Economics of Using a Bellow Seal Valve





For analyzing the cost benefits of a Bellow Seal Valve over a Piston Valve or a conventional Gate / Globe Valve we will shall consider a 15mm valve operating on STEAM at 150 psi, in three types of valve.

  • 1. Bellow Seal Valve
  • 2. Piston Valve
  • 3. Standard Globe Valve

A) Capital Cost: We can estimate the cost per unit as follows


Sr. No. Types of Valves Cost per Valve in US$ I
1 Bellow Seal Valve US$ 75
2 Piston Valve US$ 38
3 Standard Globe Valve US$ 20

B) Maintainance cost: Assuming that gland leakage will begin within a period of 6 months in a Standard Globe Valve and in a period of 9 months in a Piston Valve, then maintainance costs will be as follows:


Type of Valve Cost of Spares Cost of Labour Downtime II
Bellow Seal Nil Nil None
Piston Valve US$ 5 US$ 13 2 Hours
Globe Valve US$ 1.25 US$ 6 1 Hour
Assuming cost of spare piston rings at US$ 5 per pair of rings.
Assuming a down time of 2 hours x labour cost of US$ 6 per hour of maintainance.
Assuming cost of gland packing at US$ 1.25
Assuming a downtime of 1 hour x labour cost of US$ 6 per hour of maintainance

C) Cost of Downtime & Energy/Media Loss:

We will assume a gland clearance of 1 thou (0.001 inches) for estimation of gland leakage and a cost of US$ 20 tonne of steam. Steam will escape at a rate of 25 lbs/hr through this clearance (as per steam tables).

Type of Valve Cost of Spares Cost of Loss of Media / Energy III
Bellow Seal Nil None
Piston Priceless US$ 120 per annum
Standard Globe Priceless US$ 120 per month
If we assume leakage of 11 kgs / hrs / day =264 kgs (11 kgs x 24 hrs) of steam loss per day x 30 days = 7920 kgs x steam cost of US$ 20 / Tonne = US$ 160 per month of energy Loss which can be saved !
The cost of down time is priceless and a value as such can not be put on it. It can vary from a few hundred to millions of US$ per day

D) Total Cost of Ownership (TCO)= I + II + III


Types of Valves I II III Total
Bellow Seal Valve US$ 75 Nil Nil US$ 75
Piston Valve US$ 38 US$ 18 US$ 4/Day (US$ 120/30 Days) US$ 55 + US$ 4/Day
Standard Globe Valve US$ 20 US$ 8 US$ 4/Day (US$ 120/30 Days) US$ 26 + US$ 4/Day

- Total cost of ownership for a Bellow Sealed Valve in 1 year would be: US$ 75.
- Total cost of ownership for a Piston Valve in 1 year would be: US$ 75+US$ 4/day x 90 days (since we have assumed leakage will begin in 9 months)
- Total cost of ownership for a Standard Globe Valve in year would be US$ 28 = US$ 435 =US$ 4/day x 180 days (since we have assumed leakage will begin in 6 months) = US$ 748