Page 96 - Improving Machinery Reliability

68 Improving Machinery Reliability

The bid invitation should instruct the vendor to propose a minimum of seal types.
For example, better-than-necessary seal-face materials should be offered for some
services, or bellows seals should be considered for an expanded range of applica-
tions in order to reduce the user’s spare parts inventory.
Proposals obtained from the various bidders must be examined critically for tech-
nical differences, and pertinent deviations should be noted for follow-up by the
user’s resident expert. These technical differences must be investigated by request-
ing that vendors submit experience data. These data should include the names of
other users who may be contacted to obtain verification of satisfactory experience.
The user’s resident expert should make these contacts.
Whenever possible, seal selection and evaluation procedures should make use of
in-house feedback as to principal reasons for seal failures at that location. These
data should be discussed with the vendor and solutions proposed.
The user’s priorities should be clearly established and transmitted to potential seal
vendors. Safety, long life, standardization, and ease of maintenance all precede
cost in order of importance.

These last topics merit further elaboration. Experience shows that the emphasis
should clearly be towards standardization without sacrificing reliability. Seals should
be cartridge seals that are simple to install and maintain. They should not be vulnera-
ble to minor deviations in pump operation or properties of pumpage. Indeed, a given
seal should suit the needs of many pumping services so as to reduce spare parts inven-
tory, streamline training requirements and leave little room for maintenance errors.
These goals can be met with a well-defined selection strategy. Such a strategy
may well result in the added bonus of greatly increased seal reliability and consider-
ably lower maintenance expenditures for most petrochemical plants. Many major
manufacturers of mechanical seals have indicated their support and willingness to
cooperate in implementing our selection strategy. Specifically, this strategy requires
the development of bid request information that asks the seal vendor to identify opti-
mum seal configurations. Principal features of optimum seals are highlighted in the
following pages; for additional details see Chapter 13.

Development of Bid Request Package

The development of bid request information is a key element in a selection strate-
gy leading to the procurement of mechanical seals that comply with the user needs
previously outlined. Bid requests must be forwarded to several experienced seal
manufacturers and must clearly state that the manufacturer should submit cost pro-
posals for only those services where his seal selection is backed by solid experience.
His inability to furnish seals for some services should in no way disqualify him from
submitting bids for those services where he is competent to provide a good product.
To begin with, the user should assemble API data sheets for the various pumps
that need mechanical seals.
This pump tabulation must include and disclose all of the fluid properties and
operating parameters known to the user. With disclosure thus going beyond the typi-