The specifications for PPR pipes primarily consist of pipe diameter and wall thickness. The pipe diameter specifications include nominal outer diameter and nominal diameter, and the wall thickness specifications include pipe series and standard dimensions. In reality, the specifications for different types of pipes differ. The following provides a simple explanation.PPR pipeHow to determine the specifications?
1. Pipe diameter specificationsFirst, we need to clarify the differences between pipe outer diameter (Φ), nominal diameter (DN), and the conversion between metric and imperial units. The outer diameter of a pipe is typically denoted as "dn," which is the number following "Φ" on the pipe. Nominal diameter (DN) is the average outer diameter of a pipe, calculated as the average of the inner and outer diameters. It is usually a whole number and serves as a reference value, but there may be differences between the actual pipe dimensions. Imperial units refer to common terms such as 4-pipe, 6-pipe, and 1-inch pipe.
In PPR pipes and thin-walled metal pipes, the following relationship exists between imperial units, nominal diameter, and actual outer diameter:
Nominal diameter, originating from the wall thickness of metal pipes, is typically quite thin. Therefore, the average diameter of both the outer and inner diameters is almost equal to the outer diameter, i.e., DN = Φ. However, forPPR pipeDue to the relatively thick wall thickness, the nominal outer diameter (DN) and the actual outer diameter of the pipe differ significantly. Therefore, it is necessary to distinguish between the two.
In home plumbing installations, common external diameters for PPR pipes are 20mm, 25mm, and 32mm.
2. Pipe Series: SPipe Series S represents the wall thickness of a PPR pipe. According to the definition, Pipe Series S is a dimensionless number that relates to the nominal outer diameter and nominal wall thickness, and is used to guide the selection of pipe specifications. It is a set of integer values obtained through calculation.
The S series pipes can be calculated using the formula above.
dn – Nominal outer diameter of the pipe, in mm.
en——PPR nominal wall thickness, measured in mm;
In GB/T 18742.2-2017 "Cold and Hot Water Polypropylene Piping Systems - Part 2: Pipes", the specific specifications and parameters for series S pipes are as follows, as shown in the table below:
Pipe materials and specifications (units: millimeters)
WhenPPR pipeWhen the nominal outer diameter is constant, for a larger pipe series S, the water pipe wall thickness will be thinner, and for a smaller pipe series S, the water pipe wall thickness will be thicker.
3. Standard Dimension Ratio: SDRStandard dimensional ratios are another parameter related to PPR pipe, where PPR pipe is divided into five series: SDR11, SDR9, SDR7.4, SDR6, and SDR5, based on their standard dimensional ratio (SDR) values.
Standard dimension (S) is the ratio of the nominal outer diameter to the nominal wall thickness of a SDR (Schedule) pipe. The relationship between SDR and the PPR pipe series S is: SDR = 2S + 1.
"Similarly to the pipe series, when the nominal outer diameter of the PPR pipe is constant, a larger standard size will result in a thinner pipe wall, and a smaller standard size will result in a thicker pipe wall."
4. Specifications for PPR pipe fittingsThe nominal outer diameter (dn) of PPR fittings must always match the nominal outer diameter of the connected PPR pipe material, and this is often marked on the PPR fittings.
The wall thickness of PPR fittings should not be less than that of the same PPR pipe series. Most PPR pipe fitting manufacturers only offer one series, which is the highest standard S2, and is suitable for both cold and hot water applications.
For threaded fittings, also known as threaded components, the most commonly used thread sizes are 1/2 inch and 3/4 inch, which correspond to nominal diameters of 15mm and 20mm, respectively.