Economics Of Using A Bellow Seal Valve
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 consider a 15mm valve operating on STEAM at 150 psi, in three types of valve.1. Bellow Seal Valve2. Piston Valve3. Standard Globe ValveA) Capital Cost: We can estimate the cost per unit as follows S.No Type of Valve Cost Per Valve in UD $ 1 Bellow Seal valves 75$ 2 Piston Vlave 38$ 3 Standerd Globe Valve 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 On Spares Cost of labour Downtime Bellow Seal valves Nill Nill None Piston Vlave 5$ 12$ 2 Hours Globe Valve 1.25$ 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$ 1.25Assuming a downtime of 1 hour x labour cost of US$ 6 per hour of maintenance. B) 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 per tonne of steam. Steam will escape at a rate of 25 lbs/hr through this clearance (as per steam tables) Type of Valve Cost On Spares Cost ofDowntime Cost Of Loss Of Media/Energy Bellow Seal valves Nill Nill None Piston Vlave Priceless `12$ 160$ per month Globe Valve Priceless 6$ 160$ 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/Ton = US$ 160 per month of energy Loss which can be saved ! (USD 5 per Day Approx.) 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)= 1 + II + III Type of Valve I II III Total Bellow Seal valves 75$ Nill None 75$ Piston Vlave 38$ 17$ 5$/Day (US $ 160/30 Days) 55$ + 5$ / Day Standard Globe 20$ 7.25$ 5$/Day (US $ 160/30 Days) 27.25$ + 5$ / Day So lets estimate that if the leakage is not attended (which is not in most of the plants), the cost of the valve wouldbe as follows:
