Monday, 23 November 2020 14:16

How to lower maintenance and running costs on a 5.000 l/min @ 20 bar cutting oil distribution system?

Kenfilt installs a high-tech distribution control system to a Swiss customer.

Based on more than 50 years of experience in the filtration engineering and equipment manufacturing, KENFILT can provide a different range of products to upgrade and retrofit existing equipment with state-of-the-art technology.

A recent project is a Swiss customer of KENFILT, manufacturer of metal cutting tools, where KENFILT carried out an important upgrade to its cutting oil distribution system for the tool grinding production factory.

The following figure shows the original configuration installed in 1989 and enlarged in 1999 of the distribution systems consisting of 5 pumps, one of them controlled with a frequency drive with difficulties to maintain constant pressure in the 20bar line. Each pump delivers 1000 l/min at 20 bars with a total oil flow of 5.000 l/min @ 20 bar.

Fig01 Pumps

Fig. 1) Original cutting oil distribution pumps to the grinding machines.

Total flow 5.000 l/min @ 20 bar

The fixed flow inconveniences are well known: High energy consumption and the risk of pressure spikes, due to undefined pressure situations in the tubes when opening or closing valves at the machining centers and grinding machines.

The first step of the project was to analyze the customers working parameters. All existing data on number of machines,  type of machines (grinders or others), individual and total flow rates, working conditions as by hours per week, number of shifts, holiday stops, maintenance requirements and different possible operations modes were analyzed.

After a complete engineering study including mechanical, electrical and process engineering aspects, KENFILT finally delivered and implanted a turnkey system including all required additional equipment and components.

The following figure shows the control concept which was finally implemented at the customers facility:


Fig. 2) Final control concept of the 5 distribution pumps

The general approach was to install frequency converters and progressive starters in the distribution system as well as improve the control of the safety pressure release valve “VR” to avoid pressure spikes under certain working conditions. All this controlled by a new program for the touchscreen panel and the PLC.

A new electrical cabinet for the control system was delivered to connect with the already existing cabinet of the former central filtration system. The new cabinet included the frequency converter and progressive starter systems for the existing pumps.

The already existing electrical cabinet of the central filtration system was reviewed, upgraded with new control screens and the PLC program was adapted to the new system configuration.

Pump P1 was equipped with a frequency converter on the original installation back in 1989.  Pump P2 was equipped with a new 37kW frequency converter and pumps 3,4 and 5 with progressive starter systems. The progressive starters increase the inline pressure progressively and help the pressure control to be more stable avoiding any type of pressure spikes.

The 2 pumps with frequency converter (P1 and P2) are used to make the adjustment of the desired distribution pressure setting.

The following figure shows the new distribution pump control screen.


Fig. 3) Distribution pumps control screen

The cycle works as follows:

The system starts with the frequency-controlled pumps P1 and P2. If the target pressure cannot be reached pumps 3, 4 and finally 5 will be switched on, one after the other by a specific timer, until reaching the desired pressure and flow rates.   Once the pressure has been attained, the velocity of pumps P1 and P2 is controlled automatically to maintain the pressure on the line constant at 20bar by means of the two frequency converters.

If the pressure rises above a certain value, the system reduces de velocity of the motors of pumps P1 and P2 and if that is not enough begins the procedure of stopping pumps progressively until the working pressure stabilizes.

This system always maintains the pressure with a minimum pressure differential when starting and stopping machining centers in the tool production line. Energy consumption and noise levels of the hole clean oil distribution system will be minimized.

The overpressure safety system was also upgraded with a new safety valve. This valve is controlled by the PLC.  In case where the line pressure rises by a certain value, the progressive valve opens according to the line overpressure. The system reads the pressure of the line with the pressure switch and opens the valve as needed to prevent a pressure overload and at the same time prevent a drastic drop in pressure by opening it.

The following figure shows the safety pressure release valve control screen.


Fig. 4) Safety pressure release valve control screen

The overpressure control system usually will not be required as the basic distributions pumps control system with the frequency converters and progressive starters maintains the pressure usually on the correct value.

As another safety and control element, KENFILT installed several temperature probes (PTC) in each pump to control the temperature behavior on the impeller casing and motors.  In case of high values of temperature, the system will issue warning and alarm messages for preventive maintenance.  This allows maintenance to oversee any possible issues on the pump elements, increasing their life considerably.

KENFILT technicians carried out the final commissioning of the system at the customers cutting tool production factory. After system start up the KENFILT engineers followed up the customers experience with the system during several weeks to propose fine adjustments, were required. 

After several month of operation the initial targets of the project were confirmed: reduction of energy consumption and noise levels, reduction of mechanical stress for the pumps, valves and piping by maintaining always the right pressure level avoiding pressure spikes during change of operation modes. Higher production quality as all the machines are supplied always at the correct target pressure of 20 bars.