Based on the core advantages of the stop valve, such as its tight sealing, high pressure resistance, and high temperature resistance, the following 4 types of working conditions typically require or strongly recommend the use of stop valves, while in these scenarios, gate valves or butterfly valves often cannot meet the requirements:
1. Piping of high temperature and high pressure media (the most typical application)
This is the "home ground" of the stop valve. When the medium temperature exceeds 200℃ or the pressure is high, the sealing performance and structural strength of the stop valve are much better than those of ordinary valves.
Typical scenarios: Main steam pipelines of thermal power plants, boiler feedwater systems, and high-temperature reaction pipelines in petrochemical plants.
Why is it necessary to use it?
Pressure resistance: The valve body structure of a globe valve is thicker than that of a gate valve, enabling it to withstand higher pressure.
Thermal expansion and contraction compensation: At high temperatures, the valve stem of the stop valve can adjust slightly to compensate for the sealing gap caused by thermal expansion and contraction. However, ordinary gate valves are prone to stalling and being unable to open or close or having a sealing failure.
2. The working condition where strict sealing is required and internal leakage must be completely prevented.
At some critical isolation points, if there is an internal leakage (where the valve is closed but still some medium seeps through), it may lead to safety accidents or product scrapping.
Typical scenarios: Feed inlet of reaction vessels in chemical production, isolation of highly toxic/flammable media, and transportation pipelines for high-purity chemicals.
Why it must be used: The stop valve is a forced-sealing valve. When closed, the valve disc is forcibly pressed against the valve seat, and the sealing is more reliable than that of the gate valve (which relies on the medium pressure for self-sealing). Especially the bellows-sealed stop valve can completely prevent leakage and is the preferred choice for these hazardous or highly pure media.
3. Situations where "rough adjustment" of flow or pressure is required
Although there are dedicated regulating valves, in some small-diameter pipelines with low precision requirements, the stop valve is often used as a regulating valve as well.
Typical scenarios: Pressure control at the outlet of small pumps, sampling pipelines for instruments, and pipelines for laboratory equipment.
Why it must be used: The lift height of the valve disc of a stop valve is basically proportional to the flow change, and the adjustment stability is good (unlike ball valves which have too drastic flow changes at small openings). Note: This is usually limited to small pipe diameters of ≤ 50mm, and it is not recommended to use it in a throttling state for a long time.
4. Instruments and sampling pipelines with small diameters (DN ≤ 50)
In industrial instruments and laboratories, the pipes are usually very thin.
Typical scenarios: pressure gauges, transmitter suction pipes, sampling valves, needle valves (a variant of stop valves).
Why it must be used: The stop valve has a compact structure, a short opening and closing stroke, and is easier to manufacture and operate than the gate valve in small diameters. Moreover, its sealing surface is more durable.
Summary: When is it "necessary" to choose it?
High temperature (>200℃) steam/thermal oil | High pressure (>1.6MPa) gas/liquid | Absolutely no leakage (toxic/precious media) | Small diameter (<50mm) regulation.
