Hermetic and special doors are used in environments where controlling the indoor atmosphere leaves no room for error: cleanrooms, operating theatres, pharmaceutical facilities, food processing plants, cold storage chambers, and biocontainment areas. In all these cases, the electromagnetic locking system is one of the most critical components of the installation. It must guarantee the airtightness of the enclosure, respond accurately to control system signals, and operate reliably through thousands of cycles without functional degradation.
This article explains how solenoids work in hermetic and special doors, which technical parameters should be considered when selecting a device, and what solutions NAFSA offers to manufacturers and integrators working with these types of installations.
What is a hermetic or special door?
A hermetic door is designed to create an airtight seal between two spaces, preventing the passage of air, particles, contaminants, or biological agents. Unlike conventional automatic doors, its design incorporates perimeter compression seals, reinforced frames and, in many cases, electromagnetic locking mechanisms capable of maintaining the pressure required on the seal to ensure effective closure.
The category of special doors also includes armoured doors, cold-room doors, highly airtight fire-rated doors, and access points to segregated security zones. In all these cases, door locking is not merely a locking function, but an integral part of the environmental control or security system of the facility.
How solenoids work in hermetic doors
The operating principle is the same as in any electromagnetic locking system: an energized coil generates a magnetic field that attracts a metal armature plate, keeping the door locked. When the system interrupts the current—or applies a release pulse—the magnetic force disappears and the door can be opened.
In the case of hermetic doors, this mechanism must meet additional requirements:
- Sufficient holding force to compress the perimeter seal. The solenoid not only keeps the door closed but must also apply the force required to ensure effective sealing across the entire contact surface.
- Accurate response to the control signal. Cleanroom and operating theatre management systems work with integrated access protocols that require deterministic response times.
- IP protection rating suitable for the environment. In installations exposed to cleaning with pressurized water, steam, or chemicals, the device must have sufficient certification to guarantee its integrity.
- Compatibility with alarm and evacuation systems. In environments where regulations require immediate opening in an emergency, the type of solenoid directly affects the design of the safety system.
Types of solenoids for hermetic doors
The choice of device depends on the installation’s functional priority: intrusion security, emergency egress safety, or energy efficiency.
Fail-safe solenoids
A fail-safe system automatically releases the door when the power supply is interrupted. This configuration is mandatory for emergency exits, evacuation routes, and any access point where people must be able to leave the area in the event of a general power failure.
In hermetic doors used in operating theatres or treatment rooms, fail-safe operation allows personnel to leave the area without any additional action if power is lost. NAFSA’s VEM Series (circular electromagnetic holding magnets that retain the armature while energized and release it when power is cut) is one of the most commonly used solutions for these installations.
Fail-secure solenoids
A fail-secure system keeps the door locked even when power is lost. This configuration is suitable for access points to biocontainment areas, pharmaceutical storage rooms, or any enclosure where preventing unauthorized access during a power outage is the primary objective.
NAFSA’s CU20/CP model, a single-acting linear solenoid with reinforced shaft guidance, provides this functionality with the mechanical robustness required for intensive-duty environments.
Bistable solenoids
Bistable solenoids consume energy only when changing state: one short pulse to lock and another to release. Between pulses, the device maintains its position without continuous power. This feature makes them particularly suitable for installations where doors remain closed for long periods and electrical consumption or heat generation must be minimized.
In hermetic doors used in cold-storage chambers or precisely climate-controlled areas, bistable devices prevent the locking system itself from contributing to the thermal load of the enclosure.
Hermetic and special doors require electromagnetic locking systems that go beyond conventional locking. They must ensure airtight sealing, integrate with building control systems, and operate reliably under demanding environmental conditions. Selecting the right fail-safe, fail-secure, or bistable solution—combined with the appropriate IP protection rating and holding force—is the starting point for any project of this type.
At NAFSA, we design and manufacture solenoids for door locking systems used in industrial and high-demand environments, offering both standard solutions and custom developments tailored to each project. If you are working on a hermetic or special door installation and need technical guidance, our team can help you assess the specific requirements of your application.
Frequently asked questions about solenoids in hermetic doors
What type of solenoid is used in a hermetic operating theatre door?
Operating theatres commonly use fail-safe solenoids that automatically release the door in the event of an emergency or power failure. NAFSA’s VEM Series electromagnetic holding magnets are a common choice because of their fast response and reliable performance in repetitive-duty applications.
What IP protection rating does a solenoid require in the food industry?
It depends on the cleaning procedures used in the area. For zones exposed to direct water jets, at least an IP65 rating is required. NAFSA offers IP65-rated solenoids within the VEM Series. High-speed linear solenoids with a certain level of electrical protection are also commonly used.
Can bistable solenoids maintain locking in hermetic doors?
Yes. Bistable solenoids maintain their state without continuous power, making them ideal for hermetic doors that remain closed for extended periods. They also eliminate heat generation caused by continuously energized coils, which is particularly important in temperature-controlled environments such as cold rooms or cleanrooms.
Can solenoids for hermetic doors be custom manufactured?
Yes. When catalogue models do not meet project requirements—whether due to dimensions, holding force, operating voltage, or protection rating—NAFSA develops custom solenoids for manufacturers and system integrators. The process includes technical analysis, prototyping, and functional validation before series production.