Powered roof support - self-moving metal hydroficated lining of the production face, which is used for maintenance of the rock cover, for keeping of the breakage heading in working and safety conditions; it provides mechanization of the lining processes and controlling of the rock cover, moving and keeping of the face conveyor flight or basic beam with the cutter [1].

Hydraulic-powered support have found wide usage in mining production. They are used for keeping of the rock cover and are giving ability on holding coal production.

The main hydraulic elements of the powered roof support section are: hydraulic props (which are making forcing function of retention of the roof), hydraulic screw-jack props (which are moving sections of the lining), safety valve, distributor, monoblock multiple apparatus or hydraulically controlled unlocking valve.

The hydraulic prop consists in a power cylinder that operates commonly with a open controlled unlocking valve (having a retain function - this is the reason it is called hydraulic padlock) and with a safety valve; the operating command being given from a distributor; the mentioned apparatus may be individual or assembled in a hydraulic block and connected with the prop in a sole circuit. In the case of the powered roof support section, the hydraulic props are used in pairs or four at a time [2].

The pumping stations is used for hydraulic props and hydraulic screw-jack props feeding. The stations is usually situated at the lower entry and controlled remotely. Pumping station performance is setting to 35-70 litres per minute at pressure working value 12-20 MPa [3].

On the picture you can see hydraulic circuit of the pumping station of the powered roof support.

The pumping station consists of:

• tank for working liquid with the filter on fitting, liquid level gage and discharge cock;
• boost pump gear wheel type (this pump is also used for filling of working liquid into the tank;
• main multiple-piston pump (one or more working at the same time) with discharging automate;
• coarse filter and final filter, which is situated in the pumping main of boost pump;
• pumped-hydrostorage, which smoothing oscillations of pressure in the pumping main;
• pressure switch, which is switching off electric drive of the pump in the case of lowering pressure in the pumping main. This is exclude excessive losses of working liquid in the case of braking or crippling of the pumping main;
• Monitoring manometers, which are registering pressure in the pumping main of the main and boost pumps.

Multiple-piston pump, which is used in the pumping station of the powered roof support have some disadvantage such as: very big size, high deterioration of the pistons and pump is can not work without the safety valve.

The purpose of my work is changing of the hydraulic circuit of the pumping station:

• substitution of the piston pump by the rotary pump, which has bigger durability, because of absence of the details frictions;
• usage of group of multipliers with the rotary pump, which will allow convert big feeding and rotary pump low pressure into low feeding and high pressure in the hydro lining.

This changing's will allow to increase period of validity of the pump and decrease costs on the hydraulic equipment repairing. In this case productive capacity of the working collective will be more effective, work of hydraulic-powered support will be more stable, also it will lower idle time of the equipment and mining works at the time of it's repair.

As a result of grave condition of our country, which is depend on capacity of the mined coal, we have a great problem of increasing hydraulic-powered support (used in mining facilities) effective work. It allows to keep rock cover, it keeps breakage heading in working and safety conditions. On the stable work of lining depends stable coal production. That's why it was decided to revise the hydraulic circuit of the pumping station, which is feeding lining and to substitute elements with the low durability by more effective elements. This substitution will allow to decrease costs on the next repairs and idle time of equipment, and, as a result, economical costs which are appears after breakages.

At the moment proposed system is on the development stage, that's why I can not give an example of exact results of economical effect. They will be known closer to the finishing of my mastery work.

List of references:

1. И.В. Вернер, Г.А. Симанович, А.А. Тарасенко К ОБОСНОВАНИЮ ВЫБОРА МЕХАНИЗИРОВАННЫХ КРЕПЕЙ
2. CONSTRUCTIVE AND CALCULUS PARTICULARITIES FOR THE HYDRAULIC PROPS OF POWERED ROOF SUPPORT Sorin Vatavu, Niculina Vatavu
3. НАСОСНЫЕ СТАНЦИИ Гидрофицированная крепь очистных выработок. Под общей редакцией проф., докт. техн. наук В. Н. Хорина. М., <Недра>, 1973г., стр. 217-223