Are you UNDER_Elevated? Part 3
So far I have discussed increasing the speed of the door operation of your conveyance equipment and decreasing the floor to floor travel time. Both of these will bite off the biggest chunk of the problem of slow elevators, but, there is one thing that is rarely thought of when wait time for elevators is considered too long. Have you had your service contractor check the performance of the elevators and compare that with the “contract speed”?
Contract speed is the speed the elevators were originally designed (and approved) to run at. Codes dictate an elevator must run within plus or minus 10% of the designed speed but do you know what those are? Most of the time it’s easy enough to find the contract speed, it should be stamped on a data plate fastened to the crosshead of the elevator car. The crosshead is a sort of main beam on top of the car. Speed can be measured in several ways, by using a tachometer placed against the hoistway wall, by measuring the length of the hoistway and timing the run, or by placing an accelerometer inside the car and taking a measurement. I’m told that there is an app available on the i phone to do this. I haven’t yet seen it but I’m not at all surprised.
Speeds must be measured in both the up and down directions. If necessary the proper adjustments must be made to bring the actual speed as close to the design speed as possible.
There can be several reasons why your equipment won’t reach the contract speed. In the case of hydraulic elevators if the cab is too heavy because of an interior upgrade by a contractor who didn’t consider the weight of the new materials, or if the pump is wearing out, the up direction can be affected. Keep in mind something simple to you like a marble floor can add significant weight to an elevator car thereby affecting the performance and placing undue strain on the components. Weight can also affect the down direction. If the elevator is equipped with a rupture valve (a valve that controls the flow of hydraulic fluid in the down direction) a technician may slow down the elevator so as not to trip the valve causing an entrapment. A hydraulic system is just that, a system. Everything must be in balance to work properly. Have the technician check the weight of the car, the capacity of the main control valve, and if so equipped, the capacity and speed of the rupture valve to assure synergistic operation. If an elevator designed to run at 150 feet per minute is only traveling up at 125 feet per minute due to a strained pump, and traveling at 120 feet per minute in the down direction due to an improperly calibrated rupture valve, you are being shortchanged. There is not only the cost in time but energy costs as well. It doesn’t take long to check the speeds. Adjustment is a different matter but this is probably included in most of your contracts.
Much of the same applies in the case of a traction elevator. If contract speeds aren’t met you need to know why. If the car is too heavy it will have an effect on the motor, the brake, the sheaves, the cables and all of the system. If weight is too heavy, the elevator can “slide through the floor while the motor is trying to stop it causing undue wear on the cables and sheaves. If the governor is too sensitive and the technician slows the system down to prevent entrapments, maybe it’s time to look at a new more modern type of governor. In the case of a “heavy” car it may be possible to add more weight on the counterweight side to balance the system. To do that there must be:
1. Room in the counterweight frame for additional weights, and
2. An engineering study to assure the structural components can bear the additional weight.
A traction system, just like a hydraulic system must be in balance to work synergistically and effectively.
That’s about all for today but next time I think I need to post a little information aboutr elevator interiors.
As always, any ideas, input or comments are appreciated. Especially want to thank my regular readers for your emails and compliments and insightful questions. It shows you’re reading, understanding, and thinking!
For now I’ll leave you with the following quotes:
“When my boss asked me who is the stupid one, me or him? I told him everyone knows he doesn’t hire stupid people”
Anonymous
OR
“They say that love is more important than money, but have you ever tried to pay your bills with a hug?”
Anonymous
That Anonymous guy sure is clever. I wonder what his first name is?
Don’t forget to email me (elevatorernie@hotmail.com). Your suggestions and questions are always welcome.
Thank you,
Ernie
