Water Softener Vessel – Compress Sample

File: PVE-6161, Last Updated: Sept. 7, 2012, By: TSB/LRB

This vessel is typical of many we have designed for water service for human consumption or industrial use. The design for this type of softener often starts from a customer sketch which indicates the operating conditions, classes of materials to use and required nozzles. The specifications also indicate the painting or rubber lining which is not covered in this sample.

We start with code calculations, and then prepare a fabrication drawing. Although this vessel does not require ASME code stamping, end users typically request it. When required we can also provide Canadian registration services (CRN) on the design.


This vessel is calculated using the Compress pressure vessel code program by Codeware Inc. Compress is our favorite program for general vessel design. Its extensive library of available calculation methods make it useful for many vessel design tasks. The report is harder to read and longer than Design Calcs, but its extensive code compliance checking makes its use worthwhile. If requested, we can instead provide the calculations in the other code software we regularly use: PV Elite, Design Calcs or even our own in-house Excel spreadsheets.

IBC Seismic Calculations

Support design for this vessel was done to IBC methods as built into the Compress Design program. The most difficult part of the IBC calculations is choosing the correct R factor for structural response modification. ASCE 7-05 Table 15.4.-2 provides the correct values to use (this table is linked below):

        Elevated vessel on symmetric braced legs - R=3
	Elevated vessel on unbraced legs - R = 2

Other R factors are available when special detailing is provided. This example is a vessel on symmetric but unbraced legs – an R factor of 2 is used.


The drawing is created in SolidWorks. By default, we use SolidWorks to create vessel drawings unless AutoCAD is specified. The drawing provides all required information to order material and fabricate without referring to the calculation set – a standard in pressure vessel drawings. Solid modelling is a very useful tool in the design of vessels and other pressurized equipment.

More Information on Seismic Response Factors: