If you’re working with Belliss & Morcom WH or VH series compressors, you’ve likely heard the term suction valve actuator—but what exactly does it do, and why is it important?
In this article, we break down how suction valve actuators work in a Belliss & Morcom compressor, helping you better understand your equipment and the critical role these components play in efficient operation.
What Is a Suction Valve Actuator?
In Belliss & Morcom WH and VH range compressors, suction valve actuators are small pneumatic devices that control whether a compressor cylinder is actively compressing air or not. They do this by controlling the suction valve, which determines if air is allowed into the cylinder during each stroke.
When the actuator receives a compressed air signal, it holds the suction valve open—preventing compression from taking place. This process is called “unloading” the compressor.
Why Do Compressors Need to Unload?
Unloading a compressor isn’t about switching it off—it’s a way to manage the load and energy consumption.
If all suction valves are held open, the compressor is “off-load”—it’s running but not compressing air.
If only some suction valves are held open, the compressor runs on “part-load” or “half-load”—this reduces output and saves energy.
When the actuator releases the valve, the valve plate closes, and the compressor returns to “full-load”, resuming air compression.
This ability to switch between off-load, part-load, and full-load modes makes the compressor highly efficient and responsive to demand.
How It Works: The Simple Version
Each suction valve in the compressor is equipped with a plate depressor.
This plate depressor is controlled by a pneumatic actuator mounted on the valve cover.
When the actuator receives a signal, it pushes down the valve plate—keeping it open.
Open valve = no compression. Closed valve = compression resumes.
These actuators receive air signals from solenoid valves, which are managed by the compressor’s load control system.
Are Suction and Delivery Valves the Same?
While suction and delivery valves look similar, they perform different functions and are not interchangeable. Suction valves include the actuator system for load control. Delivery valves do not.
It’s essential during servicing to always install the correct valve in the correct chamber.
Common Issues and Tips
Air leaks from worn actuator diaphragms can affect performance.
Incorrect installation of valves can lead to inefficient operation.
Always check the O-rings and gaskets for damage during routine maintenance.
Replace damaged or worn plate depressors to ensure smooth operation.
DLJ Compression: Your Partner for Belliss & Morcom Spares
At DLJ Compression, we supply high-quality spare parts for Belliss & Morcom compressors, including:
Suction valve actuators
Delivery and suction valve assemblies
Gaskets, O-rings, and springs
Complete unloader kits
And much more!
We also provide expert support and guidance, helping you choose the right parts and understand how they fit into your system.
Need Help? Contact Us Today
Whether you’re maintaining a VH series compressor or troubleshooting a suction valve issue, our team is here to help. Reach out for expert advice or explore our full range of Belliss & Morcom parts.
📧 Email: operations@dlj-compression.com
Belliss and Morcom Actuator Spare Part Numbers
| Part Number | Description |
|---|---|
| PSB028-004 | Actuator U-CUP SEAL |
| PSB028-002 | Actuator Seal Ring |
| PSB028-FASTENERS | Actuator Fasteners |
| PSB028-038-STEM | Actuator Stem |
| PSB028-006 | Actuator Unloader Spring |
| PSB028-005-STEM | Actuator Spindle Only |
| 2-70-419-04-STEM | Actuator Stem |
| PSB028-041 | Actuator Assembly |
| PSB028-045-STEM | Actuator Stem |
| PSB028-BRASSNUT | Brass Nut |
| PSB028-001-T | Actuator Top Lid |
| PSB028-001-B | Actuator Bottom lid |
| PSB028-045 | Actuator Assembly |
| PSB028-041-RK | Actuator Repair kit |
| PSB028-038-RK | Actuator Repair Kit |
| PSB028-038 | Actuator Assembly |
| PSB028-033 | Actuator Lip seal |
| PSB028-019 | Actuator Assembly |
| PSB028-017-STEM | Actuator Stem |
| PSB028-017 | Actuator Assembly |
| PSB028-008 | Actuator Assembly |
| PSB028-007 | Actuator Assembly |
| PSB028-005 | Actuator Spindle |
| PSB028-001-RK | Actuator Repair Kit |
| PSB028-001 | Actuator Assembly |
| 2-70-641-04-STEM | Actuator Stem |
| 2-70-641-04 | Actuator Assembly |
| 2-70-419-04 | Actuator Assembly |
