The quality of the power supply system is the most important indicator of the service level of a modern data center. This is understandable: absolutely all the equipment necessary for the operation of the data center is powered by electricity. It will not be there - servers, network, engineering systems and storage systems will stop functioning until the power supply is fully restored.
We tell you what role diesel fuel and our quality control system play in the smooth operation of the Linxdatacenter data center in St. Petersburg.
You will be surprised, but Uptime Institute experts, when certifying data centers for compliance with industry quality standards, assign the primary role in assessing the power supply system to the quality of diesel generators.
Why? Data center continuity is central to the digital economy. The reality is that 15 milliseconds of data center power outage is enough to disrupt business processes with tangible consequences for the end user. Is it a lot or a little? One millisecond (ms) is a unit of time equal to one thousandth of a second. Five milliseconds is the time it takes a bee to make one wing beat. To blink, a person needs 300-400 ms. One minute of downtime cost companies an average of $2013 back in 7900, according to Emerson. Against the background of increasing digitalization of business, losses can amount to hundreds of thousands of dollars for every 60 seconds of downtime. The economy requires businesses to be 100% connected.
And yet, why are diesel generators considered by UI to be the main source of electricity supply? Because in the event of a power outage, the data center can rely on them as the only source of power to keep all systems operational until power is restored through the main channels.
For our data center in St. Petersburg, issues related to power sources play a particularly important role: the data center is completely independent of the city network and is provided with electricity from a gas-piston power plant with a capacity of 12 MW. If the gas supply is interrupted for some reason, the data center switches to work at the DGU. First, UPSs are started, the capacities of which are enough for 40 minutes of uninterrupted operation of the data center, diesel generators are started within 2 minutes after the shutdown of the gas piston station and operate on the available fuel supply for at least another 72 hours. In parallel, a contract with a fuel supplier will come into effect, which is obliged to bring the agreed volumes to the data center within 4 hours.
Preparing for Uptime Institute's Management & Operations certification has forced us to pay close attention to the process of diesel fuel supply, its quality control, interaction with suppliers, etc. This is logical: the quality of the operation of the nuclear power plant in Sosnovy Bor does not depend on us in any way, but we must be fully responsible for our section of the power grid.
DT for data centers: what to look for
In order for the generators to work for a long time, reliably and economically, one should not only acquire reliable equipment, but also choose the right diesel fuel (DF) for them.
From the obvious: any fuel has a shelf life - 3-5 years. It also varies quite a lot in various parameters: one type is suitable for use in winter, another is completely unsuitable for this, and its use will lead to a large-scale accident.
All these points must be carefully monitored in order to prevent the situation of non-starting the DGU due to expired or unsuitable fuel for the season.
One of the most important classification parameters is the type of fuel used. The quality of the selected type from a particular supplier affects the high performance and reliability of the equipment.
The right choice of DT will provide the following benefits:
- high efficiency;
- economy and low cost;
- high torque;
- high compression ratio.
Cetane number
In fact, diesel fuel has many characteristics that you can study in the passport of a particular batch of products. However, for specialists, the main criteria for determining the quality of this type of fuel are the cetane number and temperature properties.
The cetane number in the composition of diesel fuel determines the starting ability, i.e. the ability of the fuel to ignite. The higher this number, the faster the fuel burns in the chamber - and the more uniform (and safer!) The mixture of diesel and air burns. The standard range of its indicators is 40-55. High-quality diesel fuel with a high cetane number provides the engine with: the minimum time required for warm-up and ignition, uniform operation and economy, as well as high power.
Diesel fuel cleaning
The ingress of water and mechanical impurities into diesel fuel is even more dangerous than for gasoline. Such fuel may become unusable. In some cases, the presence of mechanical impurities can be detected as a sediment at the bottom of the tank with diesel fuel.
Water also exfoliates from the fuel and settles to the bottom, which makes it possible to establish its presence. In unsettled diesel fuel, water causes it to become cloudy.
Purification of diesel fuel will help improve performance. For this, there are special installations and filtering systems. The choice of equipment for such a procedure depends on what exactly it is necessary to purify the fuel from - paraffin, mechanical impurities, sulfur or water.
The supplier is responsible for the quality of fuel cleaning, which is why it is important to have a supplier control system, which we will discuss below, and not to forget about additional measures. So, for fuel aftertreatment, we installed Separ fuel separators on the fuel line of each DGU. They prevent mechanical particles and water from entering the generator.
Fuel separator.
Weather
In pursuit of quality and affordable fuel prices, companies often forget about the temperature at which the station will operate. Sometimes the choice of one fuel "for any weather" does not bring much harm. But if the station is used outdoors, it is worth choosing fuel in accordance with climatic realities.
Manufacturers divide diesel fuel into summer, winter and "arctic" - for extremely low temperatures. In Russia, GOST 305-82 is responsible for the separation of fuel according to the seasons. The document prescribes the use of summer grades of fuel at temperatures above 0 Β° C. Winter fuel is suitable for use at temperatures down to -30 Β°C. "Arctic" - in cold weather down to -50 Β° C.
For the stable operation of diesel generators, we decided to purchase winter diesel fuel -35β. This allows you not to think about seasonal changes in the weather.
How do we check fuel?
For diesel generators to work reliably, you need to make sure that the supplier is shipping the exact fuel you need.
We have been thinking about solving this problem for a long time, considering the option of taking samples and sending them for analysis to special laboratories. However, this approach takes time, and what to do if the tests come unsatisfactory? The batch has already been shipped - return, reorder? And what if such a re-order falls on the period when it is necessary to start the generators?
And then we decided to measure the quality of fuel on the spot, using octane meters, specifically using SHATOX SX-150. This device allows for express analysis of the supplied fuel, determining not only the cetane number, but also the pour point and type of fuel.
The operating principle of the octanometer is based on comparing the octane/cetane numbers of certified samples of diesel fuel/gasoline with the tested diesel fuel/gasoline. Used tables of certified types of fuel are entered into the special processor, which the interpolation program compares with the parameters of the sample taken and with corrections for the sample temperature.
This device allows you to get results of fuel quality in real time. The rules for measuring fuel quality using an octanometer are written in the regulations for the operation service.
The principle of operation of the octane meter
- The sensor of the device is installed on a horizontal surface and connected to the measuring unit.
- The device turns on when the sensor is empty. The meter displays CETANE zero readings:
- Set = 0.0;
- Tfr = 0.0.
- After checking the operation of the device, it is necessary to fill the sensor with fuel until it is completely filled. The process of measuring and updating readings takes no more than 5s.
- After the measurement, the data is entered into a table and compared with the readings of the norm. For convenience, cells are set to automatically highlight values ββwith color. With acceptable readings, it is colored green, with unsatisfactory parameters - red, which allows you to additionally control the parameters of the supplied fuel.
- For ourselves, we have chosen the following normal indications of fuel quality:
- Set = 40-52;
- Tfr = minus 25 to minus 40.
Fuel resource accounting table
| date | Fuel acceptance | Quality checking | |
| January 18 2019 | 5180 | Cetane | 47 |
| TFr | -32 | ||
| Type | W | ||
S is summer fuel, W is winter fuel, A is arctic fuel.
PROFIT! or how it worked
In fact, we began to receive the first results of the project immediately after the control system was put into operation. The first control showed that the supplier brought fuel that did not meet the declared parameters. As a result, we sent the tank back and requested a replacement batch. Without a control system, we could run into a situation where the DGU was not started due to the low quality of the fuel.
In the most general, strategic terms, this level of thoughtfulness in quality control gives complete confidence in the uninterrupted power supply of the data center, when we can completely rely on ourselves to solve the problem of maintaining 100% uptime-mode of the site.
And these are not just words: perhaps we are the only data center in Russia that, when conducting a demonstration tour for a client, can respond to the request βCan you disconnect from the main power circuit to show the transition to a backup one?β we agree and immediately, in front of our eyes, we transfer all equipment to the reserve at any time. The most important thing is that any employee with the appropriate level of clearance can do this: the processes are debugged to a sufficient extent so as not to depend on a particular performer - we are so confident in ourselves in this regard.
However, not only we: the process of quality control of diesel fuel during certification by the Uptime Institute attracted the attention of the organization's auditors, who took note of it as industry best practices.
Source: habr.com