Hydraulic Cylinders
By Ray Eleid, P.Eng.
Published in Canadian Property Management Magazine
March 2006
Introduction
On Friday, January 27, 2006 five people riding an elevator
were injured at 522 University Avenue, National Life building.
We understand from news reports and bulletins that the
hydraulic shuttle elevator fell five stories and crashed into the
pit. While there can be many causes for hydraulic elevator
crashes, we believe that this incident should raise awareness
on single bottom cylinders.
 Hydraulic Elevators Type
Hydraulic oil elevators use cylinders to go up and down. The
cylinder is driven by hydraulic fluid hence the name. There
are numerous configurations to hydraulic elevators like:
1. Direct acting (buried in the ground);
2. Holeless (installed above ground);
3. Roped hydraulic (above ground cylinder which uses
ropes as well); and
4. semiholeless (partially buried).
For our purpose of awareness, we will discuss direct acting elevators because they are the type
equipped with single bottom cylinder.
Hydraulic Cylinders
The construction of hydraulic cylinders consisted of single bottom design and more recently
double bulkhead. The advantage of double bulkhead design versus single is in the construction of
a control down valve. The double bulkhead was similar to the old design, but had the added
security of a hole in the cylinder located at the bottom wall ``Slow Leak Port''. If the cylinder
integrity is good, then the hole was encapsulated ``Reservoir Bulkhead'' and did not allow the oil to
escape, however, if the bottom cap rusted and deteriorated, then the oil would escape from the
``Slow Leak Port'' to the environment in a controlled and consistent fashion, hence allowing
maintenance personnel to notice the problem and remove the elevator from service. Therefore, if
you have cylinders with double bulkhead, you can rely on good preventative maintenance and
diligence to retain the elevator cylinder in the ground or you can plan to replace it proactively
within 50 years of installation.
Single Bottom Cylinders
Most cylinders manufactured prior to the 1970's were of the single bottom design. This design is
more susceptible to rust because the cylindrical design with flat bottom area does allow for
concentration of underground currents to a focal point shown in red. The electrolytic action
damages this weld more rapidly then other parts of the cylinder. Since we cannot inspect the
condition of the buried cylinder, it is difficult to assess the life of single bottom cylinders. While
some have lasted over 50 years others failed after only 12 years. This time span can decrease or
increase significantly given soil acidity level and water table condition. Furthermore, buried
cylinders are covered in protective coating which consists of rust inhibiting paint; tar based
protective coating or both. If the cylinder's protective coating was damaged during the installation,
this can effectively reduce the life of the cylinder even more. One thing for sure though, given the
pressure in the system, some catastrophic failures have occurred with little to no warning causing
fatality. Therefore, where single bottom cylinders are concerned, we recommend immediate
replacement of the cylinders.
Cathodic Protection
In the 1970's and 1980's there was a push for cathodic protection to prevent the cylinders from
failing. This system works by turning the cylinder into a cathode and more easily corroding metal
as the anode like magnesium. The magnesium would then corrode but the cylinder will not. The
magnesium can be replaced by an inert or iron anode if a continuous external power source is
used to hold the iron anode at a magnesium potential. Hence the problem with this system:
elevator contractors did not maintain the power source nor did they report its failure to the
building Owners and hence numerous cathodic protection system 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.
What Can You Do?
First thing to do is identify the type of hydraulic cylinder you have in the building. Your elevator
contractor can be a great resource in acquiring this information and assessing the risk. If the
cylinder is a single bottom design, then you should act.
Option 1 - Replace the cylinder. This option is a longterm option that can provide you with
peace of mind and can also improve the value of your asset. Single bottom cylinders are usually
identified during a building condition audit and the replacement value is usually deducted.
Option 2 - Retain the cylinder, but install a safety clamp. This is a good option only in cases
where the cost to replace a cylinder is prohibitive or in the event that removing the elevator from
service for three or four weeks is out of the question. The disadvantage of this option is the
limitation of the product (cannot be installed on all hydraulic elevators) and you still have to
replace the cylinder at some point.
| Options & Costs |
2 - 3 floors |
4 - 6 floors |
| Option 1 - Replace Cylinder |
$35,000 $45,000 |
$55,000 - $65,000 |
| Option 2 - Cylinder Clamp |
$12,000 $13,000 |
$14,000 $15,000 |
| Options & Schedule |
2 - 3 floors |
4 - 6 floors |
| Option 1 - Replace Cylinder |
2 Weeks - 3 Weeks |
3 Weeks - 5 Weeks |
| Option 2 - Cylinder Clamp |
1 Week - 2 Weeks |
2 Weeks - 3 Weeks |
In the Province of Ontario, the elevating devices act requires from 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. Through our site
inspections, we have noted that some contractors are not diligent in maintaining accurate oil
logbooks. We have noted for example oily pits which should indicate that there was oil loss to the
concrete from a bad packing or coupling. Yet, the oil loss is not documented at all. While there is
no need for action by the contractor to remove the elevator from service in the event that oil loss
in accounted for, there is a genuine need for contractors to report the oil loss so that adding oil
can also be noted. As properly managers, you can easily visit the machine room and inspect the
logbook. Discouraging signs to look for include:
- Presence of oil pails in the machine room;
- Visible oil leaks or drips on the floor;
- Strong scents or odours while riding the elevator;
- Notes and comments made by the elevator mechanic
with respect to leaking cylinder packing or coupling in the logbook; and
- Quantity of oily rags in the machine room.
As you can see from the photo above, we observed significant quantity of oil in an elevator pit.
While it would not have been possible for the Owners to observe this oil in the pit, the scent of oil
was present.
Ray Eleid, P.Eng., MBA
Director Strategic Development
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