In a typical installation, submersible motor/pump units are bolted together and located in a 50- to 100-gallon oil reservoir, which is located in the machine room adjacent to the motion controller. The small motors are very reliable and long-lasting, because immersed in oil there is excellent heat dissipation and the windings, encapsulated in epoxy, are exceptionally well insulated and protected from grounding out.
There are a number of conditions that will cause an elevator to cease operation. One of these, in the hydraulic elevator, is elevated oil temperature in the reservoir. High oil temperature can have many causes, including among others aged and inefficient oil, low oil level (a leak!), inefficient pump operation, continuous operation of the elevator especially with heavy loading, high ambient temperature in the machine room, and so on. All these factors work together. You can have some idea where you stand by attaching a thermometer to the outside of the tank. The top of the tank should never be used as a catch-all, especially for cloth or similar objects that could impede heat dissipation. The machine room should have adequate ventilation, and if this depends upon a fan, failure of the fan motor could be an issue.
ASME A17.3, Safety Code for Existing Elevators and Escalators, Part IV, contains design and installation requirements specifically relating to hydraulic elevators. It opens with a declaration of scope, stating that Part IV is applicable to both direct plunger and roped-hydraulic elevators. Section 4-1 notes that hoistways, hoisting enclosures, and related construction are to comply with ASME A17.3, Part II.
Section 4.2, Mechanical Equipment, contains four provisions:
■ 4.2.1 states that buffers and bumpers are to be provided. Solid bumpers are acceptable instead of spring bumpers where the rated speed is 50 feet per minute or less.
■ 4.2.2 states that car frames and platforms shall conform to the requirements of Section 3.3.
■ 4.2.3 states that car enclosures are to comply with Section 3.4.
■ 4.2.4 states that capacity and loading are to comply with Section 3.7.
Section 4.3 pertains to driving machines:
■ 4.3.1, Connection to Driving Machine, states that the driving member of a direct plunger driving machine is to be attached to the car frame or car platform with fastenings of sufficient strength to support that member.
It is further stated that the connection to the driving machine is to be capable of withstanding without damage any forces resulting from a plunger stop.
■ 4.3.2, Plunger Stops, states that plungers are to be provided with solid metal stops and/or other means to prevent the plunger from traveling beyond the limits of the cylinder. Stops are to be designed and constructed to stop the plunger from maximum speed in the up direction under full pressure without damage to the connection to the driving machine, plunger, plunger connection, couplings, plunger joints, cylinder, cylinder connecting couplings, or any other part of the hydraulic system. For rated speeds exceeding 100 feet per minute where a solid metal stop is provided, means other than the normal terminal stopping device (i.e., emergency terminal speed limiting device) are to be provided to retard the car to 100 feet per minute with a retardation not greater than gravity, before striking the stop.
■ 4.3.3, Hydraulic Elevators, provides that hydraulic elevators that have any portion of the cylinder buried in the ground and that do not have a double cylinder or a cylinder with a safety bulkhead are to:
(a) Have the cylinder replaced with a double cylinder or a cylinder with a safety bulkhead protected from corrosion by one or more of the following methods:
(1) Monitored cathodic protection
(2) A coating to protect the cylinder from corrosion that will withstand the installation process
(3) A protective plastic casing immune to galvanic or electrolytic action, salt water, and other known underground conditions; or
(b) Be provided with a device meeting the requirements of Section 3.5 or a device arranged to operate in the down direction at an overspeed not exceeding 125 percent of rated speed. The device is to mechanically act to limit the maximum car speed to the buffer striking speed, or to stop the elevator car with rated load with a deceleration not to exceed 32.2 feet per second, and is not to automatically reset. Actuation of the device is to cause power to be removed from the pump motor and control valves until manually reset; or
(c) Have other means acceptable to the authority having jurisdiction to protect against unintended movement of the car as a result of uncontrolled fluid loss.
■ Section 4.4, Valves, Supply Piping and Fittings, provides in 4.4.1, Pump Relief Valve:
(a) Pump Relief Valves Required: Each pump or group of pumps is to be equipped with a relief valve corresponding to the following requirements, except as covered by (b):
(1) Type and Location: The relief valve is to be located between the pump and the check valve and is to be of such a type and so installed in the bypass connection that the valve cannot be shut off from the hydraulic system.
(2) Size: The size of the relief valve and bypass is to be sufficient to pass the maximum rated capacity of the pump without raising the pressure more than 50 percent above the working pressure. Two or more relief valves are permitted to obtain the required capacity.
(3) Sealing: Relief valves having exposed pressure adjustments, if used, are to have their means of adjustment sealed after being set to the correct pressure.
(b) Pump Relief Valve Not Required: No relief valve is required for centrifugal pumps driven by induction motors, provided the shutoff, or maximum pressure which the pump can develop, is not greater than 135 percent of the working pressure at the pump.
■ 4.4.2, Check Valve, states that a check valve is to be provided and so installed that it will hold the elevator car with rated load at any point when the pump stops or the maintained pressure drops below the minimum operating pressure.
■ 4.4.3, Mechanically Controlled Operating Valves, provides that they are not to be used. Existing terminal stopping devices consisting of an automatic stop valve independent of the normal control valve and operated by the movement of the car as it approaches the terminals, where provided, may be retained.
■ 4.4.4, Supply Piping and Fittings, states that they are to be in sound condition and secured in place.
■ Section 4.5, Tanks, contains in 4.5.1, General Requirements:
(a) Capacity: All tanks are to be of sufficient capacity to provide for an adequate liquid reserve to prevent the entrance of air or other gas into the system.
(b) Minimum Liquid Level Indicator: The permissible minimum liquid level is to be clearly indicated.
■ 4.5.2, Pressure Tanks, provides:
(a) Vacuum Relief Valves: Tanks subject to vacuum sufficient to cause collapse are to be provided with one or more vacuum relief valves with openings of sufficient size to prevent collapse of the tank.
(b) Gage Glasses: Tanks are to be provided with one or more gage glasses attached directly to the tank and equipped to shut off the liquid automatically in case of failure of the glass. The gage glass or glasses are to be located to indicate any level of the liquid between permissible minimum and maximum levels, and are to be equipped with a manual cock at the bottom of the lowest glass.
(c) Pressure Gage: Tanks are to be provided with a pressure gage that will indicate the pressure correctly to not less than 1.5 times the pressure setting of the relief valve. The gage is to be connected to the tank or water column by pipe and fittings with a stop cock in such a manner that it cannot be shut off from the tank except by the stop cock. The stop cock is to have a T or lever handle set in line with the direction of flow through the valve when open.
(d) Inspector’s Gage Connection: Tanks are to be provided