GB2445567A

GB2445567A - A wiper seal/thermal barrier formed of exfoliated graphite for prevention of ingress of solids and liquids into a stuffing box

Info

Publication number: GB2445567A
Application number: GB0700412A
Authority: GB
Inventors: Ernest Stephenson Terry
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-10
Filing date: 2007-01-10
Publication date: 2008-07-16
Anticipated expiration: 2027-01-10
Also published as: GB2445567B; GB0700412D0

Abstract

A wiper seal/thermal barrier for the prevention of ingress of solids and liquids into the stuffing box of two stroke crosshead diesel engines comprises a wiper seal element B and back seal/thermal barrier elements C, D. Each of the seal/thermal barrier elements B, C, D is made from die-formed exfoliated graphite in a square cross-section. Each of the elements B, C, D is held in a continuous seam free seal by using set lengths cut at 10{ scarfe, the carrier rings (B in Figures 5 and 6) maintain a constant radial load using Belleville spring washers similar to those shown in Figure 8. This invention will maintain positive sealing around the piston rod and prevent damaging solids and liquids from entering the system stuffing box.

Description

Description of RPDS Part 2 Wiper/Thermal Barrier.

This invention is primarily designed to create a Wiper Seal to prevent ingress of any detritus from the under piston area in Two Stroke Crosshead Diesel Engines from entering into the system oil crankcase sump and lubricating oil system. The other primary part of this invention is to use modem materials that have been tried and tested in the nuclear industry to create a Thermal Barrier to prevent transmission of hiohpr tpmnrQfI,r. .i._.._j_. -. 2.

The method of retaining the invention in position is done by using machined / cast carriers to suit the various engine types encountered, examples of the carriers can be seen in Figure 1 items 1 a /2 a, FIgureS 5 & 6 B. Each carrier system can be in 2 or 4 sections and the method of loading the wiper seals/thermal barrier seals is by loaded Belleville Washers, as per FIgure's 8, 9, 10, the configuration and type is dependent upon engine type. Figures 3, 4, 7 show the various locating and fastening * ---Although this invention is to be used as a Retro-Fit system initially, the use of closed WiperPFhernal Barrier seal tops will eventually replace the type of top seal in open systems such as shown in Figure 5 & 6. This invention has totally dispensed with the old fashioned system of brass/ bronze/ seal, scraper and fire check rings and also dispensed with the unreliable periphery/garter spring, by removing these system designs it has been possible to use modem materials which will give a seamless seal and also give high temperature protection and chemical resistance in the under piston area. By totally sealing off the piston rod the detritus that will block current designs as in Fig-ures 11 & 2, is prevented from entering the stuffing box and therefor prolonging the life of piston rods by preventing the oxides, catalytic fines and other solids and particulates from getting into the annular spaces that can be seen in Figure 2, RPDS Part 2 is a unique design that for the first time seals off the piston rod to stuffing box thus preventing the damaging detritus from causing contami-nation of system oil and preventing carbonisation of mixed oils in the annular spaces of the stuffing box. Because the lop Box as in Figure 1 is totally sealed by Wiper Seal B in Figure 1 & the 0 Ring ORG. it is necessary to provide pressure relief valves to prevent any possible pressure build up, these are sited as E in Figure 1. Maintenance and overhaul of the RPDS system is minimal as a time factor, removal of the carrier rings is done with simple socket spanners and a torque wrench, to adjust the seal for wear a wider space ring A in Figures 1,5 & 6, is quickly installed and the carrier rings re-assembled and torqued to specification. As this invention RPDS Part 2 creates a total seal at the under-piston side of the engine contamination of the system oil will be largely pre-vented, and because of this sealing arrangement the likelihood of contaminated oil being dumped at sea will be averted. Also as this invention creates a tight seal at the piston rod the chances of un-burnt fuel oil diluting into the crankcase system oil is eliminated, this will ensure that the likes of Vanadium will not become part of the system oil analysis.

Claims

Claims: I The Retro PolyDuplex System (RPDS) Wiper SealTl'hermal

Barrier is designed to remove the problems associated with existing, conventional stuffing box top end sealing systems that al-low detritus to fill and compact within the annular space in the stuffing box housing causing wear and problematical contamination of the engine crankcase lubricating oil system, the in- vention addresses the annular space problem by using a die formed Ex-Foliated Graphite ma-terial which forms a cotinuous seal and wiper around the piston rod scaling off the annular space in the stuffing box, this invention also removes the periphery garter springs used in conventional design and uses Belleville Washers to create a constant radial force maintaining the closed wiper ring system even at the highest temperatures experienced.

2 The RPDS Wiper Seal/ Thermal Barrier as in claim I overcomes the debris that would nor-mally gather in the annular spaces within the stuffing box which would consolidate within the moving parts of conventional seal/scraper rings and also reduce the periphery spring oper-ations which leads to failure of the gas tight and scraper seals, by the inventions use of die formed materials and radially loaded carrier rings using Belleville Washers that maintain a constant force on the closing/sealing effect of the top wiper seal and the lower thermal barrier seal all debris, oils and waters are excluded flm entry.

3 To reduce material cost and improve maintenance times RPDS Wiper Seal/ Thermal Barrier has the ability to strip down the system at the top end of which ever engine type in quick time and to compensate for wear of the die formed material by the use of a hacking ring (in varying widths) which can be installed into the carrier ring and the system reassembled and back into operation with minimum time frame with no reduction in operational effectiveness.

4 The important ability of this invention RPDS Wiper Seal /Thennal Barrier as claim 1 is that which ever engine type is in use the system can be created to operate in either a closed top box or open top seal with the use of a shroud on one flange of each carrier ring in the open top system, this shroud will prevent build up of detritus into the stuffing box proper, the shroud slides with the carrier ring so no detritus build up can find its way between the carrier ring flange ends, the shroud is held in place with round head screw and serrated safety wash-ers, this system will retro fit with existing two stroke crosshead diesel engines.

As per claim I this invention could also be used for a fUll stuffing box as well as use for retro-fit into the top end of any two stroke crosshead diesel engine as the design can be utilised into the closed grooves of all existing stuffing boxes, the Belleville Washer and carrier system does lend itself into lower grooves of any stuffing box, the carrier material will be to suit the

existing material specification of the engines.

6 Claim I RPDS Wiper Seal / Thermal Barrier manufactured from Ex Foliated Graphite has the ability to operate well above the normal temperature experienced during engine operation and as the material is die formed the higher density prevents any gaseous transfer or any high tem-perature transmission to the lower seal/scraper rings, as the sections are only 75mm or 100mm in length the wiper or thermal barrier seal may be cut to dimension without material loss when fitted into the carrier sections, loading by use of Belleville Washers maintains a constant load and sealing effect during operation.

ANNEx / industry comments for Under Piston Area for Two Stroke Crosshead Engines.

The circied/arrowed area of the cross section below is the area that this invention is designed for, as this is the area of any two stroke engine where the greatest variety of problems can occur due to normal operating conditions. The area above the stuffing box is where there tends to be a mix of system oil, cylinder oil,water and possibly fuel oil which can change state due to temperature condi-tions and also the area where dew point activity can occur due to high sulphur content fuel oils.

This under piston area is where all the detritus of an operating engine settles, and due to the set-tling effect the detritus will fill in the area around the piston rod and into the first ring of the stuffmg box. This area at the top of the stuffing box fills with all the detritus, including catalytic fines from fuel, femc oxides from engine components, carbonised oil mixes with combustion deposits, sulphu-ric acids, and all other non soluble matter. Due to the gathering effect in this area it can generally be called the "Well Effect Area" where the gathering of the above detritus is retained within the area.

During operation the elevated temperature in this area will have an adverse effect on the accumulat-ed debris and the settled oils will carbonise causing a greater amount of abrasive particles within the "Well Area". The area has also to be gas tight, to prevent transmission of any gases down into the main crankcase system oil sump. Information Sketch 5 items c, d, e, f, g shows the areas where damage to the piston rod, Information Sketch 4, happens. Any section of the stuffing box that will collect under piston detritus will create wear problems to the piston rod, the solids can only be re-tained within the annular spaces they have filled, it is impossible for these solids to disperse, except possibly into the lower sections of the stuffing box. Another problcm can be caused if the springs are chemically attacked by the likes of sulphuric acids during operation. As these springs are in Tendon then their loss can affect the sealing effectiveness of the stuffing box, Infonnation Sketch 2 circled SPBK shows a spring that parted during operation. Information Sketch 3 shows a typical periphery spring holding a seal/scraper ring in place around the piston rod.

Information Sketch S A, shows a typical stuffing box general arrangement of the split housing and sets of seal/scraper rings used to prevent ingress of cylinder oil/ fuel oil into the sump, and pre-vent the sump oil mixing into the under piston area.

Cross section of typical two stroke crosshead diesel engine gii1_I _ Q1 Deli1tuaofOflmI,r/ !LINi_1-\ Water/ Catalytic fines etc JJ- ) Detrtusdepthiiinm __ __ Section wed on right, 5,000 hours ___ operation * - ________., Areao.. . *( __________ Concern ____ lorthis "k_____-product 7 ! project -*-*-*-- 1 -*-:*; ___________ -. ______ I/N \ iJpperSlrapc I Ring / Information Sketch 1..

Mid Sf a!

-_

-

Lower cnkpe / T / Ris

-___

______ -Sunip. IELJJ ?\o Seal or scraper rings are shown Information Sketch 4 4)/i. J, SPBK ___________ Information Sketch 2,)

-______

Information Sketch 3 Information for a selectibn of Two Stroke Crosshead Engines showing Circled, the top end of stuffing box that suffer the "Well Effect" of Compacting void spaces around piston rods into stuffing box. (a)

/ information Sketch 5 s4 formatjtn Sketch 5 A (d) (g)