英國(guó)斯派莎克25P減壓閥

斯派莎克25P導(dǎo)閥型隔膜式減壓閥，通過對(duì)同一主閥、不同型號(hào)異閥的多元化組合，可有效的控制蒸汽溫度和/或壓力。
  斯派莎克25P導(dǎo)閥型隔膜式減壓閥的設(shè)計(jì)制造*依據(jù)使用者的需求，其多元化的組合在工業(yè)界沒有任何其他的減壓閥可與之媲美。為了實(shí)現(xiàn)多目標(biāo)控制設(shè)備的獨(dú)立性和經(jīng)濟(jì)性，可在同一個(gè)主閥上組合多種控制，無(wú)論是溫度控制、壓力調(diào)節(jié)還是二者在一起，都能做到反應(yīng)迅速、控制精確、安全可靠。同時(shí)，25P系列減壓閥的所有零件均能夠分解檢查或保養(yǎng)，而無(wú)需移動(dòng)管路中的主閥體。正確的選型和安裝保養(yǎng)，更能保證其**的工作。

工作原理
  斯派莎克25P導(dǎo)閥型隔膜式減壓閥啟動(dòng)前導(dǎo)閥彈簧處于自由狀態(tài)時(shí)，主閥和導(dǎo)閥處于關(guān)閉狀態(tài)。導(dǎo)閥有彈簧力作用打開，蒸汽經(jīng)由導(dǎo)閥進(jìn)入主隔膜室，一部分蒸汽則經(jīng)由控制孔流出，當(dāng)導(dǎo)閥流入的蒸汽大于由控制孔流出的蒸汽，主隔膜閥中的控制壓力增大，打開主閥。隨著蒸汽流過主閥，下游壓力的增量經(jīng)由感應(yīng)管反饋，作用在導(dǎo)閥隔膜下，平衡隔膜上部的彈簧壓力，使導(dǎo)閥組建關(guān)閉節(jié)流，維持主隔膜中的壓力，控制主閥開度輸送適量的蒸汽。調(diào)節(jié)導(dǎo)閥隔膜上的彈簧即可改變下游壓力。

主要特征
  導(dǎo)閥彈簧：三種顏色的彈簧，可提供從0.2-14bar g范圍內(nèi)不同壓力的準(zhǔn)確控制。
  溫度調(diào)節(jié)刻度盤：快速準(zhǔn)確的設(shè)定所需溫度。
  溫度感應(yīng)器：在溫控元件中有無(wú)需補(bǔ)償?shù)囊后w，感應(yīng)瞬時(shí)溫度的變化，提供準(zhǔn)確的控制。
  的測(cè)試：每一個(gè)25P系列的減壓閥在出廠前都經(jīng)蒸汽測(cè)試，以確保*的操作

Many reducing valve problems are caused by the presence of moisture or dirt. A steam separator and strainer with fine mesh screen, if fitted before the valve, will help to prevent such problems. The strainer is fitted on its side to prevent the body filling with water and to ensure that the full area of the screen is effective. Large isolation valves will also benefit from being installed on their side for the same reason.

All upstream and downstream pipework and fittings must be adequay sized to ensure that the only appreciable pressure drop occurs across the reducing valve itself. If the isolating valves are the same size as the reducing valve connections, they will incur a larger pressure drop than if they are sized to match the correctly sized, larger diameters of the upstream and downstream pipework.

If the downstream pipework or any connected plant is incapable of withstanding the maximum possible upstream pressure, then a safety valve or relief valve must be fitted on the downstream side. This valve should be set at, or below, the maximum allowable working pressure of the equipment, but with a sufficient margin above its normal operating pressure. It must be capable of handling the full volume of steam that could pass through the fully open reducing valve, at the maximum possible upstream pressure.

Pilot operation also allows the reducing valve to be relatively compact compared to other valves of similar capacity and accuracy, and allows a variety of control options, such as on-off operation, dual pressure control, pressure and temperature control, pressure reducing and surplussing control, and remote manual adjustment. Three of these variations can be seen in Figure 7.3.6.

Direct acting and pilot-operated control valves can be used to control either upstream or downstream pressures. Pressure maintaining valves (and surplussing valves) sense upstream pressure, while pressure reducing valves sense downstream pressure.