Three keys to elevator compliance relating to shut off ball valves
- Safety factor of 5:1
- Working pressure is labeled at 5:1 safety factor
- Labeling shows service designation for elevators with compliance marking
- Safety factor of 3:1
- Working pressure is labeled at 3:1 safety factor
- Labeling does not show service designation for elevators
Math behind conversion between WOG and ASME A17.1/CSA B44
1000 psi WOG labeled ball valve used in an elevator system has an actual psi rating of…
X = WOG psi rating (X * 3) / 5 = ASME psi rating
Example calculation: (1000 * 3) / 5 = 600 psi
Warning…this is not a recommended pump unit configuration. With this configuration there is no way to isolate the valves in the up direction preventing proper valve adjustment and reaching your desired ride performance. If your specifications result in a need for two valves and a single pump was called out, please contact Maxton to explore other alternatives.
So you lost a pump a short while ago and then the valve stopped working correctly so you replaced that too. Then the new valve began to malfunction in a matter of days.
Based on Maxton warranty return inspections we find that during the process described above most often the tank was not cleaned, oil was not filtered, nor was the oil replaced. Basically, the oil contamination (root problem) that put the job out of order originally was not addressed and perpetuated the problem. Moral of the story…haste makes waste!
Don’t get me wrong…Maxton sells a lot of valves when critical steps are skipped like this, but we all benefit more from a job done right the first time.
Often this problem raises its ugly head when an old dry power unit on the overshoot and re-level system is modernized with a submersible power unit. The intent is to speed up flight times in the up increasing passenger flows. The problem is short cuts are often taken that produce uncomfortable harsh stops making customers unhappy with the elevator ride.
In order to prevent harsh stops in this modernization example you must remember that the dry power unit operates differently than a submersible when stopping on the pump with overshoot and re-leveling to the floor. Basically, the dry pump unit has fly wheel spin that makes a slow stop while the submersible pump stops almost immediately.
So when replacing a dry unit with a submersible you must add hoistway slowdown switches, a controller upgrade to get the increased passenger flows and maintain the soft stop by stopping on the valve not the pump. If the costs to do this are prohibitive and the customer wants comfortable stops then replace the old dry unit with another dry unit and forgo the increased passenger flows.
All Maxton valves should be rebuilt at our factory with OEM parts by Maxton certified technicians using our Valve Exchange Program or Rebuild Program. There are companies out there that offer low cost rebuilds, but they don’t use Maxton OEM parts and they are not approved by Maxton. Don’t risk your reputation, product performance nor the potential safety of riders, it’s just not worth it. Read our Maxton Safety Bulletin
Do you know what the "S Port" is for and how it can benefit your arrangement of control valve components?
All Maxton valves have three Ports to access either the system static pressure (B Port & S Port) or working/pump pressure (A Port). Why is this important you ask? Well the “S Port” is often overlooked, not used or not understood regarding functionality. Therefore, the “B Port” is then used for multiple access points through plumbing “T” fittings for gauges and low pressure switch attachment. This makes for a less professional look of plumbing and wiring. Maxton recommends using the “S Port” for the low pressure switch installation so all wiring can be cleanly tied together in one wire line while allowing direct or elbow connection of pressure gauge in the “B Port”.
Did you know SafeTach/SafeTach2 (Start, Accel & Decel) readings provide optimal value adjustment settings?
Maxton provides the optimal valve adjustment range in the adjustment procedures based on SafeTach readings for each Maxton valve. For example, the UC4 series DT (down transition) setting says:Register a down call and turn DT IN (CW) so that the car slows to provide 4 to 6 inches of stabilized down leveling.(Decel 0.04g-0.09g).The range in bold is the SafeTach decel reading you should see when the valve is properly adjusted. A softer ride will be on the low end while a firmer ride is on the higher end of this range.
This picture shows a decel rate that is outside the optimal range at 0.02g and needs adjustment (CCW).By using the SafeTach and adjusting to the readings you will increase your efficiency and the elevators performance in no time.
Maxton recommends that if you aren’t successful in troubleshooting or adjusting a valve setting in 20 minutes, stop and call Maxton tech support 1-775-782-1700. This is a “No Charge Service”. We help mechanics every day with troubleshooting and adjustment issues. No one knows our product better…let us help you get the job done efficiently and correctly. In the end you learn or re-fresh your skills, save time and come out looking like the hero.
A common mistake mechanics make when adjusting Maxton valves is to loosen the Hex “seal nuts” on the control plate (UC4/4M) or control block (UC1/1A/UC2/2A) adjusters. These nuts are often misconstrued as being “lock nuts”, which is not the case. The only time the Hex “seal nuts” should be adjusted is to maintain a proper friction seal for the adjuster. When the Hex “seal nut” is loosened or tightened, that action relates to several turns on the adjuster. Therefore, you must compensate with opposing turns on the adjuster to regain optimal ride and performance from the valve. So the rule is…don’t adjust the Hex “seal nuts” unless absolutely necessary.
A common misconception of a down leak comes from…you guessed it, oil shrinkage. For every 50°F (10°C) of cooling will result in an approximate 2% shrinkage of oil per volume. Therefore, a 6 inch piston would equal ¼ inch of oil shrinkage per foot of travel. So in 50 feet of travel the car would drop 1 foot during this drop in temperature. Next time you have a customer complaining about the elevator re-leveling during the night this example might be the culprit not a down leak.
Absolutely! Wait how will I see the car move or not? No worries. All you need is a pressure gauge, optimally two gauges. Connect gauges to A and B ports. When the pump pressure (A port) is 25 psi less than the system (static) pressure (B port) you have set the BPS. You’re the one man show.
Here is a rule of thumb to measure slower speeds: Use your handy tape measure to determine how many inches the car travels in 5 seconds. For example 10 inches in 5 seconds equates to 10 ft/min of car speed. This will get you close however we recommend you use a tachometer for accuracy…preferably a SafeTach/SafeTach2.