Blatt 1 / 9 MW Please read this manual carefully before installing, commissioning or operating the barrel dosing pump. 1. INTENDED USE The barrel dosing pump is solely intended to return refrigerant oil in a refrigeration respective heat pump system. Therefore a defined quantity of refrigerant-oilmixture is pushed by means of hotgas from the low pressure to the high pressure side at the compressor. Before any liquid refrigerant must be evaporated. From experience with ammonia systems it is common knowledge that conventional compressor oils above a temperature of 30 C work well. At lower ammonia temperatures or if there is any doubt about the viscosity of the fluid TH. WITT cannot accept any liability. In such cases a right to return the components can be agreed to. 2. Safety requirements Any work with refrigeration systems must be carried out by trained and knowledgeable personnel. All safety regulations and codes of practice concerning the use of refrigerants must be adhered to, with special attention paid to protection clothing and wearing of safety glasses. Under no circumstances are the indicated temperature- and pressure limitations on the data plate to be exceeded! Applicable standards and regulations for installing or operating refrigeration plants, e.g. EN 378 must be adhered to. Before any work on the BDP can be executed, make sure the is no residue pressure in the housing, particularly before lossening the screws. 3. TERMS OF WARRANTY To prevent accidents and for the safe operation of the refrigerant plant no modifications or alterations may be carried out to the barrel dosing pump without written approval by TH. WITT Kältemaschinenfabrik GmbH. All information for the safe operation and maintenance of these pressure vessels is based on our experience and is to the best of our knowledge. Our liability or warranty is excluded, if: The instructions in this manual are not adhered to The pressure vessel and its equipment was operated incorrectly or the handling was not in accordance with the mentioned procedures The vessel is used for purposes other than that for which it was intended to Safety devices were not used or disconnected There have been modifications made without written approval During installation or operation the safety requirements were not adhered to 4. SCOPE OF SUPPLY/CHARGE There are three sizes of BDP available: BDP03 with 0,3 Litre BDP14 with 1,4 Litre BDP38 with 3,8 litre content The standard scope of delivery includes: Threaded connection G1 for refrigerant/oil supply Weld connection for hotgas Connection for refrigerant/oil discharge with integrated check valve for a differential pressure of 3 bar
Blatt 2 / 9 MW Optional scope of supply (accessories): Stop valve EA32/G1 -I resp.. II (steel) or EA40/G1 I resp. II ( SS) Check valve for a differential pressure of 1 bar (for replacement of the standard check valve 3 bar) Adapter with gas equalization line (SS, 1.4541) WITT regulating valve EE3 or EE6 WITT flow heate xchanger DWR or evaporative heat exchanger AWE WITT oil fine filter ÖF-G1/4 5. TECHN. DATA 5.1 Materials shell, 1.4301 vent line 1.4541 threaded conn., etc. 1.4571 piston C22.8 weld connections 1.4541 gaskets Centellen O-Rings Neopren check valve C22.8 5.2 Dimensions threaded connection EA32 EA32/G1 -I EA32/G1 -II threaded connection EA40 EA40/G1 -I EA40/G1 -II Adapter weld connection (hotgas)
Blatt 3 / 9 MW 5.3 Dimensions BDP BDP 03 BDP 14 BDP 38
Blatt 4 / 9 MW 5.4 Spare parts 5.5 permissible operating pressure/temperature range 25/-1 bar between +50 C and 10 C 18,75/-1 bar between 10 C and 60 C 5.6 test pressure: 35,75 bar 6. Description of Operation 6.1 Assumptions In refrigerant /heat pump systems operated with flooded evaporators any oil that is carried over from the compressors should be returned. At low temperatures the use of an automatic operated heat tracing around the supply line and the BDP housing may be helpful. With oil soluble refrigerants the amount of refrigerant/oil mixture that is taken from the low pressure side has to be at least the amount of remaining oil after all refrigerant is evaporated that may pass the existing oil separator. (In common freon refrigeration systems with oil separators that achieve a separation of less than 200 ppm approximately 3% oil is solved in the refrigerant). When using ammonia the (conventional mineral) oil is collected at the lowest spot of the evaporator or surge drum, so that only a small amount needs to be moved for the recovery. 6.2 Refrigerant/oil mixture supply Oil, respective refrigerant/oil mixture must enter the BDP unrestricted from the low pressure side of the refrigerant system and any entrained gas should be able to raise back to the top. Therefore a connection DN 32 with matching 1 thread should be used. For installation to a smaller existing connection an adapter with gas equalization line should be used that is available as an optional equipment. The required time to fill the BDP with refrigerant/oil mixture is for freon systems a few minutes ( approximately 4 5 minutes) and for ammonia systems depending on the viscosity of the used oil approximately 30-60 minutes.
Blatt 5 / 9 MW 6.3 pressure build up To execute one pump cycle, you need to supply over a time of approximately 1 to 3 minutes refrigerant vapour (hot gas) with a differential pressure of minimum 4 bar (respective 2 bar with replaced check valve) from the high pressure side into the BDP. (If you do not have hot gas with a differential pressure of > 4 bar available you should replace the standard check valve. This check valve will open with a differential pressure of 1 bar. It needs to be ordered separately and will be delivered loose. This check valve is marked with a 1 next to the inlet connection). 6.4 Control line for hotgas It is common practice to use a WITT high pressure float regulator as a suitable place to withdraw hotgas, because there is a small regulating valve at the gas side present. (See fig., Pos 7) It is also possible to withdraw hotgas from other locations. The amount of hot gas should be regulated within a small range to avoid a sudden operation of the piston within the BDP. A regulating valve DN3 respective DN6 should be used. The control line that is coming from a solenoid valve should be installed with short distance to the BDP, because a) larger quantities of condensate may collect in front of the solenoid valve, but only gaseous refrigerant is allowed for the pump cycle b) A small volume of the control line between solenoid valve and BDP the return of the integrated piston within the BDP is facilitated upon successful operation of one pump cycle. 6.5 Discharge of refrigerant/oil mixture Due to the hotgas supply an internal piston closes the connection to the low pressure side of the refrigeration system and pressure is built up within the BDP housing. Any liquid within the BDP is pushed through a check valve towards the compressor side. 6.6 Heat exchanger at the BDP outlet In any case should the liquid that is pushed out off the BDP pass a heat exchanger before oil (with all refrigerant evaporated) is returned to the compressor. The heat intake has to be calculated so any refrigerant is securely evaporated. (Even in ammonia systems there may be residue refrigerant in the oil that needs to be evaporated.) Is has been proven good engineering practice to use a WITT flow through evaporator DWR or small oil collectors that are heated electrically or with hot gas, e.g. WITT high pressure vessel HDB. (see fig. Schematic, fig.3) 6.7 oil return to the compressor The oil return should be realized at a location within or before the compressor, where the pressure is slightly lower than the pressure within the BDP housing. Explanation: At check valve in the liquid discharge line of the BDP is set at approximately 3 bar pressure. (If there is no differential pressure > 4 bar available you may replace the check valve with one set at 1 bar.) A too low pressure at the outlet would continuously suck liquid. The engineer in charge of the design should select an appropriate location for the oil return depending on the make of compressor. The following locations have been proven good practise: When screw compressors are operated before the suction Stop valve of the compressor (instead of using a compressor port) and With common piston compressors between oil separator and crank case An undesired suction of liquid refrigerant from the BDP is avoided that way when the compressor is throttled at the suction side. (see schematic, Pos. 4) 6.8 repeating the pump cycle Upon completion of the pump cycle the piston will reopen the connection to the low pressure side. To enable the immediate opening, an equalisation line is connected through a small nozzle with the low pressure side. This nozzle is located at the BDP housing and will supply pressurized gas to the top of the piston
Blatt 6 / 9 MW 6.9 Controlling the pump cycle The solenoid valve that is installed in the hotgas line should be opened within an adjustable time frame of approximately 1 to 3 min. When oil soluble refrigerants are used a BDP with a large content and frequent pump cycles will be required. The control cycle has to be adjusted depending on the operation time and may need up to 12 pump cycles per hour depending on the oil carry over of the compressor in Freon systems. When operating an ammonia system only 1 2 pump cycles per day are normally required. If the refrigeration / heat pump system is operated with only one compressor, the most simple method is a time control. ( see schematic 6.10 a). In other cases a demand-driven control via level control of the compressor oil reservoir is required (see 6.10.b) The required electronic component with all necessary auxiliary features for mounting into a control cabinet is available as an optional scope of supply, called WITT ONG. (see 6,10 b) The distribution of the returned oil can be realized to more than one compressor by demand control. (It is only permitted to supply one compressor at a time!) 6.10 System schematic, possible installation of the BDP Description: (1) = BDP (5) = WITT HD high pressure float HR (2) = clock timer respective. WITT ONG control (6) = hot gas solenoid valve DN3 (3) = heat exchanger WITT DWR or AWE, with possible oil filter (7) = regulating valve EE3 or EE6 (4) = suction connection a) for single compressor: BDP with time control b) one (or multiple) compressor(s): BDP with demand control
Blatt 7 / 9 MW 7. Shipping and storage All openings (connections, etc.) are covered with yellow protection caps to prevent the intake of moisture or dirt. During transportation the BDP should be protected in an adequate way to prevent damages. 8. PREPARING THE INSTALLATION The BDP should be visually inspected for any shipping damages. The tube that sticks out on top of the BDP is connected with the piston inside and should easily be moved up and down. The BDP contains, due to the production process, some residue refrigeration oil. When operating the BDP with ammonia soluble oils the BDP should be flushed with an adequate solvent to remove this oil. To drain the BDP you should turn the BDP upside down and move the tube with the piston. 9. INSTALLATION It is recommended to connect the BDP inlet for use in ammonia systems to the side of an oil collecting dome. A manual oil draining connection (with stop and quick acting valve) should be installed as well., to remove any contaminated oil during commissioning. (See chapter 10). In Freon systems the connection for the BDP supply should be made in an oil-rich phase preferred in the evaporator return line. Allow sufficient space for inspection and servicing. Provide at least 20 cm underneath the BDP for easy removal. It is required that a 1 threaded connecting with the opening facing down is available for installation of the BDP. With regard to servicing larger refrigeration systems it is recommended to use a stop valve (WITT EA32/G1 -I or II) in conjunction with the 1 threaded connection mentioned above. Before installation the 1 threaded ring of the BDP should be turned all the way down. The threaded ring together with the O-ring will act as a stuffing box screw connection. When the BDP is entirely screwed into the existing 1 connection, the BDP should be positioned and sealed with the threaded ring/o-ring. Therefore the threaded ring has a cross hole for utilizing of a 6 mm Allen wrench. The two weld connections allow the use of either Ø 13 or Ø 8 x 1 tubes. The control lines should be installed using the shortest possible way (see chapter 6.4). To connect the BDP to the heat exchanger the screw connection with internal check valve should be used. Make sure all ineterconnecting pipework is stress free when installation the BDP and welding the tubes! 10. COMMISSIONING Permissible Fluids The WITT BDP is suitable for common evaporating refrigerants respective refrigerant/oil mixtures, e.g. NH 3, R 404, R134a, R404, R407c, R507 and the matching refrigerant oils, such as Fuchs Reniso KC68 or S68, Shell G68 Clavus, Reflo 68 Petro Canada, Arctic SHC 226 Exxon, provided the temperature is above 30 C!. For use with other refrigerant /oil or application below temperatures of 30 C please contact TH. WITT! Charging of the system It is recommended to charge a Freon system with approximately 3% refrigerant oil solved in the FREON. In ammonia systems the BDP and the heat exchanger should be filled with compressor. This way it can be observed whether the oil return is working properly and the compressor will not shut down due to lack of oil. Commissioning and start up of the BDP is not permitted until a safety analysis of the entire refrigeration installation has been carried out.
Blatt 8 / 9 MW On completing installation of the BDP, the refrigerant plant must be pressure tested and documentation relating to the testing kept in a safe place. Thereupon the system and the BDP should be vented properly. In principle the refrigerant /heat pump system should be started-up without the BDP, to make sure any dirt is flushed out off the system. Warranties caused by contamination of the BDP will not be accepted! (The same applies upon start-up of system after a longer stand-still or modification.!) Whether a fine filter should be used in the oil return line before entering the compressor is depending on the proper execution/cleanliness of the system and should be evaluated by the design engineer in charge. It may also be helpful to install a sight glass after the heat exchanger to observe the oil return. Please make sure that the permissible pressure is not exceeded the pressure within the BDP housing does not exceed 3 bar above the pressure in the compressor suction line (particularly during standstill, with two-stage systems or systems with open economizers). All tubes are connected according to the technical drawings required safety devices are installed and tested 11. OPERATION During operation the free flow of oil respective refrigerant/oil into the BDP must be provided, as mentioned in chapters 6.1 and 6.2. The formation of condensate or frost is an indication of the liquid charge within the BDP. Since the BDP is manufactured out of stainless steel there is no danger of corrosion. The solenoid valve that is mounted in the hotgas line should be activated over a period of 1 to 3 minutes. depending on the system concept by time or demand control to push the liquid content out off the BDP. The time frame can be adjusted upon observation of outlet temperatures and system conditions. As soon as the solenoid valve closes, the control line to the BDP should achieve the pressure of the low pressure side of the system 8see chapter 6.4). 12. SERVICE AND INSPECTION The BDP should be visually inspected according to EN 378-2 on a regular basis. Please make sure there is no pressure left in the housing before loosening the screw connection! Due to the trouble-free operation it was possible to design the BDP fully welded. Therefore besides replacement of gaskets and the mentioned below checks there is no further servicing required. 12.1 Function control When the BDP is crewed out of the system, the internal piston should be moved easily by the tube that sticks out on top. If it does not move easily the BDP is contaminated. This may be removed by flushing the BDP with an adequate solvent. The proper functioning of the internal piston can be recognized by the distinct sound of control that is created when the piston moves up and down. 12.2 Check of the nozzle The tube that is sticking into the inlet connection is closed at its end and provided with a bore of Ø 1,2 mm. It enables the immediate opening of the inlet connection upon completion of the pump cycle. The bore should always be unblocked and clean.
Blatt 9 / 9 MW 12.3 Closing of the nozzle During the 1 to 3 minutes of the pump cycle the above mentioned bore will release a little bit of hotgas. If this is disturbing (e.g. installation underneath a down pipe) the bore can be closed and the above mentioned task should be executed by an external control line. This external control line should be equipped with a throttle of Ø 1,2 mm after the solenoid valve to the low pressure side. 12.4 Replacement of the check valve In the outlet of the BDP there is a small integrated check valve, that can be screwed out off the connection. As described in chapter 6.3 this can be replaced by a special check valve with an opening differential pressure of 1 bar instead of 3 bar. 13. TROUBLE SHOOTING CAUSE CORRCTIVE ACTION 13.1 13.2 13.3 13.4 13.5 BDP does not fill with liquid Stop valve is closed Open Stop valve Gas cushion in the supply line Check valve position and slope of supply line Lack of refrigerant Check refrigerant charge and eliminate cause Supply line width too small Use larger diameter of supply line Piston remains in upper position Check solenoid valve and remove dirt if needed Too high viscosity of the fluid Install trace heating, if possible Pump cycle does not work Lack of hotgas Open regulating valve (e.g. at connection of the float valve) Solenoid valve of the control line does not work Check solenoid valve and system control Pressure increase with liquid refrigerant instead of hot See chapter 6.4 control line for hot gas gas BDP connections mistaken See chapter 8. Too high pressure of liquid discharge Check control line, heat exchanger and oil filter for blockages BDP does not fill with liquid See chapter 13.1 Continuous liquid flow through Return location has a too low pressure See chapter 6.7 oil return to the compressor Check valve defective Eliminate cause for liquid pressure Internal piston remains in upper position Contamination in the supply line Remove contamination, Piston is struck Only hot gas is permitted for the control line. Check pressure Nozzle is blocked See chapter 12.2 Too much or not enough returned oil False position of the supply line See chapter 8. False amount of pump cycles Check and change if needed Oil content in refrigerant is not appropriate Check and change if needed No oil is collected at the BDP inlet See chapter 8. False control of the pump cycle Check and change if needed