李昌美

摘 要：近年公司以EPC模式承包的境外電站項(xiàng)目中，ASME鋼印鍋爐越來(lái)越多，土耳其、摩洛哥、巴基斯坦、泰國(guó)等地EPC項(xiàng)目多數(shù)招標(biāo)文件均明確要求鍋爐必須實(shí)施ASME鋼印。本文結(jié)合摩洛哥某EPC項(xiàng)目鍋爐ASM認(rèn)證，針對(duì)無(wú)固定汽水分界線強(qiáng)制循環(huán)鍋爐安全閥PE（Professional Engineer）認(rèn)證，探討鍋爐汽水流程設(shè)計(jì)中安全閥設(shè)計(jì)認(rèn)證中值得注意的問(wèn)題，為同行進(jìn)行類似鍋爐PE認(rèn)證提供參考與借鑒。

關(guān)鍵詞：ASME；鍋爐；安全閥；認(rèn)證

中圖分類號(hào)：X933 文獻(xiàn)標(biāo)識(shí)碼：A

1.概述

ASME BPVC.1卷設(shè)計(jì)篇DESIGN PG-16.2 When the pressure parts of a forced‐flow steam generator with no fixed steam and waterline are designed for different pressure levels as permitted in PG-21.3， the owner shall provide or cause to be provided a boiler pressure system design diagram， certified by a Professional Engineer experienced in the mechanical design of power plants， which supplies the following information.

針對(duì)無(wú)固定汽水分界線強(qiáng)制循環(huán)蒸汽鍋爐，明確要求鍋爐的壓力系統(tǒng)的設(shè)計(jì)流程須經(jīng)過(guò)一個(gè)Professional Engineer（PE）認(rèn)證，而審查范圍和要點(diǎn)為16.2.1-2.4，鍋爐壓力系統(tǒng)流程通常是鍋爐廠方案及初步設(shè)計(jì)最先要考慮的問(wèn)題，所以PE認(rèn)證工作能否及時(shí)完成將直接影響后續(xù)設(shè)計(jì)、甚至成本預(yù)算工作，其重要性不言而喻。

2. PE認(rèn)證服務(wù)合同招投標(biāo)

由于PE認(rèn)證須由業(yè)主提起獲得，通常鍋爐廠默認(rèn)此項(xiàng)工作不在供貨范圍內(nèi)，所以從采購(gòu)方的角度來(lái)說(shuō)，簽訂類似鍋爐采購(gòu)合同時(shí)，應(yīng)將此認(rèn)證列入供貨服務(wù)范圍中，最大限度地縮短設(shè)計(jì)工期和溝通成本。PE工程師的認(rèn)定相當(dāng)嚴(yán)格，在全球范圍來(lái)說(shuō)都比較稀少，目前國(guó)內(nèi)基本沒(méi)有，所以PE認(rèn)證無(wú)論由誰(shuí)負(fù)責(zé)實(shí)施，提前策劃好PE認(rèn)證服務(wù)合同、落實(shí)合法有效且經(jīng)驗(yàn)豐富PE工程師都是關(guān)鍵性任務(wù)，當(dāng)然在國(guó)內(nèi)也有一個(gè)捷徑，就是通過(guò)第三方尋找或提供服務(wù)。

3. PE認(rèn)證安全閥技術(shù)評(píng)審

針對(duì)摩洛哥某項(xiàng)目廠家提供的汽水流程圖等資料，有關(guān)安全閥的認(rèn)證，PE工程師主要提出了3類問(wèn)題，安全閥的排放量、起跳壓力以及安裝位置。

關(guān)于安全閥排放量：

Comment-Current design reliving capacity for all PCVs is 57.72% of MCR， which is higher than 10-30% of MCR as stated in PG-67.4.2.實(shí)際上采購(gòu)合同中PCV閥排放量要求是不低于40%MCR，很明顯與PE工程師這一條意見(jiàn)不符合。針對(duì)這一問(wèn)題的解決過(guò)程中，PE一口咬定不要超過(guò)MCR的30%，廠家也是一味強(qiáng)調(diào)這是合同要求。為此，我們組織有關(guān)各方對(duì)ASME標(biāo)準(zhǔn)相關(guān)條款進(jìn)行了多次分析討論，ASME條款如下：

PG-67.4.1 The total combined relieving capacity of the power-actuated relieving valves shall be not less than 10% of the maximum design steaming capacity of the boiler under any operating condition as determined by the Manufacturer.

PG-67.4.2 Pressure relief valves shall be provided， having a total combined relieving capacity， including that of the power-actuated pressure-relieving capacity installed under PG-67.4.1， of not less than 100% of the maximum designed steaming capacity of the boiler， as determined by the Manufacturer， except the alternate provisions of PG-67.4.3 are satisfied. In this total， no credit in excess of 30% of the total required relieving capacity shall be allowed for the power-actuated pressure relieving valves actually installed.

PE工程師提到的不低于10%依據(jù)為上面的67.4.1條款，而不超過(guò)30%依據(jù)為67.4.2。我們重點(diǎn)對(duì)30%進(jìn)行研讀理解，以上兩條主要講了兩種安全閥的配置及組合排放占比，在總的total排放量中，單詞credi顯然是關(guān)鍵詞，應(yīng)理解為30%是理論計(jì)入的排放量，而非產(chǎn)品實(shí)際能達(dá)到的排放量，最后經(jīng)核算實(shí)際組合排放量的PCV排放量比例完全符合標(biāo)準(zhǔn)要求，此條意見(jiàn)最終予以關(guān)閉。

關(guān)于安全閥起跳壓力：

Comment-The max sustained pressures are chosen exactly the same as the MAWP. As per PG 21.2， expected max sustained pressure shall be selected sufficiently in excess of any expected operating pressure to permit satisfactory boiler operation without lifting overpressure protection devices. The problem is that the set pressure for PCV 1&2 is less than max expected pressure at superheater outlet. Same issue with reheater.

此條澄清屬于理解習(xí)慣上的偏差，廠家堅(jiān)持認(rèn)為4只安全閥全部起跳才是事故，而PE認(rèn)為正常工況不允許有安全閥起跳，最終綜合權(quán)衡整定壓力及運(yùn)行工況實(shí)際情況，統(tǒng)一修改為較高的整定壓力。

關(guān)于安全閥安裝位置：

Comment-It is suggested to locate PCVs upstream of PSVs. If hydraulic test valves are installed permanently， PSVs are located downstream of the test valves are not acceptable.

此條意見(jiàn)主要是PCV閥和PSV閥的先后位置，以及PSV閥和水壓堵閥的先后位置，也屬于習(xí)慣上的差異，PE工程師主要是考慮到減少安全閥起跳以及鍋爐安全運(yùn)行的角度，ASME標(biāo)準(zhǔn)上沒(méi)有明確規(guī)定具體位置的先后順序，最后廠家證明也能達(dá)到安全要求而關(guān)閉此條澄清。

結(jié)語(yǔ)

從公司摩洛哥項(xiàng)目PE認(rèn)證實(shí)踐來(lái)看，完成此項(xiàng)工作耗時(shí)較長(zhǎng)，最根本的原因是類似認(rèn)證國(guó)內(nèi)沒(méi)有成熟的運(yùn)作經(jīng)驗(yàn)，國(guó)內(nèi)廠家和國(guó)際PE工程師無(wú)論在設(shè)計(jì)理念還是對(duì)標(biāo)準(zhǔn)的理解上都存在較大的差異，導(dǎo)致國(guó)內(nèi)廠家認(rèn)為很成熟的一張汽水流程圖，經(jīng)PE工程師審核，提出近兩百條Comments，要關(guān)閉這些審核意見(jiàn)，需要對(duì)ASME標(biāo)準(zhǔn)和鍋爐系統(tǒng)設(shè)計(jì)都很熟悉，如何系統(tǒng)研究做好PE認(rèn)證技術(shù)評(píng)審工作，強(qiáng)化ASME鋼印產(chǎn)品認(rèn)證質(zhì)量，需要我們不斷深入研究與總結(jié)提升。

參考文獻(xiàn)

[1] Rules for Construction of Power Boilers， SECTION 1， 2015 ASEM BOILER and Pressure Vessel Code.

[2]劉貴全，宋一新.ASME安全閥法規(guī)的學(xué)習(xí)與討論[J].鍋爐制造，1998（1）：67-69.