FAQ

A control valve is a type of valve used to regulate the flow or pressure of a medium. Since the flow or pressure of the medium affects certain control processes, control valves are typically operated by remote signals from independent devices such as electric, pneumatic, or pneumatic-hydraulic actuators.

Control valves are characterized by their ability to achieve control by altering the internal flow path or the cross-sectional area of the valve orifice.

Pressure-reducing valves for liquids and those for gases have essentially the same basic design and operating principles, but their settings differ. Pressure-reducing valves designed for gases cannot be used with liquids without being re-calibrated.

The pressure characteristic of a pressure-reducing valve refers to the functional relationship between the outlet pressure and the inlet pressure under steady-state flow conditions, when parameters such as flow rate remain constant.

The flow characteristic refers to the functional relationship between the outlet pressure and the flow rate under steady-state flow conditions, when parameters such as the inlet pressure remain constant.

A direct-acting pressure-reducing valve is a type of pressure-reducing valve that uses changes in outlet pressure to directly control the movement of the valve disc.

A pilot-operated pressure-reducing valve consists of a main valve and a pilot valve; changes in outlet pressure are amplified by the pilot valve to control the operation of the main valve.

A pressure-reducing valve is a valve that reduces the inlet pressure to a desired outlet pressure through throttling by a closing element, and maintains the outlet pressure essentially constant by utilizing the energy of the medium itself when the inlet pressure and flow rate fluctuate.

The purpose of using a pressure-reducing valve is to keep the outlet pressure essentially stable.

A direct-acting safety valve is a safety valve that uses a mechanical load, such as a weight, a lever-operated weight, or a spring, to counteract the force generated by the pressure of the medium beneath the disc.

A pilot-operated safety valve is a safety valve that relies on the discharge of medium from a pilot valve for actuation or control. The pilot valve itself must be a direct-acting safety valve that complies with standard requirements.

The springs in spring-loaded safety valves designed for different pressures must be replaced.

Generally, a PN16 spring-loaded safety valve should be equipped with five springs.

The pressure ranges are specified as follows: 0 MPa to 0.3 MPa; 0.3 MPa to 0.6 MPa; 0.6 MPa to 0.9 MPa; 0.9 MPa to 1.2 MPa; 1.2 MPa to 1.6 MPa.

Frequent fluttering of a safety valve refers to the rapid, abnormal back-and-forth movement of the valve disc, during which the disc comes into contact with the seat.

Flicker refers to the rapid, abnormal back-and-forth movement of the safety valve disc, during which the disc does not come into contact with the seat.

The theoretical discharge capacity of a safety valve is the calculated discharge capacity of an ideal nozzle with a flow passage cross-sectional area equal to that of the safety valve.

The actual discharge capacity of a safety valve is the product of the theoretical discharge capacity and the discharge coefficient.

The orifice area of a safety valve refers to the area of the cylindrical or conical passage formed between the sealing surfaces of the disc and the seat when the disc lifts above the seat.

The orifice area of a safety valve should be greater than the flow passage area.

The reseating pressure of a safety valve refers to the static pressure at the inlet when the valve disc comes back into contact with the seat after the valve has discharged, i.e., when the lift is reduced to zero.

The sealing pressure of a safety valve refers to the inlet pressure during a sealing test, at which the leakage rate across the sealing surface of the closing member is measured.

The opening pressure of a safety valve refers to the inlet pressure at which the valve disc begins to lift under operating conditions; at this pressure, a measurable lift height begins, and the medium is discharged continuously in a manner that can be detected visually or audibly.

The discharge pressure of a safety valve refers to the inlet pressure when the valve disc reaches the specified lift height.

Full-Lift Safety Valve:

A safety valve with a disc lift equal to or greater than 1/4 of the seat throat diameter is classified as a full-lift safety valve.

Low-Lift Safety Valve:

A safety valve with a disc opening height of 1/40 to 1/20 of the seat throat diameter is classified as a low-lift safety valve.

A safety valve is an automatic valve that discharges a predetermined volume of fluid using the force of the medium itself, without any external force, to prevent the pressure within the system from exceeding a predetermined safety limit. Once the pressure returns to normal, the valve closes to prevent further discharge of the medium.

The load factor of a steam trap refers to the percentage of the actual hot condensate discharge during the test period relative to the maximum hot condensate discharge at the test pressure.

The operating temperature of a steam trap refers to the temperature at the inlet of the steam trap under operating conditions.

The backpressure of a steam trap refers to the pressure at the outlet end of the steam trap under operating conditions.

The higher the backpressure tolerance of a steam trap, the better.

This is because a higher backpressure tolerance allows for higher outlet pressure at the steam trap under actual operating conditions. In other words, steam traps with higher backpressure tolerance are more suitable for high-backpressure applications.

The absolute value of the difference between the condensate temperature and the saturated temperature at the corresponding pressure is the subcooling.

The valve-open subcooling refers to the absolute value of the difference between the valve-open temperature and the saturated temperature at the corresponding pressure.

The valve-closed subcooling is the absolute value of the difference between the valve-closed temperature and the saturated temperature at the corresponding pressure.

The valve-open subcooling is greater than the valve-closed subcooling.

Pressure measured relative to atmospheric pressure (set as 0) is called gauge pressure.

Pressure measured relative to absolute vacuum (defined as 0) is called absolute pressure.

Absolute pressure is the sum of gauge pressure and atmospheric pressure.

Gauge pressure is the difference between absolute pressure and atmospheric pressure.

Sensible heat:

An increase or decrease in heat does not change the state of a substance; it merely causes a change in temperature. This type of heat is called sensible heat.

Latent heat:

During a phase change, the temperature remains constant while the state of the substance changes; the heat absorbed or released by the substance at this time is called latent heat.