Centrifugal Pumps Characteristics Curves, System Resistance, Flow Problems & Solutions
Centrifugal Pumps are the industry workhorses which are very reliable and perform well with Mean Time between Failures exceeding 4 years or more. However, even experienced engineers wrongly diagnose flow related problems and propose expensive and ineffect
– S Raghava Chari, Independent Consultant While centrifugal pumps and systems are the workhorses of the industry, widely used, due to improper understanding of the problems that come up, many a times expensive and ineffective solutions are proposed even by experienced engineers. The author proves this through many case studies and solutions.
Manufacturers test each model of their centrifugal pumps (CCP) and furnish characteristic curves (CC) sheets. CC is primarily a graph showing the relationship between the flow rates - usual symbol (US) Q - usually in m3/H and the discharge pressure often mentioned as the ‘dynamic head’ – (‘h’) in meters of pumped liquid (PL) column. In addition, the graph depicts the following relationships also:
1. Q Vs kW input to the pump
2. Q Vs Efficiency
3. The above 2 for different impellor dia
4. The above for a given dia impellor at different RPMs(N)
5. Net Positive Suction Head (NPSH)
Pump selectors and manufacturers select pumps considering the CC and purchasers given System Resistance (SR) curves – explained later - in addition to the numerous other specifications that go in pump selection. A manufacturer would handle two customer orders according table 1:
Fig-1 shows the characteristic curves for the radial flow CCP and table 1 one of its use. It tells further that the Q Vs h curve for a radial flow pump is relatively flat and that the head decreases gradually as the flow increases. Note that the brake horsepower increases gradually over the flow range with the maximum normally near Q=QR the rated flow.
Mixed flow centrifugal pumps and axial flow or propeller pumps have considerably different characteristics. Radial flow CCP shut-off head i.e. the closed discharge valve head is usually 120-150% of the design head.
System Resistance: System Resistance (SR) is the resistance to flow due to pipe friction, pressure loss across the equipment e.g. heat exchangers, the suction
lift and the pressure of the destination unit e.g. boiler drum and other causes. Suction lift and destination pressures and similar items constitute constant resistances and flow dependent resistances e.g. pipe friction variable resistance. Flow dependent resistances are usually proportional to Q2. It is customary to express SR in terms of meters of PL column. Table 2 shows the SR of the various items of the hydraulic circuit.
Review of Few Important Pump operating Points: Process plants’ and other important critical pumps e.g. boiler feed water pumps come with a hot standby as in fig 3. Let us review few important pump operating points with the help of fig 3:
up: Operators starting the pump A after a turnaround, close pump A discharge block valve BV, open suction valve, open casing fill valve and fill the pump casing with water known as priming. Close the priming valve and switch on the motor. The automatic recirculating controller (ARC) does the following given functions:
1. Check Valve
2. Min flow bypass valve
3. Pressure drop dissipater to prevent high ΔP erosion of letdown internals
4. Provides warm up flow to keep bypass line warm
5. Refer to the author’s article ‘Specialty Valves Save’ for detailed information on ARC and other types of min flow bypass systems.‘
Pump A ARC bypasses the min flow large CFPs require and Pump B ARC prevents B’s reverse rotation. Using discharge BV and LCV he establishes flow required and puts LCV on automatic. Opens discharge block valve fully. Leaves the suction and discharge valves of Pump B open. About 200 Kg / H of warm up flow across pump B ARC keeps the pump and pipelines warm and ready for pump B instant start up.
Transfer to Pump B: Operator or auto cut in relay starts pump B motor. The LCV will restore the flows to original values during operator closing pump A discharge block valve. Once pump comes to zero RPM, he closes the suction block valve, drains, and hands over to maintenance if required. Pump A ARC prevents its reverse rotation even if BV is open.
The above described pump start up procedure and leaving the discharge block valve open were followed in two fertilizer plants where the author worked. This offers the following advantages:
1. Avoids the labor intensive task of rush close/open of large block valves. E.g. opening a 16” 600# valve involves high torque 20 Nos. of hand wheel rotations of around 5-10 minutes duration
2. Avoids delayed pump transfer and even process
shut downs because of stuck discharge BV making pump transfer impossible.
Still the author could not convince refinery engineers in western India to follow this procedure. The author would be happy to hear the readers’ views.
Min Safe Flow for CFP: CFP CC shows that the pump consumes around 20% rated power under closed discharge pump run. The power churns the pump fill and dissipates enormous energy e.g. 20kW for a 100 kW rated pump. This enormous energy dissipates as heat and vaporizes the small volume PL fill. The lubrication of various mating parts and rotor buoyancy support disappears resulting in severe rub damages. Hence, never run large CFPs with blocked discharge for more than ten minutes. This is the reason for large CFPs coming with ARC or some other min flow bypass arrangement.
Case Study 1 shows the importance plant designers and CFP makers assign to min flow bypass system to protect large pumps.
Case Study 1: Fig 3 shows Turbine Driven BFW Pump A feeding 5 boilers with a motor driven hot standby. After around 3-years run, steam production dropped by 15% and the hot standby started rolling backwards!
Operation engineer started that too and happily reported resuming 100% steam and thus 100% ammonia production!
The troubleshooting process engineers hastily concluded that worn CFP internals due to the 3 years of continuous runs as the cause and insisted on overhauling the pump.
No shift from the near zero shaft vibrations made the author to eliminate other causes, before opening the critical pump. Worn internals usually lead to excessive rotor vibrations. By pump circuit study, the author found that in addition to ARC, the pump has come with manual min flow bypass also (fig 3). No warm up bypass across the normally closed (NC) bypass valve puzzled the author. By drawing careful re-study, the author found that, the valve vendor had drilled a 1.5 mm dia hole in the gate to bypass ≈200 kg/h hot water. Voila, here is the culprit! The author concluded that the high ΔP hot water letdown – 120 to 1.3 bars – erosion of the 1.5 mm dia hole bypasses significant quantities of BFW and starves the 5 boilers. His insistence to lift the gate valve bonnet taking a 1 day SD paid well. Letdown had eroded the hole to ≈25 mm and wastefully bypassed estimated at 60 T/h BFW.
The author got the hole plugged by strength welding a disc at the hole and grinding the weld flush. In addition he got a ¾” bypass across the gate valve with multiple orifices restriction to bypass 200 kg/h warm up flow. Boilers resumed steam production within 8 hours. The LCVs assumed normal near 60% open. Boilers did not get enough BFW even at 100% open LCVs, before the bypass gate repair.
Thus the author’s detailed circuit study and logical thinking averted an expensive pump overhaul and few days lost production.
A urea plant replaced the worn out always running CFP with a new one. The new pump did not deliver the rated quantity and hence the hot standby became the ‘always running’. The troubleshooters came up with no solutions.
An inquisitive newly joined graduate engineer asked, “Why a discharge to suction bypass, in addition to the min flow bypass restriction? That opened the eyes of all! The erector had incorrectly installed the drain valves as in fig 4b instead of as in 4a to save a valve - an operating engineer suggestion!
Case Study 3, another low throughput problem: A pioneer centrifugal compressor technology based fertilizer plant, suffered gradual capacity fall,which went unnoticed. Fig 2 shows the hydraulic circuit. 24 months after commissioning. Appreciable production loss happened due to too high exit process gas temperatures of various water cooled heat exchangers and the large steam turbines’ surface to condensers vacuums dropping to < 600 mm Hg from 700 mm Hg. This disturbed the top manager, who ordered an immediate remedy.
The troubleshooting process engineers hastily attributed the cause to increased cooling water consumption due to various de-bottlenecking tasks during commissioning. They proposed adding another CW circulation pump - a very difficult to implement proposal costing >Rs 10 million in the eighties.
The author, - maintenance manager then - reviewing the proposal questioned the process engineers, on the SR. Their evasive answers revealed their shaky SR knowledge!
He explained SR and took them to the pump. The discharge header pr gauge read 342 kPa against 340 the
PFD specifies. The triumphant process engineers said, “We are right Sir. SR has not increased.”
To double check, the author zeroed the PG, and found it still showing 342 – obviously stuck gauge! A new gauge showed 370 kPa close to relief valve setting of 380 kPa. The relief valve must be passing heavily due to too low seating pressure from the too low margin between operating and set pressures. Acceptable margin is 10% or more of operating pr. The leak, piped back to the cooling water basin is not visible. In addition, he got the shell covers of a small shut down heat exchanger opened. Fouling was so much that one wondered how water ever flowed in it! Obviously increased SR is the cause of too low pump delivery and too poor heat exchanger performance
The author chided the process engineers for their inadequate SR knowledge, consequent hasty wrong conclusion, and resulting proposal for an expensive pump addition, which would not have solved the problem anyway. Why? The author requests the readers to solve this puzzle.
On the author’s suggestion the plant advanced the turnaround by two months, got all heat exchangers hydro jet cleaned. Pump discharge pr was only 280 kPa. In fact, operators had to throttle many heat exchanger water valves to get correct exit gas temps. Finally the pump discharge header PG settled at 310 kPa and water flow rate as shown in CC. The various heat exchangers’ gas exit temps and surface condensers’ vacuums attained normal values, and production exceeded rated capacities.
Case Study 4; Why Mechanical Seals & Thrust Bearings failed often? A turbine driven multistage CFP (fig 5) with motor driven hot standby draws 2-bar, 110oC potassium carbonate (K CO ) solution from the
CO stripper and feeds to CO absorber at 35 bars pres
2 2 sure to scrub Reformed Gases.
After 18 months of exceedingly good run since commissioning,the suction and discharge mechanical seals (MS) developed leaks. Thrust antifriction bearing (TB) also showed poor shock pulse meter readings. The renewed MSs and TB lasted 3 months only. Crew changed both and lived with both failures without proposing any solution.
The seal supplier assured that the spare MSs as good as those they supplied to pump manufacturer and requested to look for other causes. To troubleshoot, the author noted the following from failed seal, bearing inspection and drawing study and posed the Root Cause Analysis questions of why and how?:
1. The MSs have API 31 seal flush plan: 6 bars 60o C condensate flushes the seals and prevents the hot and aggressive 115o C K CO wetting the seal for
2 3 seal protection
2. Eyes of impellors 1,2&3 face left and those of 4,5&6 right to cancel rotor axial thrust towards suction usual in CFPs substantially
3. Balance Drum (BD) left side pressure is > BD right side pressure, as the seal flushing line connects it to suction seal. Thus the net force on BD towards discharge cancels more of the axial thrust.
4. The TB handles the very small magnitude residual thrust 2 and 3 leave
5. Brittle seal elastomers indicate, hot and aggressive K CO wetting the MSs; possible only if condensate
2 3 flush fails? Has it failed?
6. Poor TB lives indicate excessive TB load. How is it possible? Perhaps, too high BD left side pr →, low ΔP acrossBD → reduced force on BD towards suction → loss of thrust cancellation. Why?
7. Perhaps increased clearance betweenBD OD and BD chamber ID. BD right side pressure exceeding 6-bars would prevent flushing condensate entry, essential for long MS lives. This surmise supports the observed brittle elastomers – item 5
8. The drawing specified 3- mm thick stellite – a cobalt based – hard facing alloy – deposit of 450 BHN hardness at WR bores and BD OD to realize hardness difference of min 50 BHN with SS 316 mating parts to prevent galling.
How to confirm surmises 5, 6 and 7? Few minutes of intense thinking suggested checking the skin temp of the ¾” flush line upstream and downstream of the
NRV. With normal seal flushing it should be around 60O C.
Near ambient NRV upstream and 103OC NRV downstream contact thermometer readings confirmed the authors’ surmises of:
1. No seal flushing flow because of higher than usual ΔP i.e. higher than usual pr at BD right side
2. Surmises 5 to 7 of last paragraph.
What is the remedy? The author thought of the rem
edies as under:
1. Check BD& Wear Ring clearances during next seal change shutdown
2. Put spare wear rings if excessive clearances
3. Sleeve the BD to realize design clearances
4. An operator suggested adding rota meter to measure each seal flush flow.
The crew reported 6-mm higher clearances at wear rings and BD when they disassembled the CFP two months later for MS and TB change. The confirmation of the author’s Root Cause Analysis (RCA) based surmises delighted the author to ecstasy, because solving the problem now is easy! All over 6-mm clearance increase points out that K CO solution has corroded
2 3 away the stellite and fortunately not SS 316. The author decided not to stellite the mating parts though the mating parts become galling prone. American Petroleum Institute (API) 620 recommends increasing the clearances by 0.125 mm from those given for nongalling pair to prevent galling of even galling mating parts. Crew measured BD chamber bore dia was 500 mm and specified clearance with stellite hard facing 1.75 mm. He got a 20” Sch40 250 mm long pipe bit from a neighboring plant to sleeve the BD OD.
Machinists machined the pipe bore for medium interference fitting on to the polished BD. Soaked the pipe in 200oC oil bath for 5 minutes, wiped oil well and slid the pipe over the BD. After cooling to room temp, they finish machined the pipe bit OD to 500-(1.75+0.125) = 498.125 mm diato realize galling pair clearance and trimmed the ends flush with that of the BD sides. The resulting sleeve thickness of 10 mm exceeds 6 mm, min necessary for stable shrink fitted sleeve. crew assembled the pump back and handed over in 12 hours after putting new MS and thrust bearing because of reasons given below:Making new SS WRs and putting new wear rings involving rotor disassemblyare time consuming, and too longmotor driven pump run is risky. The shop made new wear rings from suitable SS 316 pipe bits taking care to increase the clearanc- es by 0.125 mm – galling pair- in two months leisurely. Though MS and TB failures disappeared, the author got SS wear rings put to minimize leaks and save power at a suitable shutdown opportunity. In addition, he provided a rota meter 0-1000 LPH to measure each seal flush flow, and green marked 500 – 700 LPH as normal flow.
The operation engineer heard the author wondering aloud, “how come, nonenoticed pump capacity loss, despite such enormous clearances increases. He responded, “We did notice Sir, we just increased the turbine speed by 25-50 RPM whenever we could not pump enough to the absorber. Turbine RPM was 3400, 18 months ago, it was 3570 till new SS wear rings went in and now it is back to 3400!
Seal lives exceeded 36 M and TBs never failed thereafter.
Case Study 5: why carbon bushes of submerged pumps failed often? 21 Nos. of steam turbines surface condensers of a Saudi Arabian fertilizer factory came with a turbine driven condensate pit pump mounted on top of a buried tank and a motor driven pit pump (fig 6). Often the pumps’ carbon bushes supporting the impellor eyes and the long shaft reaching the driver wrecked. The site engineer at his wits end requested the author to handle the problem.
The author watched a pump changeover: Operators opened the 3” water side valve to fill the condensate collection tank. They were about to push the motor start PB. Hold, shouted the author and asked, “have you opened the steam side valve?” The perplexed operator grinned and said, “Steam side valve, Sir, No supervisor told me to open it”. The author called the operations engineer and he too was ignorant of the steam side valve. The author explained, “the condenser is under high vacuum. Hence, unless the pit tank top is open to the same vacuum water cannot flow into the tank. So you must open both the ¾” steam side and the 3” water valves
and wait for 5 minutes to be sure of enough condensate collection in the tank and submerging the pump. So far you have been wrecking pumps because of dry running!”
The sheepish operator opened the steam side valve also and waited for 5 minutes and then changed over to the motor driven pump safely. Thus the author prevented another wreck and all future wrecks!
By a memo the author requested the operations manager to revise the pump start up procedure and hold classes for all operators and shift engineers.
What do the above discussions tell us? The above discussions tell us that CFPs are more than what meets the eye, especially during commissioning. Most manufacturers furnish sturdy and reliable CFPs. Mean Time between Overhauls exceeding 4 years is common for well installed and aligned to the driver CFPs. Most failures are due to external pump factors as the above case studies show. (see table 3)
Hence, do not modify pump installations hastily. Eliminate all external causes first.
Other improvements: Squirrel cage inductions mo- tors (SCIM) are industry workhorses because of their following benefits:
1. IMs are highly reliable and run for long periods with practically no maintenance due to simplicity of construction; just 3 parts – a stator, a rotor and supporting bearings.
2. Runs on the common and easily available 3 O (large motors) or 1O AC power supplies.
3. SCIMs self-start on push button pressing
4. Thanks to availability of motors of voltage ratings up to 13.2 KV their sizes are small even for very large motors say 25 MW.
5. Motors are available for different fixed speeds from 300 to 3000 RPM for standard 50 Hz supply.
6. Motors of different enclosures and starting torque to suit the driven machinery needs are available for use in the open, even in harsh environments.
7. Construction of hazardous area motors is simple and less expensive due to the absence of spark producing commutators. In addition, absence of wear- ing and sparking commutators eliminates periodic maintenance shutdowns. Hence, IMs offer the highest availabilities amongst all drivers.
8. IMs are the most environment friendly drives due to no emissions
9. IMs are the lowest cost drivers.
However, these workhorses suffered a serious limitation of non-amenability to speed variation till recently. Users varied the capacity of CFPs, compressors, and fans, by energy wasteful discharge valve throttling.
Advent of Variable Speed Drives: The ever-increasing energy costs and stricter and stricter environment regulations constrained industry to be energy efficient and limit pollution, creating a crying need to vary SCIM speed variation besides others.
The great strides of solid-state power electronics and the crying need as above resulted in the invention in the eighties of a device called Variable Frequency Drive (VFD). We will stick to the nomenclature VFD, though it goes by various names of VSD (Variable Speed Drives), ASD (Adjustable Speed Drives), and FC (Frequency Converter).
VFDs accept the standard 1 or 3 φ AC power supplies and outputs variable frequency and voltage conditioned power to run SCIMs at variable RPMs and torques to suit driven machinery requirements. Having got a rudimentary idea of VFDs, we will study the benefits of using VFDs for CFPs (cases 1&2) and piston / plunger pumps (PPs, case 3) capacity control, and as a ‘design out maintenance device’ to replace the existing energy wasteful, and low availabilities variable speed drives (VSDs) in few applications (Case Studies 7&8).
Case 1: CFP of predominantly Constant SR Hydraulic Circuits: The resistances a Boiler Feed Water Pump hydraulic circuit offers is negligible compared to that the boiler drum pressure of 100 bars i.e. ≈1000 m WC. In addition it is constant. CFP affinity law tells us that h = h α N2 where hPD = pump developed
PD SR head and Q flow rate. hP exponentially decreases with decreasing N, whereas, the SR remains nearly constant. Hence, flow to the boiler drum would cease at lower N. Thus VFD or any other device to
vary motor speed for flow control is useless. Discharge control valve (DCV) throttling is the only practical way to vary the flow. However, the energy lost by dissipation across DCV is inevitable and negligible for small flow variations.
CFP of predominantly variable SR circuit: VFD speed control for CFPs of predominantly variable SR and for Plunger Pumps is very beneficial and allows wide flow variations at considerable energy savings. See examples 1 and 2.
Example 1: A plant’s pump house feeds plants A to D (fig 2). Plant A draws 0.3QR when a 3 hour long batch is on and 0 at other times. Thus they draw water for 12 hours a day only. Plants ‘B to D’ are continuous process plants. A flow controller FC manipulates CFP discharge control valve (FCV) to meet flow requirements. Is VFD pump speed control instead of FCV beneficial?
VFD Retrofit Analysis:
Example 2: Assess the suitability of VFD application for the plunger pumps of data detailed below:
VFD Retrofit Analysis:
Salient Plunger Pumps Information: Plunger pumps find applications for relatively smaller throughput at high discharge pressure applications e.g. pumps to feed liquid ammonia and ammonium carbomate at 250 bars pressure into Urea Reactors in the 30 to 40 m3/H flow range. They generate the head to overcome the hydraulic circuit’s SR at all Ns. Hence, a safety valve at discharge is necessary to prevent overpressure bursts in case of inadvertently closed discharge block valve. The PP delivers a constant volume per revolution. Hence, bypassing part of the Q back to suction or varying the pump speed is the common flow control method. Urea plants vary the pump speed using a hydraulic torque convertor between pump and motor to control reactor feed carbomate flow rates, though of 30% efficiency, due to process requirements.
To summarize, running all types of pumps and compressors at necessary speeds to meet the flow requirements saves considerable power, wear and tear than running these at fixed motor speeds and resorting to other flow control methods. Torque convertors though of high MTBF, are notoriously of low efficiencies and most difficult to repair because over 100 precision small parts assembled into the casing. The author knows of two instances of other plants opening a torque converter and abandoning it. Fortunately 1:1 spare held avoided huge production loss.
These and the above discussions projected potential of very short payout period encouraged the author in 1985 to fit VFD for the 3.3 KV, 450 KW motors powering a carbomate pump and its hot standby coupled to Motor, GB and TC.
Only one vendor offered a combination of 3.3.KV/400 V step down input transformer 1 + VFD + 400.V/ 3.3 KV step up output transformer 2. It looked too complicated and the vendor could not furnish names of successful users. Hence, it did not get top management approval. The case study below shows that now HT VFDs are available and saves power and machine wear and tear:
Case Study 6: VFD powered Screw Compressor Saves: A mega sized Indian refinery came with screw compressor coupled to VFD powered 6.6 KV motor to hold crude distillation tower top pressure constant. Formerly, refineries wastefully bypassed part of the screw compressor discharge back to suction to vary the throughput to maintain the tower top pressures. Table-4 shows the recurring savings the refinery enjoys from the VFD:
VFDs ‘Design out Maintenance’: The case studies 7 and 8 explain it.
Case Study 7: VFD retrofit ‘Designs out Maintenance’ & boosts production: Mechanical vary-speeddrives (MVSD) vary the belt speeds of 12 Nos. ofBelt weigh feeders’ to vary raw materials – urea, filler, and potash – feed rates to manufacture different grades of complex NPK fertilizers at different production rates to meet market requirements. A 0.7KW Motor flanged to MSVD casing runs MSVD internals of numerous moving parts to run the input shaft of a gearbox flanged to the MSVD casing at 500 to 2500 RPM. The gearbox output shaft runs the weigh feeder conveyor belt drum at speeds of 0.5 to 2.5 m/mt. A pneumatic actuator (PA) responding to 3-15 psi output from control room panel mounted weight recording controller (WRC) adjusts a lever of MSVD to vary the output shaft speed.
A pneumatic speed transmitter ST coupled to MSVD output shaft outputs 3 15 psi pneumatic signals proportional to belt speeds. A load cell generates the signal for belt-loading (Kg/Meter)-Kg/M; a pneumatic analog computer (AC) multiplies these two signals and outputs weight rate (Kg/H) signal to WRC.
Problems of the system: MSVD failure modes are fast wear and tear of various precision mating parts, parts’ severe corrosion, consequent seizures, especially the axially travelling pulley halves on input and output splined shafts. Failed speed transmitters due to these reasons added to the poor weigh feeder availabilities, very high maintenance efforts and costs and severe production losses as high as 10%. Product NPK Quality too was poor drawing enormous customer complaints. (Fig 10)
Solution: The author eliminated the MSVD and Speed Transmitter and thus the poor weigh feeders’ poor availabilities.
Crew did the simple trial modification tasks: Discarded the MSVD; flanged the gearbox and the Motor to a shop made pedestal bolted to the MVSD base plate. Installed and set the VFD to output 17-85 Hz frequency in V/f = constant mode to meet belt conveyor torque requirements and according to 4-20 mA current signals. (Fig 11)
Thus VFD powered motors run the weigh feeder at 0.5 to 2.5 m/min according to WRC outputs as before, but at 100 % availabilities.
A purchased P-I (pressure to current) converter converts the 3 15 psi WRC outputs into 4-20 mA to vary VFD output.
The motor and hence the belt speed is proportional to frequency and hence the 4 20 mA i.e. to the 3-15 psi WRC output. Therefore WRC output itself serves as belt speed signal also, eliminating the troublesome speed transmitter too.
As discussed in the above paragraphs, by VFD use, gone are the most troublesome MSVDs and Speed transmitters boosting that weigh feeder availability to 100%. Resulting projected increased production, improved product quality, less maintenance expenses and no customer complaints of failed / delayed deliveries etc. at negligible investment pleasantly surprised the management immensely. The manager chased the author to effect the modifications within 6 weeks – VFDs rush purchase 5 wks + 1 wk installation!
Case Study 8: VFD ‘Designs out Maintenance’ & boosts cement production: Rotary Drum Kilns’ and Driers’ conventional drives are notoriously maintenance prone requiring daily chores of lubricating, freeing stuck parts, and cleaning. Consequent low availabilities result in huge production loss and enormous maintenance expenses. A typical rotary kiln drive consists of a 1000 kW motor coupled to a heavy ratio gearbox (fig 12). GB Output shaft couples to a between plummer blocks
bearings pinion shaft. The pinion meshing with the drum mounted and linked to the drum huge split gear drives the kiln at about 10 RPM. Drive System Pro
blems: Below listed are drive system problems and consequent low availabilities
1. The links linking the large split gear to the drum break often and shut down the plant
2. Split gear rotation throws large lube spills and causes serious housekeeping prob-
lems and slip hazards
3. Often breaking Links repair is tedious, time consuming, hazard prone, and often of unsatisfactory outcomes; these reduced the availabilities to around 80%
4. Lubricating the open meshing pinion with the split gear and several rollers supporting the drum is a daily tedious chore.
On the other hand a Saudi Arabian cement plant rotary kiln is a perfect example of ‘Design out maintenance’.Gone are the gearbox, open meshing gears, theirlubrication, hazard prone lube spills and the pain in the neck links coupling the large sprlit gear to the shell’. The new all electric drive is unbelievably simple and maintenance free! (Fig 13)
The kiln shell has the silicon steel rotor laminations keyed to it. Thus the shell doubles as rotor also. Windings concentric to the rotor laminations constitute the ‘120 pole stator’. The shell and stator windings thus constitute an induction motor!
Powered by a VFD accepting 6.6 KV 60 Hz 3 φ AC and set to output 10 Hz 3 φ AC the ‘motor rotor’ i.e. the kiln rotates at 10 RPM! Look how simplified and maintenance free the drive has become – Indeed a magnificent ‘design out maintenance’ example!
The author recommends all Rotary Kiln, Rotary Drum Dryer and Rotary Granulator users to check and retrofit modern drive if feasible.
Grundfos launches Dewatering pumps
Grundfos India, manufacturer of intelligent & efficient pumping technologies, has recently launched its dewatering pumps DPK and DWK. Grundfos’ reliable dewatering pumps, DPK and DWK, aim at easing the way of life while restricting the economic losses. These compact submersible pumps can dewater effectively. DPK & DWK can be used in homes, offices, gated-communities, construction sites, excavations, tunnels, underground parking, industrial drainage pits etc. Making it a perfect solution for all the water logging and drainage related issues during the monsoons.
The DPK and DWK range of dewatering pumps are conceptualized and engineered after going through many levels of stringent tests. They come with intelligent features such as:
• Built-in bi-metal sensor that protects against overheating of the motor
• Pump performance is unhindered by sand or other abrasives is required, or if the available power supply is limited
• Combining installation flexibility with reliability and ease of service. Speaking about Grundfos’ dewatering pumps, Shankar Rajaram, Vice President – Business Development, Grundfos India said, “Indian monsoons are becoming more unpredictable every passing year. It is therefore essential to be proactive in addressing issues such as water logging by being equipped with the right pumping solutions. Grundfos range of dewatering submersible pumps are designed to work optimally in such environments. These pumps are easy to install and service and therefore are a perfect solution for both commercial and domestic customers”.
For more details contact: Grundfos Pumps India Pvt Ltd, Chennai. Tel: 044-45966800 Email: email@example.com Web: www.in.grundfos.com
Aerotherm’s fluid bed dryer
Container of Aero Therm Fluid Bed Dryer is made out of MS / SS304 / SS316 /
Aluminum as per requirement.
The perforated sheet & fine wire mesh screen will be provided at the bottom for proper air distribution.
Heating can be supplied with Electrical, Steam, Thermic
Fluid or Hot Air Generator.
Electrically heated Dryer will be provided with heating element of suitable rating having
MS galvanized / Stainless steel construction. Steam / Thermic
Fluid Radiators are made out of MS / SS Tubes with MS / SS / AL Fins as per requirement.
Control Panel will consist of Digital Temp. Controller, Starter for Blower, Synchronous Timer for batch time setting, Indicating Lamps, Fuses, Main Isolator switch etc.
• Range 15 to 500 Kg
• Heating: Electrical, Steam or Thermic Fluid Radiator
• Uniform and Quick Drying
• Drying at Low Temperature.
For more details contact :
Aerotherm Systems Pvt Ltd
Phone :+ 91 79 25890158
Dexmet’s MicroGrid ® precision expanded metal and metal foil
MicroGrid precision-expanded foils from Dexmet
® are used in batteries, electronics, aerospace, medical, packaging, and wherever mesh and perforated foils with high precision, mechanical and electrical properties or EMI/ RFI shielding capabilities are required. They are available in most metals and polymers, or we
can work with your proprietary materials.
Metals we regularly produce include: aluminum, brass, copper, Monel™, nickel, steel, stainless steel, and zinc.
Expanded Metals Configurations Materials and Specifications
One-piece, single-unit structure Eliminates unraveling and contact resistance of woven mesh
Superior shielding, electrical and heat transfer properties
Wide range of sizes, patterns, angles and materials Specialized process variations, such as flattening, pulling, and annealing available. For details contact: Dexmet, USA Tel: (800) 714-8736 Fax: (203) 294-7899 Website :firstname.lastname@example.org
NSL Centrifugal Pump by DESMI
The NSL range of pumps by DESMSI represents high efficiency, low NPSH values, easy to installation and low maintenance. The NSL series is widely used within different applications and markets.
The pump is an in-line, radially split, single-stage centrifugal pump with connecting flanges according to international standards. The pump is designed for mounting with electric motors having different international flange dimensions.
The casing is equipped with a replaceable sealing ring. The impeller is made with double-curved blades to ensure low NPSH-values and high efficiency. The bearing unit is equipped with sturdy ball bearings and the small types are fitted with lifetime-lubricated bearings. In the larger types the lower bearing is a double bearing for which a lubrication point is provided. These pumps are suitable for :
• Industry water circulation
• Cooling tower distribution
• Diesel transfer
• District heating
• District cooling
For more details contact:
DESMI India LLP, Telangana, India Mobile No : +91-9949339054 Email : email@example.com Website: www.desmi.com
Koch Membrane Solutions offers spiral nanofiltration and reverse osmosis products
Koch Membrane Systems (KMS), a global leader in membrane filtration technologies, has announced the return of the FLUID SYSTEMS nano
® filtration (NF) and reverse osmosis (RO) product lines. The FLUID SYSTEMS NF
® and RO products are available in standard 8” FRP hard overwrap configuration (8040) in standard and high area construction, and are listed under ANSI/NSF Standard 61. The FLUID SYSTEMS line includes multiple products engineered to serve in potable water and industrial water applications including:
• TFC SW: High rejection seawater RO membranes ® for treatment of high TDS industrial streams and seawater desalination
• TFC HR: Robust high-rejection and low-fouling ® brackish water RO products for consistent operation when treating industrial streams and wastewater effluents
• TFC SR: Low energy NF products for water soften® ing, seawater sulfate removal and organics removal In addition to NF and RO elements, KMS offers a line of standard systems, which includes a high recovery option.
For more details contact:
Koch Membrane Systems, Wilmington, Delaware Phone: +1-978-694-7000 Website: www.kochmembrane.com