ANSI / ASME B73.1 Process Pumps Explained

What the Standard Fixes

B73.1 defines a common physical envelope so that pumps of the same size from different makers share the same footprint and connections. In practice it standardizes:

• Foot-mounting and baseplate dimensions, and shaft centerline height
• Suction and discharge flange sizes and locations, with a centerline discharge
• The overall dimensional envelope for a given pump size and frame group
• The back pull-out construction described below

Dimension Designations and Size Codes

B73.1 groups pump sizes under dimension designations such as AA, AB or A60. Sizes that share a designation share the installation dimensions the standard fixes, so the designation, not the brand or model name, is the first thing to match when an installed pump is replaced.

Size codes are not written the same way by every manufacturer. In YSM’s G196 series, which follows the Goulds 3196 pattern, the code reads discharge × suction – nominal impeller diameter: 1×1.5-6 is a 1 in discharge, 1.5 in suction pump with a 6 in impeller. In the D Mark III series, which follows the Durco Mark 3 pattern, the code reads group + suction × discharge – impeller, so the same nozzle pair is written 1K1.5×1-6. Read a code against the convention of the catalogue it came from before comparing two pumps. The full conversion table by designation is in ANSI pump size codes.

The designation tables for each pattern, with CP, D, X and the other envelope dimensions, are on the two interchange guides:

• G196 vs Goulds 3196 interchangeability
• YSM D Mark III vs Durco Mark 3

Back Pull-Out Design

The defining feature of a B73.1 pump is back pull-out construction. The bearing frame, shaft, impeller and cover can be removed as a unit from the rear while the casing stays bolted to the pipework. Maintenance does not disturb the piping or the alignment of the suction and discharge connections, which shortens downtime and simplifies overhaul.

What It Leaves to the Manufacturer

B73.1 is a dimensional and mechanical standard, not a performance specification. Hydraulic performance, materials, sealing arrangements and detailed design still vary between makers. Two pumps can share the same B73.1 envelope yet deliver different curves, so a pump is still selected on its own performance for your duty, not on the standard alone.

The standard also leaves the internal design open. Impellers, internal casing geometry, bearing frames, shafts and sleeves follow each manufacturer’s own pattern, so replacement parts are matched to the pattern of the installed pump, not to the standard. The power frame cross-reference lines up the frame and group names used by common B73.1 pump families.

Part numbers are therefore listed by pattern. The Goulds 3196 pattern parts list is arranged by pump size and frame (STX, MTX, LTX and XLTX), and the Durco Mark 3 pattern parts list by size designation and Group 1, 2 and 3; both give the OEM part number each YSM reference corresponds to.

Why It Matters to Buyers

YSM builds to this dimensional system: the G196 series follows the Goulds 3196 dimensional envelope and the D Mark III series the Durco Mark III envelope, so existing installations can be maintained without re-piping. See replacement parts for coverage.

Goulds, 3196, Durco, Mark III and Mark 3 are trademarks of their respective owners. YSM Pumps is an independent manufacturer and is not affiliated with, sponsored or endorsed by ITT Goulds Pumps or Flowserve. Interchangeability refers to dimensional interchangeability of the referenced standard designs; verify size, group and configuration from the pump nameplate before ordering.

Confirming Fit Before Order

A replacement is confirmed from data taken from the installed pump:

1. A photo of the nameplate, with the model, size code as written, frame or group, and serial number.
2. The outline or foundation drawing, if one is on file.
3. For parts: the part position number and, where the nameplate is missing, measurements of the worn part.

See what information is needed before replacing an ANSI process pump and the urgent ANSI pump parts RFQ checklist.

If the OEM part number is known, the OEM part number finder shows the corresponding YSM reference.