Horizontal vs. Vertical Design
A horizontal pump is one whose shaft is in horizontal position. It can be:
- an overhang, or between-bearing design
- a radially split, or horizontally split case design
A vertical pump is one whose shaft is in vertical position; it is always an overhang
and of radial-split case type design.
The advantages and disadvantages of a horizontal over a vertical design, and vice-
Advantages of horizontal design:
- It is easier to install, inspect, maintain, and service because its rotor and
internals are easily accessible.
- It can be coupled directly to a variety of drivers including electric motor,
engine, and turbine (steam, gas or power recovery hydraulic turbine.)
- It can be supplied in either overhang design for low suction pressure
service, or in between-bearing design for high suction pressure service.n.
- It can be supplied in various nozzle configuration to simplify, or match the
external site piping. The nozzle configuration can be of end suction top
discharge, top suction top discharge, or side suction side discharge.
- Its low headroom requirement makes it suitable for most indoor
Disadvantages of horizontal design:
- It has limited applications where the NPSHR exceeds the site NPSHA;
usually an auxiliary booster pump is required. (With a vertical lineshaft
pump, the NPSHA can be increased by lowering the setting of its impeller.
- Its maximum allowable operating temperature and working pressure are
generally lower than that of vertical design.
- It requires a bigger footprint.
Advantages of vertical design:
- It requires a smaller footprint and is suitable for installation where the
ground surface area is limited, or is at a premium.
- With a vertical lineshaft pump the impeller setting below the ground can be
lowered to increase the site NPSHA.
- It is suitable for higher temperature service. Because of its radial-split
case design it can be centerline-mounted for even thermal expansion.
- It is suitable for higher pressure service because of its simplified bolting
and confined-gasket design.
Disadvantages of vertical design:
- Most vertical design, particularly the multistage units, or the so called
"vertical lineshaft turbine pumps", require large headroom for installation,
servicing, and maintenance.
- It is usually suitable for direct coupling to electric motor. Using other type of
driver, such as engine or turbine, will require a right angle gear drive and,
possibly, a universal shaft joint and a clutch.
- Being of an overhang design, its hydraulic axial thrust is difficult to balance
in high suction pressure service.
- A multistage pump usually requires expensive sump pit and barrel.
- It is prone to mechanical seal problems when pumping liquids with high
dissolved or entrained gas which accumulates at the top of the stuffing box
or seal chamber where venting can be difficult or less effective.
File: pump horizontal vertical
"Make it simple"
Horizontal end-suction, overhang design (left), and vertical side-suction overhang design (right).