FAQ

What Types of Pumps are used in Hydraulic Elevators

Hydraulic Elevators Commonly use Gear or Screw Pumps designed to deliver high pressure, low noise and smooth flow to hydraulic cylinders. When it comes to hydraulic elevators, screw pumps are preferred due their p.

- What is the control method for Hydraulic Elevators

A hydro-electronic valve is used to control the flow lines from pumps to the hydraulic cylinders.

- What is the operating pressure range of Hydraulic Elevator pumps

Typical Pressure ranges from 15 to 60 Bar, depending on elevator load, lift height and system design.

- What is the Oil Grade recomneded for Elevator Pumps

ISO VG 32 or VG 46 or VG 68 hydraulic oil is commonly used. Its selection depends upon the ambient temperature:

Below 15 deg C ISO VG 32

15 deg C to 45 deg C ISO VG 46

Above 45 deg C ISO VG 68

- What cases noise in elevator hydraulic pumps?

Cavitation due to Low Oil levels or Oil Entrainment

Worn Out Pump Components

Poor Mounting or Loose Fittings

- What is the typical lifespan of of a hydraulic pump in an elevator ?

The lifespan is not defined and is purely depenent on the Oil Quality, Oil Cleanliness, Elevator Cycles or duty and Preventive Maintenance Cycle. However, with proper maintenance, installation of elevator pumps can last 10-15 years.

- What are the signs of Pump Failure ?

Slow Lift Movement

Jerky or Noisy Operation

Oil Leakage

Over Heating

- Can I retrofit a screw pump in place of gear pumps?

Yes, in many cases. Screw pumps offer quieter operation and longer service life but require compatibility with existing flow, pressure and mounting parameters.

- How often should the oil be changed in the system?

It depends on installation and application. Please refer to your OEM / Lift Manufacturing Company for more information.It depends on the Oil Manufacturing Company, but Typically a 250,000 cycles is a perfect time to change the oil.

- How much oil is required for typical elevator system?

Oil requirement is based on cylinder size and stroke. Refer to the chart here for more information.

- Do Elevator comes with Relief Valve or Control Valves?

No, SEIM Pumps don’t come with Relief Valve or any Control Valves.

- Can I run the pump continuously?

SEIM Pumps are for continues as well as duty cycled intermittent use. Under all circumstances, ensure that the oil temperature, viscosity and pressure are within the specified limits

- Can I get a pump curves?

Yes, just write to us the flow required, minimum and maximum pressure, oil grade and minimum and maximum puming temerpature, our engineers will get in touch with SIEM and send you the required information.

- What sensor controls are used on SEIM Screw Pumps?

SEIM Pumps don’t come with any sensors or control.

- Can I get 3D drawings or 2D drawings for the Pumps?

Yes, You can, just send us an email and we can assist you with the same.

- How do I connect the pump with Motor?, What are the Motor Options available to Connect SEIM Pumps to Motor?

There are 2 options. First is Submerged Motor and Second one is Dry Motors, i.e External Motor coupled with Pump.

Which is Better: Submerged Motor or Dry Motor for Hydraulic Elevator Pumps?

Both submerged motors and dry motors have distinct advantages and technical considerations. One critical factor that affects pump selection is the motor RPM difference between the two.

- Subermsible mtors are of S3 duty by default.

Dry motors are available from S1 to S4 duty. However, the selection has to be based on estimation of no of hot starts and cold starts for your installation of hydraulic elevators.

- Can frequent starts and stops damage the motor?

Yes, frequent short-cycle starts cause:

Motor overheating

Contact wear in starters

Higher inrush current → reduces motor life

Designing appropriate rest time between runs and using motor protection relays helps avoid premature failure.

What is a hot start, and should it be avoided?

A hot start is restarting the motor immediately after a stop without allowing it to cool.

• Should be minimized, especially in high-load scenarios.
• Use thermal overload protection and automatic restart lockout to manage hot starts safely.

What protection should be installed for the motor?

• Overload relay
• Thermal protection (bi-metallic or RTD sensors)
• Phase failure/imbalance relay
• Under-voltage/over-voltage protection
• Motor interlock with oil level and temperature

How Many Starts Are Allowed per Minute?

This depends on motor size, design, duty cycle, and cooling method. General rule of thumb for squirrel-cage induction motors:

A thermal overload relays or RTD’s in widings are receommened to protect the mtors.

How do we start the motors?

1. DOL Starter for upto 7.5 kW

2. Star – Delta Starter from 9.3 kW to more

3. VFD Soft Starter

Example:

A 15 kW elevator pump motor:

• DOL Start Current: ~90 A
• VFD Start Current: ~20–25 A (ramped in 3–5 seconds)

This results in:

• ~70% reduction in start current
• Lower heating of motor
• Smoother ride and improved motor life

Hydraulic Power Savings Caluclator ould you like a load profile simulation showing energy demand with/without VFD for your application or an Excel sheet to estimate savings?

What are the advantages of using the VFD to start hydraulic pumps:

ow Does a VFD Affect Motor Duty and Starts?

VFD Advantages:

• Controlled acceleration/deceleration reduces inrush current
• Lower thermal shock during each start
• Allows more frequent starts without crossing thermal limits
• Reduces stress on windings and contactors

VFD Start Profile vs. Acceleration Time:

A well-configured S-curve acceleration profile gives soft start, reduces torque spikes, and allows hot restarts with reduced risk.

Best Practices:

- Always configure your VFD with:

• Correct motor thermal class (B, F, H)
• Acceleration = 3–5 seconds
• Deceleration = 3–5 seconds
• Start inhibit timer to avoid multiple hot starts in <1 minute

- Monitor motor winding temperature or use a thermal model in VFD

- Select motor with appropriate S3 or S4 rating if frequent cycling is expected

Does a VFD Count Motor Starts?

Yes. Most advanced VFDs include an internal counter that tracks:

• Number of start commands issued
• Total run time (motor hours)
• Number of faults
• Thermal model status
• Some even log hot starts vs cold starts based on internal temperature models

Why Does VFD Track Starts?

1. Motor Protection:

• To ensure the number of starts/hour doesn’t exceed thermal capacity.
• Useful for S3/S4 duty motors which have strict start frequency limits.

2. Predictive Maintenance:

• Helps forecast when motor or contactors may need servicing.
• Frequent starts = more wear.

3. Warranty and Failure Analysis:

• VFD logs prove if motor was abused (e.g., >40 starts/hr for S3-25%).

Bonus: VFD Can Prevent Over-Frequent Starts

You can configure:

• Start inhibit delay: VFD will block re-start within a defined time (e.g., 30 sec)
• Thermal overload model: Disallows starts if winding is “too hot”
• Rest time enforcement: Based on previous stop duration

With VFD the life of the pump can be improved drastically. If the motor is installed with a tacometer, a closed feedback system can also be established and further with VFD, the pumps can be made to run for upto 60 Hz, or a three phase motor can be used with a single phase input supply and many other vast applications.

VFD Serves as a datalogger and also as a system to protect the pump under low voltage, high voltage and further prevent single phasing.

Does a VFD Reduce Power Consumption When Elevator Load is Less?

Yes — to an extent, but it depends on the system type.

Hydraulic Elevator Basics:

• The hydraulic pump (driven by an AC motor) supplies constant flow to lift the car.
• Pressure depends on the load (i.e., how heavy the elevator + passengers is).
• Flow rate depends on the desired speed of the elevator.

With Standard Direct-On-Line (DOL) Motor:

• The motor runs at full speed (50 Hz) regardless of load.
• The power consumed = Flow × Pressure / Efficiency
• So if the load is light, pressure is low → power consumption is lower, but motor still runs at full speed, so there’s wastage.

With VFD:

• You can adjust pump speed based on actual load and flow demand.
• If pressure demand is lower, and you reduce speed accordingly:
• Pump produces less flow and less pressure
• Power = reduced
• Current drawn by motor = reduced
• Less heat generated in oil
• So yes, with proper logic and sensors, a VFD reduces power consumption when:
• Load is lighter
• Speed is optimized
• Acceleration/deceleration is tuned
• Flow and pressure control are dynamic (using pressure sensors + PID if required)

Example:

Let’s say:

• Full load = 500 kg → 40 bar pressure → 5 kW motor load
• Partial load = 100 kg → 15 bar pressure
• If you control speed and maintain only 15 bar → motor power may drop to ~2 kW

So you save ~60% power, especially if you operate multiple short cycles in a day.

Conclusion: