污水厂清洁的第一原则：先看分区，再谈设备

First principle at a treatment plant: classification before equipment

在多数工业场所，清洁设备选型从面积、地面材质和作业窗口开始；在污水处理厂，顺序必须颠倒——先确认作业点的电气危险区域分类，再决定能把什么设备推进去。原因是污水在厌氧条件下降解产生甲烷，污泥处理与收集系统中的可燃气体可能在正常运行状态下就存在。NFPA 820《污水处理与收集设施防火标准》正是为此而设，首版发布于 1990 年，其后陆续修订，现行版本为 2024 版。它不直接规定用什么清洁机器，但它决定了哪一类电气设备被允许出现在某个房间里，从而反向约束了清洁方案。

In most industrial settings, equipment selection starts with area, floor material and cleaning window. At a wastewater treatment plant the order must be reversed: confirm the electrical area classification of the work point first, then decide what may be rolled into it. Anaerobic degradation of wastewater generates methane, and flammable gas may be present under normal operating conditions in solids handling and collection systems. NFPA 820, Standard for Fire Protection in Wastewater Treatment and Collection Facilities, exists for this reason. First issued in 1990 and revised repeatedly since, its current edition is 2024. It does not prescribe cleaning machines, but it determines which class of electrical equipment may exist in a given room, which in turn constrains the cleaning plan.

NFPA 820 的核心逻辑：通风率决定电气分类

The core logic of NFPA 820: ventilation drives classification

NFPA 820 的分类表按三大工艺类别组织：收集系统、水线处理、泥线处理。每一行工艺对应一个 NEC 分类结果——Class I（可燃气体或蒸气）Division 1 或 Division 2，Group D，或不分类。Division 1 表示危险在正常运行状态下即预期存在；Division 2 表示仅在异常状态（如管道破裂、设备故障）下出现。与固定的分区地图不同，NFPA 820 的分类结果随通风条件浮动：分类表以通风阈值为键，大致分为无通风或低于每小时 12 次换气、连续 12 ACH、连续 6 ACH、低于 6 ACH 几档，且换气量按 100% 室外新风计算。工程实践中广泛引用的例子是：封闭且无通风的进水泵房/格栅间通常为 Class I, Division 1, Group D；提供连续 12 ACH 通风后可降为 Division 2。

NFPA 820 organizes its classification tables around three process categories: collection systems, liquid stream treatment and solids treatment. Each process row assigns an NEC designation: Class I (flammable gas or vapour) Division 1 or Division 2, Group D, or unclassified. Division 1 means the hazard is expected under normal operating conditions; Division 2 means it appears only under abnormal conditions such as a rupture or equipment failure. Unlike a fixed zoning map, the designation moves with ventilation. The tables key classifications to ventilation thresholds, broadly no ventilation or less than 12 air changes per hour, continuous 12 ACH, continuous 6 ACH and less than 6 ACH, calculated on 100 percent outside supply air. A widely cited example: an enclosed, unventilated headworks space is typically Class I, Division 1, Group D, and continuous ventilation at 12 ACH can reduce it to Division 2.

典型区域的分类结果：从格栅间到消化气管廊

Typical designations from headworks to digester gas galleries

按 NFPA 820 的框架，收集系统、进水处理工艺、初沉池，以及未设初沉池时的曝气池，通常落入 Class I 范畴；所有污泥处理工艺同样按 Class I 考虑。具体是 Division 1 还是 Division 2，取决于是否封闭以及通风水平。工程文献中引用 NFPA 820-2024 表 6.2.2A 的一个例子：混合池泵站泵房无通风时为 Class I Division 2，提供 6 ACH 连续通风后可判为不分类。化验室、控制室与配电室一般通过物理分隔与通风保持在不分类状态。需要强调的是：分类结果来自设计单位依据现行版本分类表绘制的分区图纸，不存在「格栅间一律 Division 1」这样的通用规则，而且分类的有效性完全依赖通风系统被持续维护。

Within the NFPA 820 framework, collection systems, inlet treatment processes, primary clarifiers, and aeration basins not preceded by primary clarifiers generally fall into Class I, and all sludge handling processes are treated as Class I as well. Whether a space is Division 1 or Division 2 depends on enclosure and ventilation. Engineering literature applying NFPA 820-2024 Table 6.2.2A gives one example: a blending basin pump station pump room is Class I Division 2 without ventilation, and can be unclassified with continuous 6 ACH. Laboratories, control rooms and electrical rooms are usually kept unclassified through separation and ventilation. Two cautions: designations come from classification drawings prepared by your engineer from the adopted edition's tables, so there is no blanket rule that headworks are always Division 1; and a classification is only as valid as the ongoing upkeep of the ventilation system.

别忘了污泥干化：Class II Group G 的粉尘风险

Do not overlook sludge drying: Class II Group G dust

污水厂里较少被提及、但对清洁设备选型影响很大的一类是干化污泥粉尘。当设有污泥干化工艺时，相关区域可能被判为 Class II（可燃粉尘）Division 1 或 Division 2，Group G。这类区域的风险机理与甲烷完全不同：干化污泥属有机粉尘，具备可燃粉尘的基本特征，积尘层同时是二次爆炸的燃料。清洁上的含义很直接——禁止用压缩空气吹扫扬尘，应采用负压吸取，且设备与管路需具备静电控制与相应等级的防护，同时把「不允许积尘超过可见层」写进现场作业规程。

A category rarely discussed but decisive for equipment selection is dried sludge dust. Where a sludge drying process exists, the area may be designated Class II (combustible dust) Division 1 or Division 2, Group G. The hazard mechanism differs entirely from methane: dried sludge is an organic dust with the basic characteristics of combustible dust, and settled layers are the fuel for a secondary explosion. The cleaning implication is direct: no compressed air blowdown that raises a dust cloud, vacuum extraction instead, static control and appropriate protection ratings on equipment and hoses, and a written site rule that visible dust layers are not permitted to accumulate.

为什么普通清洁设备不能推进分类区

Why ordinary cleaning machines cannot enter a classified space

NFPA 820 负责给出分类，NFPA 70（美国国家电气规范）负责规定分类区内允许安装什么。在 Class I Division 1 或 Division 2 场所，普通电气设备不被允许，灯具、电机、盘柜和仪表必须采用 NEC 第 500.7 条认可的防护方式，例如隔爆型或气密封结构。一台普通的三相工业吸尘器或电机驱动的洗地机，其电机电刷、开关触点与充电接口都是潜在点火源，即便「看起来只是清扫」也不能进入分类区。可行的路径有三条：一是使用气动无电机设备（如 ylbc102），由压缩空气驱动、机身不含电气点火源；二是使用相应等级的防爆机型（如 ylbc030）并索取证书；三是在作业前通过临时强制通风与可燃气体检测，将该空间在作业窗口内降级，这需要有书面程序与检测记录支撑。

NFPA 820 assigns the classification; NFPA 70, the National Electrical Code, governs what may be installed there. In a Class I Division 1 or Division 2 space, ordinary electrical equipment is not permitted: fixtures, motors, panels and instruments must use a protection technique recognized under NEC Section 500.7, such as explosion-proof or hermetically sealed construction. A conventional three-phase industrial vacuum or a motor-driven scrubber carries brushes, switch contacts and charging connectors that are all potential ignition sources, so it cannot enter a classified space merely because the task is housekeeping. Three workable routes exist: use pneumatic motorless equipment such as ylbc102, driven by compressed air with no electrical ignition source on board; use a correspondingly rated explosion-protected machine such as ylbc030 with certificates on file; or temporarily downgrade the space during the work window through forced ventilation and combustible gas monitoring, supported by a written procedure and records.

硫化氢：清洁作业前必须做的三件事

Hydrogen sulphide: three things to do before cleaning

硫化氢（H2S）在污水厂同时具备毒性与可燃性：100 ppm 即为立即威胁生命与健康（IDLH）浓度，其爆炸下限为 4%，而原始消化气中的 H2S 浓度可超过 4,000 ppm。最危险的特性是嗅觉疲劳——H2S 会在浓度达到危险水平之前使人失去嗅觉，因此「闻不到了」往往意味着情况更糟而非好转。清洁作业前必须做三件事：一是使用连续式气体检测仪而非依赖气味判断；二是进入湿井、池底、管廊等空间前按受限空间程序办理许可、设置监护人并做进入前通风；三是确认通风系统实际在运行——分类降级的前提是通风持续有效，不是图纸上写了就算。

H2S at a treatment plant is both toxic and flammable: 100 ppm is immediately dangerous to life and health, its lower explosive limit is 4 percent, and concentrations in raw digester gas can exceed 4,000 ppm. Its most dangerous property is olfactory fatigue, deadening the sense of smell before concentrations become dangerous, so no longer smelling it usually means the situation is worse, not better. Three actions are mandatory before cleaning: use continuous gas monitoring rather than odour as the warning; follow permit-required confined space procedures with an attendant and pre-entry ventilation before entering wet wells, basin floors or galleries; and verify that the ventilation system is actually running, since any classification downgrade depends on ventilation being continuously effective, not merely drawn on a plan.

冲洗还是吸取：格栅间、沉砂池与脱水间的作业方式

Wash down or vacuum: headworks, grit channels and dewatering rooms

格栅间与沉砂池的栅渣、砂砾黏附性强，通常以高压冲洗为主，配合地漏与集水沟排走；选择电机驱动冷水高压清洗机（如 ylbd050）时，应关注设备本体的安放位置——把主机留在不分类的相邻区域，仅将喷枪与高压软管延伸进作业面，是常见且成本最低的合规做法。污泥脱水间地面多为油脂、聚合物与泥饼混合物，湿滑且易结壳，宜采用吸尘吸水机（如 ylbc112）先收湿料再冲洗，避免直接冲洗把泥饼带入排水系统造成堵塞。加药间与消毒间应单独配置清洁工具并做颜色标识，防止化学品交叉污染。所有作业均应在通风运行状态下进行。

Screenings and grit adhere strongly, so headworks and grit channels are usually cleaned by high pressure washing routed to floor drains and channels. When selecting an electric cold-water pressure washer such as ylbd050, pay attention to where the unit itself sits: leaving the machine in an adjacent unclassified area and extending only the gun and hose into the work face is the common and lowest-cost compliant approach. Dewatering room floors carry a mix of grease, polymer and cake that is slippery and crusts over; use a wet and dry vacuum such as ylbc112 to lift wet material first and wash afterwards, so cake is not flushed into the drainage system where it causes blockages. Chemical dosing and disinfection rooms should have dedicated, colour-coded cleaning tools to prevent cross contamination. All work should proceed with ventilation running.

落地：一份分区清洁作业规程模板

Deployment: a template for a classification-based cleaning procedure

建议按「区域 / NFPA 820 分类 / 允许设备 / 作业方式 / 频次 / 前置条件」六列建表，并与设计单位出具的分区图纸编号一一对应。例如：进水格栅间（Class I Div 2，12 ACH 运行时）——允许气动吸尘设备与延伸式高压冲洗，每班次冲洗一次，前置条件为通风运行 + 气体检测合格；污泥脱水间（按分区图纸判定）——先吸后冲，每日一次；干化车间（Class II Div 2 时）——仅允许相应等级防爆吸尘，禁止吹扫，每班次清理可见积尘；化验室与控制室（不分类）——常规洗地机作业，每日一次。改造项目还需注意 NFPA 820 第 1.4.1 条：除非另有规定，本标准的条款不适用于在其生效日期之前已存在或已批准建设的设施，因此老厂通常按「改到哪里、合规到哪里」推进，具体范围应由设计单位与当地消防主管部门确认。

Build a table with six columns: area, NFPA 820 designation, permitted equipment, method, frequency and preconditions, each row cross-referenced to the drawing number of the classification plan issued by your engineer. For example: inlet screening room (Class I Div 2 with 12 ACH running) permits pneumatic vacuum equipment and extended-hose pressure washing, washed once per shift, preconditioned on ventilation running and a satisfactory gas test. Dewatering room, designation per drawing: vacuum first, wash second, once daily. Drying building, where Class II Div 2: only correspondingly rated explosion-protected vacuums, no blowdown, visible dust removed every shift. Laboratory and control room, unclassified: conventional scrubber once daily. For retrofits, note NFPA 820 clause 1.4.1: unless otherwise specified, the provisions do not apply to facilities, equipment, structures or installations that existed or were approved for construction before the effective date of the standard. Older plants therefore usually comply progressively as areas are modified, with scope confirmed by the engineer and the local authority having jurisdiction.