[推荐]对常压和自然循环采暖热水锅炉安全性的质疑

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电梯直达

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发表于 2006-9-15 04:23:00 |只看该作者 |倒序浏览

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<center class="aTitle">对常压和自然循环采暖热水锅炉安全性的质疑 </center><table width="97%"><tbody><tr><td align="right">作者： </td></tr></tbody></table>论文摘要】对常压和自然循环热水锅炉的安全性提出了一些较新的不同看法，对正确设计和使用常压热水锅炉有参考价值。 1　问题的提出　　中国在采暖用热水锅炉设计方面有两次“大突破”，一次是八十年代提倡自然循环可用性，后得到大规模推广；另一次是九十年代的常压锅炉，后也获大量推广。笔者认为，如果对二者做非常有条件的认可也许可行，但两次“大突破”都被几乎无条件地赞赏和认可则是有问题的，需要重新讨论。2　常压锅炉运行安全问题分析　　以常压锅炉而论，我们要问：为什么国家标准局即使对于95/70这种出水温度仅为95℃的锅炉也规定其额定压力为0.4MPa(小于0.7MW)和0.7MPa(大于0.7MW)?为什么“热水锅炉安全技术监察规程第127条规定“钢制热水锅炉的出口压力不应低于额定出口热水温度加20℃相应的饱和压力”?额定压力为设计压力，而“安规”说的是运行压力，总之要有压力，而提倡常压与上述规定不能说没有矛盾。 　　提倡常压锅炉的人无非认为无压力则不必担心安全(无高压爆破)问题，可基本取消强度问题，可用薄材料及相对较次材料从而节约材料成本。但笔者认为，一般地说，搞常压锅炉仅提高了力学安全(降低强度要求)，但降低了热学安全——更容易发生饱和沸腾尤其是表面沸腾，且更易在热壁上结硬垢和爆管。 　　现以φ51×3炉膛水冷壁管为例，炉膛管热负荷强度约为60000kcal/m2，现计算各种水管流速下的内换热系数、管壁对水之温差、管内壁温度及该温度下的饱和温度，计算结果如表1。表1<table cellspacing="0" cellpadding="0" border="1" style="BORDER-RIGHT: medium none; BORDER-TOP: medium none; BORDER-LEFT: medium none; BORDER-BOTTOM: medium none; BORDER-COLLAPSE: collapse; mso-padding-alt: 0cm 5.4pt 0cm 5.4pt; mso-border-alt: solid windowtext .5pt; mso-table-layout-alt: fixed;"><tbody><tr><td valign="top" width="32%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 32.96%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent;">水速W，(m/s)</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.1</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.2</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.3</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.4</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.5</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-left-alt: solid windowtext .5pt;">0.6</td></tr><tr><td valign="top" width="32%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 32.96%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt;">换热系数α，(kcal/m2℃)</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">696.5</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">1213</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">1677</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">2111</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">2524</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">2920</td></tr><tr><td valign="top" width="32%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 32.96%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt;">壁温、水温差，Δt，℃</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">90.4</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">51.9</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">37.57</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">29.8</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">25</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">21.6</td></tr><tr><td valign="top" width="32%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 32.96%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt;">壁温，tw=95+Δt，℃</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">185.4</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">146.9</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">132.57</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">124.8</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">120</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">116.6</td></tr><tr><td valign="top" width="32%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 32.96%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt;">tw对应饱和压力，MPa</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">1.139</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">0.44</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">0.293</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">0.233</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">0.198</td><td valign="top" width="11%" style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #ece9d8; WIDTH: 11.18%; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt;">0.108</td></tr></tbody></table> 内换热系数按下式计算： <img height="34" src="http://www.hnsafety.gov.cn/peixun/upload/2005_10/051009133770460.gif" width="232" border="0" style="CURSOR: pointer;" alt=""/>(1)　　之所以取壁温为95+Δt是从安全角度出发而取额定出口水温为底温。 　　从表1可见，壁温和管内水流速关系很大。快装热水锅炉若采取纯自然对流循环，则管内(上升管)流速很难达到0.2m/s(计算许多锅炉的上升管水流速多为0.1m/s以下)，这时若要求不发生表面沸腾，则要求水压为0.44MPa，而表压要求0.4MPa，假定采用前苏联标准0.6m/s的上升管流速的强制循环，则水压有0.1MPa就可以防止表面沸腾。 　　设计压力即使为0.7MPa，但运行中的实际压力取决于系统流阻。小型热水锅炉所对应的热力系统的流阻常使锅炉运行压力为0.4至0.5MPa(表压则为0.3至0.4MPa)，若上升管流速确能保证0.2m/s以上，则有可能防止表面沸腾。另外，运行中常表现为进出水为低温差70℃～80℃或65℃～85℃，这时会有更低的密度差，从而有更小的升力和更小的自然循环流速，使表面沸腾更易于发生。 　　有人可能认为：若水不含盐碱则发生表面沸腾也不可怕。问题是：(1)中国含钙镁盐的水的地区相当宽广，且越来越多地用地下水，井越开越深，含盐浓度越来越高；(2)所用软化水皆为阳离子交换式，以钠代钙已不彻底，且由于使用小型热水锅炉用户的运行工人训练较差，经常不以食盐水恢复水处理设备的工作能力，也不经常对水垢进行机械清除和酸、碱清除。以上两条原因使常压和自然循环锅炉实际使用寿命缩短了许多倍。 　　还应考虑的另一个因素是：现在，常压锅炉变成谁都可搞，劳动部门基本管不着，许多完全不懂锅炉设计、制作及安装、运行的单位都可搞，变成“雨后春笋”，实际上会形成事故更加频繁得多的局面。 　　在常压锅炉设计制造中，用材方面并非节约很多，管子一样是φ51×3之类，至于锅筒及封头或管板之类，设计中有个不小于6mm的规定。6mm和8mm或10mm相比能节省多少?与日后频繁地爆管及结垢后的整体烧毁相比，经济上并不一定合算。3　结论　　笔者认为对常压和自然循环采暖热水锅炉应有条件地提倡，例如：①家庭用电加热锅炉和烧油(汽)锅炉，功率在5×104kcal/h以下；②不管何种热水锅炉，都应经过认真的具体计算，且使用的循环方式在工作压力下不会发生饱和沸腾及表面沸腾。 　　总之，为安全计，热水锅炉既要有循环流速又要有压力，必须以不发生饱和沸腾及表面沸腾为设计中的必要条件。