06-12-2012, 05:34 PM
Gaskets for cylinder heads of compressor /exhausters and delivery joints
Gaskets for cylinder heads of compressor.doc (Size: 2.59 MB / Downloads: 35)
OBJECT
A number of failures of gaskets used in compressors/EMU have been reported by the railways. The primary reasons for these failures can be attributed to selections of proper material for the gaskets and improper methods used for cutting/fitment of gaskets.
Mechanical packing:- mechanical packing is basically a non rigid member designed for inclusion in the wall of fluid container for preventing leakage from between rigid parts of such containers . The packing will stop leakage when it is exerting against confining members a compressive force which is greater than the fluid pressure in the contained vessel.
Basically the following functions are performed by these:-
1. Support forces in the container walls caused by fluid load acting across an area equal to the inside area of the gasket
2. Support any additional stresses in the container walls caused by gravity, misalignment or thermal expansion and contraction.
Permanent set or compression set is measure of permanent change in original dimensions after being compressed or stretched under compressive or tensile loading.
After the initial sealing stress is applied to a packing it is necessary to maintain sufficient sealing stress for design life of the packing.
Development of resident gasket over all portions of gasket area equal to the fluid pressure into safety factor sufficient to take care of both the initial non conformity of the gasket and natural relaxation of the gasket during intervals between tightening.
. INSTRUCTIONS
The gasket shall be preferably cut with the help of dies and if necessary these shall be obtained directly from the equipment manufacturers with gasket material.
Once the equipment is dismantled for overhaul/repairs all old gaskets must be discarded and only new gaskets should be provided.
While assembling the gasket joints, the tightening porous as recommended by the equipment manufacturers or RDSO from time to time should be maintained.
All the accessible bolts for gaskets/joints should be tightened during overhaul and IC inspections to be recommended limits as indicated in the above .
What is a gasket?
A gasket is a material which is placed in between two objects in order to prevent leakage of any kind of the pressurized or not pressurized media.
Most important is the compression set of a gasket to adapt to flange irregularities and to any dimensional changes of the flange system caused by temperature changes during operation.