Installation of mechanical seal
Ensuring a seamless mechanical seal installation involves a meticulous adherence to various checkpoints. Prior to disassembling equipment, secure the necessary permits from the company and strictly follow the safety guidelines outlined in the JSA and RA. Embrace the use of Personal Protective Equipment (PPE) specified in the permits. Implement the Lockout-Tagout (LOTO) system for electrical and process isolation, supplementing it with a thorough self-verification at the site. Execute a systematic disassembly, referencing the Standard Maintenance Procedure (SMP) or equipment manufacturer’s instructions. Record all clearances during this process. Extract the existing seal arrangement, meticulously cleaning the seal chamber and shaft, inspecting for corrosion, foreign particles, or scratches. During assembly, prioritize the use of new gaskets, ensuring cleanliness on shaft steps, threads, reliefs, shoulders, keyways, etc.
Mechanical Seal Assembly
Attention to detail continues during the assembly phase. Verify the dimensional conformity of shaft and shaft sleeve OD, seal chamber bore concentricity, seal chamber squareness, gland plate cleanliness, stud bolts diameter, stud bolt pattern, and distance to the first obstruction against the seal assembly drawing. Cross-reference with manufacturers’ seal assembly drawings for any required modifications or reworks. Crucially, guarantee proper earthing of equipment to prevent static electricity discharge-induced sparks. This comprehensive approach ensures a reliable and safe mechanical seal installation, safeguarding both equipment integrity and personnel well-being.
Check point during installation
Most important check point needs to be confirmed before installation of mechanical seal in equipment. They are following.
- Shaft Runout
- Shaft Endplay and bearing paly
- Seal chamber squareness
Shaft runout should be checked properly with the equipment manufacturer’s specifications (Recomended) and match this tolerance with the seal manufacturer. If need to rectify do accordingly. Generally, as per most manufacturer recommendation, should not exceed 0.05 mm (0.002 inches) TIR (Total Indicator Reading). At any point along the shaft for ball or roller type bearings. For sleeve type bearings, refer to manufacturer instructions. If the equipment can not completely dismantle, then verify runout near seal location. The mentioned tolerance values apply to shaft speeds in the range from1000 to 3600 RPM. Below mentioned figure explain clearly how to check runout of shaft.
Shaft Endplay and bearing paly
As per most manufacturer recommendation Shaft endplay must be within 0.25 mm (0.010 inch) TIR limits, Regardless of thrust bearing type. For case of Radial bearing play should be checked at seal chamber face area Against the equipment manufacturer’s specifications. Generally 0.05 – 0.10 mm (0.002 – 0.004 inches) will be applicable for ball or roller type bearings. For sleeve or journal type bearing tolerance will generally be 0.10 – 0.15 mm (0.004 – 0.006 inches). If equipment is found outside of the given tolerance in this article, it needs to be consulted with the equipment manufacturer representative to verify the equipment’s suitability for the seal.
Seal chamber squareness
Seal chamber squareness to be checked to the shaft centerline and should be within 0.0005 mm/mm or in inches (0.0005 inches / inches) of seal chamber bore TIR. Note: Check carefully and make sure that shaft endplay should not affect the reading chamber’s squareness reading. Verify the smoothness of the seal chamber face for a tight fitted gasket joint.
The definition of Concentricity, it is a 3-dimensional cylindrical tolerance zone that is defined by a datum axis. But for seal chamber area Concentricity of the shaft should be checked to the seal chamber bore or gland pilot register. It should be within the limit recommended by the manufacturer, 0.025 mm per 25 mm shaft diameter (0.001 inch per 1 inch shaft diameter) to a maximum of 0.125 mm (0.005 inch) TIR.
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