Page 108 - Improving Machinery Reliability

80 Improving Machinery Reliability

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CONSlDEKATlONS FUR EVALUATING CENTKIFUGAL COMPRESSOR BIDS
Item r
-- questions, Considerations and/or Action Plans
1 Have all compressor niodels been successfully operated elsewhere?
2 lire tllefe ally ddVdntageSldiSadVd0tngFs to barrel COnStrUCtlOn for this Sel-vlCe?
31 Does tlie [machine with fewer impellers produce too much head in the second section?
4)
5 Compare quoted diameters with tip speeds. Suitable for impeller fabrication method?
6) Consistent with tip speeds? Maximuin allowed continuous speed?
7)
8) Are these vdlUeS coiisistent With th? related ddtd, above? UOfS
91 tlie vendor have experience with inipellers at these tip speeds?
1u How calculated? Sufficiently far froni anticipated operating Speed range?
111 Are apparent efficiencies and losses realistic? How determined?
12 I
13 Are higher dnticipdled discharge teinperatures (Vendor 8) detriinental to process! Costly?
14 Explain significant difference in gas data for VPndor B. Reconcile witn othrr5.
15 ure capacity uiffewnces significant in liqlit of future uprate requirefiierits?
161 Nozzle ratings limy reflect desigi consei'vatism and uprat.e capablllt1c.s. llave you
171 llldde d CUlllpdfiSOll? DO VCiIdUT PtUpUSed VrlOCltieS dCCUrdteIy ref leCt Sldled gas
181 volulnes divided by nozzle et'ea? Rfcvncile discrepencies.
19)
20) Are quoted llidterldlS COllSlSterlL With specified liidterldlS? IndUSlry prdCtlteS?
21) Vendor rxperieiice with quoted nidteridls?
22 )
23 Sliould credit be given tu cast rteel construction?
24 Why is Vendor (I offeriny PTFE-Coated labyrinth Ilidteridl?
25 ) Does luwer Iiiaiiitendnce weight allow installation of less wpensive overliead
26 ) crane? Is credit due?
27 Investigate possible eifects of Veiidor C not offerinu coniiion baseplate.
78 Who is responsible for tlie design of the SUbCvntrdCtcd baseplate proposed by
Vendor C?
29 WOUlO Sepdl'dte lube dnd Sed1 011 SySlWlS lldVe been ddVdlltdgC'OUS?
30 Why docs Vendor U propose iiieclianical contact seals? Are there any ddvdntages?
31) Shat is this overhead vessel acconlplisliing? Vendor A lists tlie runduwii capacity
32) to be in excess of the vessel capacity. Is this logical?
33 hhdt i5 the CdlCuldtlUn DdSiS Used to arrive at 1000 qallOllS VS. 2000 qdllOnS
rundown capacity?
34 Any adverse experience with riveted impellers in this service?
35 ilhy does Veiidor C propose to indnufacture his own thrust bearinqs?
36 Could d IIIO~L! Suitable balance pistun design be used by Vendor C for tllrust reductlorl?
37 Lhy does Vendor ti propuse to iiianufacture his ohn journal bearings!
3M Investigate rating basis used OY rdcli vendor. h'hy thf difference?
3Y Is the clarifier intended to reiiiove only water? Water and Iiglit tiyarocarbons?
4u Coupling offer n allows for Iiiuher torque, but less iiiisaliyrrent than offer B.
Have you evaluated the pros and cons?
41 Is each control panel fully equipped with all specified instruments? Any extra ones?
42 What do we know about offers 8 and C? Long-term experience?
43 Any service problenis anticipated for the installation destination?
44 lhiportdnt orily if geared train coilfiguration.
.
45 Is Vendor C offerinu an uiitested orototvoe? Whv no urrforinarice curves?
~r
I.
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4b Low pressure rise to surge would illandate implementation of flow control scheme.
Is this possible? lnvestiqate process considerations.
47 Insist on early submittal of spare parts data frulii Vendors 8 drid C.
4n Clarify status of rotor via discussion with Vendor U.
49 Clarify status of mechanical run tests via discussion with Vendor C.
50 Verlfy no closed loop perforrliance test was Spccified. Is it desirable?
51 Why did Vendor A include winterization? What does it consist of?
52 Shipping costs, yotcntial delays. extra expediting costs, service arranqeinents
niust be understood - especially fat- overseas point of origin.
53 Discuss experience qualifications with Vendors B and C as soon as possible.
54 Vendor C nust SUbniIt full API data before further consideration Can be glwn.
Uoes he have soniethiny to Iiide?
55 YoSitiOn taken by Vendor A is not acceptable. Expedite Vendor E.
56 Verify that bearing spans are covered by vendors' previous experience.
57 I Are vendors familiar with data subiuission requirements imposed by purchaser?
58 1 kill they contractually agree to submit such data as rotor design dimensions
59) and as-built dimensions?
60 Is each impeller of proven design? Will impeller perforindnce curves be provided?
61 Are these Mach numbers sufficiently low for the gas being compressed?
67 ) Are imyeller and diffuser diinensioris large enough for potentially foulinq
63) services?
b4 Verify experience to ensure against rotor dynamics problems.
65 00 stress calculations make use of stress concentration factors or orily sTmpliftcd
calculations? Reconcile high stress quoted by Vendor C.
66 Are quoted coupling bores near niaximuni permissible diameters? How are hubs
engaged to shafts? Hydraulic fit? Who will supply special mounting tools?
67 Are couplings suitable for future uprate requirements?
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Figure 2-17. Considerations for evaluating centrifugal compressor bids.