8.2 Corrective and Preventive Mechanical Maintenance

Mechanical equipment fails in two ways: on a schedule you ignored, or in a cloud of smoke you did not plan. The AFO content outline pairs mechanical maintenance (2E) with the measurement work in the previous section. This section is about pumps, filters, heaters, and feeders as machines—what you clean, what you listen for, when you shut power down, and how you write the work down. Facility-wide preventive-maintenance calendars, chemical-controller probe care, and the full documentation system belong in later maintenance chapters. Here the question is narrower: is this piece of iron being cared for before it fails, or only after?

Independent operator teaching uses OSHA’s published energy-control rule, ordinary commercial pump-room practice, and the same pressure/flow logic you just calculated. Manufacturer instructions and the AHJ still govern intervals, licensed gas work, and what you are allowed to open.

Preventive versus corrective

Preventive maintenance (PM) is work you do while the equipment can still do its job:

• Empty the hair-and-lint strainer on a posted interval and whenever suction sag appears.
• Lubricate motor bearings only if the manufacturer requires oil or grease. Many modern motors are sealed; greasing a sealed bearing “for luck” blows the seal.
• Inspect belts and couplings for cracks, glaze, missing guards, and shafts that do not share a centerline.
• Compare or calibrate pressure gauges so a “dirty filter” reading is a number, not a stuck needle.

Corrective maintenance is repair after failure: a seized impeller, a motor that already smoked, a union that already burst, a multiport valve that already dumps to waste when the handle says FILTER. The economic story is simple even without a made-up national statistic: a basket clean is cheaper than a shaft and seal. The exam story is the classification. If the stem says “every Monday, or every 40 run-hours,” you are in preventive territory. If it says “the pump locked at 2 p.m. Saturday,” you are in corrective territory.

Pumps

The circulating pump is the heart; the strainer is the first organ you can service without a rebuild kit.

Strainer, seal, noise, heat, and valves

Strainer (hair-and-lint basket). A packed basket is a hidden closed valve. Vacuum on the suction gauge drops, flow falls, and the pump may cavitate (vapor bubbles collapse on the impeller—gravel-in-a-can noise, pitting, lost capacity). Clean the basket on a schedule and whenever the suction reading leaves the clean baseline. Seat the lid O-ring; a sucking lid is air in the eye of the impeller, which is the same starvation story as a clogged basket.

Seal leak. A mechanical seal that weeps a film that dries after shutdown can be ordinary evaporation; a steady stream while running is a failing seal. Older packing glands are adjusted to a slow drip, not to bone-dry. Water streaming onto a motor is an electrical hazard, not a mopping problem.

Noise and cavitation. Rattling, a sudden shriek, or falling flow with a hungry suction gauge often means the impeller is starving: clogged strainer, closed suction valve, low water, air leak on the lid or unions, or more total dynamic head than the pump can live with. Do not “turn it up” with a discharge valve to hide a suction problem. Cavitation does not clear itself with more chlorine.

Motor heat. Varnish smell, a thermal protector cycling, or a shell too hot to approach means blocked fan screens, a brutal mechanical-room temperature, voltage problems, or a pump working against a nearly closed valve (or a locked impeller). Site procedure may allow an infrared thermometer on the shell; it does not allow you to ignore a cycling overload.

Valve exercise. Isolation valves that sit for a season freeze in place. On a posted interval, open, close, and return each isolation valve to the marked running position so you can actually isolate the pump when a seal lets go.

Filters

Sand, diatomaceous earth (DE), and cartridge vessels all report health as pressure differential and flow.

Pressure differential. On the day you return a clean system to service, log influent and effluent psi (or influent versus your known clean number) and the flow-meter GPM. Rising influent pressure with falling flow is the classic dirty-media or throttled-valve signature. Rising pressure with steady flow can mean a gauge that is stuck—tap it, compare a second gauge, then act. Falling pressure with falling flow is often a pump story (air, worn impeller, suction leak), not a sand story.

Media replacement interval, conceptually. Sand is not eternal. Years of channeling, mud balls, and cracked laterals cut filtration even when the pressure looks “pretty good.” DE grids tear and channel. Cartridges load, then they are replaced or professionally cleaned. There is no unpublished AFO year-count that overrides the manufacturer and the AHJ. Think in condition and differential, not in a magic birthday.

Air relief. After a backwash or a lid opening, trapped air sits on top of the media. Open the air-relief until a solid water stream appears. Air in the tank is false head, noisy flow, and a crushed-grid risk on some DE units.

Multiport valve service. The handle must seat in FILTER, not halfway to WASTE. A leaking spider gasket sends filtered water to waste (mysterious falling pool level) or lets dirty water bypass. Exercise the valve through its positions during a planned shutdown. Forcing it under full pressure tears the gasket you were trying to save.

Heaters

Heaters fail from water chemistry, from no flow, and from gas or electrical faults you may not be licensed to repair.

• Scale. High calcium saturation cooks onto heat-exchanger tubes. Outlet temperature sags; the burner (or elements) work hard for little heat. Water-balance work and a qualified descaling procedure beat “turning the thermostat up.”
• Condensate. High-efficiency heaters make acidic condensate that needs a clear drain path. A clogged condensate line can shut the unit down or spill onto the floor.
• Gas train. Gas valves, unions, and burners are typically licensed work. Your job is to smell, to know the shutoff, and to lock out rather than to rebuild a gas train with a screwdriver.
• Flow switch test. The heater must not fire without proven flow. During a planned service window, confirm that stopping the pump (or closing the heater isolation valves per procedure) drops the burner or the electric elements. A jumped flow switch is a melted exchanger waiting to happen.

Feeders — mechanical faults only

Clogged injection fittings, empty solution tanks, failed solenoids, split tubing, and a pump that lost prime are mechanical feeder faults. ORP and pH probe cleaning and controller calibration are chemical-system preventive maintenance; they are outlined later with the facility PM program. Mention them here so you do not treat a dirty probe as a broken peristaltic tube—then leave the wet-chemistry PM to that chapter.

The mechanical log (not the whole records program)

Bound health-department logs, incident files, and retention rules are a documentation chapter of their own. The mechanical equipment log on this desk is narrower:

• Date, time, and run-hours (or hour-meter reading).
• Asset: pump 1, filter A, heater, feeder B.
• What you did and parts used (O-ring, basket, belt, gasket).
• Before/after suction psi, discharge or filter influent/effluent psi, and flow-meter GPM.

A belt replacement without a flow number is a receipt, not a diagnosis. Hours matter because a pump that dies at 1,800 hours with a packed strainer is a PM miss, not fate.

Lockout/tagout awareness (OSHA)

OSHA’s Control of Hazardous Energy standard, 29 CFR 1910.147, is the federal lockout/tagout (LOTO) rule for general industry. It exists so a pump cannot restart, dump stored pressure, or remain electrically live while someone has a hand in the strainer or a coupling guard off. Hazardous energy in this room includes electrical, mechanical (rotating shafts), hydraulic, pneumatic, and thermal.

Lockout is a lock on an energy-isolating device (breaker, disconnect, valve that truly isolates). Tagout is a warning tag used only where the written procedure allows it; a tag without a lock is weaker. Authorized employees apply locks. Affected employees operate the equipment in normal production and must not remove someone else’s lock. Group work uses a hasp or lockbox so every person on the job has a personal lock. Outside vendors must be told the site procedure. Cord-and-plug equipment can be an exception only when the plug stays under the exclusive control of the person doing the work.

This is awareness, not a substitute for your employer’s written energy-control program. The exam-relevant operator move is: do not service an energized circulating pump. Drain or isolate stored water pressure per procedure before you crack a lid that can still spray.

Scenario: pressure up, flow down — do not add chlorine

The filter influent gauge that used to sit near 12 psi is at 18 psi. The flow meter that used to show about 250 GPM is at 180 GPM. The water looks a little dull. An untrained response is to add more chlorine because cloudy water “must be a chemistry problem.”

Walk the mechanical loop first

1. Chemistry can wait ten minutes. Combined chlorine does not raise filter pressure.
2. Strainer. If the basket is matted, you already found a suction restriction. Clean it, reseat the lid, re-read the meter.
3. Valve positions. Multiport on FILTER? Heater bypass where you left it? Return valves open? A nearly closed discharge valve raises pressure and cuts flow the same way dirty media does.
4. Filter differential versus the clean baseline. If the rise is across the filter and valves are correct, backwash (sand/DE) or clean/replace (cartridge). Re-read flow and gauges. Log both pairs of numbers.
5. Only then look at water chemistry, and only with a test kit, not with a hope.

Pressure up plus flow down is a restriction story: dirty media or a closed path. Pressure down plus flow down can be a pump story. Chemistry is a different node.

Keep the machines on a calendar, lock them out before you open them, and write the numbers down. Chlorine does not clean a sand bed.