Vertical Turbine, Sump & Can Pumps

Vertical Turbine, Sump & Can Pumps — Sealing Overview

Vertical suspended pumps hang the bowl assembly below the motor on a column and line shaft. API 610 groups them as VS1 (wet-pit turbine), VS4 (sump pump with line-shaft bearings) and VS6 (double-casing can pump). They lift river and cooling water, drain sumps and pits, and handle light hydrocarbons with little NPSH margin.

On most vertical pumps the seal sits at the top, in the discharge head. Two consequences follow. First, any vapour or air in the pumped liquid rises to the seal chamber, so the chamber must be vented, typically with API Plan 13. Second, the seal can see a pressure close to discharge unless a throttle bushing and bleed-off line reduce it, so the seal-chamber pressure must be confirmed from the pump maker before the seal is selected.

Key Sealing Challenges

• Trapped vapour: without venting, the faces run dry at the top of the chamber and fail early. Plan 13 returns seal-chamber liquid to suction and carries vapour with it.
• Long shafts: line-shaft bearing wear allows runout and shaft whip at the seal. Check line-shaft bearings whenever a seal fails.
• Axial setting: the impeller lift is set at the motor or coupling. Setting the seal before setting the impeller lift moves the seal faces off their design length.
• Submersible pumps: the seals run inside the pump, in an oil chamber. Water in the oil is the first sign of lower-seal wear.

Fault Diagnosis Example

Symptom: Seal on a vertical cooling-water pump fails soon after every restart; faces show dry-running marks.
  ├── Incorrect Response: "Fit a seal with a higher temperature rating."
  ├── Diagnostic Evidence Required:
  │     ├── Is the seal chamber vented? Check for a Plan 13 line or vent and whether it is blocked.
  │     ├── Was the seal set before or after the impeller lift was adjusted?
  │     └── Measure shaft runout at the seal; check line-shaft bearing wear.
  └── Engineered Solution:
        ├── Add or clear a Plan 13 vent line and vent the chamber before start-up.
        ├── Set the impeller lift first, then lock the cartridge seal.
        └── Replace worn line-shaft bearings.

Frequently Asked Questions

Why do vertical pumps use Plan 13 instead of Plan 11?

Plan 11 pushes liquid into the chamber but does not remove the vapour that collects at its top. Plan 13 takes liquid from the seal chamber back to suction, so vapour leaves with it and the faces stay wetted.

Does the seal on a vertical turbine pump see discharge pressure?

It can. The seal sits in the discharge head, so its pressure depends on the throttle bushing and any bleed-off to suction. Confirm the seal-chamber pressure from the pump maker or measure it before choosing the seal.

Can Gipfel supply seals for submersible sewage pumps?

Yes, built to the pump maker’s seal design. Send the pump make, model and serial number, or the old seal.

Related: Municipal Water & Sewage · Pipelines, Terminals & LPG · Between-Bearings Pumps · All process pump solutions.

Request a Seal Selection

Send your pump make and model, fluid, temperature, pressure, shaft size and speed to info@gipfelengg.com or use our enquiry form. Gipfel Engineering (ISO 9001:2015, NSIC-registered MSME, Mumbai) designs and manufactures mechanical seals, seal support systems and process pumps.