and reduce costs. He “crawls upstream” to discover manufacturing fluid and process changes, and then reacts ahead of time. He becomes involved in water treatment issues and checks performance of equipment outside the scope of his services. The representative must recognize downsides to proposed changes. For example, reducing circulating pumps to save energy may decrease flow velocities and turn heat exchangers into sedimentation tanks. Isolating (no flow) loops for energy savings may promote corrosion and uncontrolled microbiological growth. Cycling standby equipment at greater than one week frequencies may allow proliferation of bacteria to inoculate the system upon startup. It takes an experienced water-treater to know when these types of changes are prudent. Methods have been developed that quantify the subjective portion of the evaluation. Most of these involve a matrix consisting of a comprehensive list of qualities in the first column, a weighting factor determined by the end-user in the second, and a force-ranked rating in the third. Multiplying each score by its weighting factor and totaling all scores produces a single final score.4

Once a program is established and underway, there are ongoing aspects that require continuing evaluation:

4. The Happiness Factor

5. Non-routine Service

If one accepts the premise “anything that can fail will ultimately fail,” then it follows that a well-designed program must allow for unforeseen and unscheduled equipment outages. It is in the best interest of both parties that non-routine service be addressed upfront. Although there is no single correct formula for defining this, the most common method resembles the following: Basic contract allows for x hours of routine service plus y hours of nonroutine/emergency service in conjunction with z hours of analytical laboratory work for a contracted price. Work required beyond these allowances to be charged at a predefined hourly rate.

1. Meeting Performance Metrics

The most fundamental measure of supplier performance is that all metrics and deliverables identified in the front-end elements are being met. Proof that tests were performed at their scheduled frequency, all parameters were within prescribed control limits, and performance objectives were achieved, must be clearly documented.

The most difficult portion of supplier evaluation to examine is the “happiness” factor. How much of my present satisfaction with the program is unrelated to system performance or cost?

2. Risk Management

A risk management program (that should have been jointly developed) includes a hazard analysis and risk assessment. Each portion needs to be reviewed annually to ensure it remains current for changes made during the previous year. The hazard analysis is intended to identify safety and environmental hazards by rating their severity and likelihood of occurrence, and then establishing controls to reduce or eliminate them. It is fundamental to evaluate and improve the safety of cooling water systems. A process flow diagram needs to indicate where spill prevention is required and where personnel exposure potential exists. Sensible control for strategies for hazards must be included. A Legionella-specific system assessment must review all water systems for their aerosol potential, temperature, physical condition, cleanliness, and location.3 Risk assessment data should include: makeup and system water analyses, system design, operating characteristics, and potential for equipment fouling due to scale and bioslime.

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3. Exhibiting Innovation and Foreseeing Problems

The subjective aspect of supplier evaluation is the most difficult. However, one can examine a supplier’s ability to continually demonstrate eagerness and innovation. When the representative is engaged in the treatment program, he’s not concerned solely with routine testing, but rather strives to July 2007

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If there is a component of satisfaction that is not covered in the specification, then examine whether or not that criteria is appropriate. For instance, some managers want all information immediately communicated and want to be involved in every decision (high supplier visibility); while others value quarterly reviews and exception reporting, knowing the supplier is managing the details of the program (supplier invisibility). An ongoing program evaluation process helps to reduce the reliance on the “happiness factor” for supplier retention or change. 5. Knowing When a Cost Increase is Justified

Owners are often approached for a cost increase due to a “changed condition” from the specification. The question is whether or not the so-called “changed” condition should have been foreseen during the bidding process. Manufacturing fluids and processes are constantly changing, so sometimes a cost increase is justified. Other times, it is an unjustified ploy by the supplier to increase sales or unnecessarily push one up the technology scale. Equipment and chemicals are closely interrelated. A sticking solenoid valve can cause chemical use to dramatically increase— which is not a water treatment problem but rather a maintenance issue. New production equipment, accidental contamination of the cooling water (for example, by hydraulic oil), and new discharge restrictions are examples of changes that the supplier would not have foreseen (and for which they must be compensated). However, many common occurrences ought to have been anticipated and are not to be compensated. These include: 1) Sediment buildup from wind-blown dirt into a cooling tower causing additional biocide usage; 2) A makeup float that became stuck open but was repaired in a timely manner; and 3) Legionella entering a cooling tower requiring immediate disinfection.

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Conclusions

No single “correct” method exists for selecting and managing a cooling water program. High-performance programs can range anywhere from nearly 100% vendor-managed to almost completely self-managed. Under any condition, however, it is a well-defined set of performance metrics, a disciplined data acquisition and analysis approach, and a mutual sense of ownership that drives success. Knowledge and application of several key elements during the front-end development, selection process, and ongoing periods can ensure a solid platform for balance of cost and performance. References 1. Chesney, W.W. 1996. “Preparation of bidding specifications for chemical services relating to cooling water and boiler treatments in industrial facilities.” 57th International Water Conference, p.333. 2. Simon, D.E. 1997. “Comprehensive specifications for contracted water treatment service programs.” 58th Annual International Water Conference, p.172. 3. Turvey, T., Kuchinski, J. 2006. IWC-06-01 “The Legionella shift: how the risk from Legionnaires’ disease has changed the perception of water treatment.” 67th Annual International Water Conference. 4. Howard, K., Winters, M. 2002. “A performance-driven approach to cooling water treatment evaluation.” 63rd International Water Conference, p. 629–635. July 2007

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