Document 3JR1vnZGY26ajJYJyYNVORG9a

FILE NAME: Garlock (GAR) DATE: 1966 Feb DOC#: GAR037 DOCUMENT DESCRIPTION: Trade Journal Article - Breakthrough in Packing Breakthrough in Extensive field tests at Monsanto and other companies indicate that a soft, graphite-filament material provides effective sealing for pumps handling difficult products, slashing maintenance costs Repeinad from February C H E M IC A L P R O C E S S IN G Magazine for GARIOCK, INC. Palmyra, New York 14522 PUM PING P A C K IN G &. S E A L S Breakthrough in packing Extensive field tests at Monsanto and other companies indicate that a soft, graphite-filament material provides effective sealing for pumps handling difficult products, slashing maintenance costs L asting as lon g as 2 years in pumps -- where another type of packing or mechanical seal lasted only I or 2 days -- a re cently developed braided packing m a d e from treated graphite fila ment is giving dram atic evidence that it is a b re akth rou gh in the softp a c k in g field. M a|or sa v in g s in m aintenance ore b e in g m a d e with it. A lso, it has elim inated le a k a g e on some pum ping services that cou ld not b e satisfactorily se a le d in the' past by various m ethods tried. The outstanding performance being p ro vid e d b y the p a c k in g m ainly is du e to four properties that it has. First, if ha s a thermal conductivity a p p ro a ch in g that of cast iron, al low in g the heat g e n e rate d ot the shaft/packing interface to be con ducted and radiated aw ay. Sec ond, the material has a much lower thermal expansion than metals used to construct stuffing boxe s. This m e an s that sw elling from heat is not a problem. Third, the treated gra p h ite filament is resistant to chem ical attack. Fourth, it h a s out standing temperature resistance. M onsanto's experiences Favorable experience resulting from use o f the packing is show n by the comments of Pump Engineer Edw ard C. Aselm an of Monsanto C o m p a n y 's John F. O u e e n y piant in St. Louis, the first chem ical plant to use the p acking extensively in field tests. The Q ue e ny plant m anufac tures a wide variety o f organic products, the production o f which in m any instances involves pum p ing slurries. The plant has about 1 2 0 0 pum ps in service, about 9 0 0 of which are packed and 3 0 0 of which use mechanical seals. C a re ful records kept on pum p repairs show that about twice as much per pum p is b e in g spent o n the pomps using m echanical seals as is on those that are packe d . Hence, in the view o f this experience a n d the nature of the products han d led , the plant is inclined toward the use of the packing. S o m e s e r v ic e s h a v e b e e n difficult to seal by any means. For example, a life of a few d a y s to 3 or 4 w eeks w as ail that could be obtained with different types of both m echanical seals and packing on one centrifugal pum p at the plant. The pum p operates at 1750 rpm a n d has a 2 '/ " shaft. It is used for alternating service be tween hot acid (2 8 4 F) a n d toluene (at am bient tem peratures). This tem perature ch an ge affected the oper ation o f the m echanical seals. The pum p w a s o n e o f the first o n which treated-graphite-filament packing was tried. The braided packing provided 25-m onths service, elim inating leakage. Treated-graphite-filam ent packing in a n o th e r centrifugal pum p at Q u e e n y , in to lu e n e -u n lo a d in g serv ice, ha s a lre a d y lasted 25 months, with no rings a d d e d . The four nuts on the packing gland are adjusted Vj turn a s re quired. This is a tough service, since the toluene washes out the lubricated packing. The previous packing lasted 4 weeks. Two weeks to 19 months A third pum p at O ueeny has had 19 months service from treatedgraphite-filam ent packing, with two rin gs a d d e d to the o rig in a l five. This pump, which operates at 3 6 0 0 rpm, hand les 20*/ sulfuric acid. It is a positive-displacem ent pump. The tide o f con ventional p a ckin g was only 2 weeks. Other types of packing that would have lasted longer w ould have scored the shaft, m aking replacement necestary aft er a period o f time -- at a cost of $1 50 , plus downtime costs. The a d va n ta g e of the high thermal conductivity of treated-graphite-fil am ent p a ckin g is illustrated b y a fourth installation at Q ueeny. This is con ce rn ed with a rotary, positivedisplacem ent pump, with a 2 % shaft, o p e ra tin g at 2 0 0 rpm in a lye-unloading operation. Heat would build up, d a m a g in g the p a ckin g a n d c a u sin g it to lose bulk, so the pump would leak. A water hose w as played on the pump (while it w a s o p erating) to reduce the temperature. The use of treatedgraphife-filam cnr p a ckin g elim inated the le a k a g e a n d m ad e c o o lin g of the pum p unnecessary. The pa ckin g made of lasted 15 was taken treated graphite months when the out of service. had pump Another installation at Q ueeny, us ing the first grap h ite p a c k in g a v a il able, handled a crystalline material ct 3 7 4 F. N in e-m onths service w a s obtained before removal during a bearing replacement. The normal life of previous p a c k in g s in this service w as from 1 to 4 weeks. A s a result o f this fa v o ra b le field experience, the treated-graphitefilament packin g has been adopte d as standard at the plant's pumprepair station. It is b e in g used on about 99*/. of the pumps packed, for both process a n d utility services, according to Mr. Aselm an. The p um p 's econom y in utility service is illustrated b y on e unit in boilerfeedw ater service. O n e end o f the pump has been repacked with con ventional pa ckin g three times; treated-graphite-filam ent p a c k in g it still g o in g strong in the other end. The Q u e e n y plant is also starting to purch ase new pum ps eq u ip p ed with the new pa ckin g material, re cently purchasing 32 o f the pumps. Th idea sp re ad s After hearing o f the favorable fieldtest experience at the Q u e e n y plant Pump Engineer Al Arnold, of M onsanto's W m . G . Krummrich plant across the river in East St. Louis, III., b ecam e interested in in vestigating the packing. Arnold has the responsibility for the 1 6 0 0 pum ps in use in this plant. The plcnt manufactures heavy chemi cals, such as sulfuric acid, p ho s phoric acid, phenol, chlorine and caustic, a lo n g with about 1 2 0 in termediates in smaller tonnages. The plant uses packing on about 7 0 V. of the pum ps and mechanical seals on obout 3 0 V.. M a n y of the streams contain solids and gritty motericls that would shorten the life of a m echanical seal. A c c o rd ingly, the m echanical seals are specified primarily for the clean streams, or where the products handled arc extrem ely corrosive, toxic or very costly. Because of the high initial cost. The story of treated graphite-filament packing The background on graphite-filament pacxing is typical of several others that have grown out of Harold Schneider's Maintenance Engineer ing Group at Monsanto's Queeny plant. This Group is dedicated to maintenance improve ment-- in equipment-related and worker-re lated areas. In this particular case. Michael P. Blake, a maintenance engineer concerned with rotatingequipment problems, was dissatisfied with tne progress made m pump and agitator packing. He did considerable research on the properties of packing and concluded that packing manu facturers seemed to be heading m the wrong direction with regard to several important properties-- thermal conductivity and thermal coefficient of expansion being among the most important. When he read of the development of a graphite yarn1 for an atomic-reactor application, he felt this might make a better packing material than any then in use. With this in mind, he consulted the local tech nical representative of Garlock Inc. and pro posed that some packing be made from the material and suggested tests in some pumps in use in the Queeny plant. Garlock agreed to do this and welcomed the opportunity, for such a controlled field test. Garlock's continuing and costly development and testing work coincided with the design of special machinery to handle this extremely friable material. It was necessary to develop surface treatments and reinforcing agents to process the graphite filament. Special controls were devised to assure product uniformity. Monsanto installed the packing in 1962, as did other companies introduced to the new product by Garlock. Blake made arrangements for care ful records to be kept of the pumps using the packing, with the pumps tagged so that a nut was not adjusted without a notation being made. A year later, Edward C. Aselman took over as pump engineer at the Queeny plant. About this time the Garlock technical representative called on him and asked what the Monsanto held tests showed. Aselm an's foremen had continued to keep careful records on the pumps using the treated-graphite-filament packing, and Asel man wrote a report based on these records. It showed the remarkable performance ol the new -packing. He also placed information on tti& pcking.in Schneider's newsletter, which cuollatcs W aif Monsanto plants. Garlock was soon receiving requests and orders foi^the packing,, which was then being made in-a semi-works. Allocation was necessary at that time. Based on this interest. Garlock ex panded its production capabilities so the de mand could be met. The packing has iust recently been introduced on a commercial basis. Aselman points out that, if the Monsanto fore men had not been as diligent as they were' m keeping records of the field tests, the develop ment could well have been delayed. More information on the treated-graphite-fila ment packing, trademarked Garhte 100*. and its use m pumps, agitators and other equip ment can be obtained from Garlock Inc.. Palmyra, N.Y. 14522. Circle 2761 on page 163. 1) Developed by the Carbon Products Division o f U n ion C a rb id e . 2 ) Paten? aooi.ed for mechanical jeals are normally used only w here lon g service life is e x pected. A rno ld points out that a mechanical seal costs about S I 50ZOO installed. If a centrifugal se p arator is ne ede d to remove solids, this can a d d another S I 0 0 -1 5 0 . A pump can be packed with treat ed-graphite-filament packing for a material cost of S 3 0 and S I 5 labor, for an installed cost of $45. O n an initial field test with the braided packing, Arnold solved a tough pump-maintenance prob lem a n d is n o w sa v in g a b out S I 0 0 month in p a c k in g costs on just one pump, based on an economic analysis. The product being han dled with the 1750-rpm centrifugal unit is m onochlorobenzene, con taining trace amounts of HCI and other impurities that tend to gum up and corrode a mechanical seal. The m o n och lorob en zen e ha s little lubricity. Sin c e it is a lso a n excel lent d e g re a te r, it w ould rem ove the lubricant from a lubricated packing. A m echanical seal w as tried and lasted 1 day. Conventional packing lasted 2 d a ys in this service. The treated-graphite-filam ent p a ckin g is still g o o d after 1 Vi years. S ix rings were initially installed and then two more offer a month of service. The pump ha sn 't been touched since. Braid loosely woven The treated graphited filament braid is loosely w oven and gradually com presses as the pump operates until it h a s the aspects o f a graph ite bushing. This is w hy more rings ore frequently a d d e d in early stages. The shaft o f the pum p w as found to be polished, with no scoring or grooving. The $ 1 0 0 per month be ing saved d oesn 't count the saving obtained through elimination o f the need to replace scored shafts. Another field test at Krummrich in volved a pum p handling nitroben zene. M echanical seals were being replaced every few days. The prod uct would crystallize at room tem perature. A crystal caught between seal faces would score them and cause the seal to leak. The pump w as packed with the new pa ckin g in the spring o f 1 9 6 5 a n d is still operating with no problem s. v Equally dram atic results were o b tained on eight titanium pum ps packed with treated-graphite-fila ment packing, handling saturated brine. The m echanical-seal life w as 3 weeks. The braided packing has been satisfactory since it w a s in stalled in Se pte m ber 1 9 6 5 . O n e field test at the Krummrich plant did not involve a corrosion problem, but a flow stream at 5 0 0 'F, w hich con taine d slu d g e s and tars. The pum p is m ade o f duc tile iron. Se ve ra l d o u b le m e chani cal seals were installed during a year without eliminating leakage. Since the new p acking w as in stalled in Septem ber 1965 , le a k a g e has stopped. O n e ring of packing was a d d e d in O ctober. Base d o n these field tests, the Krummrich plant is e xp a n d in g the use of treated-graphite-filament packing. Arnold hopes to stand a rd ize on just two p a c k in g s in the plant -- treated graphite filament and white asbestos im pregnated with TFE. The latter w ould be used m ainly fo r utility services. Packing training program A s a result of using the new p ack ing, Arnold set up a training program on packing of pumps for maintenance men. The treatedgraphite-filament p ackin g is no more difficult to install than any other type. However, the plant en gineers found that, w hen con ven tional packing life w a s short and the p a ckin g inexpensive, c a re in installation did not seem so im por tant. W ith the new p a ckin g, pro per installation is necessary to obtain the desired lon g life. A lso, plant engineers obviously d o not w ant to waste the relatively expensive m a terial. Although the two M on san to plants ha ve d on e most of the field testing o f the treated-graphite-filament packing, other com panies have also u se d it successfully. For example, the Union Carbide Chemicals Divi sion plant at South Charleston, W. Va., ha s it in 11 centrifugal pum ps handling concentrated sulfuric acid con tainin g su sp e n d e d carbon. The packin g has been in service since April 12, 1965, and has been found to be superior to any p a ck ing or seal arrangement used over the past 10 years. Leakage has been negligible com pared to ex perience with previous packings. The importance of installing and adjusting the p a ckin g p rop erly is em phasized by Carbide. Hot uranium salts have been han dled for 16 weeks by a pump packe d with treated-graphite-fila ment p a ckin g in operation at M a llinckrodt Chemical W orks, W elldon Sp rin gs,. M o. The best previous service w as with a mechanical seal, which lasted 5 weeks. The Hercules plant at Louisiana, Mo., has gone to the new p a ckin g on pum ps for m any services. Nalco Chemical Com pany has a pump handling an abrasive colloi d a l silicate suspension in water. The p a c k in g failed every 2 to 4 weeks, spraying product on the bearing a n d ruining it. A treated-graphitefilament packing installed October 19, 1965, has w orked all right so far, according to Don Johnson, plant engineer. The p a ckin g is in the form of lo o se ly braided graphite yarn. Four strands of glass fiber provide re inforcement. The packing remains stable in the atm osphere to 6 5 0 F a n d in steam to 1 2 0 0 F. It resists practically all chem icals. It is not recom m ended for fum ing nitric acid, oleum, dichrom ates and hot, fum ing sulfuric acid.