A Complete Guide to Globe Valve Types and Parts
The last thing an engineer or operator wants to happen out in the field is a failing valve. By
choosing the best valve for the right system under the specified conditions, you can avoid major
issues that can cause both financial and medical emergencies.
Whether you’re new to the field or just need a refresher, today we’re talking about everything you
need to know about a globe valve.
In this article you’ll learn about what these valves are, the different types, their various parts, and
how they all work together to start, stop, and regulate fluid flow.
Grab your P&ID, we’re getting started.
What is a Globe Valve?
Globe valves are linear motion valves used to control liquid or gas through a pipe. They’re used to
start and stop the fluid flow as well as regulate it.
Globe valves are used in a variety of industries like petrochemicals, pharmaceuticals, shipbuilding,
and aerospace. No matter what industry you’re in, on a P&ID you’ll see the globe valve symbol as a
colored circle with two triangles on either side.
Parts of a Globe Valve
A globe valve has several key parts:
- Bonnet: The bonnet is the outer part of the valve, which encompasses these other parts.
- Cage: The cage surrounds the stem within the valve.
- Stem: The stem connects the disk to the valve actuator or handwheel, transmitting the force.
- Disk (Plug): The part of the globe valve that moves perpendicular to the seat. It’s the moveable
physical barrier that blocks (or frees) the flow.
- When closed, the disk sits against the seat, plugging the flow. When opened, the disk sits above the
seat, allowing liquid to pass.
- Seat (Seat ring): This part of the valve provides the seal between the stem/disk and bonnet when
the disk is tightly pressed against it. It’s either integrated or screwed into the valve itself.
How Does It Work?
Globe valves are usually controlled by an automatic actuator that regulates the flow by moving the
disk perpendicular to the seat. Globe valves can control fluid flow either manually or automatically.
The right angles produce less leakage than you’d find in a gate valve.
When turned in a clockwise motion the disk lowers to the seat which physically obstructs the
liquid’s path, either reducing it or blocking it completely, depending on how low the disk moves.
Vice versa — when the valve moves counterclockwise, the disk raises. This increases the flow of
the liquid or allows it to flow completely.
Types of Globe Valves
There are various globe valve types and designs, each with their own pros and cons.
Globe Valve Arrangement Based on Fluid Flow
Disks that close against the direction of the fluid flow are great if you need a quick opening
valve. Disks that close with the direction of the fluid flow are a better a choice if you need a
quick closing valve.
Ball vs. Needle Disk Types
Things like the type of disk used vary based on the situation. For example, ball disks are more ideal
for low-pressure, low-temperature systems more so than a needle disk.
Z vs. Y Globe Valves
The Z type of globe valve is the most common where the disk and seat sit at 90° (perpendicular)
to the pipe axis, however, this often results in a drop in head.
To get around this high-pressure loss, engineers designed the Y type of globe valve where the stem
and seat of the valve seat at 45° to the pipe axis.
Whether you’re looking for a specific globe valve or O-SEAL® fittings, we can provide you with
the high-quality products and technical resources you need.
Contact us today for a free quote.