Cooling Water Chemistry and Compressor Exchanger Reliability

Cooling Water Chemistry and Compressor Exchanger Reliability

Owned decision: Link site cooling-water evidence to documented exchanger metallurgy, operating conditions and manufacturer-specific reliability requirements. Mandatory asset: Cooling Water Compatibility Review Sheet.

01 | Direct engineering answer

Cooling-water suitability cannot be inferred from a single pH or hardness result. A defensible review matches the sampled water to the exact exchanger construction, metallurgy, gasket and brazing materials, wetted coatings, flow velocity, temperature profile, dissolved oxygen exposure and duty cycle. It also separates open recirculating systems from closed loops and once-through supplies because concentration, oxygen ingress, evaporation, chemical dosing and biological exposure differ substantially. The outcome is a documented accept, conditional hold or reject decision, not a generic declaration that a water source is good or bad.

For each proposed corrective action, determine whether the problem is on the water side, the compressed-air side or the measurement system. A fouled exchanger may show higher approach temperature, but the same symptom can arise from low cooling-water flow, warmer inlet water, excess compressor duty, incorrect sensor location or air-side maldistribution. Capture simultaneous operating measurements before choosing acid cleaning, descaling, replacement or system redesign.

02 | Owned boundary and neighbouring pages

Link where appropriate without repeating their principal decisions.

This page does not specify a proprietary inhibitor, biocide dose, acid concentration, universal water-quality limit or legally required test interval. Such values depend on the actual manufacturer, materials, local water-treatment programme, environmental permits and applicable jurisdiction. It does not certify repaired heat exchangers or replace a qualified pressure-equipment inspection.

03 | The physical system and its interfaces

Map the cooling circuit from source and make-up water through storage, pump, strainers, heat exchangers, bypass valves, balancing valves, sampling ports, expansion provisions and return. Identify the location of cooling towers, chillers, plate exchangers and side-stream filtration. A drawing should show which wetted materials belong to the compressor package and which belong to site infrastructure, because mixed-metal galvanic couples may extend well beyond the exchanger itself.

For every measurement, mark the physical point and state. Supply temperature upstream of a mixing tee cannot substitute for actual exchanger inlet temperature; a sample from a treatment skid may not represent stagnant dead legs. Record whether the circuit is isolated, flowing, recently dosed, topped up, drained or experiencing production demand. Without this context a laboratory result can be precise but operationally irrelevant.

04 | Exchanger construction and material identity

Common arrangements include shell-and-tube, plate-and-frame, brazed-plate, finned and package-integrated cooling passages. Tube, plate, shell, gasket, braze and connection materials may differ. Stainless steel is not a sufficient material designation: grade, weld condition, chloride exposure and temperature determine relevant corrosion mechanisms. Copper alloys, aluminium, carbon steel, nickel alloys and elastomers each have different exposure sensitivities.

Use the as-built bill of materials, serial-specific spare-part drawing, manufacturer material declaration or verified inspection record. A replacement plate pack may introduce a new gasket formulation or solder/braze material even when the envelope dimensions are unchanged. Any unverified wetted material remains an explicit hold; do not infer it from colour, magnet response or generic catalogue photography.

05 | Duty envelope and operating states

Document design and actual water inlet and outlet temperatures, minimum and maximum flow, allowable differential pressure, pressure class, compressor stage loading, ambient range, shutdown behaviour and periods of stagnant water. The hottest metal surface can experience different deposition and corrosion conditions from a cool sample tap. Intermittent operation can concentrate salts locally and create oxygen gradients under deposits.

Use at least three operating states where practicable: stable loaded duty, reduced or cycling duty, and restart following an idle period. A sample taken after extended flushing may hide the quality of water that occupied the exchanger during shutdown. Separate temporary commissioning water, routine operating water and emergency make-up sources; each may need its own compatibility disposition.

06 | Sampling plan and chain of custody

Define representative sampling points for incoming make-up, circulating supply, exchanger return, blowdown and any known dead leg. Use laboratory-prescribed containers, preservatives, holding times and transport conditions for the selected analytes. Record date, clock time, operator, sample point, operating state, temperature, treatment additions, instrument calibration and laboratory accreditation or method. Duplicate or field-blank samples may be appropriate when contamination or handling errors are suspected.

A one-off sample is a snapshot. Chemistry can change with season, municipal source, borewell blending, cooling-tower cycles, make-up failures or dosing-system faults. Trend results with the operating log. If a laboratory reports a result below detection limit, preserve that qualifier; do not convert it to zero. If units differ, retain the original report and document the conversion.

07 | Minimum water analysis panel

The initial panel should be justified by material and circuit risk. Common candidates include pH, conductivity, total dissolved solids, calcium and total hardness, alkalinity, chloride, sulphate, silica, dissolved iron and copper, suspended solids or turbidity, microbiological indicators, dissolved oxygen, temperature and treatment residuals. Some parameters are not meaningful or stable unless sampled and analysed by the correct method and timing.

An open cooling tower may require concentration and biological-control evidence that a sealed inhibited glycol loop does not. A glycol circuit additionally requires concentration, inhibitor condition, freeze point and degradation-acid assessment. The presence of a laboratory result is not itself evidence that it meets a particular exchanger limit; the latter must be sourced and linked to the serial-specific component.

08 | Conductivity, TDS and concentration

Conductivity is a temperature-dependent measure of ionic transport and is often useful for trending dissolved salts. It does not identify which ions are present, and a conductivity-to-TDS factor is approximate and water-specific. Two supplies with similar conductivity can differ greatly in chloride, sulphate, hardness and corrosivity. Record the instrument temperature compensation and the units, usually µS/cm, before comparing results.

In an evaporative system, a simple cycles-of-concentration estimate may use circulating-to-make-up concentration for a suitably conserved tracer such as chloride, provided there is no other material source or removal. Example: 240 mg/L circulating chloride divided by 80 mg/L make-up chloride suggests about 3 cycles. This does not establish that three cycles are acceptable, nor does it substitute for a full mass balance when leakage, treatment chemicals or variable sources are present.

09 | Hardness, alkalinity and scale potential

Calcium and magnesium hardness can contribute to mineral deposition, particularly where high surface temperature and local concentration shift solubility. Alkalinity influences carbonate equilibria, but neither hardness nor alkalinity alone proves that scale will form. Evaluate measured calcium, alkalinity, pH, temperature, ionic strength and residence conditions using a suitable, documented method, then check that the method is applicable to the actual water composition.

Scale indicators are screening tools, not direct measurements of exchanger fouling or permission to dose acid. A surface deposit should be sampled and characterised before chemical removal, because calcium carbonate, calcium phosphate, silica, iron oxide and biological deposits require different approaches and present different compatibility risks. Record deposit location, appearance, mass if measured and laboratory identification.

10 | Chloride and localized corrosion

Chloride deserves attention where susceptible stainless grades, welds, crevices or high temperatures occur. Risk depends on alloy, oxygen availability, tensile stress, chloride concentration, pH, surface condition and time. It is technically unsound to publish a single universal chloride limit for all stainless heat exchangers. Crevices beneath gaskets or deposits may experience more aggressive chemistry than the bulk water.

If pinhole leakage or staining is observed, collect a damage map and examine whether attack is pitting, crevice corrosion, erosion-corrosion or mechanical damage. Confirm the metallurgy before drawing conclusions. For a replacement proposal, document supplier approval for the actual chloride range and peak operating temperature; a material name alone is not a complete compatibility determination.

11 | Sulphate, sulphide and microbiological interactions

Sulphate is a normal constituent of many waters, but its significance depends on concentration, material and biological conditions. Sulphate-reducing microbial activity may contribute to localized corrosion in suitable anaerobic niches. A sulphate result alone does not demonstrate microbial corrosion, and a single negative culture does not exclude biofilm in a poorly sampled region.

Use deposit examination, water chemistry, biological methods and metallurgical evidence together. If treatment is proposed, review the discharge implications, worker exposure, material compatibility and effect on downstream equipment. Chemical biocide selection and dose must remain with the responsible water-treatment specialist and applicable permit framework.

12 | Dissolved oxygen and corrosion cells

Dissolved oxygen can drive corrosion of susceptible metals and create differential-aeration cells beneath deposits or in stagnant zones. Its interpretation depends on circuit design: an open tower routinely contacts air, while an appropriately sealed loop may have much lower oxygen ingress. Unexpected oxygen increases in a closed loop can indicate make-up leakage, air ingress or frequent draining and filling.

Field measurement and sampling technique matter because oxygen can change rapidly when water contacts air. Record whether the reading is in situ and whether the instrument was calibrated. Oxygen is one part of a corrosion assessment; corrosion products, pH, inhibitor condition, metallurgy and hydraulic behaviour must also be considered.

13 | Iron, copper and corrosion-product transport

Rising iron or copper concentrations can indicate active corrosion, deposit mobilisation or a changed make-up source. Differentiate dissolved and total metals when the laboratory method permits. A sudden increase after chemical cleaning may reflect release of historical deposits rather than a new corrosion rate. Pair chemistry trends with filters, strainers, visual inspections and pressure-drop data.

Copper deposits on ferrous surfaces can promote local galvanic activity; conversely, iron oxides can obstruct small plate passages. Where cross-contamination is suspected, inspect the wider circuit rather than blaming the compressor exchanger alone. Use component-specific source evidence to decide whether a metal concentration is acceptable.

14 | Suspended solids, filtration and erosion

Suspended solids cause deposition, clogging and in some geometries abrasive erosion. Particle size, hardness, concentration and local velocity all matter. A clean strainer at one inspection point does not prove that fine solids are absent or that a plate channel is free of debris. Record mesh or micron rating, bypass arrangement, differential pressure and cleaning frequency.

Excessive velocity may remove protective films and accelerate damage, while insufficient velocity encourages settling and biofilm. There is no universal optimum independent of exchanger design. Confirm the manufacturer’s hydraulic envelope and evaluate flow distribution, local restrictions and pump condition before changing pump speed or orifice sizes.

15 | Biofouling and stagnant regions

Biofilm can reduce heat transfer, obstruct passages and create under-deposit corrosion environments. Microbiological counts from bulk water do not necessarily represent organisms attached to surfaces. Inspect strainers, low-flow legs, warm stagnant sections and plate pack edges where safe and permitted. Record odour, slime, discoloration, differential pressure and temperature trends as observations, not proof of a particular organism.

Biological control should integrate system design, circulation, filtration, cleaning and treatment. Repeatedly increasing biocide dose without establishing the root cause can mask inadequate flow or dead-leg design. Any disinfection programme must address worker safety, compatibility with elastomers and metals, effluent requirements and verification of efficacy.

16 | Glycol and closed-loop fluid condition

Where glycol is present, verify whether the circuit uses ethylene or propylene glycol, the exact product and inhibitor package, measured concentration and history of top-ups. Glycol changes viscosity, specific heat, density and pump duty. Ageing or overheating may produce degradation products that alter acidity and corrosion behaviour. Do not substitute automotive coolant or mix inhibitor systems without supplier approval.

For heat calculations, obtain properties at the actual glycol concentration and temperature rather than using pure-water values. Refractometer readings can be influenced by other dissolved constituents and should be interpreted with the fluid supplier’s method. Freeze protection, thermal transfer and corrosion protection are related but separate acceptance questions.

17 | Corrosion mechanisms and damage evidence

Distinguish general wall loss, pitting, crevice corrosion, galvanic attack, erosion-corrosion, microbiologically influenced corrosion, stress corrosion cracking and under-deposit attack. Each mechanism suggests different evidence and mitigation. Record damage position relative to water entry, gasket lines, welds, stagnant regions and dissimilar-metal joints. Photographs require a scale, orientation and component identification.

Pressure-boundary acceptance is not determined by a generic pit-depth threshold in this article. Qualified inspection personnel must use applicable component drawings, thickness requirements, inspection methods and repair rules. When the mechanism is uncertain, retain competing hypotheses and assign further testing rather than asserting a definitive cause.

18 | Scaling versus fouling versus insufficient water flow

High compressed-air discharge temperature with a high cooling-water outlet temperature may indicate heat-load increase or insufficient cooling-water mass flow; a small water-side temperature rise with poor cooling may indicate low duty, bypassing, instrumentation error or exchanger ineffectiveness depending on flow. Water-side differential pressure can increase with blockage, but it can also change with flow and viscosity. Always compare at matched flow and duty.

A useful diagnostic set includes compressor inlet/outlet process temperatures, water inlet/outlet temperatures, water flow, water-side differential pressure, process pressure, ambient conditions and machine loading. Interpret all channels together. Cleaning based only on a single temperature reading risks unnecessary intervention and potential damage to the exchanger.

19 | Heat-balance method and limits

For a single-phase cooling fluid, estimated heat removal is Q = m_dot × cp × (T_out − T_in). Mass flow must be in kg/s, heat capacity in kJ/(kg·K), and temperature difference in K to obtain kW. For water near ordinary cooling temperatures, cp around 4.18 kJ/(kg·K) can be an illustrative assumption, not a universal value. For glycol mixtures use concentration- and temperature-specific properties.

Example: 2.0 kg/s water with 6 K rise yields Q ≈ 2.0 × 4.18 × 6 = 50.2 kW. If measured heat removed appears inconsistent with the process-side load, first verify sensor placement, flow calibration, bypass streams, thermal transients and the assumption of steady state. The arithmetic demonstrates the method; it does not validate the actual exchanger duty.

20 | Approach temperature and effectiveness

An approach temperature can be defined as a selected hot-stream outlet temperature minus cold-stream inlet temperature, but the definition must be printed beside each reported value. Smaller approach may indicate better performance at comparable duty and flow, yet it is not an absolute health metric when operating conditions differ. Use consistent definitions for historical trends and avoid comparing counterflow and crossflow equipment as if they were identical.

For rigorous design or rating work, use the manufacturer’s method, applicable correction factors and verified stream properties. The log-mean temperature difference method is useful only when its flow arrangement, terminal temperature differences and assumptions are appropriate. A field trend can support a fouling investigation without becoming an unsupported claim of design performance.

21 | Water-side pressure loss and hydraulic integrity

Measure differential pressure across the actual exchanger taps while recording flow and fluid temperature. The same pressure loss at different flow rates is not a like-for-like condition. Increased pressure loss at matched flow can support a blockage hypothesis, but valve misposition, air binding, instrument errors and altered viscosity must be ruled out. Low pressure loss can also indicate bypass or internal flow maldistribution.

Confirm that the pressure instruments share compatible reference elevations and ranges. Where the water circuit connects to other equipment, separate package exchanger loss from piping, strainers and control valves. An exchanger pressure rating is distinct from its recommended operating differential and must be verified from the correct component documentation.

22 | Water treatment governance

A treatment programme must define the system owner, water-treatment specialist, test frequency, laboratory method, action levels, escalation route, chemical inventory, discharge obligations and response to abnormal results. The compressor service provider should not silently assume responsibility for the entire cooling-tower programme. Equally, the site water contractor should not approve exchanger metallurgy or pressure repairs without the appropriate technical authority.

Each chemical recommendation must be supported by the current safety data sheet, supplier compatibility statement and local environmental requirements. Preserve the treatment history and deviations. Record when a chemical was added relative to sample collection and when an intervention changed the system operating condition.

23 | Cleaning and restoration selection

Choose restoration after characterising the deposit, inspecting component construction and reviewing manufacturer-approved methods. Mechanical cleaning may be feasible for accessible tubes but inappropriate for thin plate channels. Chemical cleaning requires confirmed compatibility with metal, braze, gasket, seals and coatings, plus controlled circulation, containment, neutralisation and waste handling. The cleaning contractor must provide a method statement and hold points.

Cleaning success is demonstrated by controlled before/after measurements under comparable duty, supported by inspection and any required integrity tests. An improved heat-transfer trend does not prove absence of leakage or damage. A failed cleaning attempt should trigger reconsideration of the deposit identity, hydraulic arrangement and replacement decision rather than progressively more aggressive chemistry.

24 | Repair versus replacement decision

Consider remaining wall integrity, leakage history, accessibility, material compatibility, spare availability, repair method qualification, pressure-equipment requirements, downtime risk and life-cycle cost. A lower purchase price is not evidence of interchangeability. A replacement exchanger can have the same nominal duty but different pressure drop, gasket materials, connection orientation or thermal expansion behaviour.

Any substitution must reconcile model, serial, revision, wetted material list, pressure and temperature ratings, design flow, allowable differential pressure, mounting, drain and vent provisions and commissioning tests. Record whether the original manufacturer has approved the substitute and retain the written basis.

25 | Instrumentation quality and uncertainty

For temperature trends, check sensor calibration, immersion depth, response time and whether a thermowell is exposed to representative flow. For flow, verify meter installation length, fluid properties and calibration. For conductivity and pH, account for temperature compensation, calibration standards and sampling delay. An apparent small improvement can be below the combined measurement uncertainty.

Example: if inlet and outlet temperature readings each have uncertainty ±0.5 K, a reported 1.0 K change in differential temperature cannot automatically be treated as a reliable performance improvement. A formal uncertainty budget may be required for acceptance testing. Keep raw readings, calculated values and engineering interpretation as separate fields.

26 | Failure symptoms and discriminating evidence

Common symptoms include rising interstage air temperature, higher compressor discharge temperature, abnormal cooler differential pressure, frequent strainer cleaning, leaking plate gaskets, cross-contamination, visible corrosion and unplanned trips. None is uniquely diagnostic. Map each symptom to competing causes and to the least intrusive safe verification method before dismantling equipment.

A recurring leak after gasket replacement may arise from gasket selection, plate deformation, incorrect compression dimension, thermal cycling or chemical attack. A rising pressure drop may arise from deposits, closed valves or altered flow. The fault record should show what evidence supports and contradicts each hypothesis, avoiding premature single-cause conclusions.

27 | Commissioning and acceptance plan

Before introducing water, verify approved component identity, isolation plan, pressure boundary status, flow path, venting, drain availability, water-quality release, instrument calibration and responsible signoffs. Confirm that cleaning chemicals have been removed as required and that sampling points are usable. Initial circulation should follow the equipment manufacturer’s procedure, with leakage surveillance and controlled escalation.

Capture stable as-left readings at a documented compressor load and water flow. Confirm thermal response, pressure drop, alarms, interlocks, make-up behaviour and evidence of leakage or cross-contamination. Any acceptance criteria must be taken from the serial-specific manufacturer or approved project specification, not invented by this page.

28 | Ongoing reliability monitoring

Trend water inlet temperature, outlet temperature, flow, exchanger pressure loss, compressor operating state, key chemistry results, make-up volume, filtration events and cleaning dates. Use comparable conditions and note instrument changes. A monitoring programme should include clear ownership for missed samples, abnormal chemistry, failed sensors and equipment trips.

The most useful dashboard separates leading indicators (conductivity, treatment residual, make-up frequency, rising strainer differential pressure) from lagging outcomes (loss of heat-transfer performance, corrosion findings, leakage and downtime). Do not claim predictive accuracy without validated historical evidence.

29 | Responsibility and escalation boundaries

Assign the site utilities owner to source-water and treatment-system records; water-treatment specialist to chemical interpretation and dosing; compressor OEM or authorised engineer to component applicability and operating envelope; qualified inspector to pressure-boundary acceptance; service technician to controlled observations and approved work; and editorial owner to accurate publication. One person may hold multiple roles only where appropriately qualified and authorised.

If water chemistry conflicts with a supplier limit, isolate the disputed requirement and record the source, date, operating conditions and proposed disposition. Do not resolve it by selecting the least restrictive generic internet value.

30 | Evidence hierarchy and revision control

Prefer serial-applicable OEM exchanger documentation, as-built drawings, material certificates, project specifications, verified site laboratory reports and signed service records. Supplier technical bulletins and established engineering references may support methods but do not override the exact component requirement. Preserve revision numbers and dates so later supersession is traceable.

The governing R01 map defines the page intent and mandatory asset, not numerical water-quality thresholds. Accordingly, the worked numbers below are educational examples, not a claim that a named manufacturer has approved them. Each open limit is a release hold until a competent owner supplies the relevant source.

31 | Worked case A — elevated chloride and material uncertainty

Illustrative case: a site reports circulating chloride 260 mg/L and make-up chloride 90 mg/L. The exchanger plate material is described on a purchase order only as “stainless steel”; its grade, brazing method and gasket formulation are missing. At the time of sampling, water supply was 31 °C and compressor load was 82% of indicated full-load power. The numerical chloride concentration is an observation, not a pass/fail threshold.

The engineer records approximate concentration ratio 260/90 = 2.89, but explicitly notes that a ratio is not a compatibility criterion. The review remains HOLD because the wetted materials and applicable supplier limits are unknown. Next actions: obtain serial-specific material declaration, validate sample provenance, check for alternative chloride inputs and ask the exchanger supplier for a written operating envelope. No replacement or chemical recommendation is released.

32 | Worked case B — apparent fouling at mismatched flow

Illustrative baseline: water flow 2.4 kg/s, inlet 29 °C, outlet 34 °C and exchanger differential pressure 42 kPa. Current condition: 1.8 kg/s, inlet 32 °C, outlet 38 °C and differential pressure 34 kPa. Using cp = 4.18 kJ/(kg·K), baseline estimated heat removal is 2.4 × 4.18 × 5 = 50.2 kW; current is 1.8 × 4.18 × 6 = 45.1 kW.

Although the current outlet temperature is higher, flow and inlet temperature changed. The lower measured pressure drop is not evidence that the exchanger is clean, because flow is lower. The case remains INCONCLUSIVE until matched-duty/matched-flow testing, pump and valve checks, sensor verification and relevant water chemistry are completed. The record explicitly prevents an unjustified descaling order.

33 | Worked case C — suspended solids after piping work

Illustrative site history: a water-main repair preceded a rise in strainer cleaning frequency from monthly to daily. A circulating sample shows turbidity 18 NTU versus a previous typical 3 NTU; the same period has an increase in exchanger water-side differential pressure from 25 to 46 kPa at comparable flow. Neither turbidity figure is treated as a universal acceptance limit.

Inspection finds particulate deposits in a strainer and a water sample is submitted for solids characterization. The immediate decision is to review source isolation, flushing, filtration and safe inspection under the site procedure. A cleaning plan remains conditional on deposit identity and exchanger construction. As-left evidence must include verified flow, pressure drop and chemistry after system stabilization.

34 | Worked case D — glycol property error

Illustrative loop contains a declared 35% glycol mixture, but the heat-balance spreadsheet uses water cp = 4.18 kJ/(kg·K). At measured mass flow 1.5 kg/s and 7 K rise, that spreadsheet calculates 43.9 kW. If the correct supplier property at the measured composition and mean temperature were hypothetically 3.70 kJ/(kg·K), the result would be 38.9 kW—a difference of about 5.0 kW or 11.4% relative to the water-based result.

The hypothetical property is for sensitivity illustration only. The correct disposition is to retrieve the exact fluid data and verify concentration and meter calibration before issuing a performance report. It would be misleading to attribute the calculated difference to exchanger degradation.

35 | Worked case E — leakage after chemical cleaning

Illustrative event: a plate exchanger develops seepage at a gasket joint after an externally contracted cleaning operation. The cleaning agent, concentration, duration and temperature are not documented; gasket material is also uncertain. The leak is observed after restart but its mechanism is not yet established.

The engineer holds the equipment pending safe isolation and qualified inspection, preserves chemical invoices and operator logs, identifies the gasket and plate materials and requests the contractor’s method statement. Potential explanations include chemical incompatibility, disturbed gasket seating, existing deterioration or pressure/thermal cycling. The case does not assume that cleaning caused the leak. Return-to-service requires approved repair and leak/integrity testing to the applicable equipment requirements.

36 | Worked case F — seasonal source change

Illustrative facility blends municipal supply and borewell water. In summer, make-up conductivity rises from 620 to 1,140 µS/cm, chloride from 75 to 145 mg/L and total hardness from 160 to 290 mg/L as CaCO3. Water inlet temperature also rises by 5 K. The exchanger’s discharge temperature increases, but several independent variables have changed.

The review separates chemistry compatibility from thermal capacity. It requests a source-blending record, current material limits, treatment-system adjustment review and matched-load thermal testing. The outcome is CONDITIONAL HOLD, not a blanket declaration that borewell water is unsuitable. Any change to source water or treatment programme requires site and supplier approval.

37 | Cooling Water Compatibility Review Sheet — mandatory editable register

Use one record per asset and operating water source, with linked child records for samples, deviations and corrective actions. “Pass” is not permitted when the governing acceptance limit is missing. Required fields distinguish raw evidence from interpretation, and the disposition owner must sign or formally acknowledge every hold.

38 | Completed illustrative register extract

For the fictional case B, register entry “water flow” records baseline 2.4 kg/s and current 1.8 kg/s, with meter identity pending; status = REVIEW. Entry “water inlet temperature” records 29 °C baseline and 32 °C current; status = OBSERVED. Entry “fouling diagnosis” records “not established; matched-condition test required”; status = HOLD. Entry “cleaning authorisation” remains NOT APPROVED. The owner is the site utilities engineer for hydraulic verification and the OEM-qualified service lead for any exchanger intervention.

This extract shows how the worksheet separates observed values from interpretation. It also prevents an attractive but unsupported narrative that an exchanger needs descaling whenever outlet temperature rises.

39 | Acceptance decision logic

ACCEPT is available only when asset identity, wetted materials, current representative chemistry, operating envelope, applicable manufacturer limits, thermal/hydraulic verification and any required integrity evidence are complete and approved. CONDITIONAL ACCEPT requires documented limitations, monitoring and accountable authorisation under the governing equipment procedure; it is not a substitute for missing safety-critical proof.

HOLD applies to unknown material, unsourced limit, unrepresentative sample, unapproved treatment, unexplained leak or unresolved discrepancy. REJECT applies when documented conditions conflict with applicable requirements and no authorised corrective plan exists. Each outcome must identify the signer, date, revision and next review trigger.

40 | Site enquiry / evidence intake

Ask for compressor and exchanger nameplate photographs, make/model/serial, cooling circuit P&ID, water source and treatment description, recent laboratory reports with dates and methods, water flow and inlet/outlet temperature readings, pressure differential, load condition, symptoms, prior cleaning and repairs, and any existing OEM water-quality limits. An incomplete enquiry should be accepted for preliminary discussion but not transformed into a compatibility approval.

CTA: “Request a cooling-water and exchanger compatibility review. Share the equipment identity, water analysis and operating measurements so the applicable technical requirements can be checked.” No response time, stock, service radius or outcome is promised.