Siemens QPL25.050B Gas Pressure Switch

Siemens QPL25.050B is a high-performance gas pressure switch. Designed for medium and low pressure monitoring ranging from 5-50 mbar, it features IP54 protection grade and a mechanical service life of 100,000 циклы. It is widely used for safety protection of combustion systems. Check model parameters, pressure range and mounting interface during procurement to ensure full compatibility with system requirements.

1. Model Code Definition

2. Основные параметры спецификации

3. Full QPL25 Series Model List

4. Cross-brand Replacement Comparison

5. Распространенное устранение неполадок & Обслуживание

5.1 Распространенные неисправности & Причины

5.2 Рекомендации по техническому обслуживанию

1. Safety Precaution

Cut off gas supply and release pressure

Disconnect power supply

Cool down equipment to room temperature

2. Calibration Procedure

① Remove protective cover and locate adjusting screw

② Connect standard pressure source and set target value

③ Clockwise rotation increases set pressure, counter-clockwise decreases

④ Test switching action and confirm accurate trigger point

⑤ Reinstall cover and ensure tight sealing

3. Component Replacement

Diaphragm: Dismount with special tools, pay attention to gasket installation direction

Контакт: Replace whole switch module instead of single contact

Spring: Use identical specification spare part to guarantee precision

6. Application Environment & Industry Cases

6.1 Применимые сценарии

✅ Recommended Applications

Safety monitoring for industrial & civil gas burners

Pressure protection system of gas boilers

Pressure control of natural gas pipelines

Gas supply system of industrial furnaces

Pressure monitoring for biogas power generation equipment

❌ Inadmissible Applications

High-pressure gas system over 690 mbar

Corrosive gas atmosphere

Medium temperature exceeding 60°C or below -20°C

Severe vibration and outdoor exposed installation without protection

6.2 Typical Industry Applications

7. Selection Tips & Avoidable Risks

Мнемоника выбора

QPL series for gas service, 25 stands for 6A rating

Last three digits define pressure range, B means standard auto-reset

050 model fits 5-50 mbar, G1/4 thread for installation

IP54 solid protection, match gas medium properly

Ключевые примечания

1. Pressure Matching

Keep actual working pressure within 20%-80% of adjustment range to maintain accuracy.

2. Требования к установке

Mount vertically with diaphragm downward to avoid condensed water accumulation.

Install filter at pressure port to prevent internal impurity damage.

Secure wiring firmly to avoid false triggering.

3. Safety Regulations

Interlock with gas leakage alarm device.

Conduct regular inspection and calibration every 6 месяцы.

Perform pressure and leakage test after maintenance.

4. Purchase Notice

Choose genuine Siemens products; counterfeit items have unstable quality.

Keep original package and certificate for after-sales service.

Working Principle of QPL25.050B

Core principle: Air pressure deforms diaphragm, mechanical linkage drives contact on-off to realize overpressure interlock protection

1. Pressure Sensing

Gas flows into inner chamber through G1/4 port and acts on rubber diaphragm, driving axial displacement with pressure variation.

2. Mechanical Force Balance

Diaphragm thrust counterbalances preset spring tension. Rotate adjusting screw to change spring preload and set trigger pressure threshold.

3. Linkage Actuation

When pressure rises to set value, diaphragm overcomes spring resistance and pushes rod to drive lever mechanism. Spring rebounds when pressure drops below threshold.

4. Contact Switching

Lever movement switches SPDT contacts, reverses circuit status and transmits electric signal for burner start-stop and alarm interlock.

5. Differential Pressure Stabilization

Fixed pressure differential prevents frequent switching and unnecessary equipment startup/shutdown.

6. Режим сброса

Standard automatic reset; contacts recover initial state once pressure returns to normal range.

Application Scenarios of QPL25.050B

Applicable Sites

1. Low pressure monitoring and protection for gas boilers and water heaters
2. Supply pressure interlock control of oil and gas industrial burners
3. Pressure stabilization detection for commercial kitchen stoves and hot air furnaces
4. Medium-low pressure monitoring of natural gas and liquefied gas pipelines
5. Safety protection for furnace and drying equipment gas supply
6. Start-stop interlock for clean combustible gas such as biogas and coal gas

Forbidden Sites

1. Gas pipelines with pressure higher than 690mbar
2. Gas medium containing corrosion, dust and oil contaminants
3. Ambient temperature below -20℃ or above 60℃
4. Sites with fierce vibration and uncovered outdoor installation