Description

What Is Our DBB ball valve Pig Signaller?

A DBB ball valve pig signaller detects pig passage while allowing core removal under full pipeline pressure. EMT designs the SN2-TQZ series with a pressure-retrievable mechanism. The device sends visual or electrical signals when a pig passes through. Operators can service the unit without shutting down the pipeline. This feature saves significant downtime cost on critical pipelines.

The SN2-TQZ series uses a DBB (double block and bleed) valve design. This design provides two independent sealing surfaces. A bleed port vents trapped pressure between the two blocks. Maintenance teams isolate the detector core safely. Pipeline flow continues without interruption during the entire service process.

Two mounting configurations are available to match different installation requirements. REIV mounts the ball valve above the flange seat. REDV mounts the ball valve below the flange seat. Both configurations support bidirectional pig detection. Both allow core removal under pressure.

What Are the Key Parameters?

The following table lists the main technical parameters for the SN2-TQZ series. All pressure-containing parts comply with ASME B16.5 standards. Custom standards (DIN, JIS, GB) are available upon request.

Parameter	Specification
Product Type	Flange mounted, intrusive, bidirectional
Valve Design	DBB (double block and bleed) valve, pressure-retrievable
Mounting Options	REIV (top-mounted valve) / REDV (bottom-mounted valve)
Pressure Rating	CLASS 150 to CLASS 2500
Flange Standard	ASME B16.5 / DIN / JIS / custom
Base Height (TS)	150 mm standard / custom measurement available
Display Options	B (flag only) / C (flag + switch) / D (flag + timer) / CD (combined)
Under-Pressure Service	Yes — core removable with pipeline online
MFOI Compatible	Yes — dynamic seal excluded from design
Switch Type (C/D/CD)	SPDT or DPDT, no external power required
Contact Rating	3A / 24V DC
Reset Type	Auto-reset (C type) / Manual reset (B/D/CD types)

 

How Does the DBB ball valve Work?

The the valve uses two independent sealing surfaces. Each surface blocks pipeline pressure separately. The bleed port vents trapped pressure between the two blocks. This confirms both blocks seal properly before any disassembly.

When both blocks are closed, operators open the bleed port. Trapped medium vents safely to atmosphere. Pressure between the two blocks drops to zero. Then operators unbolt the detector core. They remove the core for service or replacement.

During this process, the pipeline remains fully operational. No shutdown is required. No product is lost. This design meets API 6D and ASME B16.34 isolation requirements. The entire retrieval procedure takes less than 15 minutes.

Reliability&Application Scenarios Of this design

What Makes the DBB Design Reliable?

The the DBB design provides positive isolation before core removal. Two independent seals protect the operator. The bleed port verifies isolation visually (no pressure = safe to open). This exceeds the safety requirements of most pipeline operators.

All wetted parts are available in NACE MR0175-compliant materials. Sour service configurations are available. Low-temperature grades (LTC) are available for LNG and LPG service. EMT engineering reviews each order for material compatibility.

This device suits pipelines that cannot shut down for maintenance. The following applications benefit most from the this device design:

• Long-distance oil and gas transmission pipelines (on-shore and offshore)
• Urban gas distribution networks and city gate stations
• Refinery process lines with continuous operation requirements
• LNG terminals, receiving stations, and regasification plants
• Offshore platform pigging systems with limited shutdown windows
• Any pipeline where shutdown cost exceeds $10,000 per hour

Compare this with standard pig signallers. Standard units require complete shutdown for any service. The the valve design eliminates that requirement entirely. The payback period is typically less than one avoided shutdown.

Who Is EMT and Why Trust Us?

Shenyang EMT Piping Technology Co., Ltd. manufactures pipeline pigging equipment. We hold the ASME U Stamp certification for pressure vessel manufacturing. Our factory operates CNC machining centers, automatic welding stations, and a hydrostatic test bay. Every product undergoes pressure testing before delivery. We provide the test certificate with each shipment.

We serve EPC contractors, pipeline operators, and maintenance teams worldwide. Our pig signallers operate in more than 30 countries. We understand project schedules and expedited delivery requirements. We provide technical support in English, Spanish, Russian, and Chinese. Our response time is within 4 hours during working days.

EMT offers more than individual pig signallers. Our product range covers quick-opening closures (QOC), corrosion monitoring systems, chemical injection quills, and pipeline cleaning pigs. We provide turnkey pigging solutions — from system design to site commissioning. We can act as a single-source supplier for your entire pigging system.