Maintenance, leaks and oil management

Every hydraulic on Route 7 has a binder in its machine room, and since last year a matching record in Northcrest's online maintenance system. Lena reviews them every month, and one line she always reads is oil added. "Oil does not evaporate," she told Tamsin, showing her the record for the Marlowe. "Every liter you pour into that tank went somewhere. If you can see where, fix it. If you can't, it may be in the ground." The Marlowe's record showed oil added three times in the past year, a total of about 5 gal, with no visible leak noted. That made it the first hydraulic on Route 7 Tamsin was asked to investigate on her own.

The maintenance control program

The code requires the owner of every elevator to have a maintenance control program, usually prepared and carried out by the elevator contractor. The program lists the maintenance tasks and examinations for each piece of equipment, the interval for each, the procedures to follow, and the records to keep. It must be specific to the installation, available on site to the mechanic and the inspector, and updated when equipment changes. The L&I Elevator Program and the inspector review the records at each periodic inspection, and missing or incomplete records are a common finding. For a hydraulic elevator, the program typically includes:

The intervals depend on the equipment's age, use and condition, the manufacturer's recommendations and the code. A busy hospital car gets visits more often than a quiet two-stop clinic. Northcrest's program for Holloway car 2 was rewritten when the new equipment went in, with the new valve's and soft starter's own checks added.

Where hydraulic systems leak

Leaks are the most common hydraulic maintenance problem. Knowing the usual places saves time.

• The packing at the cylinder head. Some seepage is normal and is caught by the drip ring. More than the scavenger pump can handle, oil running down the cylinder, or oil thrown on the pit walls means worn seals or a damaged plunger.
• Fittings and joints in the line: threaded fittings that have loosened with vibration, O-ring fittings with damaged O-rings, flanges with failed gaskets and welded joints with cracks.
• Hoses, at the crimped ends or through cracked covers.
• The valve block: seals on spools, solenoid tubes and adjustment screws, and the gauge port.
• The tank: the drain plug, the cover gasket, the motor lead seal and, on dry units, the pump shaft seal.
• The cooler, if it has one, and its hoses.
• The buried cylinder and any buried piping, where the leak cannot be seen.

Finding a leak starts with cleaning. Oil spreads and collects dust, so an old leak and a new one look alike. Ray degreases the suspect area, dries it, and checks it again after a few runs. A white powder spray, sold for the purpose, shows fresh oil as a dark stain. For a slow drip at a fitting, a clean paper towel held under it and checked after a few minutes tells the story. Fittings are tightened only to the manufacturer's values; overtightening cracks fittings and crushes O-rings. Many leaks need the joint remade with new seals, with the system isolated at the shut-off valve, the car landed on blocking or its buffer, and the pressure relieved.

Repacking a jack

Replacing the packing at the cylinder head is a regular job on older cars. The car is run to the bottom and landed on timber blocking or the pit buffers so that the plunger carries no load, or held by approved rigging; the manual shut-off valve is closed; the system pressure at the head is relieved through the bleeder; and the controller is locked out. The packing head is opened, the old seals removed without scratching the plunger, the plunger surface inspected and cleaned, and new seals and wiper fitted in the orientation the manufacturer shows. After the head is closed, the shut-off valve is reopened, air is bled from the head, and the car is run slowly while the head is watched for leaks. A damaged plunger will tear new seals quickly, so pits and scratches found during repacking are reported; the cure for a badly scored plunger is a new plunger, not repeated repacking.

Tracking oil: the oil log

The simplest leak detector is a record. Each time oil is added, the mechanic records the date, the amount, the oil type and the car's position when the level was read. Over months, the log shows whether the system is losing oil and how fast. Visible leaks are usually found and fixed. But oil lost with no visible leak, after the power unit, line and packing have been checked, is a sign of a buried cylinder or buried pipe leak, which the code and regulators treat seriously: the cylinder may be corroding through, and the oil is going into the ground.

# Oil added to the Marlowe power unit over a year: total, rate and what it means
log = [  # (month, oil added gal, visible leak found and repaired?)
    (2, 1.5, False),
    (6, 2.0, False),
    (11, 1.5, False),
]
total = sum(v for _, v, _ in log)
months = 12
rate_day = total / (months * 30.4)
print(f"oil added in {months} months: {total} gal, about {rate_day * 128:.1f} fl oz per day")
unexplained = sum(v for _, v, seen in log if not seen)
print(f"oil added with no visible leak found: {unexplained} gal")
threshold = 1.0    # company action level for unexplained loss per year, gal
if unexplained >= threshold:
    print("action: inspect and clean the power unit, line and packing; test the cylinder for leakage;")
    print("        report to the owner and the regulator as the rules require")
else:
    print("keep monitoring at each visit")

oil added in 12 months: 5.0 gal, about 1.8 fl oz per day
oil added with no visible leak found: 5.0 gal
action: inspect and clean the power unit, line and packing; test the cylinder for leakage;
        report to the owner and the regulator as the rules require

At the Marlowe, Tamsin found no oil on the power unit, line or packing after cleaning and checking, and no drop in the tank over a weekend when the car stood at the bottom landing with the shut-off valve closed. With the shut-off valve open and the car at the top landing, however, the level fell slowly. The oil was going from the line or the cylinder, and there was no visible leak on the exposed line. Ray reported it to Lena, who arranged a cylinder leak test with the owner.

Testing a buried cylinder

A cylinder leak test measures whether the cylinder and the buried line hold oil. A common method is to isolate the jack, hold the car at a fixed position on blocking or with the plunger at the bottom of its travel against a stop, and watch the pressure or the oil volume over time with the temperature recorded. Another is to measure the car's drift with the shut-off valve closed, as Lesson 10 described, while confirming there is no leak at the packing. The test method, duration and pass criteria depend on the regulator and the code. At the Marlowe, the test confirmed a slow leak below ground. The owner chose to replace the jack with a new protected cylinder, like Holloway's, rather than repair the old one, and the old cylinder came out with the contaminated soil around it.

Oil in the environment

Hydraulic oil that leaks into the soil can reach groundwater, and oil pumped from a pit sump can reach the storm or sanitary sewer. Both are pollution. Mechanics have three responsibilities: prevent spills, contain the ones that happen, and report what the rules require. Every service van carries a spill kit with absorbent pads, socks and granules, and bags for the used absorbent. Pit sumps on hydraulic cars should not pump oil away; many have oil-sensing controls or are kept clean so that the sump pump does not discharge oil. Oil on a pit floor is cleaned up promptly, and its source is found.

A spill that reaches the ground or water, or a buried cylinder leak, may have to be reported. In Washington, the Department of Ecology must be told of oil spills to water or that threaten water, and other spills to the environment may need reporting depending on the amount and where they go; federal rules also require reporting of oil that reaches navigable waters. The owner is usually responsible for reporting and cleanup, but the mechanic who finds the leak is responsible for telling the owner promptly and in writing. Northcrest's procedure is for the mechanic to make the area safe, contain the oil, photograph it, and call the supervisor, who contacts the owner.

Used oil and oily waste go to a licensed recycler, with the records kept. When the old Marlowe cylinder was removed, its oil, the contaminated soil and the absorbents were each handled by the environmental contractor the owner hired, and the disposal records were added to the elevator file.

Changing and conditioning oil

Hydraulic oil does not need changing on a fixed schedule if it stays clean, dry and cool. Its condition is judged from the oil analysis: viscosity still within the grade, low water content, a low acid number and an acceptable cleanliness code. Oil that has darkened, smells burnt, is milky or has failed analysis is changed. Changing oil means pumping the tank empty with the car at the bottom, cleaning the tank and strainer, refilling with new oil through a filter cart, bleeding the system and recording the volume. Between changes, a filter cart can be run on the tank, a process called kidney-loop filtration, to clean oil that has collected particles.

Records that tell the story

Good records make the next mechanic's job easier and protect the company and the owner. Each visit's record should give the date, the mechanic, the tasks done, readings taken such as oil level and temperature, motor current, pressures and run times, any defects found and what was done, oil added and parts replaced. Test results go on the forms the regulator requires. When Tamsin investigated the Marlowe leak, the most useful records were Ray's readings from previous visits: the oil level with the car at the bottom landing had fallen slowly, visit after visit, long before anyone added oil.