It is in chemical installations where hazardous fluids are transported by means of pipe lines. In the assembly of these, a series of preventive measures must be followed to avoid leaks, such as ensuring that the connections are kept to a minimum and that the pipe sections when they are welded are as long as possible, but in spite of this, there will always be a series of junction points between pipes and between the aforementioned pipes and the different elements of the process. It is at these points where sufficient watertightness must be ensured to prevent the hazardous fluid from escaping by diluting in the air and also to prevent it from penetrating into the interior of the installations.
Flange seals are used at the joints between different pipe sections. Other types of seals and sealing systems are used on the rods, pistons and rotating shafts of the different elements connected to the pipes, which must take into account the movement between the different parts and its consequences.
As important as choosing the most suitable gasket or sealing system is to respect the replacement of these elements, when necessary, with new ones in accidental or programmed maintenance interventions.
Criteria for choosing sealing gaskets
Both types of sealing will be considered, static sealing which occurs between surfaces without relative movement between them, such as pipe flanges, and dynamic sealing which occurs between surfaces with relative movement between them, such as rods, pistons and rotating shafts.Seals for pipe flanges
Consider a fluid being propelled into a flanged pipe. In order to check the flanges for the most suitable seals, the physico-chemical characteristics of the fluid in question must be known. According to Figure 1, the material compatible with these conditions can be determined. The following illustration shows different nuances of the materials for sealing gaskets:
Standards relating to sealing gaskets
It is interesting to know a non-exhaustive list of standards related to the sealing gaskets in question, and for this reason we present below a list of their references. Flat gaskets DIN 52913 Compression stability. ASTM F 36A Compressibility. DIN 52910 Transverse/longitudinal tensile strength. ASTM-oil Numbers 1 and 3 Oil immersion (weight gain). ASTM-fuel B Immersion in fuel oil (weight gain). DIN 3535 Gas permeability. DIN 3754 Resistance to immersion in fluids. ASTM F 146 Weight increase (in water/anti-freezing agent) Thickness increase. ASTM F 104 Longitudinal Tensile Strength. BS 2815 A and B Quality standards for flat gaskets. ASTM D 1170/SAE J90 Quality standards for flat gaskets. MIL-A-17472 B Quality standards for flat gaskets. NFT 48001 D Quality standards for flat gaskets. UNE 2624575 Quality standards for flat joints. BS-1 832 Quality standards for flat gaskets. DIN 3745IT-C Quality standards for flat gaskets. DIN 274 Breaking strength in longitudinal / transverse bending at room temperature. DIN 52911 Loss on ignition. DIN 3752 Soluble components in 20% HCL (in%). DIN 1259 Glass fibre insulation cord. DIN 2690 Flange gaskets with shoulder. DIN 71511 Gaskets for oval flanges. DIN 2691 Gaskets for tongue and groove flanges. DIN 2692 Gaskets for male and female flanges. DIN 86071 Gaskets for flat flanges with holes. DIN 20006 Gaskets for male and female pipe ends and flanges. DIN 2698 Corrugated gaskets with cushioning. Spiral wound gaskets API 601 Metal gasket identification colour code. MIL-G 24716 Specifications for spiral wound gaskets. 16265 21032 15342 API 601 and 605 Normal and large diameter spiral wound gaskets. BS 3381 Spiral wound gaskets. BS 4863 Spiral wound seals. O-Rings MIL-G-5514 F O-Rings made of special elastomer blends. MS - 28774 O-Ring Sizes. 28782 28783 Fabrics for sealsDIN 4102 Fire resistance of fabrics. DIN 53854 Fabric weight. DIN 53853 Number of threads of fabrics. DIN 60850/1 Fabric filament thickness. DIN 61101 Fabric weave. ISO 4603 Fabric thickness. DIN 53857 Breaking strength of fabric. DIN 4603 Fabric thickness. DIN 53857 Breaking strength of fabric. DIN 50049 Quality assurance of dimensional accuracy of expansion joints.
