The system concept is easy enough to understand, but scoping with this in mind can be a confusing process. This is where many project engineers get into trouble.
The Problem With Process Equipment Estimates
As we’ve discussed, when scoping process equipment, the piece of equipment is only part of the costs for the project. The challenge is determining what else you need when purchasing equipment.
Manufacturers typically don’t make this easy. They will likely only provide the cost of the equipment itself—and leave it up to you to determine the rest.
Further complicating matters, the equipment scopes themselves are confusing. Each manufacturer (or distributor/reseller) offers differing scopes of supply. If, for example, there are 10 suppliers for a scrubber, you could very likely get 10 scope offerings, each with different performance and different component manufacturers (for example Goulds pumps vs. FlowServe vs. Sulzer, and so forth).
It can be extremely challenging to compare apples to apples unless you ask the right questions from vendors. So how do you get to the right solution when buying something like a scrubber, or a cooling tower? What questions need to be asked?
The Solution: The Basic Unit Specification Profile
Before you go visit manufacturer websites and start price-comparing, the first order of business is to clearly define what the piece of equipment is expected to do, and the conditions under which it will operate.
This is called the basic unit specification—a document which you should provide to equipment vendors when asking for bids.
Follow the steps below to build your B.U.S. for the system you’re tasked with scoping. The guide below will apply to nearly any type of equipment, but as always, there may be exceptions or additional specifications that apply as well.
Ask: What Will the Unit Service?
This seems fairly obvious, but it is critical. A cooling tower’s service, for example, could be to provide cooling for an office HVAC system, a fermentation chiller, or a hydrocarbon distillation system.
Some vendors are more suited to industrial applications than they are commercial or light duty.
Ask: What are the Performance Requirements?
The performance requirement data will be highly variable from one type of equipment to another, but it’s important to specify exactly what the facility needs the equipment to do.
These specifications typically consist of the following major criteria:
- Required Process Rate: this can be volumetric (GPM), mass rate (#/HR), or another process rate variable.
- There may be multiple required process rates, or qualifiers. For example, an evaporator may have an evaporation rate specified in #/HR of water evaporated, but may also have a minimum or maximum feed concentration, a minimum or maximum product concentration, and may have temperature limits at both ends.
- Maximum Process Rate: this is the maximum rate at which this unit is expected to perform.
- Up-Time, Duty, or Operation Hours: it’s important to let the supplier know the expectation for runtime, whether it’s daily, weekly, yearly, etc. This might trigger discussions such as preventative maintenance, required cleanouts during down times, etc., and could lead to different models being suggested, or vendors declining to quote due to warranty or other issues.
Ask: In What Conditions Will the System Operate?
Operating and location conditions are also very important such as the following:
- Ambient Temperature
- Ambient Humidity
- Ambient Pressure: elevation, inches Hg, etc.
- Site Specific Wind Load Data
- Site Specific Seismic Load Data
- Chemical Exposure: caustic wash downs, salt water, process leaks, etc.
Ask: What Available Utilities Will the System Require?
The specifics of the material that the equipment will be processing must be known to the vendor, whether gas, liquid, bulk solid, 2-phase material, or other. Some such parameters are:
- Chemical Composition: particular concerns are chlorides, sulfates, acids, bases, oils, and solvents
- Specific Gravity
- Particle Size Distribution
- Temperature Sensitivity
- Shear Sensitivity
- Boiling Point
- Vapor Pressure
- Flowability, Cohesiveness, or Stickiness
Ask: What is the Required Delivery Date?
It’s important to let the vendor know when the equipment is required to arrive at the facility. Some suppliers may be able to meet the date, others may not. This could play a major role in making the final decision.
With your system requirements in place, it’s time to approach suppliers and vendors.