tekmar M3061 Mixing Valve Adapter Kit - Manual (Page 3)

3 of 4 Copyright © D 016 -10/00
Corrosion occurs when metals are placed in a liquid environment in which the liquid has a high oxygen or mineral content or the liquid
is very acidic. Factors such as temperature and flow rate affect the rate at which the corrosion occurs.
Preventing Oxidation
Oxidation results when oxygen dissolved in the water reacts with the
iron to form ferric hydroxide (rust). When a closed hydronic system is
filled with fresh water, oxidation occurs until the oxygen is consumed.
It is important to prevent new oxygen from entering the system and
continuing the oxidation process. The most common sources of oxy-
gen include oxygen diffusion through pipe materials and the continu-
ous addition of make up water due to leakage from the system. Fresh
air and oxygen may also enter the system if a negative pressure exists
due to an incorrect placement of the pump and expansion tank. If new
oxygen cannot be prevented from entering the system, chemical
treatments such as oxygen scavengers must be used. It is important to
note that the use of chemicals requires periodic maintenance.
Raising the pH Level of the Water
Water with a pH of less than 4.5 (acidic) greatly accelerates the corrosion
of iron and steel. One method of reducing corrosion of iron in a closed
system is to increase the pH level to produce an alkaline solution. A
water treatment specialist should be consulted for more information on
the available chemical treatments for adjusting the pH level.
Reducing Galvanic Corrosion
Galvanic corrosion results when different metals are use in the same piping network. The
mixing valve is commonly used in both copper and mild steel (black iron) piping systems.
Mild steel pipe does not cause cast iron to corrode and is the recommended piping
material for use with the mixing valve. When a small amount of cast iron is placed in a large
copper piping network, the cast iron corrodes quickly. Sections of the copper pipe can be
replaced with mild steel pipe to reduce the severity of the corrosion. Mild steel generally
corrodes more quickly than cast iron and therefore the pipe is sacrificed for the valve.
Dielectric unions can also be used to separate ferrous and copper materials in order to
reduce corrosion of the iron components.
Using a Corrosion Resistant Heat Exchanger
Heat exchangers which have a corrosion resistant liner or which are
manufactured from stainless steel can be used to isolate the cast iron
mixing valve from corrosive components. The heat exchanger is
typically used to separate oxygen permeable pipe or copper pipe from
ferrous components. A heat exchanger with a high rate of heat transfer
(Btu per hour) is recommended to prevent the valve from oscillating.
A plate type heat exchanger is typically used.
Adding a Corrosion Inhibitor
A variety of corrosion inhibitors are available which can help prevent corrosion in the system. In systems which require an
antifreeze, the corrosion inhibitor may be included as part of the antifreeze solution. For more information, it is best to consult the
individual companies who manufacture corrosion inhibitors.
Corrosion Control
type 016, 1" – Part # M3022
type 017, 1 1/4" – Part # M3022
type 018, 1 1/2" – Part # M3022
type 019, 2"
– Part # M3022
type 024, 2 1/2" – Part # M3023
type 025, 3"
– Part # M3024
type 026, 4" – Part # M3024
type 016, 1" – Part # M3017
* type 017, 1 1/4" – Part # M3018
* type 018, 1 1/2" – Part # M3018
* type 019, 2"
– Part # M3018
type 024, 2 1/2" – Part # M3019
type 025, 3"
– Part # M3020
type 026, 4" – Part # M3021
*Note: M3018 is also available
without the cast iron bonnet.
Order part# M3030.
Valve Handle &
Retaining Screw
Part # M3025
Seal Kit
(includes 3 x "O" rings, retainer, gasket)
Parts List
Make sure there
are no leaks
Always pump
away from
the expan-
sion tank.
If oxygen continues
to remain within the
system, use an oxy-
gen scavenger.
Oxygen
Scavenger
XXX
BOILER
MIXING
VALVE
To reduce localized corrosion in the mixing
valve, install steel pipe between the boiler and
the mixing valve.
M
Heating
System
tekmar
Mixing
Control
Corrosion
Resistant Fast
Acting Heat
Exchanger
Iron Components
Components
Causing Corrosion
When using plastic pipe,
an oxygen diffusion barrier
is often available.
Coupling Kit
Part # M3029
Valve Flap Assembly
(includes bonnet, gasket,
3 x "O" rings, retainer) Cast Iron
Bonnet