ELEVATOR MAINTENANCE

By Ray Eleid

In January 2006, five passengers were injured when an elevator dropped five storeys at an office building in down- town Toronto. The incident focuses attention on hydraulic elevators, and particularly those with single-bottom cylinders.

Hydraulic oil elevators use cylinders to go up and down. The cylinder is driven by hydraulic fluid, hence the name. There are numerous configurations such as:

· Direct-acting (buried in the ground);

· Holeless (installed above ground);

· Roped hydraulic (above ground cylinder that uses ropes as well); and

· Semi-holeless (partially buried).

Older direct-acting elevators are the type equipped with a single-bottom cylinder.

DOUBLE BULKHEAD CYLINDERS

Hydraulic cylinders typically have one of two designs -single-bottom design or double bulkhead. The double bulkhead design offers the advantage of a control- down valve. This adds the security of a "slow leak port" in the bottom wall of the cylinder.

If the cylinder integrity is good, then the hole is encapsulated in the reservoir bulkhead and does not allow the oil to escape. However, if the bottom cap is rusted and deteriorated, then the oil would escape from the slow leak port to the environment in a controlled and consistent fashion. This ensures maintenance personnel will notice the problem and remove the elevator from service.

Good preventative maintenance and diligence of cylinders with double bu1k- heads could result in up to 50 years of reliable service.

SINGLE-BOTTOM CYLINDERS

Most cylinders manufactured prior to the 1970s were of the single-bottom design. This design is more susceptible to rust because the cylindrical design with flat bottom area allows for a concentration of underground currents and damages the weld area more rapidly than other parts of the cylinder.

Buried cylinders cannot be inspected so it. is difficult to forecast the life cycle of single-bottom cylinders. Some have lasted more than 50 years; others failed after only 12 years. This time span can decrease or increase significantly depending on soil acidity and water table conditions.

Buried cylinders are covered in a protective coating that consists of rust- inhibiting paint and/or tar-based protective coating. If the cylinder's protective coating was damaged during the installation, this can effectively reduce the life of the cylinder. Given the pressure in the system, some catastrophic failures have occurred with little to no warning.

CATHODIC PROTECTION

In the 1970s and 1980s there was a push for cathodic protection to prevent cylinders from failing. This system turns the cylinder into a cathode to react with a more easily corroding metal, like magnesium, as the anode. Thus, the magnesium would corrode, but the cylinder would not.

An inert or iron anode, using a continuous external power source to hold the iron anode at magnesium potential, could replace the magnesium. Unfortunately, elevator contractors did not always maintain the power source nor did they report its failure to the building owners.

Numerous cathodic protection systems were left unattended and became ineffective. In some cases, the cathodic protection accelerated the deterioration of the cylinders in instances where the cylinders were touching earth or exposed to it in one spot.

PRECAUTIONS

The first thing to do is identify the type of hydraulic cylinder. Elevator contractors can help discover this information and assess the risk. If the cylinder is a single- bottom design, consider the following options.

Replace the cylinder. This is a long-tern option that can provide peace of mind and also improve the value of the asset. Single-bottom cylinders are usually identified during a building condition audit, and the replacement value is usually deducted. This option would cost about $55,000 to $65,000 in a building with four to six storeys, and take three to five weeks to complete.

Retain the cylinder, but install a safety clamp. This is a possibility in cases where the cost to replace a cylinder is prohibitive or it is impossible to take the elevator out of service for an extended period. However, the solution doesn't work in every hydraulic elevator, and it's really just delaying inevitable replacement work. This option could cost $16,000 to $18,000 in a building with four to six storeys, and take two to three weeks to complete.

LOGBOOK

In Ontario, the Elevating Devices Act requires elevator contractors to maintain an oil logbook in the machine room of each hydraulic elevator. The purpose of the logbook is to keep track of oil losses and to monitor changes in oil levels.

Invariably, however, some contractors are not diligent in maintaining accurate oil logbooks. Inspections will reveal oily pits—which generally indicates that there was oil loss to the concrete from a bad packing or coupling—but no oil loss will be documented.

There is no urgent need to remove the elevator from service if oil loss is discovered, provided that the source of the leak is identified and is minor in nature. After all, some couplings, older pumps and valves are susceptible to leaks. Nevertheless, there is a genuine need for contractors to report the oil loss.

Property managers are encouraged to visit the machine room and inspect the logbook. Even though oil that has leaked into an elevator pit can't be detected through a visual inspection of the machine room, the scent of oil likely will be present in the elevator.

Warning signs include:

·Presence of oil pails in the machine room;

·Visible oil leaks or drips on the floor;

·Oily rags in the machine room;

·Strong odours detected within the elevator cab; and

·Notes in the logbook about leaking cylinder packing or coupling.

Ray Eleid, PEng., MBA, is Director of Strategic Development with Solucore Inc., an independent elevator consulting firm. For more information, see the web site at www.solucare.ca.