IMI Buschjost indirect-solenoid-actuated valves are pilot-operated valves designed for applications with sufficient pressure differential across the system. The solenoid controls a pilot orifice, allowing system pressure to actuate the main diaphragm, enabling high flow rates with low power consumption. These valves are ideal for steam, hot water, HVAC, and industrial process applications where reliable switching and energy efficiency are critical.

What Is an Indirect-Acting Solenoid Valve?

An indirect-acting (pilot-operated) solenoid valve uses system pressure—not the solenoid coil—to open and close the main flow path.
Manufactured by IMI Buschjost, these valves are designed for applications with a defined pressure differential (ΔP) across the system.

How it works (simplified but accurate):

• The solenoid opens a pilot orifice
• Pressure above the diaphragm drops
• System pressure lifts the diaphragm
• The valve opens with minimal electrical effort

This architecture allows:

• Higher flow capacity
• Lower energy consumption
• More stable operation under load

Why Indirect-Acting Valves Dominate Industrial Systems

Let’s cut through generic claims.

1. Energy Efficiency

Direct-acting valves fight pressure.
Indirect-acting valves use it.

Result: smaller coils, lower power draw, longer service life.

2. High Flow Capability

Pilot operation enables:

• Larger orifice sizes
• Better Kv values
• Reduced pressure drop

3. Process Stability

Diaphragm-assisted opening:

• Reduces chatter
• Handles pressure fluctuations better
• Improves repeatability

Steam Systems

• Boiler lines
• Sterilization processes
• Heat exchangers

HVAC & District Heating (Critical for Nordic Markets)

• Energy-efficient flow control
• Building automation systems
• Thermal distribution networks

Process Industries

• Food & beverage (clean steam)
• Pharmaceutical systems
• Chemical processing

Compressed Air Systems

• Automation lines
• Pneumatic control

IMI Buschjost: What Makes It Different

IMI Norgren (including Buschjost) focuses on:

• Robust diaphragm design for long lifecycle
• Resistance to contamination and scaling
• Consistency under thermal stress (steam applications)

This isn’t commodity hardware.
It’s built for continuous industrial duty.

How to Select the Right Valve (Real Criteria)

Forget catalog browsing. Focus on:

• Pressure differential (ΔP) → minimum & operating range
• Media type → steam, water, air, aggressive fluids
• Temperature limits → especially for steam
• Kv / flow requirements
• Duty cycle → intermittent vs continuous
• Fail-safe position → normally closed (NC) or open (NO)

If you’re not evaluating these, you’re guessing—not engineering.

What is an indirect-acting solenoid valve?
A pilot-operated valve that uses system pressure to open and close, requiring a minimum pressure differential.

Where are indirect solenoid valves used?
Steam systems, HVAC, industrial processing, and compressed air applications.

What is the difference between direct and indirect solenoid valves?
Direct valves use coil force; indirect valves use system pressure for higher efficiency and flow.

Why is pressure differential important?
Without sufficient ΔP, the valve cannot open properly.