Chemical dosing pumps

Variable and often low levels of chemical reserve, leading to a variety of product performance problems. Often as a direct consequence of having no chemical dosing pumps on-site, or inadequate, automatic control systems, or insufficient attention to the quality of makeup water employed, or maintenance of cycles of concentration. 

Chemical dosing pumps are installed. There is no automatic bleed system installed. 

Does the customer s management fully understand what is required from their side and can they actually deliver the necessary supervisory and manpower support For example, changing from a system of simple chemical dosing pumps to a microprocessor-controlled product residual tracing and addition system will probably require more equipment inspection and calibration time. It will also require a high degree of instrumentation skill. 

There are many open recirculating cooling systems that still do not have chemical dosing pumps available. This represents a serious risk, as the... 

Without chemical dosing pumps and adequate program control measures, the matching of chemical usage to operational needs cannot be properly achieved, which may well produce the same result as if no treatment had been used. 

Many service companies offer monitoring and communications software to provide automatic adjustment to chemical dosing pumps or bleed valves, based on receiving inputs from inhibitor tracing and tagging systems that may operate in real-time, semicontinuously, or after-the-fact modes. 

Adjustable flow-rate chemical dosing pump 356 ... 

Chemical treatment consists of three weU-known treatment processes for ensuring rehable operation of RO membranes. First, a 20% sodium bisulphite (SBS) solution is injected by the chemical dosing pump (one pump is on standby). The iiyection rate is proportional to the RO feed water flow rate and is controlled by the PLC based on the chlorine concentration monitored by a chlorine analyser downstream of the in-line mixer. SBS like sodium sulphite and sodium metabisulphite is a reducing agent commonly used to dechlorinate RO feed or lower the chlorine concentration to less than 0.05 mg/1 in RO plants that use polyamide aromatic membranes. It takes 7.33 mg/1 of 20% NaHS03 solution to remove 1 ppm of residual chlorine in water on a stoichiometric basis. 

Caustic soda (50% NaOH solution) may be injected into the RO feed water line by the chemical dosing pump (one pump is on standby) to maintain the pH of RO feed water between 7.5 and 8.5 if there is no hkehhood of carbonate scaling. The iiyection rate is controlled by the PLC based on the pH value measured downstream of the in-hne mixer. At alkaline pH conditions, dissolved CO2 gas is converted to bicarbonate ions, thereby enhancing membrane rejection (lower permeate conductivity). 

The use of a chemical agent as an anti-foam is affected by an on-off algorithm with variable dosing time and time delay. If the presence of foam is detected, then the controller first activates a delay timer. This type of foam controller works with some delay and variable dosing time. If at the end of the delay period the foam is still present, then the dosing pump is activated and chemical agent is added to the bioreactor. If the foam is still detected at the end of this period, the combined system of delay and dosing is reactivated. With this method of controller, addition of any unnecessary anti-foam is prevented. 

Traditionally, boiler house operational duties include the monitoring of day tank chemical treatment levels and the top-up of additional chemicals as required. Also required is the checking of consumable inventory stock levels and the inspection of chemical feed pumps, injection points, automatic controllers, and other items of dosing and control equipment. 

Hydroquinone is not very soluble and, in order not to risk plugging dosing pumps or chemical feedlines, formulations tend to be dilute. 

A means of adding liquid chemical treatment to a FW tank by means of an overhead dripping container rather than by use of a dosing pump. From a control viewpoint, drip feed is most usually unsatisfactory as the feed rate reduces over time with decrease in treatment head pressure, and ultimately the device tends to gum up. 

Water and Effluent Treatment in Nuclear and other chemical plants. Corrosion resistant linings for water treatment vessels and pipelines, pumps, valves, flowmeters, agitators, chemical dosing tanks, effluent tanks etc. Soft natural rubber or ebonite, EPDM, butyl, neoprene or hypalon. 

Dosing pump ancillary items include chemical supply tanks (day tanks), tank mixers, flow indicators and controllers, level controllers and alarms, bulkhead fittings, corporation stops, and injection quills. 

However, given that that many biocides are hazardous to handle, a dosing pump may be a useful measure. Thus a suitable compromise may perhaps be to pump biocide to the cooling system, when tests or observation indicate a need, and to employ a manually initiated limit timer to actuate the pump. Typically, limit timers have an adjustable 0- to 90-minute timer cycle, with a 13 to 15 A output to a chemical metering pump. 

There is a growing trend for many operators not to have any direct involvement with their cooling system chemical dosing equipment (with regard to the addition of chemical, mixing and chemical dilutions, pump adjustments, and possibly even periodic equipment inspections and maintenance). The equipment may also not be owned by the customer. Rather, the water treatment service companies may lease the equipment to the customer, or provide free-on-loan equipment, together with all chemical dosing and control functions, as part of their services to the facility. 

Volume of equalisation tank shall be sufficient to accommodate the effluent generated in 24 h. Ensure that chemical dosing and mixing system is working. Sufficient stock of lime and alum stock shall be available. Check flow through primary and secondary clarifiers. Pressure gauges shall be provided for all pumps inlet and outiets of all units. 

The general plant arrangement is for a duty dosing pump to inject the liquid chemical into a water transfer main, most commonly proportional to flow to ensure consistent dosing. A standby dosing pump should also be available, preferably with automatic switch-over if the duty pump fails. 

A positive displacement dosing pump should be used that is capable of delivering the amount of chemical required into the transfer main. It is essential that the injection lance has a non-return valve to prevent back-flow. The outlets from the lance should be positioned to minimise localised corrosion and to encourage rapid mixing, a static mixer often being used to assist with rapid mixing. 

Back-up batteries and battery charging equipment Condensate chemical dosing equipment Various tanks for storing chemicals Component cooling water pumps and heat exchangers Power supply for each reactor coolant piunp s variable-speed drive Secondary sampling system Annex Building... 

Under normal operation, the chemical and volume control system is coimected to reactor coolant system cold leg No.l, and returns to the steam generator outlet chamber. The chemical and volume control system is made up of two sub-systems a chemical control subsystem, located inside containment, which consists of regenerative and letdown heat exchangers, mixed bed demineralisers and filters and a makeup subsystem, located largely outside containment and consisting of makeup pumps, mini flow heat exchangers and chemical dosing tanks. Containment isolation valves are provided on both sides of the containment penetrations. 

Metering Pumps. For small flow rates, such as dosing chemical additives where precise control is requited, progressive cavity self-contained pumping units are used. These can often handle shear-sensitive fluids or Hquids containing abrasive particles. These pumps are not as widely pubHci2ed or generally as well known in the Hterature as other pump types. 

Of course, improvements could be made to this simple program. The day tank could be heated to drive out most of the oxygen, or the chemical treatment could be added proportionally to the FW via a dosing/feed pump. As a result of the extremely low consumption, this last action most probably would require the added burden of using suitable quantities of dilution water to provide an acceptable degree of pump discharge accuracy. 

When operators believe that their HW systems do not lose water through pump mechanical seals or other places. They also commonly state that their LP steam heating systems return 100% condensate, so that no additional corrosion protection precautions need be taken above or beyond the initial fill of chemical treatment and an occasional top-up dose. 

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