A request for a “pump rod” can refer to different parts of the rod connection. Before asking for a replacement on a NOV Type P pump, identify the component on the applicable assembly drawing and preserve the evidence behind the request. A matching name or photograph is not proof of interchangeability.
How the OEM describes the connection
NOV document 25-101131, page 10, places a short sub-rod between the piston rod and the crosshead extension rod. This arrangement allows piston work without disturbing the liner. The source describes locating pilots at the sub-rod ends fitting close-tolerance holes in the adjoining rods to maintain alignment.
NOV cautions that damage such as nicks or burrs at these features can make assembly difficult and displace the piston rod from center, contributing to rapid piston and liner wear. This explains why the locating features matter; it does not provide a universal dimensional acceptance limit or diagnose an individual wear event.
Build a component-specific identification packet
The following is editorial guidance for a document review, not an OEM inspection procedure:
- Pump model, serial number and equipment tag.
- Assembly drawing number, revision and the item position for the requested component.
- Component name as written on that drawing: piston rod, sub-rod or crosshead extension rod.
- Verified part number and its source, keeping any uncertain marking clearly labeled.
- Photographs of the component and relevant end features, only where safe access has already been authorized.
- Existing inspection report references and any unresolved condition findings.
Keep each rod's identity separate. Do not transfer the part number of the complete assembly to an individual rod without documentary support. If a casting, stamped mark or handwritten label cannot be read reliably, retain the image and mark the identifier unconfirmed.
Record locating-feature evidence without inventing tolerances
Where an authorized inspection has already been performed, identify which end and which feature the finding concerns. Distinguish a locating pilot, its mating hole and a nearby surface using the applicable drawing. Record observed damage in the inspector's terms and attach the report rather than converting a photograph into a dimensional measurement.
If measurements are available, retain the feature reference, unit, measuring method, instrument reference and applicable acceptance document. A number without its feature or unit is not a fit assessment. When the acceptance criteria are unavailable, leave the disposition unresolved for the responsible maintenance authority or OEM.
Do not file, grind, force together or otherwise alter locating features based on this article. “No visible damage” is not evidence that alignment, fit or serviceability has been verified.
Separate a parts request from installation approval
A useful request states exactly which component is needed and which documents remain missing. Ask for confirmation against the installed configuration; do not assume that similar rod ends establish interchangeability across models or revisions.
The NOV 12-P-160 and NOV 14-P-220 pages provide equipment navigation. These links do not confirm a rod part number, dimensional fit or availability.
This article supplies no clamp-bolt torque, assembly sequence or repair method. Physical access and work require authorized personnel and the equipment's approved shutdown, isolation, pressure-release verification and safe-access procedures. Identification evidence alone does not authorize installation or return to service.
Source and scope
NOV, How to Treat Your Type P Triplex Mud Pump, document 25-101131, page 10, Piston Rods and Sub-Rods; checked 8 October 2026, Los Angeles time. The rod relationship, locating-feature role and damage caution come from this source. Identification fields and evidence-handling advice are editorial guidance. No interchangeability, stock, lifetime or delivery claim is made.
FAQ
Is the sub-rod the same component as the piston rod?
No. The cited NOV arrangement places a separate short sub-rod between the piston rod and crosshead extension rod.
Does the pump model alone establish the correct replacement part?
No. Verify the component and applicable configuration using the relevant drawing and part-number evidence.
Can a photograph prove the locating fit is acceptable?
No. It can document appearance, but does not replace the required measurements, criteria or assessment.
Does this checklist provide installation torque or repair approval?
No. Use the applicable approved maintenance documents and authorized assessment for physical work.