Why is a safety valve critical?

A safety valve (commonly known as a safety vent) is a protective device that automatically opens to relieve excess pressure when a pressure vessel or system exceeds its maximum allowable operating pressure, and closes again when the pressure drops to a safe level. It acts as the final safety barrier in boilers, air tanks, booster pump units, steam boilers, and process vessels.

Excessive pressure in pressurized equipment can result in explosions, equipment damage, and serious workplace accidents. Therefore, it is vital that the safety valve operates at the correct set pressure, opens in a timely manner, and closes without leakage. Over time, the valve may lose its properties due to scaling, corrosion, spring fatigue, or contamination; therefore, regular testing and inspection are necessary.

How does a safety valve work?

In the most common type, a spring-loaded safety valve, the valve disc is held in the closed position by a spring force. When the system pressure exceeds the spring force acting on the area under the disc, the valve opens and directs the fluid (steam, air, gas, or liquid) to a safe point. When the pressure drops, the spring repositions the disc and the valve closes.

• Set pressure: The pressure at which the valve begins to open.
• Opening/full release: The moment the valve discharges to its full capacity.
• Reset pressure: The pressure at which the valve closes completely again, stopping the leak.
• Blowdown (difference): The difference between the opening and closing pressure.

Legal Basis and Current Legislation

Safety valves are considered protective equipment for the pressure vessel in which they are located and are tested as part of the periodic inspection of the vessel. The framework for these inspections is defined by the Regulation on Health and Safety Conditions in the Use of Work Equipment (Official Gazette 25.04.2013 / 28628).

This regulation has been updated with the amendment published in the Official Gazette dated 23.12.2025 and numbered 33116. With this amendment, the expression 'accredited inspection body' has been revised to 'equipment inspection body'; and it has become mandatory for the employer and the person authorized to perform the periodic inspection to draw up and mutually approve a contract in accordance with the example in the ISG-KATIP system at least one day before the inspection service is performed. During the transition period, until a new regulation is made by the Ministry, inspection bodies accredited by TÜRKAK under TS EN ISO/IEC 17020 are accepted as equipment inspection bodies (transition schedule 1/1/2027).

Information: Product conformity of pressure equipment at the market placement stage is addressed under the Pressure Equipment Directive 2014/68/EU (PED), and this is separate from periodic inspection/testing during the operational phase. The service described on this page relates to the inspection of equipment in use and the adjustment/testing of valves; it does not cover product conformity (CE) certification.

What is checked during an inspection (periodic check)?

The safety valve is not evaluated in isolation, but as part of the periodic inspection of the pressure vessel to which it is connected. Within this scope, the valve's behavior under actual operating conditions is measured and recorded.

• Checking the opening behavior at the set pressure.
• Resettling check at correct pressure after opening.
• Leak test in closed position
• Suitability of discharge capacity and discharge line.
• Label/plate information, mounting location, and general physical condition (corrosion, scaling, mechanical damage)
• The valve setting pressure must match the maximum allowable operating pressure of the vessel.

Set & Seal, Discharge Test and Sealing

During periodic inspections, it may be determined that the valve's adjustment is misaligned, leaking, or requires readjustment. In this case, the valve is removed from the system, adjusted to the specified setting pressure on a test bench, the opening, closing, and leakage values are verified, and it is sealed (lead seal/plumb) to maintain the adjustment. This procedure is carried out based on the safety valve characteristics defined in TS EN ISO 4126-1 and ISO 4126 series.

Important distinction: Removing, adjusting, and sealing the valve on a workbench is a service/adjustment activity and carries a manufacturing/service dimension. This is different from a periodic on-site 'inspection' of the equipment. AES Innovation treats both activities separately and clearly states this distinction in its reports.

• Calibration of the set pressure on the test bench.
• Verification of opening, closing, and blowdown values.
• Leak test in closed position.
• Sealing (plumbing) to preserve the setting.
• The setting values and results are recorded in the technical report.

Period and Who Does It?

Unless otherwise specified in the regulations, the safety valve is tested at least once a year as part of the periodic inspection of the pressure vessel to which it is connected. Operating conditions, fluid type, and manufacturer recommendations may require more frequent inspections.

Periodic inspections of pressure vessels and protective equipment are carried out by authorized mechanical engineers who have received relevant training. AES Innovation performs this service with the assistance of an authorized mechanical engineer and documents the results with a technical report.

The Difference Between Inspection and Adjustment Services and the Scope of AES Innovation

Inspection (periodic control) is the assessment of the equipment's safe operating condition along with the system it is connected to. Adjustment/testing/sealing, on the other hand, involves removing the valve, adjusting it to the specified value on the test bench, and verifying it. While complementary, these are distinct activities; AES Innovation addresses them separately in its report.

Scope and Integrity Note: AES Innovation is an A-Type Inspection Body accredited by TÜRKAK under TS EN ISO/IEC 17020 only in the field of '6.1 Electrical Installation'. Safety valve adjustment, discharge, and testing services are outside the scope of this accreditation. Therefore, this service is presented as a technical report prepared by an authorized mechanical engineer, not as an accredited inspection report. AES Innovation does not accredit, certify, CE mark, or issue certificates for any product within this scope.

Disclaimer: This page is intended for educational and unbiased information; for precise regulatory requirements, it is recommended that you refer to the current Official Gazette texts and the opinions of qualified experts. Caution is essential in matters of uncertainty.

Related Services

• Pressure Vessels
• Compressor Air Tanks
• Steam Boiler

Frequently Asked Questions

How often should the safety valve be tested?

Unless otherwise specified in the regulations, the safety valve is tested at least once a year as part of the periodic inspection of the pressure vessel to which it is connected. Operating conditions and manufacturer recommendations may require more frequent inspections.

What is checked during a safety valve inspection?

The valve's opening at the set pressure, closing (reseat) at the correct pressure, leak-proofness in the closed position, discharge capacity, and physical condition (corrosion, scaling, damage) are checked.

What is the difference between inspection and set & seal?

Inspection is the assessment of the equipment's safe condition in situ and with its system. Adjustment/sealing, on the other hand, involves removing the valve, bringing it to the specified adjustment pressure on a test bench, verifying it, and sealing it; this is a service/adjustment activity and differs from inspection.

Is this service an accredited inspection report?

No. AES Innovation's TÜRKAK accreditation only covers the '6.1 Electrical Installation' area; safety valve adjustment/testing services are outside this scope. The service is provided as a technical report prepared by an authorized mechanical engineer, not an accredited inspection report.

Who can check the safety valve?

Periodic inspections of pressure vessels and protective equipment are carried out by authorized mechanical engineers who have received relevant training.

Which standards are used as a basis?

The characteristics of safety valves are based on TS EN ISO 4126-1 (safety valves – general) and the ISO 4126 series. These standards are product standards that define the valve's properties; the regulatory framework for control during the operation phase is the Work Equipment Regulation.