Standard code

Standard Name

Standard code

Standard Name

JB/T 9093-1999

Technical Specifications for Steam Traps

BS 6023-1981

Steam Trap Terminology

GB/T 12248-1989

Steam Trap Terminology

BS 6024-1981

Steam Trap Valve Symbol

GB/T 12249-1989

Steam Trap Valve Symbol

BS 6025-1982

Factory Inspection and Operational Performance Testing of Steam Traps

GB/T 12250-1989

Steam Trap Valve Structural Length

BS 6026-1981

Flanged Steam Traps: Structural Length

GB/T 12251-1989

Steam Trap Testing Methods

ISO 6552-1991

Automated Steam Traps Terminology

GB/T 12247-1989

Classification of Steam Traps

ISO 6553-1991

Automatic Steam Trap Symbol

ASTM F1139-1988

Steam trap

ISO 6554-1991

Flanged Automatic Steam Traps: Structural Length

BS 6022-1983

Classification of Steam Traps

ISO 6948-1981

Factory Inspection and Operational Characteristic Testing of Automatic Steam Traps

ISO 6704-1991

Classification of Automatic Steam Traps

BS EN 26948-1991

Method for Determining Steam Loss in Steam Traps

ISO 7841-1991

Method for Determining Steam Leakage in Automatic Steam Traps

BS EN 27841-1991

Steam Trap Testing

ISO 7842-1988

Method for Determining the Drainage Capacity of Automatic Steam Traps

FC185-1-1989

Hydraulic Valve Product Testing

JIS B8401-1989

Steam trap

NF E29444-1984

Automatic Steam Trap Steam Leakage Test

JIS B8402-1988

Heating Radiator Drain Valve

The Structure of Steam Traps

Type

Name

Structural Features

Mechanical type

Automatic Deflation Free-Float Type

The spherical, hermetically sealed float (ball) serves both as a valve element and as a liquid-level sensor. When the liquid level rises, the float ascends, opening the valve; conversely, as the liquid level drops, the float descends, allowing it to move closer to the valve seat along with the fluid flow, thereby closing the valve. An automatic air vent is installed at the top.

Mechanical type

Manual Deflation, Free-Float Type

The spherical, hermetically sealed float (ball) serves both as the valve’s opening/closing element and as a liquid-level sensor. When the liquid level rises, the float ascends, triggering the valve to open; conversely, as the liquid level drops, the float descends, allowing it to move closer to the valve seat along with the fluid flow, thereby closing the valve. A manual air vent is installed at the top of the device.

Mechanical type

Automatic Deflation Free-Float Type

The spherical, hermetically sealed float (ball) serves both as a valve element and as a liquid-level sensor. When the liquid level rises, the float ascends, opening the valve; conversely, as the liquid level drops, the float descends—and because it follows the flow of the medium toward the valve seat—eventually closing the valve. The automatic air vent is positioned on the outlet side.

Mechanical type

Free-floating ball valve

The spherical, hermetically sealed float (ball) serves both as a valve element and as a liquid-level sensor. When the liquid level rises, the float ascends, opening the valve; conversely, as the liquid level drops, the float descends, allowing it to move closer to the valve seat with the flow of the medium and automatically closing the valve. The automatic air vent is simplified into a thermal bimetallic element.

Mechanical type

Lever-type float

The liquid-level sensing element, action-transmitting component, and action-executing component are the float, lever, and valve clapper, respectively. The lever's design enhances the opening and closing force of the valve clapper.

Mechanical type

Double-seat lever-type float

The dual-disc design counteracts the force of the medium, ensuring that the valve disc’s opening and closing are unaffected by media pressure. The automatic air vent is positioned at the valve’s outlet.

Mechanical type

Open-top float-type

The liquid-level-sensitive component features an upward-facing opening (float chamber), with valve operation driven by changes in buoyancy. The valve's outlet is positioned above the valve itself.

Mechanical type

Leveraged Exposure with Upward-Acting Float

The more open, upward-floating type float mechanism is equipped with a lever, increasing the actuating force of the valve disc.

Mechanical type

Piston-type, open-top, float-style

Based on the open-top float-type design, a pilot valve has been added; once the pilot valve opens, the main valve is actuated by the medium's pressure.

Mechanical type

Free Semi-Floating Type

The liquid-level-sensitive component features a downward-facing opening (semi-ball float) that also serves as the actuating element (valve disc). When the semi-ball float rises, it can freely move toward the valve seat. Meanwhile, the thermally sensitive bimetallic element automatically expels cold air.

Mechanical type

Leveraged Exposure, Downward-Acting Float Type

The more freely floating semi-ball type has been equipped with a lever, increasing the valve's actuation force.

Mechanical type

Piston-lever, open-top, float-type

The lever-type float has been retrofitted with a pilot valve, whose function is identical to that of the piston-type float.

Thermodynamic type

Diaphragm-type

The main component is a metal bellows chamber filled with a temperature-sensitive liquid. Depending on the specific operating conditions, different temperature-sensing fluids are selected. When the bellows chamber is exposed to steam and condensate at varying temperatures, the temperature-sensitive liquid undergoes a phase change between vapor and liquid, causing pressure to either rise or fall. This pressure change drives the diaphragm, which in turn moves the valve disc back and forth, opening and closing the valve to effectively block steam while efficiently draining condensate.

Thermodynamic type

Diaphragm-type

The principle is the same: a high-temperature-resistant diaphragm is installed between the valve's lower body and upper cover, and the bowl-shaped component beneath the diaphragm is filled with a temperature-sensitive liquid.

Thermodynamic type

Bellows-type

The bellows, filled with temperature-sensitive liquid, serves as the thermal sensing element. When the temperature changes, the vapor pressure of the temperature-sensitive liquid inside the bellows also shifts accordingly, causing the bellows to expand or contract—and in turn, actuating the valve disc connected to it.

Thermodynamic type

Simply Supported Bimetallic Type

A set of bimetallic strips, installed as simply supported beams, serves as the thermal sensing element. They bend or straighten in response to temperature changes, thereby actuating the valve flap.

Thermodynamic type

Cantilever Bimetallic Strip

The principle is the same: a set of bimetallic strips is mounted in a cantilever configuration.

Thermodynamic type

Single-piece bimetallic strip

The principle is the same: a C-shaped bimetallic strip serves as the thermal sensing element.

Thermodynamic type

Disc-type

The valve element serves both as a sensing component and an actuating mechanism, relying on the distinct thermodynamic properties of steam and condensate flowing through it to drive its opening and closing. Meanwhile, air insulation is maintained between the inner and outer valve covers. The valve can be installed either horizontally or vertically.

Thermodynamic type

Pulsed

This valve features a relatively long valve disc, which is housed inside a cylindrical body with a slight clearance between them—this gap is referred to as the first throttling orifice. At the upper end of the valve disc, there’s a through-hole known as the second throttling orifice. When the valve starts operating, incoming air is expelled through these two throttling orifices. As condensate enters the steam trap, it pushes the valve disc upward under the force of the condensate, opening the outlet and allowing the condensate to drain out. Once the condensate has been discharged and steam begins to flow in, the pressure drop across the first throttling orifice becomes lower than the pressure drop caused by the condensate itself. This difference in pressure builds up within the control chamber, forcing the valve disc to close against the valve seat. Notably, even when the valve is fully closed, its inlet and outlet remain connected via the two throttling orifices, ensuring that the steam trap never achieves a complete shut-off. As a result, the valve operates in a state of partial flow continuity at all times.

Thermodynamic type

Orifice plate type

Depending on the different displacement volumes, simply selecting orifice plates with varying apertures can achieve the desired result—though improper selection may lead to significant steam leakage.

Multifunctional

Bellows Pulse-Type

Based on the pulse-type design, a pilot valve has been added, which is actuated by a thermally sensitive element (bellows). The inclusion of the pilot valve helps minimize steam leakage.

Multifunctional

Bellows-lever float-type

A bellows has been added to the lever float mechanism, allowing the lever's fulcrum to shift as the bellows expands and contracts, which helps efficiently expel cold air.