Introduction

Pipe-Joints with Threaded Fittings

In-Line & Pressure Relief Valves

Water Meters in Pipe Installation

Hints on the Design of Water Meter Network

Bending Knees Pre-Stressing

Liner Expansions

Calculation of the Length of Pre-Stressed Bending Knee

Expansion Sink




Introduction

Water service lines are connections that lead from the water mains to the building plumbing network. The service line consists of all pipes, valves, and fittings between the main water cabinet through the meter, and ending at the individual outlets or endpoints.
DIN 1988 Parts 1 apply to drinking water supply systems inside buildings and their networks.: It specifies requirements for design, installation, operation and maintenance of such systems in addition to alterations to these systems. It also gives particular attention to materials, components and appliances installed to supply a building with potable water. Designers and installers should make sure that only such required equipment and appliances are installed ensuring proper economic and technically qualified functioning of the system

When installation is executed, Rak therm instructions should be strictly, the following must be readily available:

• A building site plan; engineering drawing of each floor including cellars (plan view), with simplified pipe work diagram and sectional drawings.

• Pipe sizing calculation in accordance with DIN 1988 part 3; maintained.

• A detailed pipe network diag ram showing length of pipe runs, pipe nominal sizes, bore diameters, material, draw-off points (type, number and sizes or bore diameter), minimum flow pressure required, and the filling group as defined in the of DIN 4109series of standards, where necessay.
  

Rak therm Pipe-joint assemblies are designed to resist axial tension when properly supported. If such joints occur buried pipe work, properly sized supports should be located at bends and branches to counter the hydraulic forces acting on hese joints Care should be taken to ensure that the designed system has unobstructed flow at joints and where changes of direction occurs, The streamlined design of RAK therm threaded fittings, in compliance with DIN 2999 part 1, ensures that this is met.



In-line Pressure Relief Valves:

When installing a RAK therm system with pressure relief valves, the following should he taken into account to ensure fall compliance with DIN 1988 part

a.  Valves in cold and hot water systems should only have a common outlet. If this cannot be achieved, then the passage of hot water into the cold water pipe should be prevented by the provision of suitable components such as approved check valves.

b. If, in domestic applications, the water temperature at the draw-off points exceeds 45 .;, mixing valves with safety stops will have to be installed to prevent scalding when hot water is drawn. As stipulated in the (work regulation), this temperature should also. not be exceeded where water is used at places of work To ensure this, the actuator should be filled with a safety stop that prevents the temperature of the mixed water at the outlet rising above 40'C.

c. Only valves that do not unduly obstruct the flow (oblique pattern valves and ball valves) should be installed in pipes. According to DIN 3512 straight pattern valves should only be installed in main branch pipes where the pressure is adequate.

d. Only valves that have been tested for noise emission as specified in DIN 52218 part 2 should be used to control the flow.

e. Valves that can be opened and closed by a single turn through 90'-' shall not be used as in-line valves unless they are intended to serve as servicing valves.

f. Relief valves should comply with the specifications of TRD 721. A pressure-relief valve is a valve that automatically discharges to the atmosphere when a preset working (threshold) pressure is exceeded and automatically closes back again once pressure has decreased below the threshold pressure.


Water Meters in Pipe Installation

As applies to other equipment, water meters are strictly controlled by your local authorities. According to DIN standards, cold water meters are flow meters designed for water at a temperature of up to 30'C and comply with section 1 of appendix 6 to Eichordnung (Gel-man weights and measures Regulation) and according to ISO 4064 part 1. On the other hand,
heated water meters are flow meters designed for water with a maximum temperature of 90'.

Water meters are part of the water meter assembly which, viewed in the direction of flow of:

• Inlet stop valve (may be identical with service stop valve);

• Straight length of MK therm PP-R pipe

• Water meter

• Connector, variable in length, or flexible joint;

• Outlet stop valve

Hints on the Design of Water Meter Network

a.  Generally speaking, mounting fixtures should be installed in new assemblies. If old
systems are to be altered it should be ensured that stresses induced during the removal •1• of the water meter call be accommodated by the remaining pipe work.

b. Water meters should be installed in a container) area, near the wall closest to the road, which is usually ri room in which the service pipe enters the building. This room should provide protection from frost, physical interference, and tampering.

c.  Water meter assemblies should be designed to drain any escaping water when the meter replaced.

d. Water meter is replaced. Water meters should be easily accessible so as to facilitate reading, replacement and inspection.

Bending Knees Pre-Stressing

In I icghi areal, wnere i lere is no room for (] bending knee of the full leric I h, ii is possible to pre-dress the knee in a RAKtherrn pipe corner in the opposite direction of the expected linear- expansion, minimizing rho defor-rnaiion of the knee- This, if execuied properly, can conceal deformations to the raked eye. Following is on example deprciing I he colculairon aF 'he lens i n of a pre-slressed bending


Liner Expansions

Formula for Calculation of Linear Expansion

The linear expansion ∆L is calculated according to following formula:
∆L = α . L . ∆T
Where:
∆L Expanded length (mm)
α Coefficient of linear expansion (mm/mK)
L Length of segment in (mm)
∆L Temperature difference between working and installation

Linear Expansion Calculation Example:

Assuming you need to calculate the expansion (∆L) of a standard RAKtherm pipe segment (L) of 1.6 meters at a maximum working temperature of 70°C. You know that the RAKtherm standard pipe has a coefficient of linear expansion of (α = 0.15). You know that the installation was executed at the typical ambient temperature of 25°C. ∆L = α ·L · ∆L or ∆L = 0.15 *1.6 *(70°C -25°C) =10.8 mm

That means you can expect a linear expansion of 10.8 mm for this segment of pipe if the temperature difference is respected.

Alternatively, you can quickly obtain the result from the following table for different types of pipe:

Calculation of the Length of Pre-Stressed Bending Knee

Bending knees Pre-Stressing
In tight areas, where there is no room for a bending knee of the full length, it is possible to pre-stress the knee in a RAKtherm® pipe corner in the opposite direction of the expected linear expansion, minimizing the deformation of the knee. This, if executed properly, can conceal deformations to the naked eye.

Following example depicts the calculation of the length of pre-stressed bending knee.

Formula for Calculation of the Length of a Pre-Stressed Bending knee

The bending knee length Lkp is calculated according to following formula:

Lkp = c ∙ √ Ø ∙ ∆L/2
Where:
Lkp = Length (mm) of the bending knee
c = Material specific constant (equal to 15 for RAKtherm® pipes)
Ø = Outside Diameter (mm)
∆l = Linear expansion

Pre-stressing bending knee Calculation Example:

As per the previous example of bending knee calculation, we can calculate the pre-stress bending knee length required:

Lkp = 15 X √ 25.0 mm X 19.2 mm/2

Lkp = 232 mm (compared to 328.5 mm with no pre-stressing)

Therefore, the calculated minimum required pre-stressed bending knee Lkp comes up to 232 mm. A safety factor is suggested not to exceed 5% of this length.



Expansion Sink

If the linear expansion cannot be compensated through change in direction, it becomes necessary to install an expansion sink. The following example depicts the calculation of the length of an expansion sink.

Formula for Calculation of the width of an expansion sink

The bending knee length Ls is calculated according to following formula:

DWmin = EW + (∆l1 + ∆l2)
Where:
EW Expansion Sink Width (less than 160 mm is not recommended).

DWmin Designed (Fixed) Width of the expansion sink.

∆l1 Maximum expected linear expansion of the first side.

∆l2 Maximum expected linear expansion of the second side.

Expansion Sink Calculation Example:

Assuming you need to calculate the expansion sink width of length for a RAKtherm® pipe corner. Assuming the maximum linear expansion of the first side to be 30 mm and the second side to be 65 mm, then…

DWmin = 160 + (30 mm + 65 mm)

DWmin = 255 mm

• No pipe should be secured to another pipe or used as a support for other pipes.
• The arrangement of pipes should facilitate their identification. Mounting plates should be used where required.
• Pipes should be laid so as to prevent the formation of ait locks. Where pipes are likely to suffer from frost damage, drainage fittings should be provided at the lowest points of the system.
• Where pipes are laid above one another, exposed cold water pipes should be on the lowest level in order to minimise the risk of condensation.
• Where a system provides water of two or more buildings, a riser should e installed in each building.
• Where draw-off points on a storey require backflow prevention but are not individually isolated (DIN 1988 part 4), the main branch pipe should branch off from the riser not less than 300 mm above the maximum possible water level on the storey.
  
  …for more information please download Installation PDF file from Downloads menu.