Integral DBB Double Block and Bleed Ball Valve | Flange‑to‑Thread Stainless Steel Instrument DBB Valve

Product Overview:

The integral double block and bleed (DBB) ball valve combines two isolation ball valves plus one bleed needle valve within a single forged‑body unit. This flanged‑to‑thread DBB valve is widely used for instrument sampling, pressure transmitter isolation and pipeline maintenance in oil & gas, petrochemical, chemical and energy industries.

Product Features:

Available Materials:

• Body: SS304, SS316, SS316L

• Ball & Stem: Stainless steel

• Seat: PTFE / R‑PTFE

• Handle: Carbon steel with blue coating

Aplication Scope:

• Oil & gas production

• Petrochemical plant

• Chemical processing industry

• Power plant instrument system

• Pipeline sampling system

• Pressure transmitter & gauge isolation

How Does an Integral DBB Valve Work?

Integral DBB (Integral Double‑Block‑and‑Bleed) valve: two independent block seals + built‑in bleed port, all machined within one single forged valve body, replacing the traditional field assembly of 2 separate block valves plus a bleed valveAthena S.R...。

Core Structure

1. One integral forged body: no intermediate flange joints → fewer external leak points

2. Two independent sealing barriers: upstream seat / downstream seat (spring‑loaded seats for trunnion ball‑type DBB)

3. Intermediate cavity: sealed space between the two sealing seats

4. Integrated bleed valve/port: connects directly to the intermediate cavity, usually a small needle or ball valve on body side/bottom

Working Principle

① Double‑block (isolation mode)

When the valve is fully closed:

• The upstream seat forms the first pressure‑containing sealing barrier, blocking incoming process fluid.

• The downstream seat forms the second independent sealing barrier.

• Even if one seat suffers minor leakage or damage, the second seat still provides isolation safety.

• A trapped intermediate cavity is formed between the two seats.

② Bleed (vent & leak‑verification step)

Open the built‑in bleed valve:

• It vents / drains trapped pressure and residual medium inside the intermediate cavity.

• If fluid or pressure continuously comes out from bleed port, it proves the upstream seal is leaking.

• If bleed port shows zero pressure, operators confirm reliable double isolation before downstream maintenance, sampling or instrument work.

③ Normal service (valve open)

Both sealing seats lift away, fluid flows straight through the valve, bleed port stays closed.

API 6D definition: A DBB valve is a single valve with two seating surfaces that, in closed position, provides seal against pressure from both ends, with provision for bleeding the cavity between seats.