This Standard is based on the accumulated knowledge and experience of manufacturers and users of equipment in the petroleum, natural gas and chemical industries but its use is not restricted to these industries. Users of this Standard should be aware that further or differing requirements may be needed for individual applications. This Standard is not intended to inhibit a vendor from offering, or the purchaser from accepting, alternative equipment or engineering solutions for the individual application. This may be particularly appropriate where there is innovative or developing technology. Where an alternative is offered, the vendor should identify any variations from this Standard and provide details. The purpose of this Standard is to assist purchasers with the selection and operation of mechanical seals. This Standard has been drafted so that adherence to its provisions should result in a minimum of three years' life. It is expected that the average life may be substantially longer.