Having Your Elevator Serviced

Having Your Elevator Serviced

Servicing your elevator can be one of the most expensive undertakings in your budget. This is where the old adage “Pay me now or pay me later” really applies. Some owners just opt for the lowest price because they have to have a service program.  Another old saying “If it sounds too good to be true, it probably is.” These companies are not donating their services to you nor are their employees, so you have to think to yourself if they are going to stay in business there has to be a way for them to generate a profit. There is usually two ways to do it. The first is to bill you regularly and ignore the equipment until it breaks down, then you get charged for callback services. The other way is to charge you for everything under the sun when they do service it. Either way will cost you more than a reasonably priced program in the long run. The icing on the cake here is that as your equipment deteriorates due to neglect, so does your reputation. Pretty soon you end up with a facility that can only command a rent figure that’s low on the ladder. 

So how do you avoid this situation? Just because you’re paying a premium doesn’t mean you will get good service.  Ninety eight percent of building owners, managers, mechanics, and facility engineers don’t know the first thing about elevator maintenance. In some states you aren’t even allowed in the machine room or shaft unless you hold a certification or license. Most are at the mercy of the elevator contractor. This creates a need for government inspectors to maintain safety standards. It also creates a market for consultants. So back to the original premise, how do you choose your elevator service program?  I highly recommend that you either use a consultant or bring in someone knowledgeable to help you write your contract. Many owners aren’t aware that you don’t have to accept the contractors’ agreement as is. If you can’t generate a complete contract then you can make changes to the agreement that your contractor presents you with.  Some advice here is to read carefully. Do not accept a contract with vague promises about servicing “systematically” or “on a regular basis”. Write in your own language, specific language that puts the contractor on a firm schedule. Let them know that when you solicit bids from them. Language such as “monthly service before the 15^th of each month.”  Specify hours such as 2 hours per traction elevator and 1 hour per hydraulic elevator.  Confirm with check in check out procedures that must be followed in order to get paid. Add penalties such as damages of $200 per hour for any responses that take more than 4 hours. Define what a response is, not just a visit from a sales person.  Then you have to follow up on the contract and penalize the contractor for missed visits late responses and shoddy work. How does an untrained eye know how well the work is being performed? Over 50% of elevator servicing is housekeeping and cleaning. If a technician keeps everything clean and neat he/she can immediately spot leaks, wobbly parts with worn bearings etc. Your contract should require your servicing company to escort you on a yearly audit throughout the system, in the shafts and machine rooms, viewing the car tops and the pits to confirm that proper housekeeping is being performed. You should take digital photos and compare them from year to year.  Yes this will take some of your time but it should pay off well in the long run.

Don’t forget to email me if you have questions or comments. Your suggestions are always welcome.

Thank you,

Ernie

Today’s quote is from General George S. Patton

“Don't tell people how to do things, tell them what to do and let them surprise you with their results.”

Elevator Controllers…., continued

With the introduction of microprocessors on circuit boards in the eighties software became a crucial element of elevator operation. Microprocessors made many more features available and to enable those features the software needed to be written. When you think of software for an elevator, think about a program like Microsoft’s Windows. It does everything and controls all functions and add ons. Whenever you purchase a new copy of Window’s it seems as if you always get a flurry of patches repairs etc. to avoid lock ups and crashes.  Elevator software has no such leeway. Elevators are designed to serve the public and new controllers are under scrutiny from state and federal inspectors to assure public safety. That’s not to say that they don’t have software glitches. Usually the glitches are small and hidden from the public and quietly fixed by the manufacturers.  The certifying organizations make sure there are no huge problems but small things do occasionally show up. These things create callbacks for the servicing companies and it usually takes some time for them to realize that it’s a software problem, then even more time to create a patch program that doesn’t affect another function.

As we continue on into the computer revolution elevator controllers are getting smaller and smaller. Currently some manufacturers are only using one circuit board about the size of a motherboard in a laptop. Most of the space in a controller cabinet is now utilized by starters and electrical components.  It seems as if a future upgrade will be as simple as changing out one board or even plugging in a flash drive.  With these upgrades manufacturers have also greatly increased the energy efficiency of the controllers. Warning lights are now LED’s. Fault code displays are 4 inch by 1 inch LCD’s that scroll the messages by.  

Though they generate a lot less heat by themselves, today’s controllers are much more sensitive to heat than their predecessors. Anyone who has ever had a laptop overheat on them can verify that heat is an enemy of computer chips. Keeping the machine room cool AND clean is more important than ever.

While everyone touts the fact that their controllers are self diagnostic, don’t be fooled. There’s still a long, long way to go before they can truly pinpoint their own problems. Most fault codes generated only specify a general area in which the fault occurred.  It still takes a good technician and sometimes plenty of time to locate a specific fault. Foe example: Your elevator suddenly stops after you step in and push the button to go down to the first floor for lunch. The fault code that is produced may refer to a door problem. It could be that a door isn’t closing properly possibly a spirator that isn’t applying enough pressure to make a solid connection of the safety circuit. It could be that the contacts on the safety circuit have corroded and intermittently stop the flow of electricity through the circuit. It could be a broken wire, or a myriad of other things that a technician has to check out and find. Many times the problem isn’t obvious but the repairman may find and solve a potential future problem only to have the equipment fail again until he locates and remedies the real problem.  In this case we’re talking about mechanical situations. It takes many and many of these to cause the repair technician to delve into the software. Most are unqualified to do so and solutions need to come from the factory.

That’s about all that I have for controllers today. Please let me know what you would like to see in my next posting.

Thank you,

Ernie

Today’s quote is from Groucho (Julius) Marx:

"Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies."

Elevator Controllers The Brain of an Elevator

Elevator Controllers… The Brain of an Elevator

The controller is the brains of an elevator system.  In the very old days operators were needed to start and stop the elevators and to go to whatever floor the rider needed to reach.  A real human being slowed down, speeded up the elevator, applied the brake and made the adjustments to bring the car level at the floor. For those of you that think elevators are simple devices that just go up and down, this is the one that fits the bill.

In the late 1940’s manufacturers introduced automatic elevators that no longer needed an operator. Functions such as stopping, starting and changing directions were built in. This allowed the owner to reduce costs by eliminating the attendant and letting the public “drive” them selves to whatever destination they chose.  Early elevator controls used a system of relays (switches) to make up a remarkable facsimile of todays’ computers.  Although they were very simple and only performed a few functions the logic is essentially the same. A series of circuits is either in the on or off position and different combinations of on and off resulted in power being routed to different parts of the system to perform various functions.  Microprocessors today use thousands of circuits etched on silicon to duplicate the same on off positions of the circuits.

As elevators became more widely used more circuits were added to enable the equipment to do more things.  To reduce size labor and cost individual relays were employed to perform multiple tasks. For instance if relay R was the fourth in a series of circuits that were for a function such as fire recall, the same relay could be used as possibly the first in a series that controlled the re-leveling function.   Even greater demand for functions caused the controllers to grow in size and complexity.  As they grew more and more complex and each relay was responsible in a growing chain of functions servicing and repairing these became increasingly more difficult.  If a technician added a circuit for something like an alarm bell for instance he could end up disabling another function such as door re-open.  At this point anything more extensive than checking or changing out relays required the work of a higher level technician, also known as an adjuster.  Of course the safety functions are critical and when any changes are made the circuit diagrams have to be carefully studied and the new additions cautiously planned so as not to disable or change any of the available tasks that the elevator is already wired to execute. I don’t know what percentage of relay based units are still out there but I believe that it’s probably greater than 50%.

In the eighties the elevator industry began incorporating printed circuit boards to carry out some of the tasks required. The boards enabled the manufacturers to cut manufacturing costs, reduce service labor time and pack more functions into a smaller space. A side benefit was reduction of heat in the machine room which you will see in my next posting, started to become crucial.

Until then…

If you have any questions, or comments please let me know. Some of your emails have been very entertaining.  I have been thinking about possibly working on some software that can write your maintenance plan and tailor it specifically to your equipment and conditions. Please let me know if this is something you may be interested in.  Also if there are any subjects you would like me to tackle next don’t hesitate to comment or email. Otherwise I plan to write a bit about elevator controllers in the next posting.  For questions or comments please contact me at elevatorernie@hotmail.com.

Thank You,

Ernie


Today’s quote is from W. C. Fields

“When doctors and undertakers meet, they wink at each other.”

Elevator Interiors

Elevator Interiors

Today’s essay will be a short word about elevator interiors.  Most owners have heart palpitations when they find out what it will cost to redo the interior of an elevator car. In the past all of the interiors were special materials handmade and installed by experts. Today the elevator contractors are able to reduce the costs a bit by going to specialized firms that sell only elevator interior materials. They measure the cars and order the precut material and assemble it inside the car. The contractor can order panels fabricated in a factory with formica, mirror, wood, simulated granite or a number of other finishes. Those panels just clip on to the frame of the car.  Of course this work must be done by certified elevator personnel in most places because of the potential for injury that could result. For instance,  in some elevators there is nothing behind the panels.  Removing them gives access to the shaft,  if the car should move it would be a very simple matter for someone to lose a limb by sticking something out the hole in the side.  In addition most elevator buttons work off of 120 volts and someone who doesn’t know that and is trying to remove a control panel is in for a shock.

Even if all precautions are taken such as shutting down the unit and locking it off it should still be performed by qualified personnel.  One huge issue that needs to be taken into account is the weight of the new interior materials. Many property managers like the simulated granite used to replace panels but the extra weight can render the elevator system dangerous.  The same goes for adding panels usually made up of pressboard. The pressboard is so dense and heavy that it adds additional weight to the cab and can cause the system to malfunction over time.  Think of it as trying to pull a semi trailer with an ordinary ½ ton pickup. In most cases it will move the load but after a short while things like the engine, transmission and other components will start to fail. The same is true of an elevator system. It was designed to carry so much of a load and overloading will cause you the owner to suffer consequences at a later date.  A certified contractor will take those things into account and not jeopardize his license by not performing calculations. 

To take it even further if you replace the ceiling it’s always best to run new wiring to the lights. (Most elevator lights being used today are LED units which require rewiring and some of that is done from outside the car.) The contractor also has to be familiar with the codes because there are rules for lighting in an elevator car.

Most service contractors don’t like to install flooring but again because of weight restrictions they should be the ones doing it. In addition an experienced service contractor knows the structure of the floor and subfloor in the car to make sure that the material installed is flush with the sill eliminating a tripping hazard.  Never install flooring material over a damaged floor. In time the material will deteriorate and possibly crack off in pieces causing obstructions to the door and costing you for the callbacks.

A new trend taking hold today uses wrap technology to replace older dated looking interiors. Computer printed images printed on plastic sheets designed to wrap around the panels and doors of an elevator can give a new look to a scratched or faded interior. Although the life of a wrap interior will not be as long as a full new interior, the reduction in cost can justify the decision easily. Many owners are opting for advertising and changing the wraps on a regular basis. This keeps the elevators looking new and can be a small source of revenue.  For old nasty looking doors it’s a perfect fix.  That’s inside the car and outside as well.

I think I have just about timed out for today. Look for my next post soon.

As always if you have any questions, or comments please let me know. Some of your emails have been very entertaining.  I have been thinking about possibly working on some software that can write your maintenance plan and tailor it specifically to your equipment and conditions. Please let me know if this is something you may be interested in.  Also if there are any subjects you would like me to tackle next don’t hesitate to comment or email. Otherwise I plan to write a bit about elevator controllers in the next posting.  For questions or comments please contact me at elevatorernie@hotmail.com.

Thank you,

Ernie

Today’s quote is from Albert Einstein

“ When you are courting a nice girl an hour seems like a second.  When you sit on a hot cinder a second seems like an hour. …..That’s relativity.”

Elevator Car Leveling

Elevator Leveling

Elevator leveling really doesn’t sound like much but it can be a huge issue for you the owner/property manager. A passenger who trips due to an offset elevator can be injured and sue the owner, the service company and just about anyone else in the neighborhood. Many elevator service companies negotiate their way out of the lawsuits with settlements that keep the costs lower than if they went to court.

Through the years many different schemes have been used to get an elevator car to stop evenly with the floor that it’s on.  Prior to 1950 we had elevator operators.  They actually “drove” the elevators. They had a handle to accelerate, slow down, and stop.  When you entered an elevator it was their responsibility to keep you away from the door, and then when the door was closed, release the brake, start the elevator in either the up or down direction, take you to your desired floor, slow it down, and finally bring it to a stop level with the floor.  Although it must have been a boring job it did take some skill to keep from undershooting and overshooting the floors. Of course if it wasn’t perfectly level the operator would caution you to watch your step when leaving the elevator.  All of that changed with the introduction of automatic service in the 40’s.

To begin the understanding of elevator leveling you have to know that each elevator is set up with a “profile” of how it’s supposed to run. When you push the button the door closes and the elevator is ready to start in either the up or down direction. The car starts to accelerate at a slow speed to avoid jolting the passengers. Think of it as a car taking off from a stoplight. If the driver floors it immediately you get pinned to the seat. Instead the driver will gradually pick up speed until he can shift to the gear that will take the vehicle to top speed. Elevators work the same way. The distance covered between the start and the shift to full speed is called the transition zone. They also employ transition zones in the slow down phase too, as sudden stops aren’t welcomed by most passengers.

Many elevators employ a system of mechanical switches in the shaft used to slow down then stop the elevator. The positions of the switches define the transition zones.  For traction elevators these switches, once set, do not have to be repositioned very often. They can lead to a mis-leveling condition if the car is heavily loaded or for some reason starts to run faster or slower.  If the switches are placed too close together the car will overrun the floor. When they are placed too far apart it increases the floor to floor time causing increased waiting time for the elevators.  Elevators use the same switches in either the up or down direction. Most elevators do not travel at the same speed in the up direction as they do in the down.  A switch will do double duty signaling for a slowdown as well as signaling to speed up.  Stopping the elevator is done by a third switch that tells the elevator that if it cuts the power right now, the car will stop right at the floor.  For those of you who follow baseball think of the stop switch signal as the batter suddenly deciding against hitting the ball in the middle of his swing. Sometimes he can stop it in time and sometimes not. That’s when the umpire calls a strike. If the elevator is traveling a bit too fast or slow the car will miss the floor. One quarter of an inch is acceptable, however that can still cause a trip and a nasty fall.

Some newer elevators use magnets rather than switches. When a pickup on the car passes a magnet placed in the shaft it sends a signal to the controller much the same as the switches mentioned above. In addition to magnets and switches some traction elevators use encoders to pinpoint the position of the car. These encoders are used to verify the position of the car in the shaft and they work in conjunction with switches, magnets or electric eyes to confirm the location of the elevator. Electric eyes are used on some models.  A metal strip with holes in it is hung the length of the shaft and the electric eye sender is placed on one side while the receiver is placed on the other. By this method the elevator can “count” the number of holes that it has passed in any one direction and maintain it’s location within ½ inch.

Additionally some older traction elevators use a cable that travels the length of the shaft with the car. It is tied through a system of gears to a selector. This selector turns at a reduced ratio like a screw. When the elevator arrives at a floor the technician has set switches on the screw to make contact to slow then stop the elevator.  These require constant adjustment due to cable stretching, and things working loose.

In the past control over the stopping of the motor determined much longer transition zones. With the introduction of computerized controls control is much tighter. This reduces the transition zone by a significant amount and results in a much faster floor to floor time for traction elevators.

Hydraulic elevators mainly use the system of switches. They experience different leveling problems mostly due to changes in the viscosity of the oil. If the hydraulic fluid is too cold or too hot it can make a huge difference as to where the elevator will stop. For instance if the serviceman sets up an elevator that is exposed to the outdoors on a frosty day it may not stop level to the floor on a hot summer day if the oil temperature has exceeded the parameters that define a certain viscosity.  Think of viscosity as thickness of the oil. When it’s cold it’s thick and much more difficult to pump. When it’s hot it’s thin and easier pumping translates to faster speeds.  A good example is driving your car, if you cut your ignition at 60 and roll to a stop you will go further than if you cut it at 30. The solution for a hydraulic elevator is to keep the oil within a certain temperature range either by re-circulating (more on this later), or with a tank heater.

This posting is not going to go into every way to stop an elevator, just some of the major methods in use today.  Suffice to say that stopping in the right place is a complex and important issue that you should be aware of and make sure that your serviceman is paying sufficient attention to.

I would like to ask you again if you have any questions, or comments. I have been thinking about possibly working on some software that can write your maintenance plan and tailor it specifically to your equipment and conditions. Please let me know if this is something you may be interested in.  Also if there are any subjects you would like me to tackle next don’t hesitate to comment or email. Otherwise I plan to write a bit about elevator controllers in the next posting.  For questions or comments please contact me at elevatorernie@hotmail.com.

Thank you,

Ernie

Quote of the Day

“An ignorant person is one who doesn't know what you have just found out.”   - Will Rogers

Elevator Doors Continued.......

Elevator Doors continued…

Most of the elevator doors in operation today use either a GAL or a MAC operator. These types of operators transfer the circular motion of an AC electric motor into the linear motion needed to open and close the doors though the use of some cleverly designed control arms. Using links these control arms allow the door motion to reverse when they run into an obstacle or they have reached their open/close limit. This type of door system has been in use for at least fifty years and the technology is well known and proven. Recent developments in the industry have produced DC powered linear door operators with reversible motors that move the doors with a belt system.  The old circular motion door operators used a system of belts too but that was with sets of pulleys to reduce the speed of the motor and increase the power.  The linear systems utilize a long, toothed belt that pushes the door in each direction. The door actually travels along the belt path. This eliminates many of the mechanical components of the door system thereby simplifying it making door maintenance a snap and greatly reducing wear problems.

In the past the geometric configuration of the door components had a huge impact on how well the door worked. The arm connection point on the car door has to be almost exact for the system to work properly. Locate it in the wrong place and the door would always be a real load for the motor causing burned up motors, stalling doors, and other problems. It could also be in a spot that would make some doors too easy to close making them prone to slamming and hard to adjust.  For the first problem companies would just replace a standard operator with a heavy duty one creating the second problem which they consider easier to deal with.  Heavy duty operators were invented for tall doors. The taller the door the more difficult it is to close.  Not only is it heavier, if something gets stuck in the track the leverage factor kicks in and it becomes very difficult to close. Normal elevator doors are 8 feet high. Anything taller than that is more difficult to maintain and requires more attention.  With old style door operators the technician had to adjust the system to be forceful enough to close the heaviest (some main lobby doors are more ornate and thus heavier) or most difficult hoistway door to close. That causes the others to slam. With the advent of new closed loop technology the motor draws just enough energy to allow it to close the door normally, changing at each floor. Many of the systems being manufactured today actually learn the different floor patterns and automatically add or decrease energy when opening or closing on certain floors.

Although most elevator technicians are more comfortable with the old style operators, the new linear operators are gaining wide acceptance. This is due to their simplicity really, there is almost zero maintenance to perform on them. They adjust themselves. Most have switches to control the opening and closing speeds. After an inspection of the belt for wear and lubrication of a very few of the parts the tech can be on to bigger and better things. I also expect them to reduce callbacks over time. One reason being is that if the door doesn’t close all of the way or not firmly enough, the safety switch contact may not be adequate causing either an open circuit or intermittent contact. This condition will shutdown the elevator creating a callback (and probably a bill) for you the customer.  Linear operators are much more consistent.  An added benefit is that engagement of the latch release mechanism and the clutch apparatus is direct. No space is left between the two apparatus to allow pass through. Eliminating the slack in the engagement enables the doors to open silently. How many times have you heard the elevator doors bang when they start to open? A final benefit is that the doors actually use less energy to operate. Although it’s a minute amount, over time it counts.  Not available for all size doors yet, I expect that these will take over soon.

For modernization and upgrade processes there are many “drop in” closed loop replacements for conventional door operators today. These can reduce the cost of an upgrade or mod by a considerable amount by not having to rebuild the entire door closing mechanism. Allowing only the worn parts of the apparatus to be replaced and eliminating the time involved in relocation of components.  Also because all different sizes and types of doors are not yet covered by replacement linear units.

Freight doors come in two types. Hand operated and motorized. The motorized doors operate very differently from the passenger elevator doors.  Both hand and motorized utilize a system of counterweights for ease of opening. Rather than employing relating cables a system of chains is used. Like passenger elevators they have a car door (usually a gate) on the car and a set of hoistway doors at each landing.  These are bi-parting doors, they open horizontally with the top panel going up into the hoistway and the lower panel descending down.  The hoistway doors do not engage the car door. It opens (or is opened ) separately.  In most cases the door operation is activated with a separate button. After the doors are closed you can place a floor call. The elevator will stay at a floor and not answer a hallway call until the doors are closed.  Most are equipped with a bell for signaling that someone on an alternate floor needs the elevator and that the person at the current floor needs to close the doors to get the elevator to move.  Most freight doors have a small window used for checking to see if the car is at the floor.

Freight doors require a lot more lubrication and maintenance than passenger doors. Lack of maintenance can make them very hard to open and close so constant attention is needed.

There are only a few freight door manufacturers around. Almost all of these doors are custom made. To get replacement parts the technician must get the manufacturers name and the serial number from the door panel. For older units this is sometimes difficult because plates have been removed or painted over. Original prints have been lost. In some cases if you can pinpoint the year of manufacture, the original job name (usually the name of the building) and the manufacturer. They can search their files and come up with the original prints for you and assemble a rebuild kit. In the case of hand operated doors they can also offer a kit to motorize the door. There are a few companies out there that do sell replacement parts only but you need the prints and original part numbers to order what’s necessary. Rebuilding freight doors is normally a pretty big job. The components weigh much more and each one is different. They are not as straightforward as passenger doors.

Time to close the book here today. I would like to ask you again if you have any questions, or comments. I have been thinking about possibly working on some software for you to be able to write your own maintenance plan and tailor it specifically to your equipment and conditions. Please let me know if this is something that you may be interested in.  Also if there are any subjects that you would like me to tackle next please let me know. Otherwise I plan to write a bit about elevator controllers in the next posting.  For questions or comments please don’t hesitate to contact me at elevatorernie@hotmail.com.

Thank you,

Ernie

Quote for the day “ If you die in an elevator, be sure to push the UP button.”

Sam Levinson

Elevator Doors

Elevator Doors

The hardest working part of any elevator is the door system.    Every time that elevator moves the doors are required to open and close.  One of the major manufacturers states that eon average elevator doors open and close over 200,000 times per year.  In most elevators that’s a lot of components moving and a lot of wear going on.  I feel that doors are the most important part in the whole system for the simple reason that they are just about the only system the public interfaces with on a constant basis that can cause significant injuries.  Some of you may want to argue about it but doors that are set to operate too quickly can hit passengers. If the safety devices are not operating properly they can catch a hand. Delaminating door skins can catch clothing or cause cuts.  Believe me people can find some of the most unique ways to get injured on elevator doors that you can imagine.

There are many different types of elevator doors, some of which determine the type of elevator. Doors that open horizontally from the center are a part of freight elevators.  Doors that slide vertically are associated with passenger or service elevators.

There are single panel doors, two panel three and four panel doors.  These are known as single, two, three and four speed doors. They open in one direction and the panels fold under each other.  The reason that we call them two, three and four speed doors is because each panel is moving at a different speed. Check it out next time you’re standing there watching a door open.  The door that is furthest from the strike side will move slower than the one at the other end.  This type of door is used to minimize the size of the hoistway while maximizing the width of the doorway.  You see that when the doors of an elevator open they have to have somewhere to go and that’s normally into the hoistway.

There are also center opening doors and they can be either two single panels moving in opposite directions or two, three, and four panels on each side moving in opposite directions.  Known a two (ot three or four) speed center opening doors.

In every passenger elevator you have a motorized car door that travels with, and is part of, the elevator car. At each landing or floor you have a set of hoistway doors.  Hoistway doors are just dead panels. They have no capacity to open by themselves. They may be spring loaded to enhance closing and keep them closed but for the most part it’s just a sliding panel. Normally they are suspended on an overhead track. The doors have rubberized wheels attached to the top that roll back and forth on the track. Center opening doors are “related” by a cable. That means that because they are tied together with a cable whatever the position one door is in the other has to be in the same position as well.  At the bottom of the door you have devices called gibs.  Gibs are for lack of a better word, nubs that stick out from the bottom of the door. These” nubs” travel in a track in the bottom door sill. They clean debris out of the track by pushing it to holes in the sill, but their real purpose os to hold the bottom of the door in place and keep it from swinging in or out.  The motorized car door engages the hoistway doors by means of a clutch assembly.  The clutch sticks out just a bit from the car door and when the car descends the clutch engages two small rubber rollers that stick out from the hoistway door. To fit into the clutch as the car is coming down the rollers compress together which activates a mechanical apparatus that releases the lock on the hoistway doors. All hoistway doors have these locks as a safety measure to prevent  the public from opening the doors and either getting hit by the elevator car or falling down the hoistway.  Most elevators have a single clutch assembly that works the related doors but a few were built in the past that had clutches for each side of a center opening type.

Most passenger elevator doors are equipped with a safety device that will retract the door if it comes into contact with resistance from closing. That is if someone is standing in the doorway or if there is debris in the track that the gibs cannot push out.  They operate on a mechanical basis and they have to be checked regularly by a technician to insure that they generate no more than thirty pounds of force before the door motion is reversed. Some do get out of adjustment and they can give you a nasty smack if you’re not careful. Many of these types are accompanied by a set of electronic eyes that are placed at 5 inches above the floor and twenty nine inches above the floor. All you have to do to retract the door is to break either beam of light.  About twenty years ago the manufacturers improved on the beam idea by installing a device that projects many infrared beams from about 3 inches to 80 inches above the floor. These are non contact edges and are mostly what we see in elevators today.  Although the doors still have to be set to retract at a maximum of thirty pounds in the event that the device fails.  Elevator codes state that doors that are equipped with electronic eyes and infrared beams must include a feature called “nudging”. Quite a few electronic edges were installed when they first hit the market on elevators that didn’t have the nudging capability. Most of those have been weeded out through modernization and diligent state inspectors.  The nudging feature is utilized in the event that the door is blocked by something or someone or mainly if the beam is obscured by smoke from a fire.  After a set period of time an alarm sounds and the door will begin to close slowly. It still is set to no greater than thirty pounds of closing force in the event that someone may be lying in the doorway incapacitated.

Doors have so many moving and constantly wearing parts they account for at least 80% of the elevator failures today. Most of the time an elevator fails to operate due to a signal from a safety circuit. Think about it, for your elevator to operate the car door has to be closed completely and the contacts in the safety circuit providing a closed loop.  Each set of hoistway doors also has a set of contacts that are tied to the safety circuit. If they don’t complete the loop due to something like an excess of pressure in the building, a worn closer that needs the spring tightened, corroded contacts in the circuit, or any other reason that everything is not closed up tight, the elevator will not run.  We in the elevator business think that’s a good way to do things, we realize that the public is somewhat annoyed by this.

I’m out of time right now but I will be adding to this very soon. In the meantime don’t hesitate to leave a comment or send me a question at elevatorernie@hotmail.com.

Today’s quote comes from Will Rogers.

“Everything is funny as long as it is happening to somebody else. “