Start With the Installed Pump Identity
“Durco Mark III” identifies a pump family, but it does not by itself identify the exact installed configuration or approve a replacement part. Begin with the nameplate and the records for the pump in service: model and size, Group or frame where identified, serial number, drawing or bill of materials (BOM), and known modifications.
Keep the pump identity, the part identifier, and the fitment evidence together. A POS code identifies a component position; an OEM part number identifies a catalog reference; neither replaces the configuration-specific drawing or dimensional review when the mating interfaces are critical.
Use an evidence hierarchy
Start with the installed nameplate and controlled drawing/BOM. Use a POS or OEM reference to find the component. Confirm the interfaces against the applicable manufacturer document and, where needed, measured parts or an approved replacement drawing.
Choose the Right Lookup Path
| What you have | Best first step | What it does not confirm by itself |
|---|---|---|
| A POS or component-position reference | Use the Durco Mark III POS Code Finder to identify the component function. | A POS reference is not a unique OEM part number or final fitment approval. |
| An OEM part number | Search the OEM Part Number Cross-Reference, retaining the installed model and size context. | A listed cross-reference still needs the installed model, size/Group, material, and configuration checked. |
| A POS 103 or impeller request | Continue to the reverse-vane impeller fitment guide. | Impeller style, trim, shaft connection, and hydraulic duty remain configuration-specific. |
| A Group 2 part request | Use the Group 2 parts guide for Group 2 identification details. | “Group 2” alone does not establish a specific size, revision, or mating interface. |
| A nameplate, drawing, or removed part, but no usable number | Assemble the identification evidence below and request an engineering fitment review. | A photograph or nominal size may narrow the search, but may not resolve hidden dimensions or revisions. |
Verify Fitment by Component and Mating Interface
Review the requested part with the components it mates to. The checks below are evidence categories, not universal dimensions or acceptance limits; use the drawing, project specification, and the applicable IOM revision for actual values.
| Component scope | Fitment evidence to review | Decision boundary |
|---|---|---|
| Casing / volute | Pump size and configuration; suction/discharge interfaces; mounting and casing-to-cover register; material and pressure requirements. | A matching bolt pattern does not verify pressure boundary, hydraulic geometry, or the complete installation. |
| Impeller | Impeller style, size/trim, rotation, shaft connection, material, balance documentation when specified, and the curve/duty basis. | A similar outside diameter does not establish hydraulic or mechanical compatibility. |
| Shaft / sleeve / power end | Installed power-end generation, bearing and carrier arrangement, shaft/sleeve configuration, coupling interface, and controlled drawing dimensions. | Do not use a Group label or a dimension from a different measurement location as the acceptance criterion. |
| Cover / seal chamber | Seal-chamber geometry, seal type and setting data, flush ports, gasket or O-ring interfaces, material, and the mating casing/power end. | A cover that attaches to the pump may still be unsuitable for the specified seal arrangement. |
| Matched wet end / complete pump | Hydraulic duty and curve, materials, seal arrangement, installation interfaces, driver, and the project documentation scope. | Hydraulic similarity alone does not prove mechanical, dimensional, or service compatibility. |
Keep component identifiers distinct
The Mark III POS finder uses component-position references; Flowserve IOM sectional drawings also use their own item identifiers (for example, casing, cover, shaft, or impeller item numbers). Do not treat either identifier as a complete pump-specific OEM part number. Match the numbering system to its source drawing or BOM.
Do Not Infer Internal-Part Fit From an ANSI Designation
ASME B73.1 describes dimensional interchangeability for pumps with the same standard dimension designation in defined installation dimensions, including mounting, nozzle locations, input shafts, baseplates, and foundation bolt holes. That scope is useful for installation planning; it does not identify every internal replacement component or establish that parts from different pump families can be mixed.
For cross-platform questions, use the Goulds 3196 vs Durco Mark III replacement comparison. Keep the installed pump’s exact designation and controlled records as the basis for approval.
Keep Reverse-Vane Clearance Separate From Part Fitment
Flowserve Mark 3 instructions distinguish the clearance reference for reverse-vane impellers from open-vane configurations. The required setting depends on the applicable pump configuration and operating conditions; use the IOM supplied for the installed pump rather than copying a number or adjustment direction from another pump family.
In the cited Flowserve IOM revision, one cast indicator pattern on the bearing carrier corresponds to 0.1 mm (0.004 in) of axial impeller movement. That is an adjustment increment, not the required running clearance, a shaft tolerance, or a universal acceptance limit. For the setting procedure and source-specific limits, see the dedicated reverse-vane impeller guide and the applicable manufacturer IOM.
From part request to fitment decision
Each step adds evidence; stop and request a drawing review when the installed configuration cannot be resolved.
Record pump identity
Nameplate, model, size, Group/frame, serial and known revision.
Identify the component
POS, OEM reference, drawing/BOM item, or clear removed-part evidence.
Check mating interfaces
Use the applicable drawing, IOM, material specification, and required measurements.
Agree evidence for supply
Document what is verified and any open checks before quotation or release.
Separate Material Identification From Service Approval
A material name or proprietary code is a cross-reference clue, not a complete corrosion assessment. Confirm the specified product form and material specification against the original records, then evaluate the actual fluid composition, concentration, temperature, contaminants, solids, and service history. Use the ANSI pump material selection guide for the broader material decision.
Agree inspection and documentation requirements in the RFQ or purchase documents. Depending on the part and project, these may include an approved drawing/revision, heat-specific material records, PMI when specified, dimensional inspection of critical interfaces, balance records for rotating components, pressure testing when required, and a certificate of conformance.
Write acceptance requirements into the request
Documentation and testing are not identical for every replacement part. State what is required for this purchase and confirm the supplier can provide it for the specific material and component.
Decide Whether to Replace One Part, the Wet End or the Complete Pump
| Possible scope | When it may fit the maintenance decision | Evidence still needed |
|---|---|---|
| One component | The remaining assembly has been inspected and is acceptable for continued service. | Part identity, mating interfaces, material, condition and any hydraulic effect. |
| Matched wet end | Several wetted components need replacement while the power end and installation can be reused. | Casing, impeller, cover/seal chamber, shaft-side interfaces, duty and metallurgy as one assembly. |
| Complete pump | The replacement scope includes power end, driver, baseplate, installation interfaces, or changed process duty. | Datasheet, performance curve, installation dimensions, motor, seal, materials and project requirements. |
For performance data, use the Technical Resources hub and the approved curve for the specific configuration. For the commercial scope and replacement routes, see the Durco Mark III replacement page.
Durco Mark III Fitment FAQ
Are all Durco Mark III replacement parts interchangeable?
No. Confirm the installed configuration, size, component reference, material and mating interfaces. The family name alone does not establish that a specific part fits.
Is a Group number enough to order a part?
No. Group narrows the identification path, but the pump size, exact component, revision, material and relevant interfaces still need to be checked.
Does ASME B73.1 prove that internal parts are interchangeable?
No. The standard describes dimensional interchangeability for the same standard dimension designation in defined installation dimensions. Verify internal components against the applicable pump records and drawings.
Does every reverse-vane impeller use the same clearance?
No. Follow the applicable IOM for the installed pump and operating conditions. Do not transfer a value or adjustment procedure from another configuration or pump family.
What should I send for a fitment review?
Send the complete nameplate, model and size, Group/frame if known, serial number, POS or OEM reference, drawing/BOM, photos or measurements, material/service requirements, seal details and any required inspection documents.
Technical Sources and Limits
- ASME B73.1 — Specification for Horizontal End Suction Centrifugal Pumps for Chemical Process. Use the standard’s defined dimension designation and scope; it is not a substitute for the installed pump’s parts documentation.
- Flowserve Mark 3 User Instructions, PUIOM000712–00, 04-17. This is a specific manual revision; use the IOM supplied for the applicable installed pump when confirming dimensions or maintenance settings.
- Flowserve Durco product-family information for the distinction between Mark 3 ANSI and ISO product families and their configurations.
Durco, Flowserve and Mark 3/Mark III are third-party trademarks and model designations used only to identify installed equipment and replacement-reference context. ANSI Pumps Pro is an independent aftermarket supplier; no OEM affiliation or endorsement is implied.
