| FAQ to Selcoperm SES-195 |
Technology
What does Selcoperm do?
Which chemicals are needed to run Selcoperm?
What is the product concentration?
What is the difference between chlorine and hypochlorite?
What is the difference between electrolytic and commercial hypochlorite?
What are the by-products?
Is it possible to remove excess sodium chloride from the product?
How is hydrogen handled?
Why do I need softened water?
Which material used in the water softener?
Which capacities are available?
What are the requirements for salt quality?
What conditions apply to the inlet water?
What authorizations have been issued to Selcoperm?
Application
Where can Selcoperm be used?
What dosing concentrations of chlorine are used?
How is the required system capacity calculated?
How do you size the brine tanks?
How do you size the product tanks?
What has to be considered for operation in circulation systems like in swimming pools?
Can Selcoperm be used for seawater applications?
Installation
Which components are required for operation?
Where can Selcoperm be installed?
What is the maximum distance between all components?
Which dosing pumps should be selected for the hypochlorite dosing?
How can the concentration of free chlorine be measured in the treated water?
How far from the dosing point should the chlorine measurement be installed?
What interfaces does Selcoperm have?
Do you have to install a gas detector for chlorine gas?
What are the requirements for the ventilation system?
Operation
Who is allowed to commission a Selcoperm?
What settings/adjustments does the service engineer have to make during commissioning?
What does the operator need to set/adjust on the equipment?
How often is maintenance required?
What does maintenance involve?
How often is electrode cleaning required?
What happens with the waste water from the water softener when it is regenerated?
Is it possible to connect several brine tanks to one Selcoperm?
Is it possible to connect several product tanks to one Selcoperm?
Is the degree of water softening adjustable?
Where can I find the disc number for the "Water softener regeneration"?
Technology
What does Selcoperm do?
Selcoperm systems are electrolytic chlorine generators which produce sodium hypochlorite solution for
water or wastewater disinfection tasks. Undivided electrolytic cells are used, not divided (membrane) cells.
Which chemicals are needed to run Selcoperm?
The Selcoperm device only needs salt (sodium chloride), water and electricity. No dangerous chemicals are used.
What is the product concentration?
The concentration of the product (sodium hypochlorite) is between 6-8 g/l, typically 7 g/l (=0.7%).
What is the difference between chlorine and hypochlorite?
Chlorine is a dangerous chemical which is not easy to handle and transport. It requires for instance special
chlorine gas rooms for storage. Electrolytically generated sodium hypochlorite is easy to handle, it has no
special requirements, no dangerous chemicals are used and it is considered much safer. Moreover, disinfection
with chlorine requires pH correction whereas in most cases electrolytically generated sodium hypochlorite does
not need it because the pH of the product solution is between 8-8.5.
What is the difference between electrolytic and commercial hypochlorite?
Commercial hypochlorite is not stable and it breaks down within a very short period of time forming by-products (i.e.
chlorate) while the electrolytic hypochlorite is much more stable. As commercial sodium hypochlorite breaks down it
evolves oxygen which can lead to "air" blockages in dosing pumps.
In addition, commercial hypochlorite has a higher pH value which can lead to blockages and requires regular maintenance
of the dosing pumps and accessories.
What are the by-products?
The main by-products formed during the electrochlorination process are sodium chlorate, sodium chloride (salt) and hydrogen.
In addition, small quantities of combined chlorine could be formed depending on water quality.
Is it possible to remove excess sodium chloride from the product?
With this method of elecrochlorination it is not possible to remove the excess sodium chloride.
How is hydrogen handled?
Hydrogen with a higher concentration than 4% is explosive. Therefore, Selcoperm has multiple protections: it has a dual
contained electrolyser, a degassing column to remove the majority of the hydrogen produced in the process, and a dual
contained hydrogen ventilation pipework to safely vent the hydrogen into the atmosphere. Moreover, it has a quantitative
air sensor monitoring the air flow through the dual containment. In case of a hydrogen leak, the air flow dilutes the
hydrogen to below the explosive limit ensuring that the system is safe at all times. The vertical position of the electrolyser
ensures that there is no hydrogen accumulation in the electrolyser at any stage. Many competitor products have horizontal
systems which can accumulate the hydrogen within the cell and can potentially lead to an explosive situation.
Why do I need softened water?
If the water used for electrochlorination is not soft (below 20mg/l CaCO3), then calcium will settle on the electrodes
and the elecrochlorination process will not work efficiently. Continued build-up of calcium for a longer period of time
will lead to a system shut down. High calcium deposits must be removed by acid cleaning.
Which material is used in the water softener?
The filling material used for the water softener is standard resin for ions exchange.
Which capacities are available?
At the moment the following capacities are available as standard: 125/250/500/1000/2000 g/h chlorine. Bigger capacities
are available upon request. For smaller capacities the Selcoperm Pro will follow.
What are the requirements for the salt quality?
The salt used for electrochlorination should be food grade salt (DIN 19604). For drinking water disinfection, a salt
with low bromide concentration should be used (max. 0.01%).
What conditions apply to the inlet water?
The inlet water used in electrochlorination should be filtered water in good quality (particle size < µm, required at
a pressure of 2-15 bar). If there is insufficient pressure, then either a booster pump or a non-standard softener will
have to be used.
What authorizations have been issued to Selcoperm?
We have the CE and Approval for Use Certifications issued by the UK government, additionally our systems have been
checked by a third party specialising in compliance of the ATEX regulation. In Poland, we also have a hygiene
certification, elaborated by the Polish National Institute of Hygiene.
Application
Where can a Selcoperm system be used?
Selcoperm is used to disinfect drinking water or wastewater, for chlorination of industrial process water and for
disinfection of swimming pool water.
What dosing concentrations of chlorine are used?
The dosing concentration of chlorine is different for each application. Moreover, the norms for chlorine dosing are
different in each country. The typical dosing rate for drinking water is between 0.5 and 1 ppm.
How is the required system capacity calculated?
To calculate the system capacity the average daily water flow which must be disinfected (m3/h) and the needed dosing
concentration of chlorine (mg/l or g/m3) are required. By multiplying both values we get the capacity of the system.
Please refer to system sizing tool.
How do you size the brine tanks?
For the preparation of 1 kg chlorine, between 3-3.5 kg salt is required. If we know the average chlorine required per day,
we can calculate the salt quantity needed per day (by multiplication of salt need/kg chlorine and averaged produced chlorine/day).
The required tank size depends on how often the brine tank should be filled with salt - this is typically once a week.
How do you size the product tanks?
The preparation of 1 kg chlorine produces 142 litres of hypochlorite solution with an average concentration of 7 g/l chlorine.
Taking into account the average dosage concentration of sodium hypochlorite into the application, you can size the product tank.
It is recommended that the sodium hypochlorite product tank is sized for 12 to 48 hours of storage.
What has to be considered for operation in circulation systems like in swimming pools?
In recirculation systems several parameters such as the water capacity, pool volume, maximum chloride concentration admissible
(for stainless steel is around 500mg/l), average of added chlorine, amount of water and how often it is used for filter flushing,
number of swimmers in a swimming pool and how much water is added per person (for example in Germany 30 l/guest must be added weekly
by law) must be considered. Therefore the ratio of refreshing water is an important parameter which must be taken into account.
Can Selcoperm be used for seawater applications?
No, a Selcoperm system is not designed for the electrolysis of seawater.
Installation
Which components are required for operation?
At least one Selcoperm electrochlorinator, one brine and one product tank are needed in combination with dosing pumps.
Where can a Selcoperm be installed?
Selcoperm can be installed in applications such as: drinking water treatment, municipal and industrial waste water treatment, swimming
pool water treatment, commercial building services applications and in food & beverage applications. It is a packaged system that can
easily be installed in an existing plant room.
What is the maximum distance between all components?
The Selcoperm unit requires access to three sides of the system so that the key components (control panel, brine dilution and
electrolyser chamber) can be maintained easily. We recommend that a minimum of 500mm of clear access space is provided to these
three sides. The fourth side which houses the hydraulic connection can be fitted up against a wall. All the equipment can be
installed in the same plant room.
Plan view of a typical Selcoperm 125 installation
Side view of a typical Selcoperm 125 installation
Which dosing pumps should be selected for the hypochlorite dosing?
The dosing pump should be either a DDI or a DMX pump - depending on the application. The capacity of the pump should be selected
based on the peak demand of the product solution in the application.
How can the concentration of free chlorine be measured in the treated water?
The compact system Conex with a chlorine sensor can be used for online-measurement of the free chlorine concentration in the treated
water. For manual measurements a hand photometer can be used.
How far from the dosing point should the chlorine measurement be installed?
The minimum distance between the injection point and the chlorine measuring point should be 5 m (downstream of injection point)
to ensure that the chlorine is adequately mixed in the water line.
What interfaces does Selcoperm have?
The process can be manually inhibited during operation or remotely inhibited from an external alarm or control contact. The main
controller screen displays the following information: system status, system information. The main screen displays amperage and
voltage for the electrolyser as well as the air flow rate and operating hours. Digital communication ports (Profibus, etc.) are
not available for Selcoperm.
Do you have to install a gas detector for chlorine gas?
The system does not evolve chlorine gas and therefore no chlorine detector is required.
What are the requirements for the ventilation system?
The hydrogen ventilation system is a dual containment system. The internal and external ventilation pipes must be conducted to the
exterior of the building as direct and straight as possible, ideally within 10 meters from the electrochlorination unit (for longer
ventilation lines please contact Grundfos Alldos directly). The ventilation line should be continuously rising. At the highest point
a venturi tee should be installed; this serves as a siphon break and provides a negative pressure within the storage tank to extract
the remaining hydrogen. From the tee a pipe should be installed to a safe discharge point.
Operation
Who is allowed to commission a Selcoperm?
Components may be installed by a company specialising in industrial installations, but subsequent commissioning must be carried out by
a member of the Grundfos service team or an authorised Grundfos service partner. It is vital to set the dosing correctly and avoid
overdosing.
What settings/adjustments does the service engineer have to make during commissioning?
The commissioning engineer will check the following
- sufficient water pressure and flow in the electrochlorination unit
- correct performance of the water softener
- correct operation of the brine dilution system by checking the specific gravity of the brine produced
- production of the sodium hypochlorite within the correct parameters
- correct operation of the ventilation system and correct fitting of the venturi tee
What does the operator need to set/adjust on the equipment?
Once the system has been setup there should be no need to adjust the settings on Selcoperm.
How often is maintenance required?
Maintenance is required once a year.
What does maintenance involve?
The operator must check the electrodes, O rings, valves, pumps, water softener and other parts for signs of wear and correct operation.
If the electrodes show signs of significant calcium deposits, an acid cleaning may be required. Other maintenance areas are: overhaul
solenoid valve, check water flow when unit is switched off (there should be none), clean flowmeter tube if required, overhaul brine pump,
water softener maintenance, wipe down and clean salt saturator, check operation of salt saturator ball valve.
How often is electrode cleaning required?
Unless there is a softening fault or poor quality water/salt is used, there should be no need to acid clean more frequently than at the annual interval.
What happens with the waste water from the water softener when it is regenerated?
The regeneration of the water softener resin is done automatically by the water softener. If one column of the dual column water softener
is in regeneration mode, the other column is working. The brine which enters the softener, leaves after the automatic regeneration via the
"rinsing water outlet (E)" (see page 8 data booklet) and it contains calcium ions from exchange between Ca and Na. The life time of a water
softener resin is > 5 years. However, the resin should be checked annually during maintenance using the softener test provided in the
electrochlorination test kit.
Is it possible to connect several brine tanks to one Selcoperm?
Yes, the outlet of the brine tanks should be communed up before connecting to the Selcoperm.
Is it possible to connect several product tanks to one Selcoperm?
Yes, the tanks must be connected at the lowest level first. The tanks should be individually isolable so that each tank can be isolated
from the system for maintenance purposes. The pressure sensor supplied with the Selcoperm unit to measure the tank level should be fitted
on the common line of both product tanks to ensure it continues to measure tank level even if one tank is isolated.
Is the degree of water softening adjustable?
No, it is not adjustable.
Where can I find the disc number for the "Water softener regeneration"?
The disc number as well as the information which column of the softener is regenerating can only be read from the water softener disc.
It is not shown on the display of the unit.